CN113652220B

CN113652220B - Resistance reducing agent, water-based fracturing fluid containing resistance reducing agent and application of water-based fracturing fluid

Info

Publication number: CN113652220B
Application number: CN202010399429.8A
Authority: CN
Inventors: 白立涛; 林厉军; 刘付臣; 杨振周
Original assignee: Beijing Huamei Shiji International Technology Co ltd; China National Petroleum Corp
Current assignee: Beijing Huamei Shiji International Technology Co ltd; China National Petroleum Corp
Priority date: 2020-05-12
Filing date: 2020-05-12
Publication date: 2023-04-07
Anticipated expiration: 2040-05-12
Also published as: CN113652220A

Abstract

The invention provides a resistance reducing agent, a water-based fracturing fluid containing the resistance reducing agent and application of the water-based fracturing fluid. The resistance reducing agent comprises: the oil phase component comprises gas-liquid synthetic base oil, an emulsifier and a brine reversal agent, the water phase component comprises salt-resistant polymerization monomers, an initiator and water, the gas-liquid synthetic base oil is degradable synthetic base oil, the brine reversal agent is a surfactant with an HLB value of 3-9, and the weight ratio of the oil phase component to the water phase component is 1 (0.5-8). The resistance reducing agent with the composition has good resistance reducing performance, salt resistance, high temperature resistance and shearing resistance, and simultaneously has good environmental protection performance because the resistance reducing agent does not contain mineral oil.

Description

Resistance reducing agent, water-based fracturing fluid containing resistance reducing agent and application of water-based fracturing fluid

Technical Field

The invention relates to the field of oil and gas exploitation, in particular to a resistance reducing agent, a water-based fracturing fluid containing the resistance reducing agent and application of the resistance reducing agent.

Background

The hydraulic fracturing technology is widely applied to yield increase of shale/compact oil and gas reservoirs, and a small flow guiding flow channel is created for oil and gas flow of low-permeability oil and gas reservoirs. Slickwater systems have been one of the most commonly used fracturing fluids in the past decade.

The water-skiing system consists of water, a propping agent, a bactericide, a scale inhibitor and a resistance reducing agent. During slickwater hydraulic fracturing operations, fracturing fluid is pumped at high speed to carry proppant and create fractures. Drag reducers are key components for successful slickwater fracturing. The resistance reducing agent changes turbulent flow into laminar flow, so that the ground pumping pressure is effectively reduced, the injection speed is improved, the fluid friction resistance is reduced, and the energy consumption is reduced. In the fracture extension process, the viscosity of the slickwater fluid is relatively low, and the slickwater fluid is easy to flow back.

The resistance reducing agents mainly include two types: dry powder type and oil-based emulsion type drag reducers. The dry powder type resistance reducing agent has better effect and saves the transportation cost. However, the dissolution time of the dry powder friction reducer is found to be long in field operation. The hydraulic fracturing site requires specialized equipment to formulate the solution. Thus, it requires a larger footprint and space on the well site is at a premium. The emulsion type resistance reducing agent can be added in time and rapidly. The emulsion type friction reducer has the disadvantage of low efficiency because the formula contains 70-80% of water and oil. Another disadvantage of emulsion type friction reducers is that they are environmentally unfriendly due to the mineral oil in the formulation. To save on the cost of water, more and more flowback and produced water is used as fracturing fluid. The flowback and produced water contains high-concentration salt water. Conventional drag reducing agents are salt sensitive and fail when used in high brine concentrations.

Conventional fracturing fluids have a density of about 1g/ml and the prior art and equipment are not capable of producing sufficiently high downhole pressures. To increase the fracturing pressure and lower the wellhead pressure, one obvious strategy is to use a high density fluid to make a weighted fracturing fluid by adding salt, which will increase the fluid column pressure. However, the high density brine has a much higher friction than fresh water at high pump speeds and the fluid friction will offset the increase in pressure of the brine downhole. Drag reducing agents may be used to reduce the friction pressure loss of conventional fresh water fracturing, but in the case of saturated brine, the high ionic strength hinders the hydration process, so that conventional drag reducing agents do not work, while their effectiveness is further reduced under shear.

In view of the above problems, there is a need to develop a resistance reducing agent with good salt resistance, high temperature resistance and stable shearing performance.

Disclosure of Invention

The invention mainly aims to provide a resistance reducing agent, a water-based fracturing fluid containing the resistance reducing agent and application of the resistance reducing agent, and aims to solve the problem that the existing resistance reducing agent cannot meet application requirements in salt resistance, shear stability and high temperature resistance.

In order to achieve the above object, according to one aspect of the present invention, there is provided a resistance reducing agent comprising: the oil phase component comprises gas-liquid synthetic base oil, an emulsifier and a brine reversal agent, the water phase component comprises salt-resistant polymerization monomers, an initiator and water, the gas-liquid synthetic base oil is degradable synthetic base oil, the brine reversal agent is a surfactant with an HLB value of 3-9, and the weight ratio of the oil phase component to the water phase component is 1 (0.5-8).

Furthermore, in the oil phase components, the weight ratio of the gas-liquid synthetic base oil to the emulsifier to the brine reversal agent is (10-70) to (1-20); in the water phase components, the weight ratio of the salt-resistant polymerization monomer, the initiator and water is (5-45): (0.001-1) and (20-80).

Furthermore, in the oil phase component, the weight ratio of the gas-liquid synthetic base oil to the emulsifier and the brine reversal agent is (10-30) to (1-5), and in the water phase component, the weight ratio of the salt-tolerant type polymeric monomer to the initiator to the water is (15-35): (0.01-0.5) and (30-50).

Further, the salt-tolerant polymeric monomer is selected from acrylamide, and one or more of the following monomers: acrylic acid, methacrylic acid, acrylamide glycidic acid, 2-acrylamido-2-methylpropanephosphonic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-allyloxy-2-hydroxy-1-propanesulfonic acid, vinylphosphonic acid, maleic acid, itaconic acid, styrenesulfonic acid, vinylsulfonic acid, ethyl acrylate, acrylonitrile, methyl methacrylate, dimethylaminoethyl methacrylate quaternary ammonium, N-vinylpyrrolidone, styrene, N-D-dimethylacrylamide, ethyl acrylate, methyl acrylate, ethyl methacrylate; preferably, the salt-tolerant polymerized monomer is a mixture of acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid and acrylic acid, and the weight ratio of the acrylamide to the 2-acrylamido-2-methyl-1-propanesulfonic acid to the acrylic acid is (1-30) to (0.1-20).

Further, the emulsifier is selected from sorbitan monostearate and/or ethoxylated sorbitan fatty acid ester.

Further, the initiator is selected from ammonium peroxodisulfate, tert-butyl ammonium hydroperoxide, dimethanesulfonyl peroxide, potassium persulfate, benzoyl peroxide, lauroyl peroxide, sodium persulfate, 2,2' -azobiscyanovaleranilide (isobutyronitrile), 2,2' -azobiscyanovaleranilide (4-methoxy-2,4-dimethylvaleronitrile), 2,2' -azobiscyanovaleranilide (2,4-dimethylvaleronitrile), 2,2' -azobiscyanovaleranilide (2-methylpropionic acid), 2,2' -azobiscyanovaleronitrile (2-methylbutanol) nitrile), 1,1' -azobiscyanovaleranilide (cyclohexane-1-carbonitrile), 2,2' -azobiscyanovaleranilide [2- (2-imidazolin-2-yl) propane ] dihydrochloride, 2,2' -azobiscyanovaleranilide (2-methylpropionamide) dihydrochloride, 2,2' -azobiscyanovaleranilide [ N- (2-carboxyethyl) -2-methylpropionamide ] tetrahydrate, diethyl 2,2' -azobisisobutyrate, dimethyl 2,2' -azobisisobutyrate, 2-methyl 2' -ethylizo diisobutyrate, 2,2' -azobis (isobutyrate), 2,2' -azobis [2- (2-imidazolin-2-yl) propane ], 2,2' -azobis [ 2-methyl-N- (2-hydroxyethyl) propionamide ], (methyl-ethyl-isobutyrate), 4,4' -azobis (4-cyanovaleric acid).

Further, the saline water reversal agent is a surfactant with HLB value more than or equal to 10; preferably, the surfactant is selected from one or more of linear and branched alcohol ethoxylates, ethoxylated sorbitol, octyl l or nonylphenol ethoxylates, ethoxylated castor oil, ethoxylated octyl or nonylphenol formaldehyde resins, dioctyl sodium succinate and ethoxylated octyl nonylphenol.

Furthermore, the resistance reducing agent also comprises a pH regulator, so that the pH value of the resistance reducing agent is 6-8.

In another aspect of the present application, there is also provided a water-based fracturing fluid comprising a resistance reducing agent, wherein the resistance reducing agent is the above resistance reducing agent.

The application further provides an application of the resistance reducing agent in the field of oil and gas exploitation.

By applying the technical scheme of the invention, the gas-liquid synthetic base oil in the resistance reducing agent has good degradability, and compared with mineral oil, the environment-friendly property of the resistance reducing agent can be improved by adding the gas-liquid synthetic base oil; the saline water inverter can enable the resistance reducing agent to be rapidly converted into an oil-in-water emulsion from a water-in-oil emulsion in the application process, so that the resistance reducing performance of the resistance reducing agent is improved. The gas-liquid synthetic base oil is used as a continuous phase, and the salt-tolerant polymerization monomer and the initiator are added to enable the resistance reducing agent to be polymerized in the application process. The unsaturated functional group is contained in the gas-liquid synthetic base oil, so that the unsaturated functional group can participate in polymerization reaction when being used as a continuous phase in inverse emulsion polymerization, and the resistance reducing agent has good salt resistance and high temperature resistance. Meanwhile, the weight ratio of the oil phase component to the water phase component is limited in the range, so that a stable emulsion system can be formed, and the performance stability of the resistance reducing agent can be greatly improved. On the basis, the resistance reducing agent with the composition has good resistance reducing performance, salt resistance, high temperature resistance and shearing resistance, and simultaneously has better environmental protection performance because the resistance reducing agent does not contain mineral oil.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 shows drag reduction ratios in water of the drag reduction agents prepared in examples 1 to 2 and comparative examples 1 to 2;

FIG. 2 shows the drag reduction ratio of the drag reducer prepared in examples 1-2 in a 1.4g/ml sodium bromide solution;

fig. 3 shows the resistance reducing ratio of the resistance reducing agent prepared in examples 1 to 2 in a saturated sodium nitrate solution.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.

As described in the background, the existing resistance reducers have the problems of salt resistance, shear stability and high temperature resistance which do not meet the application requirements. In order to solve the above technical problem, the present application provides a resistance reducing agent, including: the oil phase component comprises gas-liquid synthetic base oil, an emulsifier and a brine reversal agent, the water phase component comprises salt-resistant polymerization monomers, an initiator and water, the gas-liquid synthetic base oil is degradable synthetic base oil, the brine reversal agent is a surfactant with an HLB value of 3-9, and the weight ratio of the oil phase component to the water phase component is 1 (0.5-8).

In the resistance reducing agent, the gas-liquid synthetic base oil has good degradability, and compared with mineral oil, the environment-friendly property of the resistance reducing agent can be improved by adding the gas-liquid synthetic base oil; the saline inversion agent enables the friction reducer to be quickly converted from a water-in-oil emulsion to an oil-in-water emulsion during application, thereby being beneficial to improving the resistance reducing performance. The gas-liquid synthetic base oil is used as a continuous phase, and the salt-tolerant polymerization monomer and the initiator are added to enable the resistance reducing agent to be polymerized in the application process. The unsaturated functional group is contained in the gas-liquid synthetic base oil, so that the unsaturated functional group can participate in polymerization reaction when being used as a continuous phase in inverse emulsion polymerization, and the resistance reducing agent has good salt resistance and high temperature resistance. Meanwhile, the weight ratio of the oil phase component to the water phase component is limited in the range, so that a stable emulsion system can be formed, and the performance stability of the resistance reducing agent can be greatly improved. On the basis, the resistance reducing agent with the composition has good resistance reducing performance, salt resistance, high temperature resistance and shearing resistance, and simultaneously has better environmental protection performance because the resistance reducing agent does not contain mineral oil.

In order to further improve the comprehensive performance of the resistance reducing agent, in a preferred embodiment, the weight ratio of the gas-liquid synthetic base oil to the emulsifier and the brine inverting agent in the oil phase component is (10-70) to (1-20), and the weight ratio of the salt-tolerant type polymeric monomer to the initiator to the water in the water phase component is (5-45): (0.001-1) and (20-80). More preferably, the weight ratio of the gas-liquid synthetic base oil to the emulsifier and the brine inverting agent in the oil phase component is (10-30) to (1-5), and the weight ratio of the salt-tolerant type polymeric monomer to the initiator to the water in the water phase component is (15-35): (0.01-0.5) and (30-50).

In a preferred embodiment, the salt-tolerant polymeric monomer includes, but is not limited to, a salt-tolerant polymeric monomer selected from acrylamide, and one or more of the following monomers: acrylic acid, methacrylic acid, acrylamide glycidic acid, 2-acrylamide-2-methylpropanephosphonic acid, 2-acrylamide-2-methyl-1-propanesulfonic acid, 3-allyloxy-2-hydroxy-1-propanesulfonic acid, vinylphosphonic acid, maleic acid, itaconic acid, styrenesulfonic acid, vinylsulfonic acid, ethyl acrylate, acrylonitrile, methyl methacrylate, dimethylaminoethyl methacrylate quaternary ammonium, N-vinylpyrrolidone, styrene, N-D-dimethylacrylamide, ethyl acrylate, methyl acrylate, ethyl methacrylate. Compared with other polymerized monomers, the salt-tolerant polymerized monomers are favorable for further improving the salt resistance and the high-temperature resistance of the resistance reducing agent. More preferably, the salt-tolerant polymerized monomer is a mixture of acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid and acrylic acid, and the weight ratio of the acrylamide to the 2-acrylamido-2-methyl-1-propanesulfonic acid to the acrylic acid is (1-30) to (0.1-20).

The molecular weight of the polymer ultimately formed in the aforementioned drag reducer may range from hundreds of thousands to tens of millions. In one embodiment, the molecular weight of the friction reducer is between 100 and 3000 ten thousand. In one embodiment, the molecular weight is from 500 to 2000 ten thousand. In one embodiment, the polyacrylamide copolymer has a molecular weight of about 1000 million.

Among the above-mentioned resistance-reducing agents, the emulsifier may be selected from those commonly used in the art. In a preferred embodiment, the emulsifier includes, but is not limited to, sorbitan monostearate and/or ethoxylated sorbitan fatty acid ester. The HBL value of the emulsifier is 4-10, which is beneficial to improving the stability of the emulsion formed by the resistance reducing agent, and compared with other emulsifiers, the two emulsifiers are selected to be beneficial to further improving the shearing resistance of the resistance reducing agent.

In the above-mentioned resistance reducing agent, the initiator may be a radical initiator commonly used in the art. In a preferred embodiment, the initiator includes, but is not limited to, ammonium peroxodisulfate, t-butyl ammonium hydroperoxide, dimethanesulfonyl peroxide, potassium persulfate, benzoyl peroxide, lauroyl peroxide, sodium persulfate, 2,2' -azobiscyanovaleranilide (isobutyronitrile), 2,2' -azobiscyanovaleranilide (4-methoxy-2,4-dimethylvaleronitrile), 2,2' -azobiscyanovaleranilide (2,4-dimethylvaleronitrile), 2,2' -azobiscyanovaleranilide (2-methylpropionic acid), 2,2' -azobiscyanovaleranilide (2-methylbutanol) nitrile), 1,1' -azobiscyanovaleranilide (cyclohexane-1-carbonitrile), 2,2' -azobiscyanovaleranilide [2- (2-imidazolin-2-yl) propane ] dihydrochloride, 2,2' -azobiscyanovaleranilide (2-methylpropionamide) dihydrochloride, 2,2' -azobiscyanovaleranilide [ N- (2-carboxyethyl) -2-methylpropionamide ] tetrahydrate, diethyl 2,2' -azobisisobutyrate, dimethyl 2,2' -azobisisobutyrate, 2-methyl 2' -ethylizo diisobutyrate, 2,2' -azobis (isobutyrate), 2,2' -azobis [2- (2-imidazolin-2-yl) propane ], 2,2' -azobis [ 2-methyl-N- (2-hydroxyethyl) propionamide ], (methyl-ethyl-isobutyrate), 4,4' -azobis (4-cyanovaleric acid). The initiator may also be a mixture comprising both an oxidizing agent including, but not limited to, a persulfate or a hydroperoxide and a reducing agent including, but not limited to, ascorbic acid, formaldehyde sulfoxide, tetramethylethylenediamine or sodium metabisulfite. Compared with other initiators, the initiator can reduce the temperature of polymerization reaction, and can prepare polymers with higher molecular weight by well controlling the reaction, thereby being beneficial to improving the comprehensive performance of the resistance reducing agent.

To prepare a water-in-oil emulsion, the aqueous phase of the water-in-oil phase component should be dispersed using one or more low Hydrophilic Lipophilic Balance (HLB) surfactants. Surfactants are molecules having hydrophobic (oil-soluble) and effectively hydrophilic (water-soluble) moieties. Surfactants act as emulsifiers by lowering interfacial tension and reducing coalescence of dispersed droplets. Suitable nonionic surfactants are determined as emulsifiers using the HLB method. In some embodiments, the desired HLB range for the inverse emulsion is from 4 to 6. In other embodiments, the HLB may be in the range of 3 to 9. In some cases, the preferred HLB is 6 to 8, depending on the oil type and the formulation of the emulsion. The combination of high and low HLB surfactants is often used to achieve the desired values, in part because the packing effect and efficiency at the interface is demonstrated. The oil phase and oil-water ratio have a significant impact on the required HLB. However, this does not mean that an emulsifier or mixture having a particular HLB value will work. The correct chemical composition is also very important for a stable emulsion.

In order to further improve the comprehensive performance of the friction reducer, in a preferred embodiment, the saline water reversal agent is a surfactant with an HLB value of more than or equal to 10. More preferably, the above surfactants include, but are not limited to, one or more of linear and branched alcohol ethoxylates, ethoxylated sorbitol, octyl l or nonylphenol ethoxylates, ethoxylated castor oil, ethoxylated octyl or nonylphenol formaldehyde resins, dioctyl sodium succinate, ethoxylated octyl and nonylphenol. The selection of the surfactants is beneficial to improving the matching performance of the resistance reducing agent and the fracturing fluid, and further improving the high temperature resistance, the shearing resistance and the resistance reducing performance of the resistance reducing agent.

In a preferred embodiment, the resistance reducing agent further comprises a pH adjusting agent, so that the pH value of the resistance reducing agent is 6 to 8. Limiting the pH of the resistance reducing agent within the above range is beneficial to further improving the comprehensive performance of the resistance reducing agent. Because the amount of pH modifier used is small, the amount of pH modifier used is not typically calculated in the amount of friction reducer used.

The traditional inverse emulsion type polyacrylamide resistance reducing agent takes inert hydrophobic liquid as a continuous phase, and can be mineral oil, kerosene, paraffin oil, naphthene, cyclic aromatic hydrocarbon or hydrogenated benzene, aromatic hydrocarbon, xylene, toluene or branched chain hydrocarbon. The flowback waste water contains resistance reducing agent base oil. Thus, hydrocarbon contamination in the environment is a very serious problem. Part of the resistance reducing agent has higher content of cyclic aromatic hydrocarbon. High ring aromatics are common environmental pollutants. Many cyclic aromatics are toxic and have mutagenic/carcinogenic effects. Most cyclic aromatic hydrocarbons are fat soluble and are absorbed from the gastrointestinal tract of mammals. They are rapidly absorbed by a variety of tissues and have a pronounced tendency to localize in body fat. These chemicals pose serious threats to human and environmental health. Cyclic aromatics are considered to be resistant to degradation due to their low reactivity. The united states Environmental Protection Agency (EPA) has classified these compounds as preferential pollutants of natural resources. If possible, the addition of aromatics to the hydraulic fracturing fluid should be avoided. In a new trend, branched hydrocarbons are widely used. However, most branched hydrocarbons have a long degradation period and recent studies have shown that the concentrations that accumulate in soil, aquatic and atmospheric environments are high. Environmental pollution is a concern because hydrocarbons in flowback fluids are toxic to all forms of life.

Although bacteria are challenged by the hydrophobicity of hydrocarbons, which is known to have toxic effects on bacteria and limit their absorption by hydrocarbons, bacteria are able to degrade aliphatic hydrocarbons very slowly by aerobic and anaerobic pathways. Branched and cyclic hydrocarbons are also digested to some extent at a very slow rate by bacteria. The molecular weight and structure of the hydrocarbons have a large influence on the absorption/degradation rate. For example, high molecular lysine hydrocarbons are poorly absorbed by bacteria due to slow and difficult dissolution. Thus, the degradation rate of high molecular weight hydrocarbons is much slower than that of low molecular weight hydrocarbons.

In a preferred embodiment, the gas-liquid synthetic base OIL includes, but is not limited to, castrol biodegradable OIL (BIO OIL RD 100)&BIO BOLT)、BioSynthetic ^TM Base oil (BT),

Synthetic oil (` Harper `)>

00LF、/>

200、/>

300、/>

365、/>

625、/>

628 From Shrieve, G-OIL from Green globe technologies, inc. (Kluber Summit DSL 32,46,68 and 100), belray's biodegradable Hydraulic OIL, the biological Natural Range of biodegradable OILs from Condat groups, hydro

Easily biodegradable and nontoxic vegetable oil such as coconut oil, corn oil, rapeseed oil, soybean oil, rapeseed oil, etc. The gas-liquid synthetic base oils have low or undetectable aromatic content, excellent kinematic viscosity, low pour point, improved occupational health profile, and enhanced biodegradability, reduced marine toxicity. Compared with other gas-liquid synthetic base oils, the gas-liquid synthetic base oils have lower molecular weight, more proper unsaturation degree and viscosity, so that the degradability and drag reduction rate of the drag reducer are improved.

The friction reducers described above can be effective in reducing various types of friction in hydraulic fracturing applications, including but not limited to fresh water, produced water, flowback fluids, and heavy weight water (saturated brine). The heavy water is an aqueous solution formed by one or more of sodium nitrate, sodium bromide or sodium formate and water. Drag reducing agents are used to weigh water containing strong brine to increase fluid density.

Another aspect of the present application further provides a preparation method of the above resistance reducing agent, where the preparation method includes: preparing an oil phase: mixing a gas-liquid synthetic base oil and an emulsifier to form an oil phase; preparation of an aqueous phase: mixing the salt-tolerant polymerized monomer with water to form a water phase; mixing the oil phase and the water phase to form emulsion, then blowing with nitrogen, adding initiator, carrying out polymerization reaction, and then adding a saline water inverter into the product system of the polymerization reaction to obtain the required resistance reducing agent.

Preferably, the pH of the aqueous phase is adjusted to 6 to 8 prior to forming the emulsion.

In a preferred embodiment, the temperature of the polymerization is 35 to 70 ℃, more preferably 40 to 45 ℃.

In one embodiment, the free radical inverse emulsion polymerization is carried out as follows: the aqueous solution of the monomer is prepared by mixing the monomer in water, and the pH of the solution is adjusted to a range of 6 to 8. The oil phase is formed by mixing an emulsifier and oil. The aqueous phase is then homogenized into the oil phase by a homogenizer or high speed stirrer. The monomer emulsion is then free-radically polymerized by adding an initiator or heating under a nitrogen purge. Optionally, a high HLB inversion surfactant may be added to enhance the inversion of the emulsion when mixed with water. Any technique known to those skilled in the art for preparing inverse emulsions may be used. In another aspect, the present application further provides a water-based fracturing fluid comprising a resistance reducing agent, wherein the resistance reducing agent is the above resistance reducing agent provided by the present application.

The resistance reducing agent with the composition has good resistance reducing performance, and also has good environmental protection, salt resistance, high temperature resistance and shearing resistance, so that the water-based fracturing fluid can have good salt resistance, high temperature resistance and shearing resistance when being applied to preparation of the water-based fracturing fluid.

The resistance reducing agent with the composition has good resistance reducing performance, and also has good environmental protection, salt resistance, high temperature resistance and shearing resistance, so that the comprehensive performance of the water-based pressure fluid can be greatly improved when the resistance reducing agent is applied to the field of oil and gas exploitation, and the oil recovery rate is further greatly improved. The novel resistance reducing agent provides an economic and effective solution for the treatment of the industrial produced water of the oil field, and can also reduce the formation damage and the operation cost.

The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.

Example 1 (

Oil, salt tolerant monomer)

The composition of the resistance reducing agent is as follows:

oil phase: 18 parts of gas-liquid synthetic base oil, 2 parts of emulsifier and 1.8 parts of brine inverting agent (linear alcohol ethoxylate conversion surfactant);

water phase: 20 parts of AM, 2 parts of AMP, 8 parts of AA, 40 parts of water and 0.01 part of initiator.

The preparation method of the resistance reducing agent comprises the following steps:

the terpolymer of 2-acrylamide-2-methyl-1-propanesulfonic Acid (AMPS), acrylamide (AM) and Acrylic Acid (AA) invert emulsion is prepared by adopting a free radical polymerization method.

The oil phase is prepared by synthesizing 20 parts of natural gas and liquid

Oil was mixed and purchased from Schliff chemical company and contained 2 parts of emulsifier. The emulsifier is prepared by combining>

60 (sorbitan monostearate) and->

61 (ethoxylated sorbitol fatty acid ester) surfactant, and has HLB of 6.5. The resulting oil phase was mixed by an overhead mixer.

The aqueous phase was mixed with 20 parts AM, 2 parts AMPS, 8 parts AA and 40 parts water, and the pH of the aqueous solution was adjusted to 6-8 by the addition of sodium hydroxide. The oil phase was mixed with the water phase by a high speed stirrer and the resulting mixture was emulsified until the emulsion viscosity increased to 200cp.

The water in the above oily emulsion was charged into a glass jacketed kettle equipped with a paddle stirrer and a thermometer, the emulsion was purged with nitrogen for 30 minutes to remove oxygen, and then 0.01 part 2,2' -azobiscyanovaleranilide (isobutyronitrile) (AIBN) was added as an initiator to the emulsion. The temperature of the reaction system was raised from room temperature to 40 ℃ within 30 minutes, and after 3 hours of reaction at 40 ℃, the reaction was carried out at 50 ℃ for 1 hour, and then the reaction was carried out at 70 ℃ for 1 hour. Then 2wt% (based on total system weight) of a linear alcohol ethoxylate conversion surfactant (containing 12-15 carbon units, HLB 13.3) was added dropwise to the emulsion.

The resulting emulsion readily dissolves in water to provide a polymer solution. Inversion of the inverse emulsion can be accomplished by a dynamic method of adding it to water, from about 0.1 to about 10 gallons of emulsion polymer per thousand gallons of water, forming a drag reducing treatment solution. The viscosity of 1% solution of the inverse emulsion polymerization product is 600-1000 cp.

Example 2 (

Oil, salt-free monomer)

The composition of the resistance reducing agent is as follows:

oil phase: 20 parts of gas-liquid synthetic base oil, 2 parts of emulsifier and 1.84 parts of brine inverting agent (linear alcohol ethoxylate conversion surfactant);

water phase: 20 parts of AM, 10 parts of AA, 40 parts of water and 0.01 part of initiator.

a copolymer of Acrylamide (AM) and Acrylic Acid (AA) inverse emulsion was prepared in a similar manner to example 1, except that AMPS was not added.

The oil phase is synthesized by mixing 20 parts of gas into the liquid

Oil is mixed with 2 parts of an emulsifier which is prepared by mixing->

60 and ^ 6.5HLB providing>

61 surfactant. The resulting oil phase was mixed using an overhead stirrer.

The aqueous phase was mixed with 20 parts AM, 10 parts AA and 40 parts water and the pH of the aqueous solution was adjusted to 6-8 by the addition of sodium hydroxide. The oil phase was mixed with the water phase by a high speed stirrer and the resulting mixture was emulsified until the emulsion viscosity increased above 200cp.

The aqueous emulsion obtained above was charged into a glass jacketed kettle equipped with a paddle stirrer and a thermometer, and the emulsion was purged with nitrogen for 30 minutes to remove oxygen. 0.01 part of AIBN as initiator was added to the above aqueous emulsion. The temperature was raised from room temperature to 40 ℃ within 30 minutes, and after 3 hours of reaction at 40 ℃, the reaction was carried out at 50 ℃ for 1 hour, and then the reaction was carried out at 70 ℃ for 1 hour. 2% by weight of a linear alcohol ethoxylate surfactant (containing 12-15 carbon units, HLB of 13.3) was slowly added dropwise to the above emulsion.

Comparative example 1 (Paraffin oil, salt tolerant monomer)

The composition of the resistance reducing agent is as follows:

oil phase: 20 parts paraffin oil and 2 parts emulsifier and 1.84 parts brine inverting agent (2 wt.% ethoxy linear alcoholate conversion surfactant);

water phase: 20 parts of AM, 2 parts of AMPS, 8 parts of AA, 40 parts of water and 0.01 part of initiator.

terpolymer of 2-acrylamido-2-methyl-1-propanesulfonic Acid (AMPS), acrylamide (AM) and Acrylic Acid (AA) invert emulsion was prepared by a similar method to example 1, but using paraffin oil instead of paraffin oil

And (3) oil.

The oil phase is prepared by mixing 20 parts of paraffin oil and 2 parts of emulsifier, wherein the emulsifier is prepared by mixing

60 and->

61 surfactant, the surfactant has HLB of 6.5. The resulting oil phase was mixed by an overhead stirrer and the clear oil phase solution was ready for emulsification.

The aqueous phase was mixed with 20 parts AM, 2 parts AMPS, 8 parts AA and 40 parts water. The pH of the aqueous solution is adjusted to 6 to 8 by adding sodium hydroxide. The oil phase was mixed with the water phase using a high speed mixer. The resulting mixture was emulsified until the emulsion viscosity increased to over 200cp. The water in the resulting oil emulsion was charged to a glass jacketed kettle equipped with a paddle stirrer and thermometer. The emulsion was purged with nitrogen for 30 minutes to remove oxygen. Then, 0.01 part of AIBN as an initiator was added to the emulsion. The temperature of the reaction system was raised from room temperature to 40 ℃ within 30 minutes, and after allowing the polymerization to react at 40 ℃ for 3 hours, the reaction was allowed to react at 50 ℃ for 1 hour, and then the temperature was maintained at 70 ℃ for 1 hour. Then 2wt.% of an ethoxy linear alcoholate conversion surfactant (containing 12-15 carbon units, HLB of 13.3) was added dropwise to the emulsion.

Comparative example 2 (Paraffin oil, no salt tolerant monomer)

The composition of the resistance reducing agent is as follows:

a copolymer of Acrylamide (AM) and Acrylic Acid (AA) invert emulsion was prepared by a similar method as in example 2, but using paraffin oil instead of paraffin oil

Oil phase is prepared by mixing 20 parts of paraffin oil with 2 parts of emulsifier selected from ^ based on/or on/based on HLB to give 6.5HLB>

61 surfactant and->

60 are mixed to prepare the composition. The resulting oil phase was mixed by an overhead stirrer and the clear oil phase solution was allowed to emulsify.

20 parts AM, 10 parts AA and 40 parts water were mixed to make the aqueous phase. The pH of the aqueous solution was adjusted to 6 to 8 by adding sodium hydroxide. The oil phase was mixed with the water phase using a high speed mixer. The resulting mixture was emulsified until the emulsion viscosity increased to over 200cp. The water in the resulting oil emulsion was charged to a glass jacketed kettle equipped with a paddle stirrer and thermometer. The emulsion was purged with nitrogen for 30 minutes to remove oxygen. Next, 0.01 part of AIBN as an initiator was added to the emulsion. The temperature of the reaction system was raised from room temperature to 40 ℃ within 30 minutes, and after 3 hours of reaction at 40 ℃, the reaction was carried out at 50 ℃ for 1 hour, and then the reaction was carried out at 70 ℃ for 1 hour. Then 2wt% of a linear alcohol ethoxylate inversion surfactant (containing 12-15 carbon units, HLB 13.3) was added dropwise to the emulsion.

Performance testing

To evaluate the performance, the friction reducer emulsion samples (FR 1-FR 4) prepared in examples 1-2 and comparative examples 1-2 were tested on a Chandler flow loop equipped with either 1/2 "or 3/4" outer diameter tubing. The test was conducted at a rate of 8 gallons per minute. The 1/2 "tube results are shown in FIGS. 1 to 3. All samples were tested in houston tap water (hereinafter HTW). Selected samples were also tested in 1.4g/ml sodium bromide solution. Other products were also tested for salt tolerance in sodium nitrate and sodium chloride solutions.

Resistance reduction time: the four drag reducers prepared in examples 1 to 2 and comparative examples 1 to 2 were tested in HTW at a dose of 0.25 g/ton (0.025%).

As can be seen from FIG. 1, compared to the conventional paraffin oil-based drag reducer product, the use of the product is advantageous

The oil drag reducer product has better performance.

When the above samples were added to water, FR1 and FR2 immediately formed hydrates and could reach maximum performance in a few seconds. FR1 and FR2 have similar properties in fresh water. At the 0.025% dose, both showed a reduction in friction of about 78%.

The traditional resistance reducing agent based on paraffin oil (FR 3, FR 4) has the maximum resistance reducing amount of only 56 percent under the dosage of 0.025 percent. Furthermore, FR3 and FR4 take 3 to 6 minutes to reach maximum performance.

The hydraulic fracturing fluid may only take a few minutes to reach the formation through the wellbore. If the hydration time is longer than this, the friction reducer will not work. Thus prepared in the examples based on

The novel resistance reducing agent of the oil has more excellent performance than the traditional resistance reducing agent.

Shear stability: in practice, the fracturing fluid is pumped at high speed, while the chemicals in the fracturing fluid are subjected to high shear forces. As shown in FIG. 1, FR1 and FR2 were both quiet and stable throughout the test. Only a few percent of resistance reduction is shown. Both FR1 and FR2 have excellent properties in fresh water.

Salt resistance: to evaluate

The performance of oil drag reducers in weighted brines, FR1 and FR2 were tested in 1.4g/ml sodium bromide solution, as shown in figure 2. The sodium bromide is widely applied to hydraulic fracturing, and the density of the fracturing fluid is improved. Saturated sodium bromide is used to maximize the fluid density. Saturated sodium bromide causes the problem of failure of conventional drag reducing agents. FR1 and FR2 are both->

Oil is synthesized by continuous phase. Compared with the traditional resistance reducing agent, the performance of the material is greatly different. FR1 can reach the maximum resistance reduction of about 75 percent. FR2 can only reach 65% of the maximum resistance reduction amount. The results show that the FR1 monomer component has greatly improved salt resistance due to its salt resistance. Both FR1 and FR2 hydrates are fast and have good shear stability. After a few minutes, FR1 decreased slightly. FR2 has a small resistance-reducing effect and shows excellent performance in shear performance.

In fig. 3, the salt resistance FR1 was also tested in a saturated sodium nitrate solution. Saturated sodium nitrate solution is another inexpensive option for weighting fracturing fluids. In this case, the conventional resistance reducer has very poor performance due to the interaction between ions. FR1 was measured in saturated sodium nitrate, and the results were good. Even if the adding amount is 0.25 g/ton, the friction drag reduction rate can reach 69%. When the adding amount is increased to 0.5 g/ton, the drag reduction rate can reach 74%. In both cases, the product can be hydrated within a few seconds, which is very fast.

Environmental protection performance: the base oil used in FR1 and FR2 is a synthetic hydrocarbon fluid that is extracted from natural gas by the gas-to-liquid (GTL) process. It provides excellent performance for FR1 and FR2 with good environmental properties.

The oil has a low viscosity, provides better performance at low temperatures, increases friction reduction efficiency, and increases reverse speed. Biobased oils are readily biodegradable, non-bioaccumulating, non-toxic, and have marine chemical notices for the north sea (OCN) group E (lowest environmental hazard). The ASTM 5790 modified test method indicates that benzene, toluene, ethylbenzene and xylenes (BTEX) are not detectable. Biodegradation studies have shown that, based on economic cooperation and development of tissue 301F (synergetics 301F),

the oil can be degraded by 75% in fresh water within 28 days. OECD 301F is a solution biodegradation test, the biodegradability being determined by measuring the oxygen consumption. Biodegradation in ocean waterStudies have shown that economic cooperation and development organization 306 (symphysis 306) can degrade 62% within 28 days. Economic collaboration and development organization 306 measures biodegradability in seawater by both the shake flask method and the closed flask method. The inverting surfactants used herein are also readily biodegradable. Thus, the final emulsion is environmentally friendly.

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects: in the resistance reducing agent, the gas-liquid synthetic base oil has good degradability, and compared with mineral oil, the environment-friendly property of the resistance reducing agent can be improved by adding the gas-liquid synthetic base oil; the saline water inverter can enable the resistance reducing agent to be rapidly converted into an oil-in-water emulsion from a water-in-oil emulsion in the application process, so that the resistance reducing performance of the resistance reducing agent is improved. The gas-liquid synthetic base oil is used as a continuous phase, and the salt-tolerant polymerization monomer and the initiator are added to enable the resistance reducing agent to be polymerized in the application process. The unsaturated functional group is contained in the gas-liquid synthetic base oil, so that the unsaturated functional group can participate in polymerization reaction when being used as a continuous phase in inverse emulsion polymerization, and the resistance reducing agent has good salt resistance and high temperature resistance. Meanwhile, the weight ratio of the oil phase component to the water phase component is limited in the range, so that a stable emulsion system can be formed, and the performance stability of the resistance reducing agent can be greatly improved. On the basis, the resistance reducing agent with the composition has good resistance reducing performance, salt resistance, high temperature resistance and shearing resistance, and simultaneously has better environmental protection performance because the resistance reducing agent does not contain mineral oil.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A drag reducer, characterized in that said drag reducer comprises: an oil phase component and an aqueous phase component, wherein the oil phase component comprises a gas-liquid synthetic base oil, an emulsifier, and a brine inverter; the water phase component comprises a salt-resistant polymerization monomer, an initiator and water; the gas-liquid synthetic BASE oil is prepared by mixing 20 parts of natural gas and 18 parts of liquid synthetic BIO-BASE oil, and can be purchased from Schroff chemical company, wherein the weight ratio of the oil phase component to the water phase component is 1 (0.5-8);

the HBL value of the emulsifier is 4-10, and the emulsifier is selected from sorbitan monostearate and/or ethoxy sorbitol fatty acid ester;

the saline water reversal agent is a surfactant with HLB value more than or equal to 10, and is selected from straight chain alcohol ethoxylate and branched chain alcohol ethoxylate;

the weight ratio of the gas-liquid synthetic base oil to the emulsifier to the brine reversing agent is (10-30) to (1-5); in the water phase component, the weight ratio of the salt-resistant polymerization monomer, the initiator and water is (5-45): (0.001-1) and (20-80);

the salt-resistant polymerized monomer is selected from acrylamide and one or more of the following monomers: acrylic acid, methacrylic acid, acrylamide glycidic acid, 2-acrylamido-2-methylpropanephosphonic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, 3-allyloxy-2-hydroxy-1-propanesulfonic acid, vinylphosphonic acid, styrenesulfonic acid, vinylsulfonic acid, ethyl acrylate, acrylonitrile, methyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminoethylmethacrylate quaternary ammonium, N-vinylpyrrolidone, styrene, N-D-dimethylacrylamide, ethyl acrylate, methyl acrylate, ethyl methacrylate;

the resistance reducing agent is prepared by the following preparation method:

preparing an oil phase: mixing the gas-liquid synthetic base oil and the emulsifier to form an oil phase;

preparation of an aqueous phase: mixing the salt-tolerant polymerized monomer with water to form a water phase;

and mixing the oil phase and the water phase to form an emulsion, then blowing the emulsion by using nitrogen, adding the initiator, carrying out polymerization reaction, and then adding the saline water inverter into a product system of the polymerization reaction to obtain the resistance reducing agent.

2. The friction reducer of claim 1, wherein the brine inverting agent is selected from one or more of ethoxylated sorbitol, nonylphenol ethoxylate, ethoxylated castor oil, ethoxylated octyl, or nonylphenol formaldehyde resin.

3. The resistance reducing agent according to claim 1, wherein the weight ratio of the salt-tolerant type polymerized monomer, the initiator and the water in the aqueous phase component is (15-35): (0.01-0.5) and (30-50).

4. The resistance reducing agent according to claim 1, 2 or 3, wherein the salt-resistant polymerized monomer is a mixture of acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid and acrylic acid, and the weight ratio of the three is (1-30): (0.1-20).

5. The resistance reducing agent according to claim 1, wherein the initiator is selected from ammonium peroxodisulfate, tert-butyl ammonium hydroperoxide, dimethanesulfonyl peroxide, potassium persulfate, benzoyl peroxide, lauroyl peroxide, sodium persulfate, 2,2' -azobiscyanovaleranilide (isobutyronitrile), 2,2' -azobiscyanovaleranilide (4-methoxy-2,4-dimethylvaleronitrile), 2,2' -azobiscyanovaleranilide (2,4-dimethylvaleronitrile), 2,2' -azobiscyanovaleranilide (2-methylpropionic acid), 1,1' -azobiscyanovaleranilide (cyclohexane-1-carbonitrile), 2,2' -azobiscyanovaleranilide [2- (2-imidazolin-2-yl) propane ] dihydrochloride, 2,2' -azobiscyanovaleranilide (2-methylvaleranilide (323264-3264-azobisisobutyric acid hydrochloride, 3482 ' -azobiscyanopropionamide [ 3482 ' -N- (2-imidazolin-2-yl) propane ] dihydrochloride, 3434 ' -azobisisobutyric acid-N-diethylacetamide, 3482 ' -azobisisobutyric acid hydrochloride, 2-methyl 2' -ethyl azo two isobutyrate, 2,2' -azo two methyl ester (isobutyrate), 2,2' -azo two [2- (2-imidazoline-2-yl) propane ], 2,2' -azo two [ 2-methyl-N- (2-hydroxyethyl) propionamide ], 4,4' -azo two (4-cyanovaleric acid) one or more.

6. The friction reducer according to claim 1, further comprising a pH adjuster to adjust the pH of the friction reducer to 6-8.

7. A water-based fracturing fluid comprising a friction reducer, wherein the friction reducer is as defined in any one of claims 1 to 6.

8. Use of the friction reducer of any one of claims 1 to 6 in the field of oil and gas production.