CN112126422B

CN112126422B - Drag reducer with high stability and preparation method and application thereof

Info

Publication number: CN112126422B
Application number: CN202010976290.9A
Authority: CN
Inventors: 崔仕章; 刘小芳; 侯云福; 郭鑫; 丁松松
Original assignee: Deshi Energy Technology Group Co Ltd; Shandong Deshi Chemical Co Ltd
Current assignee: Deshi Energy Technology Group Co Ltd; Shandong Deshi Chemical Co Ltd
Priority date: 2020-09-16
Filing date: 2020-09-16
Publication date: 2022-05-24
Anticipated expiration: 2040-09-16
Also published as: CN112126422A

Abstract

The application provides a drag reducer with high stability, which is prepared from the following raw materials in parts by weight: 40-60 parts of acrylamide monomer, 1-5 parts of cross-linking agent, 1-5 parts of dispersing agent, 30-50 parts of water, 40-70 parts of oil solvent, 30-60 parts of surfactant and 0.5-0.9 part of initiator; the cross-linking agent adopts a glycidyl ether type cross-linking agent and a polyamine cross-linking agent. The drag reducer provided by the application is convenient to use on site, high in dissolving speed and good in salt resistance, the stability of the product can reach 7 months, and compared with a common emulsion drag reducer, the performance of the product is improved to some extent, and long-term storage and long-distance transportation can be further met.

Description

Drag reducer with high stability and preparation method and application thereof

Technical Field

The application relates to the technical field of oilfield chemicals, in particular to a drag reducer with high stability and a preparation method and application thereof.

Background

The fracturing modification is an important process technology in the field of oil and gas field development, and the fracturing fluid plays a decisive role in the fracturing construction process. With the development of fracturing technology and the research and development of fracturing fluid, slickwater fracturing fluid is widely applied due to low viscosity and low friction resistance.

The drag reducer is a key component in the slickwater fracturing fluid, determines the performance of the slickwater fracturing fluid to a great extent, and particularly for low-porosity and low-permeability shale reservoirs, the requirement on the performance of the drag reducer is also provided due to the large using amount of slickwater of the fracturing fluid and the need of flowback after fracturing. Currently, the polyacrylamide type drag reducer has become the most common drag reducer for on-site use due to its excellent drag reducing performance and low cost, and various acrylamide polymers, such as cationic, anionic and zwitterionic, or new drag reducers formed by copolymerizing one or more different monomers, have been provided in the prior art, and the dosage forms are mainly powders or emulsions, wherein emulsion dosage forms are more commonly used.

However, the existing polyacrylamide drag reducers still have the following problems: when the slickwater prepared is used for a low-porosity and low-permeability shale reservoir, the sand carrying capacity is limited, and the dispersion of the propping agent is not facilitated; the flowback fluid contains a large amount of salt ions, such as Na⁺、Mg²⁺、Ca²⁺The resistance reduction rate of the existing polyacrylamide drag reducer in a flowback liquid containing salt ions is obviously reduced, namely the salt resistance is poor; the existing polymer drag reducer with good salt resistance or sand carrying capacity has large molecular weight and viscosity, is easy to adsorb and retain on the wall surface of a rock crack and in matrix pores, and further causes great damage to a shale reservoir; the emulsion drag reducer which is not prepared into slickwater has short stabilization time at normal temperature, generally has layering within about 2 months, greatly weakens the drag reduction capability, is not beneficial to long-term storage and long-distance transportation, and is not convenient for on-site preparation and use if being directly prepared into slickwater products, thereby limiting the application of the slickwater products.

Disclosure of Invention

In order to solve the problems, the application aims to provide the drag reducer which is good in storage stability, free of layering after being stored for a long time, low in adsorption damage to a shale reservoir stratum and particularly suitable for preparing oilfield fracturing fluid slickwater while having remarkably improved sand carrying capacity and salt tolerance.

In one aspect, the present application provides a drag reducer prepared from the following raw materials in parts by weight: 40-60 parts of acrylamide monomer, 1-5 parts of cross-linking agent, 1-5 parts of dispersing agent, 30-50 parts of water, 40-70 parts of oil solvent, 30-60 parts of surfactant and 0.5-0.9 part of initiator; the cross-linking agent adopts a glycidyl ether type cross-linking agent and a polyamine cross-linking agent; the glycidyl ether type cross-linking agent is selected from one or more of 1, 4-butanediol diglycidyl ether, allyl glycidyl ether, glycerol diglycidyl ether, trimethylolpropane triglycidyl ether and pentaerythritol tetraglycidyl ether; the polyamine cross-linking agent is selected from one or more of propane diamine, triethylene diamine and triethanolamine.

The drag reducer is prepared by carrying out reverse polymerization and emulsification on a water-phase raw material and an oil solvent in the raw material components, wherein an acrylamide monomer is crosslinked by a crosslinking agent while initiating polymerization, so that the obtained polymer chains are obviously and effectively prolonged and are mutually crosslinked to form a three-dimensional network structure, and further the drag reducer has larger molecular weight and viscosity and can show good drag reduction rate and sand carrying capacity. The application also finds that when the glycidyl ether type cross-linking agent and the polyamine cross-linking agent are added and cross-linked in sequence, the obtained drag reducer has obviously improved storage stability, salt resistance and sand carrying capacity, and has a certain protection effect on a reservoir stratum.

Optionally, the water is deionized water. It is to be understood that the acrylamide monomers described herein are nonionic monomers.

For example, patent CN111154009A provides a method for preparing a diepoxide cross-linking agent modified xanthan gum, which improves the salt tolerance of xanthan gum by means of cross-linking modification, but the viscosity of modified xanthan gum is improved, but the gum breaking of natural insoluble substances is more difficult, and the modified xanthan gum also has residues and increases the damage to the reservoir.

Further, the cross-linking agent is prepared from the following components in a mass ratio of (1-1.8): (0.2-1) trimethylolpropane triglycidyl ether and triethylene diamine.

The crosslinking agent comprises trimethylolpropane triglycidyl ether and triethylene diamine, wherein the trimethylolpropane triglycidyl ether can form a three-dimensional network structure with higher order when acrylamide is crosslinked, the triethylene diamine can also play a role in promoting crosslinking when acrylamide is crosslinked, the crosslinking is further expanded and ordered due to the interaction of the trimethylolpropane triglycidyl ether and the acrylamide, and adsorption groups on branched chains or free adsorption groups are maintained in the network, so that the sand carrying capacity and the salt resistance are improved, the adsorption on the shale surface is reduced, and the stratum is protected.

Further, the surfactant is selected from one or more of span, tween, sodium dodecyl benzene sulfonate, alpha-sodium alkenyl sulfonate, ethoxylated sodium alkyl sulfate, dodecyl dimethyl betaine, octadecyl dimethyl betaine, lauramidopropyl betaine and the like; preferably, the surfactant is span, tween and lauramidopropyl betaine in a mass ratio of (3-4) to (1-2) to (0.2-0.3).

In the application, under the condition of a cross-linked polymer obtained by using a specific cross-linking agent, the composition of the surfactant is further optimized to obtain a uniform and stable emulsion after emulsification, and the effect of improving the salt resistance of the drag reducer is achieved.

Further, the complexing agent is selected from one or more of tripolyphosphate, pyrophosphate, hexametaphosphate, nitrilotriacetate, ethylene diamine tetraacetate, diethylenetriamine pentacarboxylate and the like; preferably, the complexing agent is hexametaphosphate, nitrilotriacetate and ethylenediamine tetraacetate in a mass ratio of (0.2-0.3) to (0.1-0.2).

The addition of the complexing agent enables the acrylamide monomer to be complexed while being polymerized and crosslinked, so that the obtained drag reducer has better salt resistance, and can also improve the dispersibility of the polymer in an oil solvent, thereby enabling the polymer to be stable in storage. Preferably, the components of the complexing agent are all sodium salts.

Further, the initiator is selected from one or more of ammonium persulfate, potassium persulfate, sodium bisulfite and sodium thiosulfate; preferably, the initiator is sodium bisulfite and ammonium sulfate in a mass ratio of 1: 1.

Further, the dispersing agent is selected from one or more of fatty alcohol-polyoxyethylene ether, modified polyester, micromolecular polyacrylamide and polyisobutylene succinimide; preferably, the dispersing agent is fatty alcohol-polyoxyethylene ether and polyisobutylene polysuccinimide in a mass ratio of 1: 1.

Further, the oil solvent is selected from one or more of toluene, xylene, cyclohexane, cyclopentane, kerosene, diesel oil and white oil; preferably, the oil solvent is white oil.

In the raw material components, an oil solvent forms an oil phase in the raw materials, water, an acrylamide monomer, a cross-linking agent and a dispersing agent form a water phase in the raw materials, the oil phase raw materials and the water phase raw materials are mixed and subjected to reverse polymerization and emulsification under the action of an initiator, a surfactant and a complexing agent at a specific temperature, and finally the drag reducer is obtained. Therefore, the drag reducer provided by the application has better effects of salt resistance, stability, sand carrying capacity and protection effect and is a result of combined action when all the raw material components are adopted for preparation.

In another aspect, the present application also provides a method for preparing the drag reducer, comprising the steps of:

the method comprises the following steps: respectively taking water, an acrylamide monomer, a cross-linking agent and a dispersing agent according to the weight part ratio, and mixing and stirring to obtain a water-phase raw material;

step two: and (2) adding a surfactant into an oil solvent, then adding the water-phase raw material obtained in the step one, introducing nitrogen to remove oxygen, controlling the temperature, adding an initiator and a complexing agent, and uniformly stirring to obtain the water-soluble organic silicon dioxide.

Further, the stirring speed in the first step and the second step is 70-80 r/min; and the step of controlling the temperature in the step two is to control the temperature to be 50-60 ℃.

On the other hand, the application also provides the application of the drag reducer and/or the drag reducer prepared by the preparation method in preparation of the oil field fracturing fluid.

In another aspect, the present application further provides a slickwater comprising the drag reducer as described above, and/or the drag reducer prepared by the preparation method as described above, wherein the drag reducer is present in the slickwater in an amount of 0.03 wt% to 5 wt%.

The following beneficial effects can be brought through the application:

the drag reducer with high stability can be added into flowback fluid after shale reservoir fracturing modification to prepare slickwater, and compared with the existing polyacrylamide drag reducer, the drag reducer has the advantages that sand carrying capacity and salt tolerance are obviously improved, the damage rate to the stratum is obviously reduced, and the environmental pollution is effectively reduced; meanwhile, the drag reducer provided by the application is convenient to use on site, high in dissolving speed and good in salt resistance, the stability of the product can reach 7 months, and compared with a common emulsion drag reducer, the performance of the product is improved to some extent, and long-term storage and long-distance transportation can be further met.

Detailed Description

In order to more clearly explain the overall concept of the present application, the following detailed description is made of the overall scheme of the present invention by way of example. In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention.

Unless otherwise specified, the starting components in the examples described below are all commercially available in analytical purity.

Example 1

The embodiment provides a drag reducer suitable for preparing an oil field slickwater fracturing fluid, which is prepared from the following raw materials in parts by weight:

40 parts of deionized water, 45 parts of acrylamide monomer, 2 parts of cross-linking agent, 1 part of fatty alcohol-polyoxyethylene ether, 1 part of polyisobutylene-polysuccinimide, 40 parts of white oil, 30 parts of sorbitan fatty acid ester Span-80, 11 parts of polyoxyethylene sorbitan fatty acid ester Tween-80, 0.8 part of sodium ethylene diamine tetracetate and 0.655 part of initiator, wherein the initiator consists of sodium bisulfite and ammonium sulfate, and the mass ratio of the sodium bisulfite to the ammonium sulfate is 1: 1.

The drag reducer is prepared from the raw material components by the following method:

the method comprises the following steps: preparation of aqueous solutions

Adding 400kg of deionized water into a clean stainless steel reaction kettle, starting stirring, controlling the stirring speed to be 70-80 r/min, adding 450kg of acrylamide monomer, stirring for 20min, adding 20kg of cross-linking agent, stirring for 5min, adding 10kg of fatty alcohol-polyoxyethylene ether and 10kg of polyisobutylene-polysuccinimide, and stirring for 15min to obtain an aqueous phase solution.

Step two: preparation of surfactants

Adding 300kg of sorbitan fatty acid ester Span-80 into a clean stainless steel reaction kettle, starting stirring, controlling the stirring speed to be 70-80 r/min, adding 110kg of polyoxyethylene sorbitan fatty acid ester Tween-80, and stirring for 20 min.

Step three: emulsion polymerization

Adding 400kg of white oil into a cleaned and dried stainless steel reaction kettle, starting stirring, controlling the stirring speed to be 70-80 r/min, adding 410kg of the surfactant obtained in the second step, stirring for 15min, and adding 890kg of the aqueous phase solution obtained in the first step; introducing nitrogen to remove oxygen for 60min, controlling the temperature of the solution at 55 ℃, and sequentially adding 6.55kg of sodium bisulfite and ammonium sulfate, wherein the mass ratio of the sodium bisulfite to the ammonium sulfate is 1: 1. wherein, the sodium bisulfite and the ammonium persulfate are respectively dissolved by a small amount of water and then are added rapidly according to the sequence to avoid excessive oxygen, the temperature of the system after the initiation reaction is kept at 55 ℃, the stirring is continued for 120min, 8kg of sodium ethylene diamine tetracetate is added, and the stirring is continued for 30min, thus obtaining the sodium ethylene diamine tetracetate.

The drag reducer 1# to 10# is prepared by the method, and the difference is that different specific types of crosslinking agents are adopted under the condition that the added mass of the crosslinking agent is not changed (namely, 20kg), wherein a plurality of crosslinking agents are adopted and are respectively added in a sequential adding mode during adding. Wherein, the drag reducer prepared by the method is stable and uniform emulsion liquid with white appearance and the density of 0.95g/cm³-0.98g/cm³In the meantime.

The drag reducer 1# to 10# prepared by the method is respectively tested for sand carrying performance, core damage performance, salt resistance and storage stabilityThe test method was as follows: 1. sand carrying performance: the method comprises the following steps of utilizing a simulated crack sand suspension system to evaluate, adding 2 wt% of ceramsite sand into a water solution containing a drag reducer under the stirring condition, pumping a fluid with sand into a crack template with scales under the condition that the constant discharge capacity is 1L/min, measuring the maximum displacement of the ceramsite sand in the crack template in the movement in the cracks, wherein the flow rate of the fluid is 1L/min^-1Time 130s was measured. 2. And respectively testing and calculating the damage rates of the natural rock core and the artificial rock core by referring to an industrial standard SY/T5107-2016 water-based fracturing fluid performance evaluation method, and taking the maximum value as final damage rate data. 3. The test and calculation of drag reduction rate can refer to the industry standard SY/T6578-2009 drag reduction agent drag reduction effect indoor test method, wherein the drag reduction agent is respectively used with pure water and No. 1 salt water (composition: 4% NaCl, 0.535% MgSO) ₄、1.465％CaCl₂) And brine No. 2 (composition: 12% NaCl, 1.535% MgSO₄、6.465％CaCl₂) And preparing a solution for testing and calculating the drag reduction rate. 4. And (4) testing the storage stability: the prepared emulsion drag reducer is respectively kept stand and stored at 0 ℃ and 30 ℃, and whether the delamination condition visible to naked eyes appears or not is observed every day.

In the tests of sand carrying performance, damage rate and salt tolerance, the drag reducer is prepared into slickwater fracturing fluid with the addition amount of 1 wt%, wherein when the drag reducer obtained in each example is prepared into slickwater fracturing fluid, the dissolution speed in water is high, and floccules and gels do not exist. The specific crosslinker types employed for each example, as well as the data obtained for each performance test of the drag reducer, are shown in table 1.

TABLE 1

As can be seen from the data in table 1, under the conditions of fixing other raw material components and the respective dosage ratios, the properties of the obtained drag reducer end product are greatly different under the conditions of using different cross-linking agents to perform polymerization cross-linking on acrylamide monomers and further using specific surfactants, dispersants and complexing agents to perform further processing. Comparing the drag reducer of the comparative example without using the cross-linking agent with the drag reducer of examples 1-13, the use of the cross-linking agent in the process of initiation and polymerization of acrylamide monomers can significantly improve the sand-carrying performance and drag reduction ratio of the drag reducer, because the cross-linking agent can significantly and effectively extend and cross-link polymer chains to form a three-dimensional network structure, thereby having a larger molecular weight and viscosity. On the premise of fixing other raw material components, the crosslinking effects brought by different types of crosslinking agents are different, and for most of single crosslinking agents, the salt resistance drag reduction rate and sand carrying performance of the single crosslinking agents are obviously improved, meanwhile, the single crosslinking agents have larger damage to the stratum, and the storage stability is not obviously improved. However, examples 14-16, which used both glycidyl ether-based and polyamine-based crosslinkers, exhibited lower formation damage rates and greatly improved storage stability at 0-30 ℃ while having better sand-carrying capacity and salt tolerance.

However, the salt tolerance, storage stability and protection of the formation of examples 14-16 are still further improved. The following examples, based on the raw material composition of example 16 with the best overall performance, were conducted by adjusting or adding the remaining additives, and the sand-carrying capacity, formation protection, salt tolerance and storage stability were measured again, and the specific types of additives and test results are shown in tables 2-3.

TABLE 2

The kind and amount of the complexing agent were controlled based on the raw material components of example 18 in table 2, as shown in table 3.

TABLE 3

As can be seen from the data in tables 3 to 4, the types and amounts of the surfactant and the complexing agent have little effect on the storage stability, little effect on the sand-carrying capacity and formation protection, and a large effect on the salt resistance of the drag reducer. In example 24, the salt tolerance is greatly improved compared to example 16 before adjustment, but the storage stability and the formation protection are still further improved, so how to compound the crosslinking agent to achieve the optimal crosslinking effect becomes the key to improve the above performance. The kind and ratio of the glycidyl ether type and polyamine crosslinking agents in the crosslinking agent were continuously adjusted using the auxiliary agent of example 24 as a base material, and the specific results are shown in table 4.

TABLE 4

As shown in table 4, when the cross-linking agent is trimethylolpropane triglycidyl ether and triethylene diamine in a mass ratio of 1.6:0.4, the storage stability of the obtained drag reducer can be up to more than 7 months, after the drag reducer is prepared into slickwater, the damage rate to the stratum is as low as 4%, and the drag reducer in saline solution No. 2 is up to 87%, so that the protection property, the salt resistance and the storage stability of the drag reducer to the stratum are remarkably improved.

Meanwhile, the initiator type and the initiator proportion in example 1 are optimized, but the initiator plays a key role in polymerization of acrylamide monomers, and crosslinking and subsequent emulsification and dispersion, so that the preparation of the drag reducer adjusted according to the initiator fails, for example, the dosage of the acrylamide monomers is reduced, or the dosage of the initiator is increased, the prepared drag reducer is yellowish in appearance, and is layered after being placed for about 24 hours, and the stability is poor. The remaining examples, which fail, either fail to produce a more stable emulsion or produce an emulsion that is less uniform in appearance, are not described in detail herein.

In summary, the drag reducer for the oilfield fracturing fluid provided by the present application has the following most preferable raw material components and the following amounts: 40 parts of deionized water, 45 parts of acrylamide monomer, 1.6 parts of trimethylolpropane triglycidyl ether, 0.4 part of triethylene diamine, 1 part of fatty alcohol polyoxyethylene ether, 1 part of polyisobutylene succinimide, 40 parts of white oil, 30 parts of sorbitan fatty acid ester Span-80, 11 parts of polyoxyethylene sorbitan fatty acid ester Tween-80, 3 parts of lauroyl amido propyl betaine, 0.3 part of sodium ethylene diamine tetracetate, 0.3 part of sodium hexametaphosphate, 0.2 part of sodium aminotriacetate and 0.655 part of initiator, wherein the initiator consists of sodium bisulfite and ammonium sulfate, and the mass ratio of the sodium bisulfite to the ammonium sulfate is 1: 1. the process for making the drag reducing agent of the present application using the above-described feedstock components is as described previously herein. The drag reducer prepared by the raw material components in the amount ratio by the preparation method provided by the application is convenient to use on site, high in dissolving speed, free of floccules and gel, high in sand carrying capacity, small in damage to stratum, good in salt resistance and capable of meeting long-term storage and long-distance transportation requirements.

The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art to which the present application pertains. Any modification, equivalent replacement, improvement or the like made within the spirit and principle of the present application shall be included in the scope of the claims of the present application.

Claims

1. The drag reducer is characterized by being prepared from the following raw materials in parts by weight: 40-60 parts of acrylamide monomer, 1-5 parts of cross-linking agent, 1-5 parts of dispersing agent, 30-50 parts of water, 40-70 parts of oil solvent, 30-60 parts of surfactant, 0.5-0.9 part of initiator and 0.8 part of complexing agent;

the cross-linking agent adopts a glycidyl ether type cross-linking agent and a polyamine cross-linking agent; the glycidyl ether type cross-linking agent is selected from one or more of 1, 4-butanediol diglycidyl ether, allyl glycidyl ether, glycerol diglycidyl ether, trimethylolpropane triglycidyl ether and pentaerythritol tetraglycidyl ether; the polyamine cross-linking agent is selected from one or more of propane diamine, triethylene diamine and triethanolamine;

the complexing agent is a compound with the mass ratio of 0.3: 0.2: hexametaphosphate, nitrilotriacetate and ethylenediaminetetraacetate salts of 0.3.

2. The drag reducer of claim 1, wherein said cross-linking agent is in a mass ratio of (1-1.8): (1-0.2) trimethylolpropane triglycidyl ether and triethylene diamine.

3. The drag reducer of claim 1, wherein the surfactant is selected from one or more of span, tween, sodium dodecylbenzenesulfonate, sodium alpha-alkenylsulfonate, sodium ethoxylated alkyl sulfate, dodecyl dimethyl betaine, octadecyl dimethyl betaine, and laurylamidopropyl betaine.

4. The drag reducer of claim 1, wherein the surfactant is span, tween and lauramidopropyl betaine in a mass ratio of (3-4): (1-2): (0.2-0.3).

5. The drag reducer of claim 1, wherein said initiator is selected from one or more of ammonium persulfate, potassium persulfate, sodium bisulfite, and sodium thiosulfate.

6. The drag reducer of claim 1, wherein said initiator is sodium bisulfite and ammonium sulfate in a mass ratio of 1: 1.

7. The drag reducer according to claim 1, wherein said dispersant is selected from one or more of fatty alcohol-polyoxyethylene ether, modified polyester, small molecule polyacrylamide, polyisobutylene-polysuccinimide.

8. Drag reducer according to claim 1, characterized in that the dispersant is fatty alcohol polyoxyethylene ether and polyisobutylene succinimide in a mass ratio of 1: 1.

9. Drag reducer according to claim 1, characterized in that the oil solvent is selected from one or more of toluene, xylene, cyclohexane, cyclopentane, kerosene, diesel oil, white oil.

10. Drag reducer according to claim 1, characterized in that the oil solvent is white oil.

11. A process for the preparation of a drag reducing agent as defined in any of claims 1-10, comprising the steps of:

step two: adding a surfactant into an oil solvent, adding the water-phase raw material obtained in the step one, introducing nitrogen to remove oxygen, controlling the temperature, adding an initiator and a complexing agent, and uniformly stirring to obtain the water-phase composite material;

in the first step and the second step, the stirring speed is 70-80r/min, and the temperature in the second step is controlled to be 50-60 ℃.

12. Use of a drag reducer as defined in any one of claims 1 to 10, and/or of a drag reducer produced by the process of manufacture defined in claim 11, in the preparation of an oilfield fracturing fluid.

13. A slickwater comprising a drag reducer as defined in any of claims 1-10, wherein the drag reducer is present in the slickwater in a mass percentage of 0.03wt% to 5 wt%.