TW201442990A - Self-suspending proppants for hydraulic fracturing - Google Patents

Abstract

The invention relates to modified proppants, comprising a proppant particle and a hydrogel coating, wherein the hydrogel coating localizes on the surface of the proppant particle to produce the modified proppant. The proppant particles can be solids such as sand, bauxite, sintered bauxite, ceramic, or low density proppant. Alternatively or additionally, the proppant particle comprises a resin-coated substrate. Optionally, the modified proppant further comprises an adhesion promoter, optionally affixing the hydrogel coating to the resin-coated substrate. The hydrogel coating preferably comprises a water-swellable polymer. The hydrogel coating can be manufactured form a water soluble polymer. The preferred weight average molecular weight of the polymer is about 1 million g/mol, preferably about 5 million g/mol.

Description

Self-suspending proppant for liquid cracking

This application generally relates to systems, formulations and methods of rupture techniques.

In the process of producing oil and/or natural gas from a well, it is often necessary to stimulate the hydrocarbon stream via liquid cracking. The term "rupture" refers to the method of pumping a fluid into a well until the pressure is increased to the extent that the subterranean geological formation containing the trapped material is broken. This process causes the fractures and fractures of the lower layer to collapse, allowing the hydrocarbon product to be carried to the well to be drilled at a significantly higher rate. However, unless pressure is maintained, the newly formed opening will be closed. In order to open the passage and maintain it, the proppant is injected with the hydraulic fluid to create the support needed to protect the production port. As the crack forms, the slurry transports the proppant, and when the hydraulic pressure is released, the proppant forms a stone wall or pillar that remains open.

In order to achieve placement of the proppant inside the fracture surface, the particles are suspended in the fluid and then pumped to its underground end point. In order to prevent particle settling, high viscosity fluids are often required to suspend. Fluid viscosity is typically manipulated by the addition of synthetic or natural based polymers. There are three common types of polymer-enhancing fluid systems commonly used for suspending and transporting proppants during liquefaction operations: slickwater, linear gels, and crosslinked gels.

In slickwater systems, anionic or cationic polyacrylamide is typically added as a friction reducing additive to maximize fluid flow with minimal pumping energy. Because liquid cracking has a high pumping energy requirement (in the 10,000 to 100,000 horsepower rating), a friction reducing agent is added to the slippery fluid to enable high pumping rates while avoiding the need for even higher pumping energies. Although these polymers are effective as friction reducing agents, they are not highly effective as tackifiers and suspending agents. The slick polymer solution typically contains from 0.5 to 2.0 gallons of friction reducing agent polymer per 1000 gallons of slick water, and the solution has a low viscosity, typically on the order of 3 to 15 cps. With this low viscosity, the turbulent flow stops and the suspended proppant particles can quickly settle out of the suspension. For this reason, the slick water is used in a rupture stage without a proppant or a proppant having a small particle size or a low proppant load.

The second type of polymer-promoting fluid system is known as a linear gel system. Linear gel systems typically contain a sugar polymer such as gum, hydroxyethyl cellulose, hydroxyethyl gum, hydroxypropyl gum, and hydroxypropyl cellulose. These linear gel polymers are typically added in an amount of from 10 to 50 pounds of polymer per 1000 gallons of linear gel fluid. These linear gel polymer concentrations result in fluids with improved proppant suspension characteristics compared to slick water fluids. The linear gel fluid is used to transport proppant at a loading level of about 0.1 to 1 pound of proppant per gallon of fluid. Above this proppant loading level, a more viscous solution is typically required to make a stable suspension.

Crosslinked gels are the most viscous types of polymeric propellant fluids used to transport proppants. In a crosslinked gel system, a linear gel fluid such as described above is crosslinked with an added reagent such as borate, zirconate, and titanate in the presence of a base. When the linear gel fluid cross-links the gelled fluid, the viscosity is higher and the proppant can be effectively suspended. Linear gels and crosslinked gel fluids have certain advantages, but they require expensive polymers at high dose rates.

The modified proppant particles can be advantageously used to improve their performance as a liquid cracking system. First, if the proppant particles are more buoyant, a less viscous suspension fluid can be used that still transports the particles to the target area, but it is easier to pump into the formation. Second, after the proppant has been injected into the fracture line, it is desirable to maintain its life through the well. If the well is changed within the oil layer during the manufacturing force at the proppant exit position, the manufacturing equipment can be damaged, and as the oil layer pores are replaced by the proppant plug, the conductivity of the oil formation formation can be reduced. Third, once the proppant of the system is placed on the crack, it should resist the closing stress. The closed stress range can range from 1700 psi to some shale gas wells to as high as 15,000 psi in deep, high temperature wells. The proppant must be taken care of without any loss under this stress, lest it be crushed into fine particles, which will migrate to undesired locations in the well, thereby affecting manufacturing. What is desired is that the proppant should resist diagenesis during the treatment of the crack. The combination of high pressure and temperature with the chemicals used in the cleavage fluid can adversely affect the proppant particles, causing them to diagenetic, and ultimately produce fine particulate matter that can scale proportionally and reduce well productivity over time.

Recent proppant systems and polymer-promoting rupture fluids have attempted to take such considerations that the proppant can be carried by the rupture fluid and, once it reaches its target end point, can remain in the correct location and resist the closing stress in the formation. One way of preparing a suitable proppant comprises coating the proppant material with a resin. The resin coated proppant can be fully cured or partially cured. By assisting in the distribution of stress between the particles, the fully cured resin provides the shatter resistance of the proppant substrate. The fully cured resin can be further assisted in reducing fine migration by encapsulating the proppant particles. If the initial part is solid Once the resin is placed in the cracked surface, it can become completely cured. This approach can have the same advantages as using the initial fully cured resin. Even as the proppant keeps it open, the resin reduces the conductivity and permeability of the crack. Moreover, the resin will lose its effect, so that it loses its advantages. Resin-based systems tend to be expensive, and they are still susceptible to sedimentation from the suspension.

In addition, there are health, safety and environmental considerations associated with handling and processing proppants. For example, fine particles ("fines"), such as crystalline ceria dust, are typically found in naturally occurring sand deposits. These fines can be released into dust suitable for breathing during handling and processing of the proppant sand. With chronic exposure, this dust can be harmful to workers, leading to various inhalation-related conditions such as silicosis, chronic obstructive pulmonary disease, lung cancer, and the like. In addition to these health effects, fine materials can cause "polluting dust" problems, such as fouling equipment and polluting the environment.

Another way to prepare a proppant involves mixing the additive with the proppant itself, such as fibers, elastomeric particles, and the like. The additive can also affect the rheological properties of the transport slurry, making it more difficult to transport the proppant to the desired location within the fracture surface. In addition, the use of additives can prevent the proppant mixture from being evenly placed in the crack. While the methods known in the art suggest limitations of the proppant system, certain problems remain. Therefore, the art needs to improve the proppant system, which enables precise placement, preserves crack conductivity after placement, protects manufacturing efficiency and equipment life, simplifies liquid cracking operations, reduces environmental impact, and promotes worker health and safety. Further want to improve the system cost.

[Summary of the Invention]

The present invention is directed to a modified proppant comprising proppant particles and a hydrogel coating wherein the hydrogel coating is localized on the surface of the proppant particles to produce a modified proppant. The proppant particles can be solids such as sand, bauxite, sintered bauxite, ceramic, or low density proppants. Alternatively or additionally, the proppant particles comprise a resin coated substrate. Optionally, the modified proppant further includes an adhesion promoter, optionally attached to the resin coated substrate. The hydrogel coating preferably comprises a water swellable polymer. Hydrogel coatings can be produced from water soluble polymers. The preferred weight average molecular weight of the polymer is about 1 million g/mol, preferably about 5 million g/mol. Preferably, the proppant is dry and free flowing when dried and/or free flowing at 25 to 35 ° C to confer relative humidity of from about 80% to 90% for one hour. Hydrogel coatings are preferably durable and have a shear rate of ≧ 0.6 as determined by shear analysis tests.

The present invention relates to a method of producing a proppant and a proppant produced by the method. Preferably, the hydrogel coating is applied to the proppant particles as a liquid coating formulation, the blending Drying forms a substantially continuous film on the surface of the proppant particles. The modified proppant can be made by a reverse phase emulsion coating technique in which a proppant particle substrate and a reverse phase emulsion are combined, wherein the oil phase forms an emulsified continuous phase, and the superabsorbent polymer forms a discontinuous emulsion phase in a water solution or dispersion.

The hydrogel coating preferably comprises a polymer selected from the group consisting of polypropylene decylamine, hydrolyzed polypropylene decylamine, copolymer of acrylamide and ethylenically unsaturated ionic comonomer, acrylamide and Acrylate copolymer, poly(acrylic acid) or its salt, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, guar gum, carboxymethyl gum bean, carboxymethyl hydroxypropyl guar Glue, hydrophobically related expandable emulsion polymer, and latex polymer. The amount of hydrogel coating can be less than about 5% by weight total dry weight.

The modified proppant is preferably self-suspending. Preferably, the proppant of the present invention can undergo a volume expansion of at least 100%, preferably at least 500%, upon hydration of excess water.

The modified proppant can include additional excipients such as cationic/anionic polymer pairs including cationic polymers and high molecular weight anionic polymers. The cationic polymer may be selected from the group consisting of poly-DADMAC, LPEI, BPEI, polyglucosamine, and cationic polyacrylamide.

Preferably, the modified proppant further comprises or is used with an oxidative breaker or an enzyme breaker. The oxidative breaker may be selected from the group consisting of peroxide, magnesium peroxide, calcium peroxide, persulfate, nitrate, borate, ozone, and oxidized chlorine species. The oxidative fragmentation agent can be a cationically modified oxidative fragmentation agent capable of associating a hydrogel by ionic interaction. The enzyme fragmentation agent can be a cationic enzyme fragmentation agent capable of associating a hydrogel by ionic interaction. The modified proppant can further comprise a hydrophobic outer layer. For example, the hydrophobic outer layer may be selected from the group consisting of a fatty acid, an aliphatic amine, a hydrophobic quaternary amine, an aliphatic decylamine, a hydrogenated oil, a vegetable oil, a castor oil, a triacetin, a wax, a polyethylene oxide, and a polyepoxy. A group of propane. Alternatively, the modified proppant may further comprise a delayed hydration additive, such as a low hydrophilic-lipophilic balance surfactant, a mutual exclusion agent capable of eliminating trimming surfactants, an ionic crosslinking agent, a covalent crosslinking agent, and / or monovalent salt charge shielding agent. The modified proppant further includes an alcohol selected from the group consisting of ethylene glycol, propylene glycol, glycerin, propanol, and ethanol. In the embodiment, the modified proppant of claim 1 further comprises an anti-caking agent such as a hydrophobic layer material, a finely divided particulate material and/or a crosslinking agent. Examples of anti-caking agents include calcium citrate, calcium carbonate, talc, kaolin, bentonite, diatomaceous earth, cerium oxide, colloidal cerium oxide, microcrystalline cellulose, and attaplugate. They can also contain smoked Ceria, calcium citrate, calcium carbonate, kaolin, bentonite and attapulgite. The hydrogel coating can include additives such as chemical additives or tracers.

The modified proppant preferably contains less fines than the unmodified proppant particles.

The present invention comprises a liquid cleavage formulation comprising a modified proppant as described herein and an oxidative fragmentation or enzyme fragmentation agent. The invention also encompasses a method of rupturing a well. Preferably, the method comprises the steps of preparing a liquid split formulation of the invention, and introducing the liquid split formulation into the well at an effective volume and at an effective pressure of the liquid split to rupture the well.

In an embodiment, the method of rupturing a well comprises: preparing a liquid fission formulation comprising the modified proppant of the present invention, introducing the liquid fission formulation into the well in an effective volume and at an effective pressure of liquid cleavage, providing an oxidative fragmentation agent or The fragmentation formulation of the enzyme fragmentation agent, and the fragmentation formulation is added to the well in an effective volume and in an effective volume to rupture the well.

In the method, a fragmentation formulation can be added to the well before, during or after the liquid split formulation is introduced into the well. The fragmentation formulation can be added in one or more steps.

In the process of rupturing the geological formation penetrated by the well, wherein the fracing fluid is loaded into the geological formation by pulse pressure, the present invention comprises a method of reducing the amount of thickener added to the supporting fluid, including selecting the modified invention. A proppant acts as a proppant. Preferably, the modified proppant of the present invention is substantially completely hydrated within 2 hours (e.g., within 10 minutes) to first combine the support fluid.

The invention includes a method of producing a modified proppant. The method can include the steps of: providing a proppant base particle and a fluid polymeric coating composition; and applying the fluid polymeric coating composition to the proppant base particle; drying the modified proppant as appropriate; wherein the fluid polymeric coating composition comprises A hydrogel polymer in which a hydrogel polymer is localized on the surface of proppant base particles to produce a modified proppant. The drying step can dry the fluid polymeric coating such that a substantially continuous film is formed on the surface of the modified proppant. Method can occur better in Or near the point of use of the modified proppant, such as the location of the sand, ceramic, low density proppant, resin coated substrate, and/or bauxite. The method can further comprise adding an alcohol selected from the group consisting of ethylene glycol, propylene glycol, glycerin, propanol, and ethanol during or prior to the step of mixing the proppant base particles with the fluid polymer coating composition.

Preferably, the method comprises adding a reversal accelerator and/or an anti-caking agent during or after the step of mixing the proppant base particles with the fluid polymer coating composition.

The method of producing a hydrogel-coated proppant can also include providing a proppant base particle and a formulation comprising a coating precursor, wherein the coating precursor is capable of forming a hydrogel on the surface of the proppant base particle by in-situ polymerization. a gel coat; applying the formulation to the proppant base particles; and juxtaposing the paint precursor with the proppant base particles to form a hydrogel coated proppant.

The method preferably results in a substantially continuous coating film on the surface of the proppant base particles.

100‧‧‧Production process

120‧‧‧ polymer

122‧‧‧Transportation belt

124‧‧‧Mixed container

126‧‧‧Dryer

128‧‧‧Transformed sand

130‧‧‧Self-suspending proppant

132‧‧‧ sand

134‧‧‧Pump and nozzle device

Figure 1 shows uncoated sand (left) and hydrogel coated sand (medium and right) in water vials.

Figures 2A through 2C show microscopic images of time-dependent hydration of the hydrogel layer on the proppant.

Figure 3 is a flow chart of the production process of the self-suspending proppant.

Figure 4 (Figures 4A and 4B) shows SEM images of hydrogel coated proppant particles without the addition of glycerol (Figure 4A) and the addition of glycerol (Figure 4B).

Figure 5 shows an SEM image of a dried hydrogel coating on the surface of proppant particles.

Figure 6 is a graph of bed height vs. shear time for three sets of self-suspending proppant samples.

Figure 7 is a plot of bed height vs. mixing time for two sets of self-suspending proppant samples.

Figure 8 is a plot of bed height vs. mixing time for two sets of self-suspending proppant samples.

Figure 9 is a bed height vs. mixing time graph of a series of treated self-suspending proppant samples.

Figure 10 is a bed height graph of the amount of calcium citrate added to the self-suspending proppant sample.

Figure 11 is a graph of bed height vs. drying time for a series of pretreated and unpretreated proppant samples.

Figure 12 shows a graph of bed height vs. drying time at various temperatures.

Figure 13 shows a graph of temperature vs. mixing time for a series of treated self-suspending proppant samples.

Figure 14 shows the bed height and loss on ignition (LOI) vs. drying time graph.

Modified proppant particles

Disclosed herein are systems and methods for forming and using proppant particles having a hydrogel surface layer that enhance the hydrodynamic volume of the supporting particles during fluid transport and create resistance to deposition and separation before the proppant can reach the desired target end of the fracture surface And a more stable proppant suspension that is screened. Further advantages of the hydrogel-coated proppants as disclosed herein include lower corrosion equipment tendencies, lower coefficient of friction in wet conditions, good inter-bonding after placement at the crack faces, resistance to uncontrolled fines formations, and Attributable to the anti-soil properties of hydrophilic surfaces. In the embodiment, the revealing system for forming proppant particles can be applied to the most widely used types of proppant substrates, such as sand, resin coated sand, bauxite, low density proppants, and ceramics. In other embodiments, proppant particles can be formed from a variety of substrates, including those available to those of ordinary skill in the art. In some embodiments, the proppant particles can be made such that they are resistant to crushing or deformation such that they are resistant to displacement such that they can be suspended in a less viscous fluid carrier that is transported into the formation.

The present invention encompasses a modified proppant comprising proppant particles and a hydrogel coating wherein the hydrogel coating is localized on the surface of the proppant particles to produce a modified proppant. In the embodiment, the self-suspending proppant is formed by modifying the particulate substrate with a water swellable polymer coating such as a hydrogel. In the embodiment, the particulate substrate may be modified by a polymeric coating prior to introduction of the fracture fluid into the particulate substrate. In the embodiment, the hydrogel polymer coating can range from about 0.1 to about 10%, based on the weight of the proppant. In the embodiment, the hydrogel layer applied to the surface of the proppant substrate can be from about 0.01% to about 20% of the average proppant substrate diameter of the coating thickness. Upon hydrating and expanding the hydrogel layer in the rupture fluid, the hydrogel layer can be enlarged with water such that the expanded hydrogel layer thickness can become from about 10% to about 1000% of the average proppant substrate diameter. Figure 1 shows three vials containing the same amount of proppant in water, with the left vial containing the proppant of the anhydrous gel coat, the central vial containing the proppant of the 1% hydrogel coating, and the right vial containing the 3% hydrogel. coating The proppant. In each vial, the proppant was mixed with water and then allowed to settle for 24 hours without agitation. The settled bed volume of the hydrogel coated proppant was significantly greater than the settled bed volume of the uncoated proppant, indicating that the hydrogel coated proppant remained suspended in the water. Figures 2A, 2B, and 2C show three light microscopy images of the same hydrogel coated proppant particles, respectively, wherein each image was imaged after hydration of the hydrogel coated proppant in water for different amounts of time. In Figure 2A, the hydrogel coated proppant particles have been in water for 15 seconds; in Figure 2B, the hydrogel coated proppant particles have been in water for 45 seconds; in Figure 2C, the hydrogel coated proppant The granules were already in the water for 120 seconds. Such a graph shows that the hydrogel layer grows rapidly and the size expands significantly as the hydration time increases.

While it is known in the art to coat a superabsorbent polymer to form a hydrogel coating on a single proppant particle substrate (see, for example, U.S. 2008/0108524), the formulations and methods disclosed herein differ from such techniques in an important advantageous manner. As disclosed herein, the hydrogel formulations used have certain outstanding properties. More specifically, the formulations disclosed herein include hydrogels selected and applied to proppant particles to form modified particles in the following manner: (a) free flowing when dry and/or (b) hydrated with water The hydrogel coating is durable and/or the hydrogel coating is expanded in volume such that the hydrated modified proppant volume is at least 20% greater than the dry modified proppant volume, or from about 20% to about 50% greater than dry. The modified proppant volume, or between about 50% to about 100% greater than the dry modified proppant volume, or between about 100% to about 200% greater than the dry modified proppant volume, or between about 200 % to about 400% is greater than the dry modified proppant volume, or greater than about 400% dry modified proppant volume.

As the term "drying" is used herein, it will be understood that when the moisture content is 1% by weight or less, the modified proppant is dried. Preferably, the moisture content of the modified proppant is ≦ 0.5% by weight, or even 0.1% by weight. In the embodiment, the dried hydrogel coating on the modified proppant can be less than 10 microns thick and often less than 2 microns. In the embodiment, the hydrogel polymer is hydrated to the aqueous suspension in essence within 2 hours, or within 1 hour, or within 30 minutes, or within 10 minutes, or within 2 minutes or even within 1 minute at 20 ° C. Contact with excess tap water. As used herein, the description of hydrogel coated proppant as "essentially fully hydrated" means that when fully hydrated to water, the volume increase of the hydrogel coated proppant is at least 80% hydrogel coated support. The total volume increase of the agent.

In the embodiment, the modified proppant formed according to such formulations and methods will flow freely when dried, and any clumps or cohesives will rapidly disperse by gentle agitation. Modified support If the agent exhibits a certain degree of clumping or cohesion, it should still be considered as free flowing, provided that the clumps and cohesives can be broken by gentle agitation.

The use of a sedimentation bed high analytical test can determine the volume expansion of the proppant. For example, in a 20 mL glass vial, 1 g of the dried modified proppant to be tested is added to 10 g of water (such as tap water) at about 20 °C. The vial is then agitated for about 1 minute (eg, the vial is repeatedly inverted) to wet the modified proppant coating. The vial is then left to stand undisturbed until the hydrogel polymer coating has become hydrated. The height of the bed formed by hydration of the modified proppant can be measured using a digital caliper. The bed height is then divided by the height of the bed formed by the dry proppant. The number obtained indicates the volume expansion factor (multiple). Moreover, for convenience, the bed height formed by the hydration-modified proppant can be higher than the bed formed by the uncoated proppant, as shown in Working Example 5 below.

The durability of the coating can be measured in accordance with the shear analysis test. For example, 1 L of water (such as tap water) is added to a square 1 L beaker (eg, a beaker having a total volume of approximately 1.25 L, with a fill line at the 1 L mark). The beaker was then placed in an EC Engineering CLM4 paddle mixer. The mixer was set to mix at 300 rpm. Once the mixing started, 50 g of the modified proppant to be tested was added to the burnt in dry form. After mixing for 30 seconds at 300 rpm, the mixing rate was reduced to 200 rpm and mixing continued until the hydrogel polymer coating hydrated. The mixture was then poured into a graduated 1 L cylinder and settled, after which the settled bed height of the modified proppant was measured as indicated above. The settled bed height ("sheared bed height with shear") is then higher than the sedimentation bed of the hydration-modified proppant that has not been subjected to this shear treatment ("no shear settling bed height"). This shearing treatment reduces the durability of the hydrogel coating by measuring the amount of the settled bed of the modified proppant. For the purposes of this disclosure, a hydrogel coating is considered durable if the ratio of the sheared bed height to the shear-free settling bed height ("shear ratio") is at least 0.2. It is desirable for the modified proppant to exhibit a shear ratio greater than 0.2, greater than or equal to 0.3, greater than or equal to 0.4, greater than or equal to 0.5, greater than or equal to 0.6, greater than or equal to 0.7, greater than or equal to 0.8, or greater than or equal to 0.9.

As indicated above, the type and amount of hydrogel polymer used in the modified proppant can be selected as disclosed herein such that the volume expansion of the modified proppant as determined by the above settled bed high analytical test is increased by a factor of at least 1.2. In a particular embodiment, as shown in Working Example 5, the factor can be greater than or equal to about 3, about 5, about 7, about 8, and even about 10.

As also indicated above, this reveals that the modified proppant flows freely when dried. In specializations, even after granting high humidity conditions, such as midsummer found in the southern United States These modified proppants are free flowing. For this purpose, the modified proppant to be tested can be subjected to a humidity test condition of 80 to 90% relative humidity for 1 hour at 25 to 50 °C. The modified proppant, which is still free flowing after granting such humidity test conditions, is considered to be free flowing even after the conditions of high humidity are granted.

A method of modifying a proppant comprises spraying or saturating a liquid polymer formulation onto a proppant substrate followed by drying to remove water or other carrier fluid. The drying process can be accelerated by applying heat or vacuum and tumbling or agitating the modified proppant during the drying process. Heating can be imparted by forced hot air, convection, friction, conduction, combustion, exothermic reaction, microwave heating, or infrared radiation. Agitation during the proppant upgrading process has the further advantage of providing a more uniform coating on the proppant material.

FIG. 3 illustrates a production process 100 for preparing a self-suspending proppant 130 in accordance with the present disclosure. In describing the embodiment, sand 132 (e.g., dry sand having less than 0.1% moisture) is transported into mixing vessel 124 via conveyor belt 122, and liquid polymer composition 120 is sprayed along conveyor belt 122 via pump and nozzle assembly 134. On the sand 132. Sand 132 exposed to liquid polymer 120 is reported to low shear mixing vessel 124 where it is further blended to form modified sand 128. After mixing, the modified sand containing the liquid polymer is sent to a dryer 126 to remove water and/or organic carrier fluid associated with the liquid polymer 120. After the drying step, the dried modified sand 132 is passed through an end step 134, which may include a shaker and/or other size sorting device (eg, a screen) to remove excess size of the binder. Ending step 134 may also impart dry modified sand 132 to a mechanical mixer, shearing device, mill, crusher, etc. to break up the aggregate to pass the material through a suitably sized screen. The finished material 130 is then stored for shipment or use.

In the embodiment, the sand or other substrate used to make the self-suspending proppant is pre-dried to a moisture content of <1%, preferably <0.1%, prior to upgrading the hydrogel polymer. In the embodiment, the sand or other substrate temperature ranges from about 10 to about 200 ° C, preferably from about 15 to about 80 ° C or from 15 to 60 ° C when mixed with the liquid polymer.

In the embodiment, the proppant substrate is contacted with the liquid polymer composition by spraying or injection. The liquid polymer composition is added in an amount ranging from about 1 to about 20%, preferably from about 2 to about 10% by weight of sand. The proppant substrate and the liquid polymer are blended for 0.1 to 10 minutes. In a better embodiment, the mixing device is a relatively low shear type mixer, such as a drum, a vertical conical screw blender, a v-cone blender, a double cone blender, a kneader, a paddle Mixer, or belt blender. In the embodiment, the mixing device may be equipped with forced air, forced hot air, vacuum, external heating, or other means of causing evaporation of the carrier fluid.

In the embodiment, the modified proppant substrate containing the liquid polymer is dried to remove water and/or an organic carrier fluid associated with the liquid polymer. The dryer equipment can be of the transport oven, microwave oven, or rotary kiln type. In the embodiment, the drying step is carried out in such a manner that the dried modified sand contains less than 1% by weight of residual liquid, including water and any organic carrier fluid associated with the liquid polymer composition.

In the embodiment, the same equipment can be used to blend the proppant substrate with the liquid polymer, and dry the blended product in a single processing stage or in a continuous line.

In other embodiments, the method of modifying the proppant comprises synthesizing the hydrogel coating in situ or in the presence of proppant particles, resulting in a hydrogel layer encapsulating the surface of the proppant particles. As an example, combining the proppant particles with the coating precursor monomer and/or macromonomer, followed by a polymerization step, can complete the in situ synthesis of the hydrogel. In other exemplary embodiments, the water soluble polymer is soluble in the monomer with or without solvent, followed by polymerization in the presence of proppant particles, resulting in the formation of an interpenetrating polymer network as a proppant coating. In other exemplary embodiments, the water soluble polymer is dispersed in the monomer with or without solvent, and subsequent polymerization will result in the proppant being encapsulated by a hydrogel which is a water soluble polymer that is properly locked by the newly formed polymer. Particle composition. The monomer or macromonomer used may be selected from monomers which result in a water soluble polymer. In other exemplary embodiments, the particles may be encapsulated by a water insoluble polymer which will then be modified or hydrolyzed to form a water soluble hydrogel coating. As is known to those of ordinary skill in the art, the encapsulating layer can be formed by different polymerization techniques with or without solvent. Polymerizing the polymer in situ on the surface of the proppant particles can have the advantage of reducing or eliminating the drying step.

For example, the hydrogel coating or the in-situ polymerized water-soluble monomer may be selected from the following monomers or salts thereof: acrylic acid, methacrylic acid, acrylamide, methacrylamide, and the like, carboxy Ethyl acrylate, hydroxyethyl methacrylate (HEMA), hydroxyethyl acrylate (HEA), polyethylene glycol acrylate (PEG-acrylate), N-isopropyl acrylamide (NiPA), 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), sodium salt of styrene sulfonate, vinyl sulfonic acid, (meth)allyl sulfonic acid, vinyl phosphonic acid, N-vinylacetamide, N-methyl-N-vinylacetamide, N-vinylformamide, N-methyl-N-vinylformamide, N-vinylpyrrolidone, N-butyrolactam or N-vinyl caprolactam, maleic anhydride, itaconic acid, vinyl acetate, dimethyldiallylammonium chloride, quaternized dimethylamine ethyl Acrylate (DMAEMA), Chlorinated (meth) acrylamidopropyltrimethylammonium chloride, methylvinylimidazole chloride, 2-vinylpyridine, 4-vinylpyridine, and the like. The ratio of ions to nonionic monomers can be selected to produce hydrogels having different charge densities. In several instances, for example, a hydrogel having a higher charge is desired to produce a coating with faster hydration or swelling properties. In the embodiment, the hydrogel polymer has an ion content or charge density in the range of 10 to 70% ion, and based on the equilibrium nonionic, based on the molar percentage of the monomer. In a preferred embodiment, the hydrogel polymer has a charge density in the range of 25 to 55%, based on the percentage of moles. In other examples, the free monomer can be selected to have a higher or lower free constant to produce a hydrogel that is more stable or less stable in a saline environment. Other advantageous properties can be imparted by selecting an appropriate charge density.

In an embodiment, the coating precursor can comprise a polyfunctional monomer that contains more than one polymerizable group and will direct crosslinking or branching to the hydrogel. Examples of such monomers are: pentaerythritol triallyl ether, PEG-diacrylate and methacrylate, N, N'-methylenebis acrylamide, epichlorohydrin, divinyl fluorene, and Glycidyl methacrylate. When such a monomer is used, the crosslinking monomer will range from 0.001 to 0.5% of the total monomer content. In the context of the choice of cross-linking agent, it will be appreciated that the addition of an excess of cross-linking agent (e.g., in an amount greater than 0.001 to 0.05% of the total monomer content) can form a brittle hydrogel that can be broken or degraded under pressure. In the embodiment, the addition of a crosslinking agent forms a hydrogel that is less likely to become detached from surface particles under extreme conditions.

In the embodiment, the monomer/macrosystem used is selected from the coating precursor monomers that will form the water-insoluble coating. Further modification after application of the coating will result in a water swellable polymer. As an example, a polymeric coating containing hydrolyzable groups can be formed which is subsequently hydrolyzed to form a hydrogel. Examples of the monomer falling into this category are esters, anhydrides, nitriles, and decylamines; for example, methyl acrylate or tributyl acrylate can be used as the ester monomer. As a further example, monomers containing vinyl functionality can be formed into hydrogels by different polymerization techniques, with or without solvent. Polymerization techniques include bulk, suspension, near micelles, solution polymerization.

In other embodiments, a coating monomer or precursor can be selected to form a hydrogel-containing self-suspending proppant comprising a polyurethane or polyurea. A list of suitable monomers for forming polymers with polyurethane and/or polyurea functionality is: polyols such as ethylene glycol, propylene glycol, glycerol, trimethylolpropane, 1,2,6-hexane Triol, neopentyl alcohol, sorbitol, sucrose, a-methyl glycoside, polyoxyalkylenes such as PEG, copolymers of PEG-PPG, Pluronics, Tetronics, polyamines such as Jeffamines. Among the isocyanates, mention may be made of toluene-diisocyanate, naphthalene diisocyanate, Xylene-diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, trimethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexyl-1,2-diisocyanate, cyclohexyl- 1,4-diisocyanate or the like. Other suitable polymers may include HYPOL® hydrophilic polyurethane prepolymer from Dow, DESMODUR® and MONDUR® resins from Bayer (2,4'-diphenylmethane diisocyanate, 4,4'-two Phenyl methane diisocyanate, and mixtures thereof) and CONATHANE® from Cytec (polyisocyanate functionalized prepolymer of toluene diisocyanate and poly(butylene glycol)), and the like.

Proppant particle coatings having a polyurethane (PU) hydrogel can be carried out by conventional methods. In the embodiment, the coating can be performed overall without the use of a solvent. For example, typical formulations of crosslinked PU hydrogels can be prepared in a single step polymerization process using diisocyanates, polyoxyalkylenes, and polyfunctional crosslinkers. In the embodiment, the formulation will contain from 10 to 80% polyoxyalkylene having a polyoxyalkylene molecular weight of from 200 to 25,000.

An additional method of forming the in situ hydrogel layer can be to dissolve or suspend the water soluble polymer in the monomer formulation followed by polymerization of the monomer. The monomer can be selected from the list of previously water soluble monomers. In the case where the water soluble polymer is dissolved in the monomer mixture, the resulting coating will be present in the interpenetrating hydrogel network where the initially water soluble polymer and the in situ formed polymer. In the case where the water-soluble polymer is suspended in the monomer mixture, the resulting coating will consist of a hydrogel coating that properly locks or coats the water-soluble particles. For example, such particles can be captured inside a newly formed hydrogel coating, or the like, can be joined to a newly formed polymer. The water soluble polymer can be dissolved or suspended in the monomer formulation in the presence or absence of a solvent, and the polymerization can be carried out by various techniques.

Suitable water-soluble polymer to be mixed with monomer can be selected from polypropylene decylamine, polyacrylic acid, copolymer of acrylamide and acrylate, polyethylene glycol, polyvinylpyrrolidone, polyvinyl alcohol, carboxymethyl Cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, guar gum, carboxymethyl gum bean, carboxymethyl hydroxypropyl guar, hydrophobically related expandable emulsion polymer, starch, latex polymer Group of equal parts.

An additional method of modifying proppant particles comprises a hydrophilic polymer that is chemically grafted onto the particles. The polymer linkage can be accomplished on the surface of the particle by, for example, Huisgen cycloaddition and other coupling reactions or addition reactions that immobilize the polymer on the surface of the particle.

The proppant particles that can be selected for such purposes have surface functional groups such as epoxy, vinyl, amine, hydroxyl, and the like. The groups can then react with the polymer, the polymer There are groups that are capable of reacting with functional groups on the surface of the particles. For example, proppant particles including cerium oxide may be surface modified with decane (e.g., amino decane, vinyl decane, epoxy decane, etc.).

In the embodiment, the polymer that reacts with the functionalized particles is a hydrophilic linear or branched polymer or copolymer. The polymer can have one or more graft moieties. In the embodiment, the polymer may have a functional group such as an amine group, a carboxyl group or a salt thereof, a hydroxyl group, a mercapto group, an acid anhydride, an acid chloride, and/or an isocyanate group, which is capable of covalently bonding to a particulate functional group. Examples of polymers that can be used to react with the functionalized particles are: epoxy functionalized PEG, amine functionalized PEG, azide functionalized PEG, polyamidimide, polyacrylic acid, polyvinyl alcohol, and the like.

In the embodiment, in addition to having swellable properties, the resulting hydrogel can have temperature response or pH-responsive properties. The resulting swellable behavior of the proppant can thus be coordinated. This is an added advantage of transporting the proppant down to the wellbore because the temperature is lower in the early stages, where the proppant is transported and wants to fully expand; the higher temperature is expected to be inside the crack, where the lower expanded hydrogel The layer wants to be improved in packaging. The hydrogel-coated proppant monomer used to make the temperature response may be selected from N-isopropyl acrylamide (NiPA), ethylene oxide, propylene oxide, or a giant sheet exhibiting a lower critical solution temperature. Body/polymer (LCST).

In the embodiment, the process of converting a substrate (e.g., sand) into a self-suspending proppant can be performed at or near the point of use, such as at the preparation of a liquid cracked oil or gas well. This method has the advantage of converting commodity materials (such as sand), which are high in material disposal costs, into specialized materials with additional features. For upgrading at the point of use, the sand can be obtained from a local source or shipped directly from a sand mine or warehouse. This avoids having to ship the sand first into the blending plant and then from the blending plant to the point of use a second time. In sand situations, shipping costs can be higher than material costs, so avoiding additional shipping wants to control costs.

Sand and upgrade chemicals can be added to the continuous mixer during the demonstration production process. After the mixing is complete, the mixture can be (a) ready to use or (b) sent to the drying step. The drying step can include a thermal or vacuum drying process, which can include the addition of an anti-caking agent. The finished product can be stored in a container at the well. Examples of mixing equipment are continuous belt blenders or kneaders. The drying step can be a separate process from mixing, and the drying step can be designed to avoid over-shearing the finished product, such as a conveyor or tunnel dryer. Other types of drying mechanisms include rotary kilns, microwave dryers, paddle dryers, and vacuum dryers.

In the embodiment, the system and method disclosed herein can be used to modify the proppant Hydrogel polymers can be guided by oil-based emulsions, suspensions, water-based emulsions, latexes, solutions, and dispersions. In the embodiment, the hydrogel polymer can be directed as a distillate emulsion, such as an oil that has been partially evaporated to remove the carrier fluid portion as the primary emulsion. This provides the advantage of reducing the need for drying compared to conventional emulsions. In the embodiment, the hydrogel polymer can be an alkaline swellable emulsion in which the hydrogel properties of the polymer are fully developed until the polymer is contacted with the base. In this embodiment, the alkaline swellable emulsion can be applied to a proppant substrate to form a modified proppant that can be suspended in the rupturing fluid in the presence of an alkaline material.

In the embodiment, an additive (eg, an alcohol selected from the group consisting of ethylene glycol, propylene glycol, glycerin, propanol, and ethanol) can be added during or prior to the mixing step of the proppant base particles and the liquid polymer coating composition. In the embodiment, the reversal promoter useful as an additive in the polymer coating formulation of the self-suspending proppant may comprise a high HLB surfactant, such as a polyethylene oxide lauryl alcohol surfactant, (ETHAL LA from ETHOX) -12/80%), ethylene glycol, propylene glycol, water, sodium carbonate, sodium hydrogencarbonate, ammonium chloride, urea, cesium chloride, and mixtures thereof. In the embodiment, the inversion promoter can serve as an easy to release the active polymer component from the internal phase of the oil-based emulsion polymer into the (typically aqueous) processing fluid to be treated. Because this process converts the oil continuous polymer into a continuous water environment, it can be characterized as a reverse rotation.

In other embodiments, the proppant substrate can be modified with a polymer formulation without the need for a drying step. This can be accomplished by using a solventless polymer formulation or a curable formulation. In some simplified methods, the dry or liquid polymer formulation can be applied to the proppant substrate via inline mixing, and the modified material thus prepared can be used without further processing. The moisture content of the proppant substrate can be modified by the addition or removal of water or the addition of other liquids to enable the substrate to be effectively coated, disposed, and transported into the fracture fluid.

The modified proppant can be further modified with a wetting agent (e.g., a surfactant or other hydrophilic material) to effectively disperse into the fracture fluid. When the hydrogel-modified proppant is suspended into the rupturing fluid, it is considered to be self-suspending if it requires a lower viscosity fluid to prevent the particles from sinking out of the suspension.

The modified proppant can be further modified to improve flow and handling during processing, transportation and storage. The moisture absorbing surface of the modified proppant can in some cases be caused by the cohesiveness of the modified proppant to negatively impact the overall solid flow of the modified proppant, particularly in wet and/or high humidity environments. The modified proppant can be given anti-caking property through further modification. To reduce the tendency of the modified proppant to absorb moisture during processing, transportation, and storage, or to reduce surface interaction between adjacent modified proppants during processing, transportation, and storage, or both. Reduce or eliminate cohesion. In the embodiment, once the modified proppant is added to the aqueous fluid for the end use application, the anti-caking agent cannot impact the desired properties of the modified proppant. The modified proppant can be treated with an anti-caking agent such as a finely divided solid or a second outer layer or both. The second outer layer can be a low cross-linked modified proppant surface, or a solid non-hygroscopic layer, or a cationic salt layer, or an oily water transfer layer, or a combination thereof. Modified proppants with anti-caking agents can have improved handling properties such as free-flowing properties, resistance to clumping, ease of transport, ease of metering, and ease of discharge from storage or shipping containers. In the embodiment, the modified proppant with an anti-caking agent can have reduced drying requirements such that the final product can be manufactured with reduced energy, time, and equipment.

In the embodiment, the anti-caking agent is subdivided into solids including clay, tannin material, organic matter, metal oxide or fatty acid salt. In other embodiments, the anti-caking agent is subdivided into, for example, calcium citrate, magnesium citrate, calcium carbonate, talc, kaolin, bentonite, attapulgite, diatomaceous earth, cerium oxide, colloidal cerium oxide, and smoked A solid of cerium oxide, corn starch, carbon black, microcrystalline cellulose, iron oxide, aluminum oxide, calcium stearate, magnesium stearate, or a combination thereof.

In the embodiment, the anti-caking agent is a second outer layer formed by crosslinking the surface of the modified proppant. The addition of species capable of crosslinking the swellable polymer on the surface of the proppant is effective in reducing the ability of the polymer layer to prematurely expand. Reducing polymer swelling will reduce the tendency of the modified proppant to undergo agglomeration or cohesion during transport and storage. In an embodiment, the cross-linked species has the ability to form a bond with a hydroxy functional group, a carboxy functional group, an amine functional group, or a guanamine functional group. The crosslinked species may be selected from organic compounds containing aldehyde, amine, anhydride, or epoxy functional groups. Crosslinked species can also be organometallic compounds. In the embodiment, the crosslinked species form bonds that can be broken or removed under mechanical shear. Organometallic compounds capable of being associated with and/or bonded to hydroxy and carboxy functional groups are examples of crosslinked species that form shear-sensitive linkages. Upon high shear pumping associated with liquid cleavage, the degradable polymer crosslinks, and once the modified proppant is introduced into the cleavage fluid, the polymer can expand unimpeded.

In the embodiment, the anti-caking agent is a thin second layer of a solid non-hygroscopic material, such as a fatty acid, a hydrogenated fatty acid, a hydrogenated oil, a wax, a polyethylene, a polyethylene oxide, a polypropylene oxide, a copolymer of polyethylene oxide and polypropylene oxide, or a combination thereof. Examples of fatty acids suitable for use as the second layer include stearic acid, palmitic acid, lauric acid or bovine fatty acids containing stearic acid, palmitic acid and/or lauric acid. An example of a hydrogenated oil suitable for use as the second layer comprises hydrogen Castor oil. Examples of waxes suitable for use as the second layer include paraffin, petroleum gum and pine wax. A thin solid layer can be applied to the surface of the modified proppant to create a barrier that prevents the swellable polymer layers on adjacent modified proppant particles from sticking to each other during storage. The solid outer layer utilized may include water soluble, water insoluble or a combination of both. The solid outer layer is non-hygroscopic. The solid outer layer is selected such that it remains solid at a temperature below 38 ° C and has a melting point in the range of 40 ° C to 120 ° C. In the embodiment, the outer layer is selected such that the melting point is low enough that the outer layer will be in the liquid phase during the drying process for producing the modified proppant, and the melting point is high enough that the outer layer will be in a solid phase during storage and transportation of the modified proppant. . The solid outer layer acts as a barrier to prevent/reduce the agglomerated proppant agglomerated due to the wet environment. The solid outer layer may be added to the modified proppant in a finely divided powder, tablet, solution in an oil vehicle or as a warm liquid. The solid outer layer can be added to the modified proppant immediately prior to the polymer, simultaneously with the polymer, with the polymer, or can be added some time after the polymer is added but before the drying step. Preferably, the solid outer anti-caking agent is added after the polymer has been well mixed with the modified proppant but before the modified proppant is dried.

In the embodiment, the anti-caking agent is a second layer salt having a monovalent cationic charge, which can be added to the modified proppant, such as a cationic surfactant or unit price, in a liquid or oil solution at a temperature below 100 ° C. Salt hydrate. A cationic surfactant comprising a hydrophobic amine-containing quaternary amine (eg, Adogen 464 or Arquad 2HT-75 from Akzo Nobel) can be used as the second coating to impart a modified proppant aquifer while also neutralizing The potential anionic charge of the polymer. Many salt hydrates (eg, sodium acetate trihydrate and sodium aluminum sulfate dodecahydrate) have a melting point below 100 ° C and can be added to the modified proppant and melted during the drying process of the modified proppant. Second floor. In both cases of the cationic surfactant grade salt hydrate, a concentrated layer of cationic charge is completed on the surface of the modified proppant, which reduces the swelling potential of the anionic polymer. Upon directing the modified proppant to the aqueous stream, the monovalent salt is sufficiently diluted to effect the modified proppant as expected.

In the embodiment, the anti-caking agent is applied to the second layer of the hydrophobic lubricating oil of the modified proppant selected from the group consisting of helium oxide oil, mineral oil, petroleum gum, triglyceride or a combination thereof. A helium oxygen oil suitable for use as the second layer of hydrophobic lubrication comprises polydimethyl siloxane. Triglycerides suitable for use as the second layer of hydrophobic lubrication comprise corn oil, peanut oil, castor oil and other vegetable oils. Preferably, the hydrophobic lubricating oil has a point of smoke and a boiling point higher than the temperature used in the drying stage of the modified proppant. Preferably, the smoke point of the oil is above 200 °C. Preferably, the smoke point of the oil Is at least 175 ° C.

The hydrogel-modified proppant of the present invention advantageously utilizes a localized polymer concentration on the surface of the proppant in a conventional manner for making the entire fluid medium viscous. This localized hydrogel layer allows for higher efficiency of use of the polymer, resulting in a lower total amount of polymer compared to, for example, conventional polymer-enhanced fracture fluids such as slick, linear gel, and crosslinked gel. Can be used to suspend proppants. Although hydrogel-modified proppants are considered to be self-suspending, they can be used in combination with anti-wear agents, linear gels, and cross-linked gels.

As disclosed herein, hydrogel-modified proppants can have the advantage of transporting the friction reducing polymer into the rupturing fluid such that when the hydrogel-modified proppant is used in a liquid-cracking operation, other anti-wear agents are polymerized. Things may not be needed or may require less amount. In the embodiment, several hydrogel polymers can be desorbed from the surface of the proppant to impart friction reducing advantages or viscosity characteristics to the fracture fluid. Although the present invention demonstrates the specific focus of hydrogel-modified proppants for liquid lysis purposes, other uses of hydrogel-modified proppants can be envisioned, among which the ability to retain water retention or friction can be exploited. For example, hydrogel-modified proppants can be used to absorb water from a humid environment, form moisture-retaining particles that can be removed from the environment, and carry unwanted moisture. As a further example, a hydrogel-modified proppant can be used to advantageously add water to the environment. The hydrogel-modified proppant can be saturated with water or an aqueous solution, and then used as a soil remediation additive such as a dry environment. The hydrogel-modified proppant can be formed from sand or other substrates compatible with the soil, which can be transported to the region of interest in a dry form; they can then be saturated with water and used as a soil amendment. In other embodiments, hydrogel-modified proppants can be used in a dry form as a soil amendment, wherein they can absorb and contain moisture from the environment, from irrigation, from rainfall, and the like. In such embodiments, the moisture-containing properties of the hydrogel-modified proppant can be advantageously utilized. In the embodiment, the hydrogel-modified proppant can be used to reduce corrosion of topsoil, nursery, spray mixture, and the like. In the embodiment, the hydrogel-modified proppant can be used as a vehicle for introducing other compatible agents into, for example, the soil zone. As the hydrogel degrades or as it absorbs moisture and expands, the hydrogel-modified proppant can include additional formulations that filter out or pass through the hydrogel layer into the environment. Examples of such formulations include fertilizers, seeds, plant growth regulators, herbicides, insecticides, fungicides, and the like. Other uses of hydrogel-modified proppants prepared according to such formulations and methods are contemplated to be consistent with their properties described herein.

In the embodiment, a hydrogel polymer for preparing a hydrogel-modified proppant These may include, for example, polypropylene decylamine, copolymers of acrylamide and anionic and cationic comonomers, hydrolyzed polypropylene decylamine, copolymers of acrylamide and hydrophobic comonomers, poly(acrylic acid), poly(acrylic acid) salts. , carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, guar gum, alginate, carrageenan, locust bean gum, carboxymethyl gum bean, carboxymethyl hydroxypropyl guar A polymer of a gel, a hydrophobically related swellable emulsion (HASE) polymer, a latex polymer, a starch, or the like. In the embodiment, the hydrogel polymer may have a molecular weight (g/mol) greater than 1 million, such as in the range of 10 million to 40 million Daltons. In the embodiment, the hydrogel polymer can be a water-soluble and linear structure high molecular weight vinyl addition polymer.

In the embodiment, the hydrogel polymer can be crosslinked as described above to enhance the water absorption and expansion properties of the polymer. The crosslinker can be directed as an element of the hydrogel base polymer, or the like can be directed as a chemical modifier for the preformed polymer. The cross-linked species can be added directly to the polymer used to coat the proppant, while being added to the proppant with the polymer with agitation, or added some time before the polymer is added to the proppant but before drying.

Localizing the polymer around the surface of the proppant as described herein can result in more efficient use of the polymer and can prevent the proppant from sinking out of the polymer solution. In the embodiment, the polymer layer is hydrated around the proppant to effectively prevent proppant/proppant (interparticle contact) contact. This prevents the proppant from forming a tightly settled bed and can result in a proppant that is more easily resuspended in the ruptured fluid. The resuspension properties of the modified proppant can be important if the fluid flow is interrupted during the liquid splitting operation. In this case, it may be important to resuspend the proppant as the flow continues to avoid proppant loss or unexpected blockage of the fluid passage.

When the polymer swells, polymer surface modification as described herein can result in an increase in the effective hydrodynamic radius of the proppant surface. This can result in increased drag on the proppant and effective change in overall hydrogel/particle density. Both can result in proppant particles with slower settling rates and excellent transport properties.

The hydrogel-modified proppants of the present invention advantageously utilize a localized polymer concentration on the surface of the proppant. Preferably, many hydrogel polymers remain associated with the proppant surface after the hydrogel is hydrated to water and exposed to shear conditions (e.g., catheter transport). In the embodiment, the production process of coating the substrate particles with a hydrogel polymer results in a physical or chemical attachment of the polymer to the surface of the proppant. This attachment can be caused by entanglement of the polymer chain upon drying of the hydrogel film, resulting in the hydrogel coating resisting desorption upon exposure to shear in a hydrated state. In the embodiment, by chemical reaction The polymer chain should be assisted by or polymer chain interactions. In the embodiment, a linear non-crosslinked hydrogel polymer is used as a coating to enable the linear polymer chain to become entangled when the polymer coating is formed. In the embodiment, the polymer entanglement is assisted by a drying process during production and using a coalescing aid. The coalescing aid is an additive that causes the individual emulsion droplets of the coating formulation to coalesce into a continuous film upon drying. In the embodiment, the coalescing aid is an alcohol such as propanol, glycerin, propylene glycol, or ethylene glycol. Figures 4A and 4B show two scanning electron micrographs (SEM) demonstrating that the glycerol effect causes the coated polymer to coalesce into a continuous film. In the scanning electron micrograph image of Fig. 4A, the proppant was coated with a hydrogel formulation of an anionic polypropylene guanamine emulsion without added glycerin, and then dried at 100 ° C for 1 hour. In the image of Figure 4A, the surface of the fully coated proppant particles is seen, but individual emulsion drops of about 1 micron diameter are still visible. In the SEM image of Fig. 4B, the proppant was coated with the same anionic polypropylene guanamine emulsion but with 10% by weight of glycerin as a coalescent, and then dried at 100 ° C for 1 hour. The coalescent effect is evident on the appearance of the dried film: the SEM image of Figure 4B shows substantially fully coated proppant particles, and in this case the emulsion drops have coalesced into a more continuous film. Figure 5 shows an SEM image of a dried hydrogel film made in the same manner as the sample of Figure 4B. The hydrogel film of Figure 5 shows that the emulsion droplets coalesce well into a film and completely cover the surface of the proppant particles.

In the embodiment, polymer pairing (optionally combined ion coupling) can be used to modify the hydrogel polymer to stay on the surface of the proppant particles. For example, a cationic polymer is deposited on the proppant as a first layer to lock the second layer containing the hydrogel (e.g., high molecular weight anionic polymer) to the correct location by ionic coupling. In the embodiment, the cationic polymer may be polychlorodiallyldimethylammonium (poly-(DADMAC)), linear polyethylenimine (LPEI), branched polyethylenimine (BPEI), poly-grain Amine sugar, epichlorohydrin/dimethylamine polymer, dichloroethane, dimethylamine polymer, or cationic polypropylene decylamine. The cationic polymer layer can be disposed on the proppant before or after the anionic hydrogel layer is modified to the surface of the proppant. The ionic coupling interaction acts as an anchoring mechanism to assist in preventing the anionic polymer from desorbing in a high shear environment, such as through a pump or pumping down to the wellbore. Cationic polymers can also improve polymer retention by causing delayed hydration and elongation of the anionic polymer chain. It is believed that less polymer chain extension during the pumping process will result in higher polymer retention (i.e., less desorption) on the proppant.

In the embodiment, covalently crosslinking the hydrogel polymer layer on the surface of the proppant can improve polymer swelling properties and shear tolerance to prevent premature release of the hydrogel from the proppant. The covalent crosslinking agent may comprise the following functional groups: epoxide, anhydride, aldehyde, diisocyanate, carbon decylamine, two Vinyl, or diallyl. Examples of such covalent crosslinking agents include: PEG diepoxypropyl ether, epichlorohydrin, maleic anhydride, formaldehyde, glyoxal, glutaraldehyde, toluene diisocyanate, methylene diphenyl diisocyanate , 1-ethyl-3-(3-dimethylaminopropyl)carbodiamine, methylenebis acrylamide, and the like. Covalently crosslinking the hydrogel polymer layer on the surface of the proppant effectively creates a swellable "polymer cage" around the proppant. The covalent bond prevents the polymer from completely desorbing into the solution. The micro-insoluble polymer layer is capable of expanding and producing a hydrated polymer layer.

To further prevent possible detachment of the hydrogel from the surface of the particles, the proppant particles can be treated to impart functionality that will also participate in the polymerization process. For example, the sand particles can be treated with decane to form particles having vinyl functionality, hydroxyl groups, epoxy groups, and the like.

A delayed/controlled hydrated polymer layer may be desired to delay hydration of the polymer surface during the handling of the proppant and initial pumping through the wellbore. Environmental factors such as moisture and rain can cause premature hydration of the polymer coating, which makes it difficult to effectively meter the proppant dose into the blender during the liquid splitting operation. It is also believed that the fully hydrated polymer layer can be more readily desorbed under pumping rupture fluid to tube-related high shear conditions. For these reasons, it is advantageous to manipulate surface modifying proppants having slower or delayed hydration properties. In the embodiment, the delayed hydration can be achieved by adding a low hydrophilic-lipophilic balance (HLB) surfactant, excluding the high HLB trimming surfactant, reducing the solubility of the comonomer, using the monovalent salt charge shield, or borrowing By combining a hydrophobic layer such as a fatty acid or a fatty alcohol.

In the embodiment, a hydrophobic group can be incorporated into the hydrogel polymer to allow hydrophobic interaction. This method improves the salt tolerance of the hydrogel layer such that the hydrogel layer remains expandable even in aqueous fluids containing elevated salt concentrations.

Since the goal of hydrogel coatings is to improve the hydraulic transport of the proppant, it is important that the hydrated hydrogel layer remains attached or localized to the surface of the proppant when exposed to shear conditions during fluid transport. However, when the hydrogel coated proppant is placed in the fractured well, the hydrogel polymer should degrade or loosen away from the proppant particles and produce a proppant stone wall with sufficient water conductivity to enable the fluid to be made. Removal of the hydrogel layer from the proppant is caused by environmental factors such as elevated temperature, microbial action, fragmentation, brine, and/or hydrocarbons. In a preferred embodiment, after the hydrogel-coated proppant is pumped into the well, the hydrogel is degraded, loosened, dissolved, or detached with the aid of a fragmenting agent such as an oxidizing agent or enzyme. The oxidizing agent type of the fragmenting agent may be peroxide, magnesium peroxide, calcium peroxide, persulfate, sodium bromate, sodium hypochlorite, ozone, sodium nitrate or the like. in A blend of a lower temperature activated first oxidant (e.g., ammonium persulfate) and a second oxidant activated at a higher temperature (e.g., magnesium peroxide) may improve hydrogel formation after placement of the hydrogel coated proppant Cracking. Enzyme-based fragmentation agents are known in the art and are generally used to damage the fluid viscosity of a pump pumped into a well. Enzymes promote the degradation or cleavage of polymer linkages. In some cases, the enzyme fragmentation agent provides a more efficient fragmentation because it aligns and binds to the hydrogel polymer. Enzyme fragmenting agents are typically more effective at lower or moderate temperatures and can be combined with higher temperature activated oxidants. Hydrogel fragmentation can be improved by selecting an appropriate enzyme fragmentation agent based on hydrogel polymer identity and downhole conditions.

Also disclosed herein is the use of a hydrogel coated proppant in combination with a non-hydrogel coated proppant. For example, a hydrogel coated proppant can act as a suspending agent without a hydrogel coated proppant.

In a particular embodiment, the hydrogel polymer is selected such that at least until the modified proppant carrying the hydrogel polymer reaches its end point, its hydration is essentially completed. In the embodiment, the end point of the downhole application is to enter the well region of the geological formation to be fractured by the modified proppant, for example, the traveling direction of the liquid cracking fluid changes from vertical to horizontal, or the direction of the drill string begins to change from vertical to horizontal. This reveals that the self-suspending characteristics of the modified modified proppant can be particularly developed in liquid-cracking fluids which are generally moved horizontally. In the embodiment, the hydrogel polymer of the modified proppant is selected such that its hydration is essentially completed within 2 hours, within 1 hour, within 40 minutes, within 30 minutes, within 20 minutes, or even within Contact with tap water at 20 ° C for 10 minutes.

Also disclosed herein is a method of improving well productivity using hydrogel coated proppants to improve proppant placement. The hydrogel-coated proppant can be more efficiently transported into the distal end of the fracture surface, providing higher oil and gas productivity from the well. Because it is disclosed herein that surface modified proppants may be less prone to settle out of the fluid and are more readily resuspended and transported through the fracture surface, it is believed that proppant placement will be more effective. The ability to further transport the proppant into the fracture surface can significantly increase the effectiveness of the rupture stimulation operation, resulting in a larger volume of higher density fracture surface. Such split channels can advantageously allow gas/concentrate to flow more easily from the reservoir into the wellbore.

Also disclosed herein is an improved method of using a low viscosity fluid with proppant placement. As disclosed herein, surface modified proppants utilize polymers more efficiently to suspend/transport proppant particles. Surface modification allows the proppant to self-suspend, thereby reducing or eliminating the need for a highly viscous fluid/gel to transport the proppant. Thus, a lower viscosity fluid can be used in combination with a surface modified proppant to transport the proppant into the fracture surface. This advantageously simplifies the ruptured gel formulation used with the proppant.

Also disclosed herein is a more efficient method of rupturing a well using less proppant. Because surface-modified proppants that are easily transportable as disclosed herein can be used to achieve highly effective proppant placement, it is expected that a smaller amount of such a warp will be required for any given rupture operation than systems using conventional proppants. Surface modification proppant. As the rupture grade sand/proppant increasing demand and the desired shape sand reduction supply for the proppant use, it is advantageous to provide systems and methods such as those disclosed herein in which less proppant can be used to achieve a better outcome than using current technology. Or excellent results.

After the hydrogel coated proppant of the present invention has been pumped into the well, the chemical, thermal, mechanical, and biodegradable hydrogel layers are utilized. In particular, polymeric surface modification on the proppant can be aided by chemical breakers such as ammonium persulfate, magnesium peroxide, or other oxidizing agents. The polymeric surface modification on the proppant can be damaged by the help of surrounding oil layer conditions, such as increased brine content, elevated temperature, and contact with hydrocarbons. Controlling hydrogel fragmentation when the target temperature or amount of time is reached in the fluid can be used as a means of directing the proppant to the desired location in the fracture surface. Degradation of the hydrogel layer is also beneficial to ensure adequate conductivity through the supported fracture surface after completion of the liquid cleavage operation. In the embodiment, the hydrogel layer may demonstrate a stimulating response property such that upon exposure to the first set of conditions, such as a certain first temperature or pH, it swells in water, when a set of conditions is granted, such as a second temperature or pH, which loses water, lost volume, lost thickness, or even collapses.

For example, in the embodiment, a temperature responsive hydrogel can be applied to the proppant material. When the first set of conditions are exposed to water, such as a water temperature of 50 to 100 °F, the temperature responsive to the hydrogel layer is expandable and then collapsed upon exposure of the second set of conditions, such as a water temperature of 110 to 450 °F. Using this stimulation response mechanism, at initial water temperatures, such as 50 to 100 °F, the rupture fluid can have self-suspending properties when it is placed on the ground surface of the temperature-responsive hydrogel-coated proppant. When the coated proppant encounters a higher temperature zone of the subterranean formation, such as 110 to 450 °F, the hydrogel layer can collapse, depositing and consolidating the proppant of the fracture. The temperature-responsive hydrogel may be a water-soluble polymer or copolymer composition comprising a group selected from the group consisting of alkyl acrylates, N-alkyl acrylamides, propylene oxide, styrene, and vinyl caprolactam. Hydrophobic monomer. The N-alkyl substituted acrylamide may be N-isopropyl acrylamide, N-butyl acrylamide, N-octyl acrylamide or the like. The alkyl acrylate may be substituted with an alkyl chain having from 1 to about 30 carbons. In a preferred embodiment, the temperature-responsive hydrogel polymer comprises N-isopropyl acrylamide and contains up to 90% hydrophilic comonomer units. The type and amount of hydrophobic monomer substituents in the hydrogel polymer can be selected by experimental optimization techniques. To adjust the water solubility and temperature response properties of the hydrogel polymer.

Also disclosed herein is a method of incorporating an additive into a hydrogel layer of a modified proppant to deliver an additive (eg, a chemical additive) into a proppant stone wall. The additive may comprise chemical additives that may advantageously pass into the hydrogel layer, such as scale inhibitors, biocides, breakers, wax control agents, asphaltene control agents, and tracers. The chemical additive may be in the form of a water soluble material, water insoluble particles, fibers, metal powder or flakes. Chemical additives may be selected such that they slowly dissolve or decompose to release their chemical activity.

In the embodiment, the chemical additive can be chemically bonded to the polymer of the hydrogel layer, such as by covalent bonding, ionic bonding, hydrophobic association, hydrogen bonding, or encapsulation. The chemical additive can be added to the proppant separately from the hydrogel, or the like can be combined with the hydrogel coating formulation to produce a coated proppant. A fragmenting chemical such as a persulfate, a peroxide, a permanganate, a perchlorate, a periodate or a percarbonate may be added to the delivery method. Transporting and transporting these chemicals with hydrogel-coated proppants has the advantage of delivering chemical targets to the cracked or proppant stone walls. This method provides the advantage of concentrating the chemical additive in a functional location that requires it to be more efficient, more efficient, and deliver chemical additives at lower concentrations. In the embodiment, desorbing, oxidizing, or degrading the hydrogel polymer can result in controlled release of the chemical additive from the self-suspending proppant.

In the embodiment, the liquid cleavage operation can have multiple rupture stages; the proppant injected at each stage can contain a unique chemical additive that acts as a tracer. Tracers are typically used for liquid cleavage and include tracers that can be detected by high performance liquid chromatography (HPLC), gas chromatography (GC), ultraviolet or visible light absorption, and radiation signal measurements. Analysis of fluids produced from fractured wells provides information on the relative productivity of each rupture stage from the presence and concentration of unique tracers in the corresponding stages. In other embodiments, an additive that acts as a fragmentation agent can be carried in the hydrogel layer, such as by physical bonding or entanglement with the polymer layer. In the embodiment, the fragmentation agent can be modified by a cationic surface coating to provide an anchoring mechanism for attaching the fragmentation agent to the anionic hydrogel of the self-suspending proppant. For example, the magnesium peroxide powder can be coated with a cationic polymer such as poly-DADMAC, and the cationically modified magnesium peroxide can be blended with the hydrogel coated proppant before or after the proppant is introduced into the liquid cleaved water stream. . In this manner, the fragmentation agent is transported to the same location as the hydrogel proppant so that the fragmentation agent can be efficiently aligned with the hydrogel layer. Oxidative breakers can have accelerated activity at higher temperatures. Using this method, the fragmentation chemistry incorporated into the hydrogel layer can become activated upon placement in the fracture surface, for example Take the oil layer of oil by warming up.

In other embodiments, the fragmenting agent can be pumped into the subterranean formation before and/or after the hydrogel coated proppant is directed. In the case of a pre-propellant pumping splitting agent, the fluid containing excess fragmenting agent will flow back through the proppant stone wall and will have the ability to assist in the degradation of the hydrogel layer after the proppant has reached its end point. If the breaker is pumped into the supported formation after the proppant, the fragmentation agent can penetrate the proppant stone wall and have the effect of damaging the hydrogel layer. In the embodiment, the fragmentation agent can be added multiple times to assist in the fragmentation of the hydrogel layer. In the embodiment, the fragmentation agent may be used in combination of the following types, for example, a lower temperature activated fragmentation agent (for example, ammonium persulfate) may be used for rapid effects, combined with a packaged, longer acting, or higher temperature activated crush. A cracking agent, such as magnesium peroxide, produces a durable effect of the fractured hydrogel layer as it flows back and the well is subjected to manufacturing.

In the embodiment, the proppant particulate substrate can be coated with a selected polymer in a single layer or in a multiple coating series. The coating (in single or multiple layers) can exhibit convertible behavior under certain circumstances. As used herein, "convertible behavior" or "conversion behavior" refers to a change in nature as a function of the environment, such as a set of properties from the transport phase and a change in another set of properties within the fracture surface. For example, the conversion behavior can be seen when the particles demonstrate hydrophilic properties in the fracture fluid and adhesion properties at the correct location within the fracture surface. Such behavior can be triggered by an environment like high closed pressure inside the cracked surface, so that the outer layer of the paint itself is rearranged to exhibit more favorable properties.

In the embodiment, the coated particles can be converted from hydrophilic to hydrophobic when high pressure is imparted inside the crack. In an exemplary embodiment, during transport phase, when the hydrophilic covering particles are exposed to a water-based rupture fluid, they will tend to be fully expanded. As a result, the coating can provide the particles with lubricity in this state, making it easy to move through the proppant slurry. However, when the particles have been transported to the end point in the fracture surface of their formation, where the high pressure will overcome the steric repulsion of the outer hydrophilic polymer chain, forcing the outer layer itself to rearrange to expose the inner layer. In the embodiment, the switchable inner layer can be hydrophobic or adhesive, or both. When the inner layer becomes exposed, its properties can reveal itself. If the inner layer has adhesive properties, for example, it can fix particles to each other to prevent it from flowing back. In case the proppant particles fail, the inner layer can also be assembled to capture the fines. Furthermore, the remaining intact hydrophilic groups present in the outer coating allow the oil to flow easily through the proppant stone walls.

In the embodiment, coated proppant particles bearing the following coating layers can be made. First, a pressure activated fixative polymer can be used to coat the proppant substrate. This coating can be a bullet To provide the strength of the proppant stone wall by assisting the cohesion and distribution stress of the proppant particles. In addition, the coating can encapsulate the base particles and retain any fines that would otherwise be produced if the substrate failed. Second, the block copolymer can be adsorbed or otherwise disposed of on the first layer of the coating. The copolymer may have a portion of high affinity for the first polymer layer, promote strong interaction (hydrophobic interaction), and may have additional hydrophilic moieties to facilitate proppant transport to the transport fluid.

In some embodiments, a stronger interaction between the first and second coatings can be useful. In order to accomplish this, an expansion-expansion technique can be performed. For example, the block copolymer can be adsorbed onto the surface of the elastomer coated particles. The first coating can then be expanded with a small amount of organic solvent that causes the hydrophobic block of the copolymer to penetrate deeper into the first coating and become entangled in the elastomeric coating. By removing the organic solvent, the layered polymeric composite slurry swells, resulting in a stronger interaction of the copolymer with the elastic particles. Useful expansion-swelling techniques are described in "Swelling-Based Method for Preparing Stable, Functionalized Polymer Colloids", A. Kim et al, J. Am. Chem. Soc. (2005) 127: 1592-1593, The content is hereby incorporated by reference.

In the refinement, a proppant system using a coating as disclosed herein reduces the amount of voiding particles associated with proppant production. For example, inhalable dust containing fine crystalline ceria dust associated with disposal and processing of proppant sand can be captured and held by the proppant coating during processing thereof. In the embodiment, a coating agent having a particular affinity for particles in an environment that adversely affects worker safety or creates annoying dust problems may be added. In the embodiment, the hydrogel coating on the proppant particles can act as a binder or capture agent by mechanically trapping or adhering the dust particles.

Although the system described herein refers to a two-layer coating system, it is understood that multiple (i.e., greater than two) coatings can be formed to form the composite proppant particles disclosed herein, each multiple coating having several or all of the two coatings described above. The trait, or one or more multiple coatings, provides additional properties or characteristics.

The addition of species capable of crosslinking the swellable polymer on the surface of the proppant is effective in reducing the ability of the polymer layer to prematurely expand. Reducing polymer expansion can reduce the tendency of the polymer coated proppant to undergo agglomeration during storage of wet conditions. In several embodiments, once the polymer coated proppant is dispersed in an aqueous fluid, such as a liquid cleaving fluid, the crosslinker will not hinder the hydration/expansion of the polymer coating. In the embodiment, the cross-linked species has the ability to form carboxyl functional groups, guanamine functional groups, or both. In some aspects, the crosslinked species form a bond that can be broken or removed by mechanical shear or by chemical fragmentation. Cross-linked species can be directly added for coating The polymer of the proppant is added to the proppant with the polymer at the time of mixing, or added after the polymer is added to the proppant but at some time before drying.

The crosslinked species may be selected from organic compounds containing aldehyde, amine, anhydride, or epoxy functional groups. Crosslinked species can also be organometallic compounds. Organometallic compounds capable of associating and/or bonding with carboxyl functional groups are examples of crosslinked species that form shear sensitive linkages. In such an embodiment, the organometallic compound can reduce the tendency of the polymer coated proppant to expand by crosslinking the carboxyl groups prior to introduction of the proppant into the cleavage fluid. Then, when the crosslinked polymer coating encounters pumping high shear forces associated with liquid cracking, the cross-linking on the degradable polymer causes the polymer to expand unimpeded as the proppant introduces the liquid-cracking fluid.

In some embodiments, a thin, non-hygroscopic coating can be applied to the hydrogel coated proppant surface to create a barrier that prevents the swellable polymer layers on adjacent proppant particles from sticking to each other during storage. The outer layer utilized may include a compound that is water soluble, water insoluble, or both. In the embodiment, the outer layer is adapted such that it maintains a solid phase at a temperature below 40 ° C and has a melting point in the range of 40 ° C to 120 ° C. Preferably, the outer layer is formulated such that the melting point is low enough that the outer layer will be in the liquid phase during the drying process in the production of the polymer coated proppant, but at a high melting point during the storage and transport of the polymer coated proppant during the outer layer. It exists as a solid phase.

In such refinements, the outer layer acts as a barrier to reduce agglomeration of the coated proppant in a humid environment. As used herein, the term "caking" refers to the formation of a clump or solid mass by adhesion of loose particulate material. For material disposal purposes, do not want to agglomerate proppant during storage. The hydrophobic outer layer can be added as a finely divided powder or as a liquid to the modified proppant. In the embodiment, the outer layer material can be melted prior to the addition of the coated proppant; in other embodiments, the outer layer material can be added as a solid or waxy material that can be melted during the drying process. The solid outer layer can be added to the proppant simultaneously with the polymer, or can be added some time after the polymer is added but before the drying process. The outer layer may include fatty acids, hydrogenated oils, vegetable oils, castor oil, waxes, polyethylene oxide, polypropylene oxide, and the like.

2. Particulate substrate material

The use of a wide variety of proppant base particles can form composite proppant particles in accordance with such systems and methods. For use with the present invention, the proppant particulate substrate can comprise graded sand, resin coated sand, bauxite, ceramic materials, glass materials, walnut shells, polymeric materials, resinous materials, rubber materials, and the like, and combinations thereof. Special proppants (such as ceramics, bauxite, And the resin coated sand) to make the self-suspending proppant ("SSP") disclosed herein. With the combination of sand SSP and characteristic SSP, proppant injection can have suitable strength, permeability, suspensibility, and transportability. In the embodiment, the substrate may comprise a naturally occurring material, such as a nut shell that has been thinned, milled, ground or crushed into a suitable size (eg, walnut, walnut, coconut, almond, ivory, brazil, etc.) Or, for example, has been thinned, milled, ground or crushed into a suitable size seed casing or fruit core (such as plum, olive, peach, cherry, apricot, etc.) or, for example, from other plants such as ear of corn. Cut, grind, grind or crush the material. In the embodiment, the substrate may be derived from wood or processed wood, including but not limited to wood such as oak, pecan, walnut, mahogany, poplar, and the like. In the embodiment, an aggregate formed by bonding or bonding with an organic material forms an aggregate. Desirably, the proppant particulate substrate will comprise particles (either individual or any combination of two or more substances) having a mesh size of approximately 4 to 100 dimensions (US standard sieve number). As used herein, the term "microparticles" encompasses all materials of known unrestricted shape, such as spherical materials, elongate materials, polygonal materials, fibrous materials, irregular materials, and any mixtures thereof.

In the embodiment, a particulate substrate can be formed from the binder and the filler material as a composite. Suitable filler materials may include inorganic materials such as solid glass, glass microspheres, fly ash, ceria, alumina, smoked carbon, carbon black, stone mill, mica, boron, zirconia, talc, kaolin, titanium dioxide, strontium Calcium acid and the like. In some embodiments, the proppant particulate substrate can be reinforced to increase its resistance to high pressure formations that are otherwise crushed or deformed. The reinforcing material may be selected from materials that are capable of imparting structural strength to the proppant particulate substrate, such as high strength particles such as ceramics, metals, glass, sand, etc., or any other material that can be combined with the particulate substrate to provide additional strength.

In addition to the bare or uncoated substrate, a composite hydrogel coated proppant can be formed from a substrate that has undergone previous treatment or coating. For example, familiar artisans are familiar with various resin coated proppant particles. The above formulations and methods for coating are suitable for use with coated or treated proppant particles, including curable and precured resin coated proppants.

In the treatment of the resin coated sand, the above expandable hydrogel layer can be applied to the resin coated sand to improve its suspension characteristics. In the embodiment, a species that acts as an adhesion promoter may be included to attach the hydrogel to the resin layer. The adhesion promoter can be, for example, a block copolymer composed of both hydrophilic and hydrophobic monomers. The block copolymer may be added after the base sand is coated with the resin or simultaneously with the resin coating. In addition to the block copolymer, cationic species such as fatty amines, polyquaternary amines, and cationic surfactants can be used.

In some embodiments, proppant particulate substrates can be made in two or more different materials that provide different properties. For example, a core particle substrate having a high compressive strength can be combined with a higher compressive strength material having a lower density of buoyancy material. Combining these two materials as an aggregate provides the core particles with an appropriate amount of strength while having a relatively lower density. As lower density particles, they can be sufficiently suspended in the less viscous rupture fluid, making the ruptured fluid easier to pump, and allowing the proppant to be more dispersed within the formation as it is pushed into the more distal zone by the less viscous fluid. High density materials (eg, sand, ceramic, bauxite, etc.) used as proppant particulate substrates can be combined with lower density materials (eg, hollow glass particles, other hollow core particles, certain polymeric materials, and naturally occurring materials (nuts) Shell, seed shell, fruit core, wood, or other naturally occurring material that has been thinned, milled, ground or crushed)) produces a less dense agglomerate that still has the proper compressive strength.

The use of a technique of interconnecting the two components forms an agglomerate suitable for use as a proppant particulate substrate. As a method of preparation, the proppant particulate substrate can be mixed with a buoyant material having a particle size similar to that of the proppant particulate substrate. The two types of particles can then be mixed together and combined by an adhesive, such as a wax, a phenol-formaldehyde varnish resin, etc., to form a population of biaggregated collective particles, one subgroup having a proppant particle substrate attached to another similar particle, a subgroup A proppant particulate substrate having buoyancy particles attached thereto, and a sub-population having buoyancy particles attached to additional buoyancy particles. The three sub-populations may be particularly equal in density difference: the first sub-group will sink into the water, the second sub-group will remain suspended in the liquid, and the third sub-family will float.

In other embodiments, the proppant particulate substrate can be designed such that the surface of the particulate substrate is covered with a foamed material to make it less dense. The thickness of the foamed material can be designed to produce a composite of effective neutral buoyancy. To produce such coated proppant particles, the particles having the desired compressive strength can be coated with a reactant for the foaming reaction followed by exposure to other reactants. As the foam is triggered, the foam coated proppant particles will be produced.

As an example, a water-foamed polyurethane foam can be used to provide a coating around the particles that reduces the overall particle density. To make such coated particles, the particles may initially be coated with a reactant A, such as a mixture of one or more polyols with a suitable catalyst such as an amine. This granule can then be exposed to Reactant B containing the diisocyanate. The final foam will form on the granules, for example when steamed while shaking; the agitation will prevent the granules from sticking to their surface in the form of a foam.

In the embodiment, fibers containing biodegradable fibers can be added together with SSP In the rupture of fluid. Fibers comprising biodegradable fibers can form a web that assists in carrying the proppant with the fluid. Skilled artisans are familiar with many types of fibers that are added to the fracture fluid. As is known to the artisans, the fibers added to the fracture fluid can be degraded under downhole conditions and the channels formed in the proppant stone wall. The channel then has a higher permeability and is therefore a flow path for hydrocarbons to travel from the formation to the wellbore.

The term "fiber" can refer to synthetic or natural fibers. As used herein, the term "synthetic fiber" includes fibers or microfibers produced in whole or in part. Synthetic fibers comprise rayon fibers in which the natural precursor material is modified to form fibers. For example, cellulose (derived from natural materials) can constitute rayon fibers such as Rayon or Lyocell. Cellulose can also be modified to produce cellulose acetate fibers. Examples of such rayon-based synthetic fibers. Synthetic fibers can be formed from inorganic or organic synthetic materials. Exemplary synthetic fibers can be formed from materials such as substituted or unsubstituted lactide, glycolide, polylactic acid, polyglycolic acid, or copolymers thereof. Other fiber-forming materials include glycolic acid polymers or copolymers formed therefrom, which are familiar to those skilled in the art.

As used herein, the term "natural fiber" refers to a fiber or microfiber derived from a natural source without artificial modification. Natural fibers include plant derived fibers, animal derived fibers, and mineral derived fibers. Most of the plant-derived fibers are cellulose, such as cotton, jute, flax, hemp, kenaf, ramie, and the like. Plant derived fibers may comprise fibers derived from seeds or seed coats, such as cotton or kapok. Plant derived fibers may comprise fibers derived from leaves, such as agar or agave. Plant-derived fibers may comprise fibers derived from the epidermis or phloem around the stem of the plant, such as flax, jute, kenaf, hemp, ramie, rattan, soy fiber, vine fiber, jute, kenaf, industrial hemp, nettle , rattan, and banana fiber. Plant derived fibers may comprise fibers derived from plant fruits, such as coconut fibers. Plant derived fibers may comprise fibers derived from plant stems such as wheat, rice, barley, bamboo, and grass. Plant derived fibers can comprise wood fibers. Animal derived fibers typically include proteins such as hair, silk, horses, and the like. Animal-derived fibers can be derived from animal hair such as sheep wool, mountain wool, alpaca hair, horse hair, and the like. Animal-derived fibers can be derived from body parts of the animal, such as gut, sputum, and the like. Animal-derived fibers can collect dry mites or other secretions from insects or their isotonics, such as those obtained from silkworm cocoons. Animal derived fibers can be derived from bird feathers. Mineral derived fiber systems are obtained from minerals. Mineral derived fibers can be derived from asbestos. Mineral-derived fibers can be glass or ceramic fibers, such as glass wool fibers, quartz fibers, alumina, tantalum carbide, boron carbide, and the like.

The fibers may be advantageously selected or formed such that they are equivalent to a specified pH or temperature degradation, or degrade over time, and/or are chemically compatible with the specified carrier fluid used for proppant transport. Useful synthetic fibers can be made from solid cyclic dimers or solid polymers of organic acids known to be hydrolyzed under specific or tunable conditions such as pH, temperature, time, and the like. Advantageously, the fibers can be broken down into locations that have been transported under predetermined conditions. Advantageously, fiber decomposition produces an environmentally intimate decomposition product.

material

●30/70 mesh liquid cracking sand

●30/50 mesh liquid cracking sand

●40/70 mesh liquid cracking sand

● Polydiallyl diallyldimethylammonium (Aldrich, St. Louis, MO)

●LEPI 500 (Polymer Chemistry Innovations, Tucson, AZ)

●Ethanol, 200 Proof (Aldrich, St.Louis, MO)

● Hexane (VWR, Radnor, PA)

●FLOPAM EM533 (SNF)

● polyethylene glycol diepoxypropyl ether (Aldrich, St. Louis, MO)

Glyoxal, 40% by weight solution (Aldrich, St. Louis, MO)

●HFC-44 (Polymer Ventures, Charleston, SC)

● Carboxymethyl cellulose, sodium salt (Sigma-Aldrich, St. Louis, MO)

● ammonium persulfate (Sigma-Aldrich, St. Louis, MO)

Ethoxylated lauryl alcohol surfactant (Ethal LA-12/80%) (Ethox Chemical Co, SC)

●Glycerin (US Glycerin, Kalamazoo, MI)

● Potassium chloride (Morton Salt, Chicago, IL)

● Smoked cerium oxide (Cabot, Boston, MA)

Example 1: Preparation of an internal polymer layer

200 g of 30/70 mesh liquid split sand was added to a FlaclkTek Max 100 can, and a 100 ppm internal polymer layer was prepared on the sand sample. 85 g of tap water and 2 g of a 1% polydiallyl diallyldimethylammonium (PDAC) solution were added to the sand. Then shake the sample by hand for about 5 minutes, vacuum Filter and dry in an oven at 80 °C. The sand samples were then removed from the oven and used for subsequent testing.

The same method was used to prepare a 10 ppm internal polymer layer coating as described above except for the use of only 0.2 g of 1% PDAC solution.

The internal polymer layer in the maximum polymer loading ("maximum PDAC") was formulated using the same method as described above except for the use of 1 g of a 20% by weight PDAC solution. After the treatment, the sand was washed with excess tap water, vacuum filtered and dried in an oven at 80 °C. The sand samples were then removed from the oven and used for subsequent testing.

Example 2: Preparation of an internal polymer layer

0.2 g of LPEI 500 was dissolved in 10 g of ethanol to form a 2% LPEI 500 solution in ethanol to prepare a 100 ppm internal polymer layer on the sand sample. 0.75 g of a 2% LPEI 500 solution was added to 70 g of ethanol in a 250 mL round bottom flask. 150 g of 30/70 mesh liquid split sand was then added to the round bottom flask. The solvent was removed using a rotary evaporator in a 65 ° C water bath. The sample was then removed from the flask and used for subsequent testing.

Example 3: Preparation of an outer polymer layer

The sand and liquid Flopam EM533 polymer were mixed under different conditions and the outer polymer layer was applied to the sand sample. In one coating process, the polymer product is added neat. In an additional coating process, it is diluted with hexane to extend the polymer product. For hexane dilution, 10 g of polymer was added to 10 g of hexane in a 40 mL glass vial and vortexed until homogenization. The polymer was then added to a 30 g 30/70 mesh split sand sample in a FlackTek Max 100 jar. The sample was placed in a FlackTek DAC150 SpeedMixer at 2600 rpm for approximately 25 seconds. Samples were removed from the SpeedMixer and dried overnight in an oven at 80 °C.

Example 4: External polymer layer properties, settling time

The sand samples prepared in the previous examples were evaluated for sedimentation test performance. All sand samples were screened through a 25 mesh screen prior to testing. 1 g of sand sample was added to 100 mL of tap water in a 100 mL graduated cylinder. The cylinder was then inverted about 8 times and then the time required for all sand to settle at the bottom of the cylinder was recorded. Each sample was recorded three times. The settling time is reported in Table 1.

Example 5: Performance of the outer polymer layer, high sedimentation bed

The outer polymer layer of the sand sample prepared in Example 3 was also evaluated by observing the sedimentation bed height in water. In a 20 mL glass vial, 1 g of sand sample was added to 10 g of tap water. Invert the bottle about 10 times to make the sand treatment fully wet. The bottle was then left undisturbed for about 30 minutes. Then use a digital caliper to record the height of the sand bed in the bottle. The results are reported in Table 2.

Example 6: Ion crosslinking of an external polymer layer

A 40 g 30/70 mesh liquid sand sample was treated with an outer polymer layer which was charged with 1.3 g of Flopam EM533 polymer in 40 g of sand in a FlackTek Max 100 can and the can was shaken by hand for 2 minutes. The sand was then screened through a 25 mesh screen. In order to evaluate the retention of the polymer on the sand under shear, the test was carried out by adding 10 g of treated sand to 200 g of tap water with different levels of PDAC in a 300 mL glass beaker. It is believed that the PDAC will interact ionically to stabilize the polymer layer on the sand. The slurry was then agitated at 900 rpm for 5 minutes using a flat overhead mixer using a flat overhead mixer. The mixing was then stopped and the sample allowed to settle for 10 minutes. The viscosity of the supernatant was then measured at 60 rpm using a Brookfield DV-III+ rheometer with LV-II spindle. The height of the settled sand in the beaker was also recorded using a digital caliper. The results are reported in Table 3.

Example 7: Covalent crosslinking of an external polymer layer -PEGDGE

Four samples of 30/70 mesh liquid split sand were treated with Flopam EM533, which added 0.66 g of polymer to 20 g of sand in a FlackTek Max 100 can and was shaken by hand for 2 minutes. Various amounts of fresh 1% polyethylene glycol diglycidyl ether solution were then added to the treated sand sample in deionized water. The sample was shaken again by hand for 2 minutes and then placed in an oven at 100 ° C for 1 hour. Samples were then removed from the oven and screened through a 25 mesh screen. A 1 g sample of sand was added to 10 g of tap water in a 20 mL glass vial, and the bottle was inverted about 10 times to allow the sand treatment to be sufficiently wet, leaving the bottle undisturbed for about 10 minutes, and the bed height was measured for four samples. The bed height is then measured using a digital caliper. The results are shown in Table 4.

Example 8: Covalent crosslinking of an external polymer layer - glyoxal

Four samples of 30/70 mesh liquid split sand were treated with Flopam EM533, which added 0.66 g of polymer to 20 g of sand in a FlackTek Max 100 can and was shaken by hand for 2 minutes. 0.25 g of 40% by weight of glyoxal was added to a 20 mL glass vial and diluted to 10 g with ethanol to prepare a 1% glyoxal solution in ethanol. A varying amount of 1% glyoxal solution was then added to the treated sand sample, the sample was shaken by hand for 2 minutes, and placed in a 100 ° C oven for 30 minutes. Sand samples were then removed from the oven and screened through a 25 mesh screen. For the sedimentation bed height measurement, 1 g of sand was added to 10 g of tap water in a 20 mL bottle, inverted about 10 times, and settled for about 10 minutes. The bed height was measured with a digital caliper. The results are shown in Table 5.

Example 9: Cationic/Anionic Polymer Treatment

Three samples of 30 g of 30/70 mesh split sand were treated with Polymer Ventures HFC-44 in a FlackTek Max 100 can. Shake the can by hand for 2 minutes. Flopam EM533 was then added to each sample. Shake the can again by hand for 2 minutes. The sample was then dried overnight at 80 °C. Sand samples were removed from the oven and screened through a 25 mesh screen. For the sedimentation bed height measurement, 1 g of sand was added to 10 g of tap water in a 20 mL bottle, inverted about 10 times, and settled for about 10 minutes. The bed height was measured with a digital caliper. The results are given in Table 6.

Example 10: Sand coated with macromolecular particles

30 g of 30/70 mesh liquid split sand was added to a FlackTek Max 100 can. On the sand 0.3 g of paraffin wax was added. The sample was placed in a FlackTek DAC 150 SpeedMixer and mixed for 2 minutes at 2500 rpm. After mixing, 1 g of carboxymethylcellulose was added to the sample. The sample was again placed in a FlackTek DAC 150 SpeedMixer and mixed for 1 minute at 2500 rpm. Sand samples were screened through a 25 mesh screen. For the sedimentation bed height measurement, 1 g of sand was added to 10 g of tap water in a 20 mL bottle, inverted about 10 times, and settled for about 10 minutes. The sand of this sample immediately clumped together and was not dispersed in water, and it was impossible to obtain an accurate measurement of the bed height.

Example 11: Modified sand fragmentation test

A 30 g 30/70 mesh liquid sand sample was added to a FlackTek Max 100 can. Sand was treated with Flopam EM533, which added 0.45 g of polymer to the can and was shaken by hand for 2 minutes. The sample was then dried overnight at 80 °C. After drying, the samples were removed from the oven and screened through a 25 mesh screen. After the screening, 1 g of the treated sand was added to 10 g of tap water in a 20 mL bottle to prepare four samples. Invert the bottle about 10 times and leave it for 10 minutes. 2 g of ammonium persulfate was added to 18 g of tap water to prepare a 10% ammonium persulfate solution. A varying amount of 10% ammonium persulfate solution was added and then added to the vial. The sample was inverted and mixed several times, and then placed in an oven at 80 ° C for 1 hour. After 1 hour, the sample was removed and the sedimentation bed height was observed. Table 7 shows the results.

Example 12: Emulsifying additive

To determine the effect of the emulsified additive on the performance of the self-suspending proppant ("SSP"), we added glycerin and ETHAL LA-12/80% to the emulsified polymer EM533 prior to application of the proppant sand. Make three different polymer samples as follows:

●SSP polymer: 10g EM533, no additives

●SSP+glycerol: 9g EM533 and 1g glycerin

• SSP + glycerol + Ethal: 9 g EM533 + 0.9 g glycerol + 0.1 g Ethal LA-12 / 80%.

The above samples were vortex mixed for 30 seconds to ensure homogenization. To make the modified proppant, 50 g of 40/70 sand was combined with 1.5 g of more than one polymer sample and then mixed for 30 seconds. The shear stability of the modified proppant was evaluated in a 1 liter shear test. This test involved adding 50 grams of modified proppant to 1 liter of water in a square plastic beaker, followed by mixing at 200 rpm (corresponding shear rate of approximately 550 s ^-1 ) paddle/tank mixer (EC Engineering Model CLM-4) for different times. the amount. The sample was sheared and then poured into a 1000 mL graduated cylinder and settled by gravity for 10 minutes, then the bed height of the settled proppant sand was recorded. For comparison, the unmodified proppant sand will have a bed height of 10 mm after any mixing amount. Due to the hydrogel layer of the encapsulated sand particles, the self-suspending claimant sample will produce a higher bed level than the unmodified proppant. In general, increasing the shear rate or time can result in a decrease in the bed height of the self-suspending proppant as a result of the desorption of the hydrogel layer from the surface of the modified proppant. For this reason, the bed height is as high as possible in this test, especially after shearing. The following results show the bed height and shear stability of the added glycerin modified product. The addition of glycerol and Ethal improved the initial bed height, but the long-term shear stability decreased slightly. These results are plotted in Figure 6.

Example 13: Glycerin and processability

This experiment sought to determine the effect of glycerin and other additives on the performance of the self-suspending proppant (hereinafter referred to as SSP). 1 kg of dry 40/70 sand was added to a bowl of a KitchenAid vertical mixer (model KSM90WH) equipped with a paddle attachment. 3.09 g of glycerin was mixed with 27.84 g of EM533 emulsifying polymer, and then the mixture was added to the top of the sand and soaked for 1 minute. At time 0, the mixer is started at speed 1 (72 rpm main rotation). Samples were collected at intervals of 1 to 2 minutes and dried at 90 ° C for 1 hour. Then, each sample was given a 1 liter shear test in which 50 g of SSP was added to 1 L of water and sheared at 200 rpm (about a shear rate of about 550 s ^-1 ) for 20 minutes. After the water/SSP mixture was transferred to a 1 liter cylinder and settled for 10 minutes, the bed height was recorded. The experiment was repeated with 30.93 g of EM533 added to 1 kg of sand alone. These results are shown in Figure 7. As shown, the glycerin additive significantly increases the bed height.

The performance difference is even more pronounced when the experiment is repeated at a higher mixing speed. Here the mixer is set to speed 4 (150 rpm main rotation). At low mixing times, sample mixing was insufficient, resulting in incomplete sand coating during the shear test and rapid desorption of the polymer from the SSP surface. As the mixing time of the coating process increases, the performance is as high as the maximum bed height of the sample until the desired coating is achieved. Thereafter, a progressively worse (lower) bed height is seen at higher mixing times, possibly due to the wear of the coating during extended mixing. This process occurs even faster at higher mixing speeds, so that the processing window of the separately emulsified polymer is less than 1 minute. Adding glycerin and using a lower mixing speed, the processing window is relaxed for approximately 15 minutes. Comparing tests with separate emulsion polymers, glycerol causes processing windows Relaxation, indicating that the preparation of SSP with glycerol is more robust. At the same time, glycerin causes the polymer to emulsify more completely, resulting in better coating and increased bed height. The test results in the combination of glycerol and emulsion polymer EM533 at a higher mixing speed showed the results shown in Figure 8.

Example 14: Modified proppant with anti-caking agent

For comparison, a modified proppant sample was made and used. For sample A, 50 g of 40/70 sand was added to the FlackTek tank. 1.5 g of EM533 emulsion polymer was added to the sand and the samples were mixed for 30 seconds. After mixing, 0.25 g of calcium citrate was added to the sample, and the sample was mixed again for 30 seconds. The sample was then dried at 85 ° C for 1 hour. After drying, the sample was poured onto a 25 mesh screen and shaken slightly for 30 seconds. The amount of sand passed through the screening is then measured. For sample B, 50 g of 40/70 sand was added to the FlackTek tank. 1.5 g of EM533 emulsion polymer was added to the sand and the samples were mixed for 30 seconds. The sample was then dried at 85 ° C for 1 hour. After drying, the sample was poured onto a 25 mesh screen and shaken slightly for 30 seconds. The amount of sand passed through the screening is then measured. Table 8 shows the results.

Screening test results show that the combined anti-caking agent effectively improves the handling properties of the modified proppant.

Samples A and B were each added with 1 L of water and then sheared for 20 minutes in a 200 rpm EC engineering mixer. After shearing, the sample was transferred to a 1 L graduated cylinder and allowed to settle for 10 minutes. After settling, the bed height was measured, showing no significant loss in shear stability due to the combined anti-caking agent results. Table 9 shows these results.

Example 15: Dissolving a water soluble polymer in a monomer formulation followed by polymerizing a monomer to hydrogel coated sand

Acrylic acid (Aldrich 147230), poly(ethylene glycol) methyl ether acrylate (Aldrich 454990), and polyethylene glycol dimethacrylate (Aldrich 437441) in molar ratio: 2.5 / 0.1 / 0.1 of 2.5g mixture with 7.5g of polyethylene glycol (Aldrich 202371) and 1% by weight of ammonium persulfate mixing. The solution can be mixed with 100 g of 30/70 mesh sand under nitrogen and the temperature can be increased to 70 ° C for 5 hours. Thereafter, the obtained solid was washed with methanol, vacuum filtered and dried in an oven at 80 °C.

Example 16: Polyurethane hydrogel coated sand

100 g of 30/70 mesh liquid split sand can be added to a Hobart type mixer and heated to 120 °C. Thereafter, 6 g of polyethylene glycol (Fluka 81190) was added and mixed for 1 minute. Desmodur N75 from Bayer will then be added. After a further 1 minute of mixing, a drop of the catalyst 1,4-diazabicyclo[2.2.2]octane (Aldrich D27802) was added and the mixture was allowed to react for a further 5 minutes. The solid obtained was washed with methanol, vacuum filtered and dried in an oven at 80 °C.

Example 17: Shear stability test

The coated sand samples prepared in Examples 15 and 16 were tested for shear stability. 1 L of tap water was added to a square beaker having a capacity of 1.25 L and marked at a level of 1 L. The beaker was then placed in an EC Engineering CLM4 paddle mixer. The mixer was set at 300 rpm. Once the mixing started, 50 g of the coated sand sample was added to the beaker. After mixing at 300 rpm for 30 seconds, the mixing was reduced to 200 rpm and continued for 20 minutes. At the end of this mixing, the mixture was poured into a 1 L graduated cylinder and settled. After 10 minutes, the sedimentation bed height was recorded as shown in Table 10. Higher bed heights indicate better proppant performance.

Example 18: Saline tolerance

Two 20 mL bottles were filled with 10 mL of tap water. Separately, the other two 20 mL bottles were filled with 10 mL of 1% KCl solution. 1 g of the sand prepared in Example 15 was added to a bottle containing tap water, and 1 g was added to a bottle containing 1% KCl. Further, 1 g of the sand prepared in Example 6 was added to a bottle containing tap water, and 1 g was added to a bottle containing 1% KCl. All four bottles were inverted ~7 times and then settled for 10 minutes. After settling, the bed height was measured. The results are shown in Table 11.

Example 19: Abrasion test

Three 250 mL beakers were filled with 50 mL of tap water. An aluminum sheet having a mass of about 5.5 to 6 g was placed in each beaker. A 2 Torr stirrer was also placed in each beaker. Place all three beakers on their own magnetic stir plate and set the plate speed to 5. Add six grams of 40/70 sand to the first beaker. Six grams of the sand prepared in Example 15 was placed in a second beaker. The third beaker has no added sand at all. Allow each beaker to stir for 2 hours. After stirring, the aluminum sheets were removed, washed and then dried. Then measure the mass again. The results shown in Table 12 indicate that the sand prepared in Example 15 resulted in a less abrasive metal surface upon contact than the unmodified sand.

Example 20: Effect of glycerol on mixing

1 kg of dry 40/70 sand was added to the bowl of the KitchenAid vertical mixer (model KSM90WH) fitted with the paddle attachment. 3.09 g of glycerin was mixed with 27.84 g of EM533 emulsifying polymer, and then the mixture was added to the top of the sand and soaked for 1 minute. At time 0, the mixer is started at speed 4 (150 rpm main rotation). Samples were collected at intervals of 1 to 2 minutes and dried at 90 ° C for 1 hour. Then, each sample was subjected to a shear test in which 50 g of SSP was added to 1 L of water and sheared at 200 rpm (about a shear rate of about 550 s ^-1 ) for 20 minutes. The bed height was recorded after 10 minutes of settling. The results of these shear tests are shown in Figure 9. The graph demonstrates that both insufficient and excessive mixing can affect the behavior of the coated proppant, resulting in dissociation of the polymer from the sand during the shear test. In this embodiment, the optimum mixing amount is between about 5 and 20 minutes. Effect on performance during mixing duration It is recommended that the coating be brittle when wet and more durable once it is dry. Compared to coating tests with separate emulsion polymers, coatings with glycerin blended emulsions revealed a widening of the processing window. In addition, glycerin-incorporated emulsion coatings exhibit more complete conversion, resulting in better coating properties such as increased bed height.

Example 21: Using a kneader to make a self-suspending proppant

Batch self-suspending proppants were made using a 3 cubic kneader type mixer. Approximately 50 pounds of 40/70 mesh sand was added to the kneader. In a 1 L beaker, about 756 g of SNF Flopam EM533 was added to mix 84 g of glycerol into the polymer. The entire mixture was then poured evenly over the top of the sand of the kneader. The kneader was turned on and mixed at about 70 rpm. Samples were taken after mixing 30, 60, 120, 180, 240, 300, 420, and 600 seconds. Dry the sample for one hour. After drying, 50 g of each sample was added to 1 L of water and mixed in EC Engineering CLM4 at 200 rpm for 20 minutes. After mixing, the sample was poured into a 1 L graduated cylinder and allowed to settle for 10 minutes. After settling, the bed height was measured. The results are shown in Table 13.

Example 22: Wet aging

400 g of a self-suspending proppant (SSP) sample was produced in the same manner as in Example 15. 400 g of SSP was divided into 50 g samples and placed in a sealed container at room temperature. After drying for various amounts of time, the samples were tested in the same manner as in Example 21. The results are shown in Table 14.

Example 23: SSP plus uncoated proppant

10 mL of tap water was added to the 20 mL bottle. Proppant sand - according to Example 15 Both the SSP prepared without modification of 40/70 were then added to the bottle. The bottle was inverted several times and settled for 10 minutes. After settling, the bed height was measured. The results are shown in Table 15.

Example 24: Anti-caking agent added to SSP

A 400 g batch SSP was produced in the same manner as described in Example 15. The sample was divided into about 50 g subsamples, and then 0.25 g of smoked ceria having an aggregate size of 80 nm was mixed into each sample. The sample was then covered and aged at room temperature. Samples were tested in the same manner as described in Example 21. The results are shown in Table 16.

Example 25: Inhalable dust

200 g of uncoated and hydrogel coated sand (40/70 mesh) samples prepared according to Example 15 were screened using a 140 mesh screen, and fine particles screened through 140 mesh were collected and weighed. The coated sand samples demonstrated 86% reduction in the amount of fine particles relative to the uncoated sand samples. The results are shown in Table 17.

Example 26: Anti-caking agent with different particle sizes

50 g of 40/70 mesh sand was mixed with 2 g of SNF Flopam EM533 using a speed mixer at 800 rpm for 30 seconds. Then 0.625 g of anti-caking agent was added and the material was again mixed in a speed mixer for 30 seconds. The sample was allowed to stand for 3 hours, then tested in a 20 minute shear test, and settled for 10 minutes, and the bed height was measured. The results are shown in Table 18. The anti-caking agent improves the bed height with a wide range of particle sizes after the shear test.

Example 27: Chemical composition of an anti-caking agent

A wide variety of anti-caking agents were tested, as listed in Table 19. For each of the tested reagents, 700 g of 40/70 sand was mixed with 21.65 g of 10% glycerol/90% EM533 mixture at a speed of 1 (144 rpm) in a KitchenAid mixer. A 50 g sample was isolated and mixed with an appropriate amount of anti-caking agent in a speed mixer. Immediately in the shear test, three samples were tested, which were mixed with 1% calcium citrate, 1.5% diatomaceous earth, and 1.5% kaolin, respectively, while the other 7 samples were combined with the control sample and no anti-caking agent at 80. Dry in an oven at °C for 1 hour. All samples were tested in the same manner as in Example 17. Table 19-A shows the bed height at which the anti-caking agent was applied after the wet (un-dried) sample was shear tested. Table 19-B shows the bed height at which the anti-caking agent was applied after the shear test was dried (1 hour at 80 ° C).

Example 28: Anti-caking agent: the amount required for drying

Seven 50 g 40/70 sand samples were added to small plastic cans, followed by 2 g of each 10% glycerol/90% emulsion polymer mixture. After mixing for 30 seconds at speed, 0.25 g, 0.375 g, 0.5 g, 0.675 g, 0.75 g, 1 g, and 2.5 g of calcium citrate powder were added to the seven samples, and the sand was mixed again for 30 seconds. The test sample was sheared without further drying steps and the sedimentation bed height was recorded in mm. The results are shown in Figure 10. Similar experiments were performed using cerium oxide as an anti-caking agent. These tests show that the hydrogel-coated sand can be treated with an anti-caking agent to produce a product that does not require a separate drying step to produce an acceptable bed height after shearing.

Example 29: Ceria anti-caking agent

50 g of 40/70 sand was added to the canister followed by the addition of 2 g of 10% glycerol/90% EM533. The cans were mixed at 800 rpm for 30 seconds, then an appropriate amount of smoked cerium oxide was added, as listed in Table 20, and allowed to mix for another 30 seconds. The sample was subjected to a 20 minute shear test and the recording bed was high. Drying without oven. The results are shown in Table 20.

The batch of coated sand was mixed into a KitchenAid mixer and divided into several 50 g samples. Then, 1% by weight of various sizes of smoked cerium oxide were added to each of the three samples, and the mixing and shear tests were carried out. The results of these tests are shown in Table 21.

Example 30: Preheated sand

500 g of 30/50 sand was placed in an oven at 90 ° C for 1 hour with occasional stirring until the temperature of the sand was balanced. The sand was then mixed in a commercial planetary mixer until it reached the desired preheat temperature (45 ° C, 60 ° C or 80 ° C) with 20.8 g of SNF Flopam EM533 added and the sample mixed for 7 minutes. The samples were then separated and dried in an oven at 80 ° C for a series of times. For the unpreheated sample, 500 g of 30/50 sand and 20.8 g of polymer emulsion were placed in a mixer bowl, mixed for 7 minutes, and then dried for a varying amount of time. All samples were tested using standard procedures: 50 g of sand was added to 1000 g of tap water, stirred at a shear rate of 550 s ^-1 for 20 minutes, and then settled in a 1 L graduated cylinder for 10 minutes. The results are shown in Figure 11. These results suggest that the sand can be preheated to 45 ° C, but 60 to 80 ° C results in a lower bed height in the shear test.

Example 31: Forced air drying

50 g of 40/70 sand and 4% of the emulsified polymer (2 g) prepared according to Example 14 were mixed using a speed mixer for 30 seconds. Transfer the sample to a container equipped with a hot air gun set at 90, 95 or 100 °C. The sample was placed under hot air for a total of 30 minutes and 5 g samples were taken at 5, 10, 15 and 30 minutes. These samples were then tested using a small shear test as follows: Rotate at 500 rpm using a 2 Torr stirrer, stir 100 mL tap water in a 300 mL beaker; add 5 g sand sample to the beaker and shear for 3 minutes; transfer all solution To a 100 mL graduated cylinder, invert once, settle for 5 minutes, and measure the bed height. The results of these tests are shown in Figure 12. As shown, the higher temperature of the forced air causes more complete drying and better bed height. To test the SSP's sensitivity to shear in forced air drying, pull the seven-pointed ridge back and forth through the sample to stimulate slight shear during drying. Two 50 g batches of SSP were prepared and air dried at 110 ° C for 30 minutes. The first one is completely stationary while the second one continues to sweep during the 30 minute drying period. Both samples were tested for 20 minutes with a settling time of 10 minutes using a large shear test. The sedimentation bed volume was given to a statically dried sample of 100.63 mm; and the sample with a slight shear drying was given a sedimentation bed volume of 109.49 nm.

Example 32: Mixing with a vertical screw

Construct a small-scale vertical screw blender. Sand and SNF Flopam EM533 were added to the vessel and then mixed with a screw rotating at approximately 120 rpm. The sample was then divided into two 50 g portions, one dried at 80 ° C in the oven and the other mixed with 0.5 g (1 wt %) smoked ceria. Both were then awarded a shear test as described in Example 17. The bed height measurement results were as follows: oven drying, bed height 101.34 mm for 1 hour; no drying, adding 1% 7 nm smoked cerium oxide, giving bed height 91.47 nm. The oven is dried and an anti-caking agent is added to produce a high bed height with the dried product.

Example 33: Microwave drying

50 g of 40/70 sand was added to a small plastic can and then mixed with 2 g of a blend containing 10% glycerol/90% emulsion polymer at 800 rpm for 30 seconds in a speed mixer. The sample was placed in a 700 W microwave oven and heated for 45 seconds on a high fire. Samples were screened and cooled and then sheared at 200 rpm for 20 minutes in an EC Engineering CLM4 mixer. After mixing, the samples were transferred to a 1 L beaker and left to settle for 10 minutes. After settling, the bed height was measured in millimeters and the bed height was 52.43 mm. Microwave heating gives an acceptable bed height with a relatively short drying time.

Example 34: mixing and heating with an anti-caking agent

500 g of 40/70 sand and 20 g (20% glycerol / 80% emulsion) were mixed in a KitchenAid mixer for 8 minutes. Thereafter, 0.44% Cabot EH-5 smoked cerium oxide was added and mixed for 2 minutes, and then the sample was heated with a hot air blower. A 50 g sample was collected at 13, 18, 24 and 26 minutes mixing time. These were subjected to a shear test for 20 minutes and the record bed was high. The results are shown in Figure 13. The combination of glycerin and cerium oxide produces a longer processing window.

Example 35: Microwave drying

400 g of 30/50 sand was combined with 16 g (4% by weight) of the emulsified polymer prepared according to Example 14 and mixed in a KitchenAid vertical mixer for 7 minutes. A 50 g sample was dried using an oven (80 ° C), and 7 other samples were placed in a 700 W microwave oven for 5, 10, 20, 30, 45, 60 and 120 seconds, respectively. The sample was run as described in Example 12 for the shear test (20 minutes long) and the loss on ignition (LOI) test. The LOI test consisted of the addition of 10 g of sand to the tare weight which was placed in an oven at 960 ° C for 1 hour. After heating for one hour, the crucible was cooled in a desiccator for 1 hour and then weighed. The drying time, bed advanced LOI series are shown in Table 22. The initial and final weight differences are expressed as a percentage of the total initial sand weight, as shown in FIG.

These tests suggest that the microwave drying technique removes most of the water from the coated sample, rather than the oil.

Example 36: Vacuum Drying

250 g of 30/50 sand was combined with 10 g of the emulsifying polymer as described in Example 14. The sand mixture was stirred at a minimum speed for 7 minutes in a KitchenAid vertical mixer, then divided into 50 g samples, and dried at 25 ° C, 50 ° C and 85 ° C for 1 hour, 1 hour, and 30 minutes under a vacuum of 24 Torr Hg. The samples were cooled to room temperature, screened, and shear tested (as described in Example 12) for 20 minutes. The results are shown in Table 23.

None of the samples were completely dry during these tests, but further testing showed that higher temperatures could affect more complete drying.

Example 37: Hydrogel coating from sand adsorbed by microcells

250g 30/70 liquid split sand can be added to 500ml of previously degassed aqueous solution containing 0.6mM cetyltrimethylammonium bromide (CTAB) surfactant (equal to the critical microcell concentration of 2/3 CTAB), and 6mM monomer (A mixture of acrylic acid/acrylamide which has a molar ratio of 30/70). The adsorption of CTAB and monomer onto the sand particles can be carried out at 25 ° C for 24 hours with gentle agitation. Then, 0.6 mM ammonium persulfate can be added to the reactor, and the polymerization will be carried out at 80 ° C for 3 hours. Excess polymer and surfactant can be rinsed with several volumes of water and the sample will be dried overnight in a vacuum oven at 80 °C.

Example 38: Hydrogel coating from reversed suspension polymerization sand

60 ml of DI water, 6.6 g of acrylamide, 3 g of acrylic acid, 2.4 g of N,-methylenebisacrylamide, 0.1 g of ammonium persulfate, 2.0 g of sodium chloride and 2 drops of N, N may be added to the flask. N',N'-tetramethylethylenediamine. To this solution, 200 g of 30/70 mesh liquid split sand can be added and the entire mixture will be maintained at a temperature <10 °C. To this mixture was added 200 ml of cyclohexane, and the entire mixture was vigorously stirred under nitrogen. Thereafter, the temperature was increased to 60 ° C, and the reaction was allowed to proceed for 6 hours. The obtained coated granules were filtered and washed with hot water, acetone, and dried under reduced pressure at 45 °C.

Example 39: Coating Polymer

A mixture of coated proppants was prepared by combining 10 g of glycerin with 90 g of Flopam EM533 in a glass vial and mixing in a vortex mixer for 30 seconds. This polymer mixture was used in the following examples.

Example 40: Preparation of 40/70 mesh self-suspending proppant ("SSP")

A sample of 40/70 mesh size SSP was prepared by adding 500 g of 40/70 liquid split sand to the bowl of the KitchenAid mixer. 20 g of the coating polymer of Example 39 was added to the sand. Start the mixer at setting 1 and mix the sand and polymer mixture for 7 minutes. After mixing, the sample was dried at 85 ° C for 1 hour. After 1 hour, the sample was removed from the oven and any agglomerates were broken into individual particles.

Example 41: Preparation of a 30/50 mesh self-suspending proppant ("SSP")

A sample of 30/50 mesh size SSP was prepared by adding 500 g of 30/50 liquid split sand to the bowl of the KitchenAid mixer. 20 g of the coating polymer of Example 39 was added to the sand. Start the mixer at setting 1 and mix the sand and polymer mixture for 7 minutes. After mixing, the sample was dried at 85 ° C for 1 hour. After 1 hour, the sample was removed from the oven and any agglomerates were broken into individual particles.

Example 42: Self-suspending proppant ("SSP") vs. sand reduction fines

A standard mesh sieve stack was prepared with 40 mesh holes in the top, 70 mesh holes in the middle, and a weighing pan at the bottom. The tare weight of each clean/dry sieve was measured and recorded. 50 g of the 40/70 mesh of Example 20 was added to the top of the sieve stack and the stack was shaken by hand for five minutes. After shaking, unpack the stack and weigh each sieve. The mass retained on each sieve is calculated as the percentage of the original sample mass percentage, and the amount of sample remaining in the weighing pan represents the fine fraction, as defined by the 70 mesh cutoff. Repeat the procedure to make unsubstituted 40/ 70 mesh liquid split sand was replaced by 40/70 SSP. The results in Table 24 show the particle size distribution of 40/70 SSP. Table 25 contains particle size analysis of unsubstituted 40/70 liquid split sand. The results show that the amount of material passing through the 70 mesh screen is reduced by 40/70 SSP (1.2% vs. 4.8%). The SSP shows that the SSP can contain a reduced amount of fine particles compared to the sand sample.

Example 43: Friction reduction

1 L of tap water was added to the square beaker and the beaker was placed in an EC Engineering CLM-4 mixer. The mixer was turned on and set at a mixing speed of 200 rpm. 120 g of the 30/50 SSP of Example 21 was added to tap water. The slurry was mixed for 20 minutes, then transferred to a 1 L graduated cylinder and left to settle for 10 minutes. After settling, the supernatant was collected. This procedure was repeated until 2 L of supernatant fluid was collected. The flow loop device is used to determine the friction reduction of the collection fluid. The flow circuit consists of a 0.12 inch (ID) by 3 inch stainless steel test line and a pump that delivers a constant flow rate of 55 gph. These conditions correspond to a Reynolds number of 23,000, confirming that the fluid is turbulent. The pressure at the inlet and outlet of the test line was measured at a constant flow rate and the experiment determined the percent friction reduction (%FR). The following equation calculates the percentage of friction reduction: % FR = 100 * (1 - ΔP _i / ΔP ₀ ), where ΔP _i is the pressure drop across the test line using the SSP supernatant fluid, ΔP ₀ is Use tap water to pass the pressure drop across the test line. The pressure values are ΔP _i = 11.8 psi and ΔP ₀ = 38.5 psi, and the corresponding friction reduction (%FR) is 69%. This shows that the SSP significantly contributes to the reduction in friction of the associated fluid, indicating a reduction in pumping demand.

Example 44: Hydraulic conductivity test

To shape the conductivity of the simulated proppant stone wall, 48 g of the 30/50 mesh size SSP of Example 21 was mixed into 1 liter of water. Ammonium persulfate was added at a level of 0.1% and the mixture was heated to 185 °F for 1 hour. After cooling to room temperature, the mixture was filtered through a 2.25 inch ID column with a 100 mesh screen at the bottom to separate the particles from the fluid. The granules were formed on a 100 mesh screen to a bed depth of 0.5 Torr, and the flow rate of various fluids through the bed was measured by gravity flow. A flat sand bed was constructed in a similar manner to compare the flow rate with the bed delivered by the SSP. Using this method, the flow rates obtained from SSP (250 mL effluent at 28 sec) and flat sand (250 mL effluent at 25 sec) were nearly identical, indicating that the SSP was treated with an oxidative breaker such as ammonium persulfate on a sand bed or The conductivity of the simulated proppant stone wall does not have a harmful effect.

Example 45: Self-suspending proppant ("SSP") with anti-caking agent

In addition to the anti-caking agents that can replace the drying step, they can be used to generally improve the quality of the SSP. Many different particulate materials were tested as anti-caking agents, as set forth in Table 26 below. To prepare samples for each material, 800 g of 30/50 mesh sand was mixed with 32 g of the coating polymer of Example 19 at a speed of 1 (144 rpm) in a KitchenAid mixer. A 20 g sample was taken and blended with the selected anti-caking agent in a mixer, and the anti-caking agent dosage was calculated as the percentage of total sand in the sample. The consistency of the sample was observed and recorded as "pre-dry appearance", which was then dried at 85 ° C for 1 hour. The consistency was again observed and recorded as "appearance after drying". The samples were then subjected to 80% to 90% relative humidity conditions at 25 to 35 ° C for one hour to evaluate their anti-caking properties, and the consistency was observed and recorded as "appearance after humidity exposure". The results are shown in Table 26 below, indicating that the anti-caking agent improves the handling properties of the SSP, with free flowing being the desired feature.

Example 46: Treatment of resin coated sand with SMA 4000i

Coating the resin coated sand system with SMA 4000i 25 g of resin coated sand was added to a 250 mL round bottom flask. Separately, 0.25 g of SMA 4000i was dissolved in 3.57 g of tetrahydrofuran (THF) to prepare a 7% solution. 1.43 g of THF solution was then added to the resin coated sand in a round bottom flask. Additional THF was added to the round bottom flask until the sand was concave. The THF was then evaporated from the sample using a rotary evaporator.

Example 47: Treatment of resin coated sand with SMA 4000i

Coating the resin coated sand system with SMA 4000i 25 g of resin coated sand was added to a 250 mL round bottom flask. Separately, 0.25 g of SMA 4000i was dissolved in 3.57 g of tetrahydrofuran (THF) to prepare a 7% solution. 0.72 g of THF solution was then added to the resin coated sand in a round bottom flask. Additional THF was added to the round bottom flask until the sand was concave. The THF was then evaporated from the sample using a rotary evaporator.

Example 48: Treatment of resin coated sand with SMA 2000i

Coating the resin coated sand with SMA 2000i 25 g of resin coated sand was added to a 250 mL round bottom flask. Separately, 0.25 g of SMA 4000i was dissolved in 3.57 g of tetrahydrofuran (THF) to prepare a 7% solution. 1.43 g of THF solution was then added to the resin coated sand in a round bottom flask. Additional THF was added to the round bottom flask until the sand was concave. The THF was then evaporated from the sample using a rotary evaporator.

Example 49: Treatment of resin coated sand with SMA 2000i

Coating the resin coated sand with SMA 2000i 25 g of resin coated sand was added to a 250 mL round bottom flask. Separately, 0.25 g of SMA 2000i was dissolved in 3.57 g of tetrahydrofuran (THF). To make a 7% solution. 0.72 g of THF solution was then added to the resin coated sand in a round bottom flask. Additional THF was added to the round bottom flask until the sand was concave. The THF was then evaporated from the sample using a rotary evaporator.

Example 50: Treatment of resin coated sand with Pluronic L31

20 g of resin coated sand was applied to the FlackTek canister by coating the resin coated sand system with Pluronic surfactant L31. 0.025 g of a surfactant was added to the resin-coated sand. It was then mixed using a FlackTek speed mixer at 800 rpm for 30 seconds.

Example 51: Treatment of resin coated sand with Pluronic L35

20 g of resin coated sand was applied to the FlackTek canister by coating the resin coated sand system with Pluronic surfactant L35. 0.025 g of a surfactant was added to the resin-coated sand. It was then mixed using a FlackTek speed mixer at 800 rpm for 30 seconds.

Example 52: Treatment of resin coated sand with Pluronic L81

20 g of resin coated sand was applied to the FlackTek canister by coating the resin coated sand system with Pluronic surfactant L35. 0.025 g of a surfactant was added to the resin-coated sand. It was then mixed using a FlackTek speed mixer at 800 rpm for 30 seconds.

Example 53: Treatment of resin coated sand with ARQUAD® 2HT-75

Coating the resin coated sand with ARQUAD® 2HT-75 25 g of resin coated sand was added to a 250 mL round bottom flask. Separately, 0.25 g of ARQUAD® 2HT-75 was dissolved in 3.57 g of IPA to make a 7% solution. 0.72 g of IPA solution was then added to the resin coated sand in a round bottom flask. Additional IPA was added to the round bottom flask until the sand was concave. The IPA was then evaporated from the sample using a rotary evaporator.

Example 54: Treatment of resin coated sand with ADOGEN® 464

20 g of resin coated sand was applied to the FlackTek canister by coating the resin coated sand system with ADOGEN® 464. 0.025 g of ADOGEN® 464 was added to the resin coated sand. It was then mixed using a FlackTek speed mixer at 800 rpm for 30 seconds.

Example 55: Coating Polymer Mixture

9 g Flopam EM533 (SNF) was combined with 1 g glycerol in a 20 mL bottle. The bottles were then mixed on a vortex mixer for 30 seconds.

Example 56: Hydrogel coating of sand samples

Preparation of sand samples was carried out by placing 20 g of the samples prepared in Examples 46 to 54. FlackTek small cans. 0.6 g of the coating mixture prepared in Example 35 was added to each can. The contents were then mixed for 1 minute at 800 rpm using a FlackTek speed mixer. The sample was then dried at 100 ° C for 30 minutes. After drying, 1 g of each sample was added to a 20 mL bottle containing 10 mL of tap water. The bottles were gently mixed for 1 minute and then settled for 10 minutes. After settling, the bed height was measured to determine the hydration of the polymer. The test results are shown in Table 27.

Example 57: Humidity Aging Test (Metal Chelate Crosslinking Agent)

Tyzor TZ is an 80% solution of triethanolamine titanium chelate in ethanol. Tyzor TEAZ is a 100% active triethanolamine zirconium chelate product. These metal chelates are dispersed in castor oil at different concentrations and applied to the proppant in a second addition step during the coating process. Preparation of a coated proppant sample A 3 g blend of Flopam EM533 and glycerol was added to a 100 g 30/50 mesh proppant white sand in a FlackTek Max 100 can. The samples were then mixed in a FlackTek speed mixer for 30 seconds at 850 rpm. The sample is then removed from the speed mixer and treated in several cases with a metal chelate/castor oil blend. The sample was then returned to the speed mixer and mixed for 30 seconds at 850 rpm. Samples were then removed from the speed mixer, transferred to watch glass, and dried in a forced air laboratory oven at 100 °C for 30 minutes. After drying, the samples were screened through a 18 mesh screen. For humidity aging, 50 g of the formulated sample was placed in a Max 100 FlackTek tank and placed in a humidity chamber for 1 hour. The relative humidity of the chamber is maintained between 60 and 70%. After humidification, the samples were tested for 30 seconds in a Carver Press cell with an external load of 1,000 lbs (2.25" I.D.). The samples were visually evaluated for agglomeration and compared to the control group (none) The second addition). The degree of sample agglomeration was scored from 1 to 4, with a score of "1" indicating solid agglomeration and a score of "4" indicating free-flowing, agglomerated material. The results are shown in Table 28.

(Table 14's agglomeration score: "1" - a solid agglomerate that can be touched without being scattered, "2" - most solid agglomerates that begin to break when touched, "3" - agglomerate leaves the extrusion slot Fragile, "4" - no agglomeration).

Example 58: Humidity Aging Test (Powder Additive)

The coated proppant sand sample was formulated by adding 3 g of Flopam EM533/glycerol blend to 100 g of 30/50 mesh proppant white sand. The samples were mixed in a FlackTek speed mixer for 30 seconds at 850 rpm. The sample is then removed from the speed mixer and treated as a dry powder in several cases. The sample was then returned to the speed mixer and mixed at 850 rpm for 30 seconds to evenly distribute the powder to the sample. Samples were then removed from the speed mixer, transferred to watch glass, and dried in a forced air laboratory oven at 100 °C for 30 minutes. After drying, the samples were screened through a 18 mesh screen. For humidity aging, approximately 50 g of the formulated sample was placed in a Max 100 FlackTek tank and placed in a humidity chamber for 1 hour. The relative humidity of the chamber is maintained between 60 and 70%. After humidification, the samples were tested for 30 seconds in a Carver Press tank (1.25" ID) with an external load of 1,000 lbs. The samples were visually evaluated for agglomeration and compared to the control group (no second addition). The degree of sample agglomeration was scored as From 1 to 4, the score "1" indicates a solid agglomerate, and the score "4" indicates a free-flowing, non-caking material, as shown in Table 29.

(Table 15 agglomeration score: "1" - solid agglomerate that can be touched without being scattered, "2" - most solid agglomerates that begin to break when touched, "3" - agglomerate leaves the extrusion slot Fragile, "4" - no agglomeration).

Example 59: Oil-based additive

Several oil-based or relatively hydrophobic materials were tested to determine their effectiveness in reducing agglomeration in wetted samples of self-suspending proppants (SSP). Samples were prepared by mixing 300 g of 30/50 sand (preheated to 45 °C) with 9 g of 10% glycerol/90% Flopam 533 mixture at speed 1 in a KitchenAid mixer. After mixing for 1 minute, a second additive (typically 0.2% by weight sand) was introduced and the mixture was allowed to mix for a further few minutes. The samples were dried under moderate shear conditions using a hot air blower and KitchenAid. The sample was then given >50% RH in a humidity chamber for 1 hour. They then undergo compression tests and individual test agglomeration behavior. This composition was compressed by using a Carver Press in a compression tank at 200 PSI for 30 seconds, then removed from the tank and observed. The resulting agglomerates (see Table 16, compression tests) are graded into the following grades: "1" - solid agglomerates that can be touched without being scattered, "2" - most solid agglomerates that begin to break when touched, " 3" - The agglomerates leave the extrusion channel fragile, "4" - no agglomeration, as stated in Table 30.

Samples treated with Adogen 464 showed little or no agglomeration in this test, even at lower doses.

Equivalent

The specific embodiments of the invention have been disclosed herein, but are not intended to be limiting. Although the invention has been particularly shown and described with reference to the preferred embodiments of the invention, it will be understood that Many of the inventive variations will become apparent to those skilled in the art upon reviewing this specification. All numbers expressing reaction conditions, amounts of ingredients, and the like, as used in the specification and claims, are to be modified by the term "about" in all instances. Accordingly, unless indicated to the contrary, the numerical parameters set forth herein are approximations, which may vary depending upon the desired properties sought for the invention.

Although the invention has been particularly shown and described with reference to the preferred embodiments of the invention, it will be understood that

100‧‧‧Production process

120‧‧‧ polymer

122‧‧‧Transportation belt

124‧‧‧Mixed container

126‧‧‧Dryer

128‧‧‧Transformed sand

130‧‧‧Self-suspending proppant

132‧‧‧ sand

134‧‧‧Pump and nozzle device

Claims (56)

A modified proppant comprising proppant particles and a hydrogel coating, wherein the hydrogel coating is localized on the surface of the proppant particles to produce the modified proppant. The modified proppant of claim 1, wherein the proppant particles comprise sand. The modified proppant of claim 1, wherein the proppant particles comprise bauxite, sintered bauxite, ceramic, or a low density proppant. The modified proppant of claim 1, wherein the proppant particles comprise a resin coated substrate. The modified proppant of claim 3, further comprising an adhesion promoter, wherein the adhesion promoter adheres the hydrogel coating to the resin coated substrate. The modified proppant of claim 1, wherein the hydrogel coating comprises a water swellable polymer. A modified proppant according to claim 6 wherein the weight average molecular weight of the polymer is about 1 million g/mol, preferably about 5 million g/mol. A modified proppant according to claim 1 wherein the proppant is free flowing when dried or at a relative humidity of from about 80% to about 90% at 25 to 35 ° C for one hour. The modified proppant of claim 1, wherein the proppant is dry. A modified proppant as claimed in claim 1 or 8 wherein the hydrogel coating is durable. For example, the modified proppant of claim 10, wherein the shear analysis test determines the shear rate of the proppant ≧ 0.6. A modified proppant according to claim 1 wherein the hydrogel coating is applied to the proppant particles as a liquid coating formulation which is dried to form a substantially continuous film on the surface of the proppant particles. A modified proppant according to any one of the preceding claims, wherein the modified proppant is produced by a reverse phase emulsion coating technique in which a proppant particle substrate and an inverse emulsion are combined, wherein the oil phase forms an emulsified continuous phase, superabsorbent The solution or dispersion of the polymer in water forms a discontinuous emulsified phase. The modified proppant of claim 1, wherein the hydrogel coating comprises a selected from the group consisting of a polymer of the group consisting of polypropylene decylamine, hydrolyzed polypropylene decylamine, copolymer of acrylamide and ethylenically unsaturated ionic comonomer, copolymer of acrylamide and acrylate, poly( Acrylic acid or its salt, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, guar gum, carboxymethyl gum bean, carboxymethyl hydroxypropyl guar, hydrophobically related expandable emulsification Polymers, and latex polymers. A modified proppant according to claim 1 wherein the modified proppant undergoes a volume expansion of at least 100%, preferably at least 500%, upon hydration of excess water. A modified proppant according to claim 1 wherein the amount of hydrogel coating is less than about 5% by weight total dry weight. The modified proppant of claim 1 further comprising a cationic/anionic polymer pair of a cationic polymer and a high molecular weight anionic polymer. The modified proppant of claim 17, wherein the cationic polymer is selected from the group consisting of poly-DADMAC, LPEI, BPEI, polyglucosamine, and cationic polyacrylamide. The modified proppant of claim 1 further includes an oxidative fragmentation agent or an enzyme fragmentation agent. A modified proppant according to claim 19, wherein the oxidative fragmentation agent is selected from the group consisting of peroxides, magnesium peroxide, calcium peroxide, persulfates, nitrates, borates, ozone, and oxidized chlorine species. The group that makes up. A modified proppant according to claim 19, wherein the oxidative fragmentation agent is a cation-modified oxidative fragmentation agent capable of associating a hydrogel by ionic interaction. A modified proppant according to claim 19, wherein the enzyme fragmenting agent is a cationic enzyme fragmenting agent capable of associating a hydrogel by ionic interaction. The modified proppant of claim 1, further comprising a hydrophobic outer layer. The modified proppant according to claim 23, wherein the hydrophobic outer layer is selected from the group consisting of a fatty acid, an aliphatic amine, a hydrophobic quaternary amine, an aliphatic decylamine, a hydrogenated oil, a vegetable oil, a castor oil, and a triacetin. , a group of waxes, polyethylene oxide, and polypropylene oxide. The modified proppant of claim 1, further comprising a delayed hydration additive. The modified proppant according to claim 25, wherein the delayed hydration additive is selected from the group consisting of a low hydrophilic-lipophilic balance surfactant, a mutual exclusion agent capable of eliminating the trimming surfactant, an ionic crosslinking agent, and a covalent cross-linking agent. A group consisting of a combination of a crosslinking agent and a monovalent salt charge shielding agent. The modified proppant of claim 1, further comprising an alcohol selected from the group consisting of ethylene glycol, propylene glycol, glycerin, propanol, and ethanol. For example, the modified proppant of claim 1 of the patent scope further includes an anti-caking agent. The modified proppant of claim 28, wherein the anti-caking agent is selected from the group consisting of a hydrophobic layer material, a finely divided particulate material, and a crosslinking agent. The modified proppant according to claim 28, wherein the anti-caking agent is selected from the group consisting of calcium citrate, calcium carbonate, talc, kaolin, bentonite, diatomaceous earth, cerium oxide, colloidal cerium oxide, micro A group consisting of crystalline cellulose and attaplugate. A modified proppant according to claim 30, wherein the anti-caking agent is selected from the group consisting of smoked ceria, calcium citrate, calcium carbonate, kaolin, bentonite and attapulgite. The modified proppant of claim 1, wherein the hydrogel coating comprises an additive. For example, the modified proppant of claim 32, wherein the additive is a chemical additive. For example, the modified proppant of claim 32, wherein the additive is a tracer. The modified proppant of claim 1, wherein the modified proppant contains less fines than the unmodified proppant particles. A liquid fission formulation comprising a modified proppant and an oxidative fragmentation agent or an enzyme fragmentation agent according to any one of claims 1 to 35. A method of rupturing a well comprises: preparing a liquid split formulation of claim 36, and introducing the liquid split formulation into the well in an effective volume and at an effective pressure of the liquid splitting, thereby rupturing the well. A method of rupturing a well comprising: preparing a liquid fission formulation comprising a modified proppant of claim 1 Introducing the liquid fission formulation into the well in an effective volume and at an effective pressure at the liquid cleaving to provide a fragmentation formulation comprising an oxidative fragmentation agent or an enzyme fragmentation agent, and adding the fragmentation formulation in an effective volume and in an effective volume Well, thereby rupturing the well. The method of claim 38, wherein the splitting formulation is added to the well after the liquid splitting formulation is introduced into the well. The method of claim 39, wherein the addition of the fragmentation formulation to the well is performed prior to introduction of the liquid split formulation into the well. The method of claim 40, further comprising adding an additional amount of the fragmentation formulation to the well after the liquid fission formulation is introduced into the well. A method of reducing the amount of thickener added to a supporting fluid in the process of rupturing a geological formation penetrated by a well, wherein a support fluid containing a proppant is loaded into the geological formation by pulse pressure, reducing A method of adding a thickener to a support fluid, which comprises selecting a modified proppant of claim 1 as a proppant. The method of claim 42, wherein the modified proppant is first fully hydrated within two hours to first combine the support fluid. The method of claim 43, wherein the modified proppant is first fully hydrated within 10 minutes to first combine the support fluid. A method of producing a modified proppant comprising: providing a proppant base particle and a fluid polymeric coating composition; and applying a fluid polymeric coating composition to the proppant base particle; wherein the fluid polymeric coating composition comprises hydrogel polymerization The hydrogel polymer is localized on the surface of the proppant base particles to produce a modified proppant. The method of claim 45, further comprising the step of drying the modified proppant. The method of claim 45, wherein the drying step dries the fluid polymeric coating to form a substantially continuous film on the surface of the modified proppant. For example, the method of claim 45, wherein the production occurs at or near the modified branch The point of use of the proppant. The method of claim 45, wherein the proppant base particles comprise sand, ceramic, low density proppant, resin coated substrate, and/or bauxite. The method of claim 45, wherein the proppant base particles are obtained at or near the point of use of the modified proppant. The method of claim 45, further comprising adding a group selected from the group consisting of ethylene glycol, propylene glycol, glycerin, propanol, and ethanol during or before the step of mixing the proppant base particles with the fluid polymer coating composition. alcohol. The method of claim 45, further comprising adding a reversal promoter during or after the step of mixing the proppant base particles with the fluid polymer coating composition. The method of claim 45, further comprising adding an anti-caking agent to the modified proppant. The method of claim 53, wherein the anti-caking agent is selected from the group consisting of a hydrophobic layer material, a finely divided particulate material, and a crosslinking agent. A method of producing a hydrogel coated proppant comprising: providing a proppant base particle and a formulation comprising a coating precursor, wherein the coating precursor is capable of forming a hydrogel on the surface of the proppant base particle by in situ polymerization a gel coat; applying the formulation to the proppant base particles; and juxtaposing the paint precursor with the proppant base particles to form a hydrogel coated proppant. The method of claim 55, wherein the hydrogel-coated proppant comprises a substantially continuous coating film on the surface of the proppant base particle.