Salt-tolerant anti-swelling slick water and application thereof

Abstract

The invention belongs to the technical field of oil and gas field hydraulic fracturing, and particularly provides salt-tolerant anti-swelling slick water and application thereof.The slick water is obtained by directly dissolving resistance reducing agents with different concentrations in water, and one agent forms a system; the problems of on-site rapid liquid preparation and real-time viscosity change required by a slick water system are solved, the purposes of saving fresh water resources and protecting the environment are achieved by adopting direct liquid preparation of high-salinity formation water or flowback fluid, meanwhile, the system has anti-swelling performance, an anti-swelling agent does not need to be added, the formula is simplified, and the cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic fracturing in oil and gas fields, and in particular to salt-resistant and anti-swelling slippery water and applications thereof. Background Art

[0002] With the depletion of conventional oil and gas resources, low-pressure and low-permeability unconventional oil and gas resources have become the key areas and hot resources for exploration and development. At present, unconventional oil and gas production mainly adopts multi-stage and multi-cluster close-cut volume fracturing technology. This technology requires high-displacement pumping of low-friction fracturing fluid system to achieve large-scale fracture creation in the early stage, and the use of high-viscosity glue to carry a large amount of proppant to fill the cracks in the later stage to ensure that the cracks have long-term conductivity. Therefore, continuous mixing is achieved at the fracturing site, and the real-time viscosity of the slick water system is achieved. The direct transition from the slick water system to the sand-carrying glue system can ensure the smooth implementation of the close-cut volume fracturing technology, and can also solve the inconvenience caused by limited space at the construction site in mountainous areas. The fracturing fluid used for a single layer of this technology generally exceeds 2000m 3 , the construction displacement is usually greater than 10m 3 / min, the scale of construction has excessively consumed precious fresh water resources and significantly increased construction costs and prices.

[0003] In addition, the current slippery water system mainly suppresses clay expansion by adding anti-swelling agents and other additives, which has disadvantages such as difficult to ensure compatibility, complex liquid preparation, and high cost. In addition, powder drag reducers have poor solubility and are difficult to achieve online mixing. Common emulsion drag reducers generally contain oil phases, are expensive and cause great damage to the reservoir.

[0004] Therefore, in the current fracturing technology for unconventional oil and gas reservoirs, the main problems that need to be solved by the slick water system include: (1) rapid on-site fluid preparation and real-time viscosity change to ensure construction requirements; (2) direct preparation of high-mineralization formation water or return fluid to avoid large-scale use of fresh water resources. The use of high-mineralization formation water or return fluid to directly prepare fluid can not only save fresh water resources but also avoid the discharge of formation return fluid to pollute the natural environment; (3) the drag reducer has multiple effects in one dose, which can simplify the formulation, reduce costs and increase efficiency; (4) water-in-water emulsion fracturing fluid can be mixed online and does not contain oil phase to protect the reservoir. Summary of the invention

[0005] The present invention aims at the shortcomings of the current slippery water system and provides a salt-resistant and anti-swelling slippery water, which can realize the rapid on-site liquid preparation and real-time viscosity change of slippery water, and can use high-mineralization on-site water or return water for liquid preparation, saving fresh water resources, while having an anti-swelling effect, simplifying the formula, reducing costs and increasing efficiency, and using a water-in-water emulsion that does not contain an oil phase, effectively solving the purpose of environmental protection.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a salt-resistant and anti-swelling slippery water, including a drag reducing agent, wherein the drag reducing agent is an aqueous dispersion of polyacrylamide; a method for synthesizing the aqueous dispersion of polyacrylamide, comprising reacting a reaction system of acrylamide I, a cationic monomer I, an inorganic salt, a stabilizer and an initiator I to obtain the aqueous dispersion of polyacrylamide; wherein the stabilizer is a binary mixture of a cationic copolymer containing a polyacrylamide segment and polyethylene oxide.

[0007] According to some embodiments of the present invention, based on the total mass of the salt-resistant and anti-swelling slippery water being 100%, the mass percentage of the drag reducing agent is 0.1% to 6.7%, and the remainder is water.

[0008] According to some embodiments of the present invention, the mass ratio of the acrylamide I, the cationic monomer I, the inorganic salt and the stabilizer is 36: (4.32-5.76); 10: (270-275).

[0009] According to some embodiments of the present invention, the added amount of the initiator I is 0.1% to 0.5% of the mass of the acrylamide I.

[0010] According to some embodiments of the present invention, the cationic monomer I is selected from one or more of acryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl dimethyl benzyl ammonium chloride, and 2-acrylamido-2-methylpropyl trimethyl ammonium chloride.

[0011] According to some embodiments of the present invention, the inorganic salt is selected from ammonium salts; preferably, the ammonium salt is selected from at least one of ammonium sulfate and ammonium persulfate.

[0012] According to some embodiments of the present invention, the initiator I is selected from aqueous initiator I and / or thermal initiator I; preferably, the aqueous initiator I is selected from at least one of V-50 and VA-044; the thermal initiator I is selected from at least two of ammonium persulfate, sodium bisulfite, and potassium persulfate.

[0013] According to some embodiments of the present invention, the conditions of reaction I include: temperature of 25° C. to 45° C., and time of 1 hour to 6 hours.

[0014] According to some embodiments of the present invention, the preparation of the stabilizer includes: in the presence of an initiator II and an inactive atmosphere, mixing a cationic monomer II, acrylamide II, and polyethylene oxide in water to obtain a mixed solution, and performing a reaction II to obtain the stabilizer.

[0015] In the present invention, polyoxyethylene does not participate in the polymerization reaction during the preparation of the stabilizer, that is, the cationic copolymer containing polyacrylamide segments and polyoxyethylene in the binary mixture do not react with the polyoxyethylene, and the role of polyoxyethylene is to stabilize the cationic copolymer.

[0016] According to some embodiments of the present invention, the mass ratio of the cationic monomer II, acrylamide II, polyethylene oxide and water is 72:60:(30-100):(160-260).

[0017] According to some embodiments of the present invention, the added amount of the initiator II is 0.1% to 0.5% of the mass of the cationic monomer II.

[0018] According to some embodiments of the present invention, the cationic monomer II is selected from one or more of acryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl dimethyl benzyl ammonium chloride, and 2-acrylamido-2-methylpropyl trimethyl ammonium chloride.

[0019] According to some embodiments of the present invention, the polyoxyethylene is selected from polyoxyethylene with or without end capping; preferably, the molecular weight of the polyoxyethylene is 2000Da to 200000Da; further preferably, the polyoxyethylene with end capping includes single-end capped polyoxyethylene and double-end capped polyoxyethylene; further preferably, the single-end capped polyoxyethylene is selected from polyoxyethylene monomethyl ether; the double-end capped polyoxyethylene is selected from polyoxyethylene dimethyl ether; the polyoxyethylene without end capping is polyethylene glycol.

[0020] According to some embodiments of the present invention, the initiator II is selected from aqueous initiator II and / or thermal initiator II; preferably, the aqueous initiator II is selected from at least one of V-50 and VA-044; the thermal initiator II is selected from at least two of ammonium persulfate, sodium bisulfite, and potassium persulfate.

[0021] According to some embodiments of the present invention, the inactive atmosphere is selected from at least one of nitrogen and argon.

[0022] According to some embodiments of the present invention, the conditions of reaction II include: temperature of 30° C. to 80° C., and reaction time of 5 hours to 10 hours.

[0023] According to some embodiments of the present invention, the reaction II further includes dilution; preferably, the stabilizer is cooled to room temperature, and then a certain amount of water is added to dilute the stabilizer to a mass concentration of 5wt% to 10wt%, to obtain an aqueous solution of a binary mixture of a cationic copolymer containing polyacrylamide segments and polyethylene oxide.

[0024] The second aspect of the present invention provides the use of the above-mentioned salt-resistant and anti-swelling slippery water in hydraulic fracturing of oil and gas fields.

[0025] Beneficial effects:

[0026] The present invention provides a salt-resistant and anti-swelling slippery water. The slippery water system has a simple formula. A single drag reducing agent (aqueous dispersion of polyacrylamide) has both drag reducing and anti-swelling functions. It is completely dissolved in salt water or return flow liquid with a mineralization of 0 to 300,000 mg / L within 5 to 30 seconds. The drag reduction rate in the laboratory can reach more than 71%, and can reach more than 85% on site.

[0027] The present invention can also achieve real-time viscosity change of the slippery water system by changing the added amount of the drag reducing agent (polyacrylamide aqueous dispersion). A low-viscosity slippery water system with a viscosity of 1mPa·s to 10mPa·s is prepared by adding 0.1% to 1.0%; a medium-viscosity slippery water system with a viscosity of 10mPa·s to 25mPa·s is prepared by adding 1.0% to 2.0%; a high-viscosity slippery water system with a viscosity of 10mPa·s to 25mPa·s is prepared by adding more than 2.0%. The viscosity increases rapidly and can be used as a glue. The slippery water system has good heat and shear resistance at a temperature of 120°C. The laboratory uses salt water with a mineralization of 300,000 mg / L, and the viscosity of the slippery water is basically not reduced compared with that of the clean water. On-site use of high-mineralization backflow fluid and the drag reducing agent of the present invention for continuous mixing, the viscosity becomes real-time after the crack is made and sand is carried into the crack, and the sand addition compliance rate is as high as 97%;

[0028] The present invention solves the problems of rapid on-site liquid preparation and real-time viscosity change required for the slippery water system, and realizes the purpose of saving fresh water resources and protecting the environment by directly preparing the liquid using high-mineralization formation water or return fluid. Moreover, when the addition amount is ≥1.0%, the anti-swelling rate of the slippery water system is greater than or equal to 75%, which meets the on-site anti-swelling requirements and achieves the purpose of simplifying the formula, reducing costs and increasing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The relationship between the apparent viscosity of slippery water of different concentrations prepared with clean water and 300,000 mg / L mineralized brine and the amount added.

[0030] Figure 2 Different concentrations of slippery water prepared with clean water were heated at 120℃ and 170s -1 Results of rheological tests under shear conditions.

[0031] Figure 3 Different concentrations of slippery water prepared with 300,000 mg / L saline solution were heated at 120°C for 170 seconds. -1 Results of rheological tests under shear conditions.

[0032] Figure 4 This is the construction curve of a slickwater with super salt resistance and anti-swelling function in a certain section of a well on a shale gas platform.

[0033] Figure 5 The construction curve of a slickwater with super salt resistance and anti-swelling function in a section of a well on a shale gas platform. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with the embodiments, but the present invention is not limited by these embodiments.

[0035] The three-necked flask and three-necked bottle used in the examples of the present invention are common commercially available products unless otherwise specified.

[0036] In the present invention, methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, acrylamide, polyethylene glycol, VA-044 initiator, ammonium sulfate, ammonium persulfate, and sodium bisulfite are all common commercially available reagents unless otherwise specified.

[0037] Unless otherwise specified, the room temperature in the embodiments of the present invention is 25°C.

[0038] Preparation Example 1

[0039] This preparation example provides a binary mixture containing a cationic copolymer and polyoxyethylene.

[0040] In a three-necked flask, 60 g of an aqueous solution of methacryloyloxyethyl trimethyl ammonium chloride with a mass concentration of 80%, 30 g of an aqueous solution of acryloyloxyethyl trimethyl ammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 30 g of polyethylene glycol (PEG20000, molecular weight 20000 Da), 0.10 g of VA-044 initiator and 160 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature. 2900 g of water was added to dilute the mixture into an aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene with a mass concentration of 5%, i.e., stabilizer A1.

[0041] This preparation example further provides an aqueous dispersion of polyacrylamide.

[0042] At room temperature, 36 g of acrylamide, 5.4 g of an aqueous solution of 80% methacryloyloxyethyltrimethylammonium chloride, 270 g of the above-mentioned stabilizer A1 (an aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene with a mass concentration of 5%) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. The mixture was then degassed and deoxygenated and filled with nitrogen. The temperature was raised to 45° C., 1 mL of a degassed and deoxygenated VA-044 aqueous solution (the concentration of the VA-044 aqueous solution was 40 mg / mL) was added, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B1.

[0043] Preparation Example 2

[0044] This preparation example provides a binary mixture containing a cationic copolymer and polyoxyethylene.

[0045] In a three-necked flask, 60 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 30 g of an aqueous solution of acryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 30 g of polyethylene glycol (PEG20000, molecular weight 20000 Da), 0.10 g of VA-044 initiator and 160 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature, and 2900 g of water was added to dilute it into an aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene with a mass concentration of 5%, i.e., stabilizer A1.

[0046] This preparation example further provides an aqueous dispersion of polyacrylamide.

[0047] At room temperature, 36 g of acrylamide, 5.4 g of an aqueous solution of methacryloyloxyethyl trimethyl ammonium chloride with a mass concentration of 80%, the above-mentioned 270 g of stabilizer A1 (a 5% aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene with a mass concentration) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. Then, nitrogen was charged after degassing and deoxygenation, and the temperature was raised to 30° C., and 0.60 mL of a degassed and deoxygenated aqueous solution of ammonium persulfate (the concentration of the aqueous solution of ammonium persulfate was 40 mg / mL) and 0.40 mL of an aqueous solution of sodium bisulfite (the concentration of the aqueous solution of sodium bisulfite was 40 mg / mL) were added respectively, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B2.

[0048] Preparation Example 3

[0049] This preparation example provides a binary mixture containing a cationic copolymer and polyoxyethylene.

[0050] In a three-necked flask, 90 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 100 g of polyethylene glycol (PEG20000, molecular weight 20000 Da), 0.10 g of VA-044 initiator and 260 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature, and 4130 g of water was added to dilute it to a mass concentration of 5% aqueous solution containing a binary mixture of cationic copolymer and polyethylene oxide, i.e., stabilizer A2.

[0051] This preparation example further provides an aqueous dispersion of polyacrylamide.

[0052] At room temperature, 36 g of acrylamide, 5.4 g of an aqueous solution of 80% methacryloyloxyethyltrimethylammonium chloride, 270 g of the stabilizer A2 (a 5% aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. The mixture was then degassed and deoxygenated and filled with nitrogen. The temperature was raised to 45° C., 1 mL of a degassed and deoxygenated VA-044 aqueous solution (the concentration of the VA-044 aqueous solution was 40 mg / mL) was added, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B3.

[0053] Preparation Example 4

[0054] This preparation example provides a binary mixture containing a cationic copolymer and polyoxyethylene.

[0055] In a three-necked flask, 90 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 100 g of polyethylene glycol (PEG20000, molecular weight 20000 Da), 0.10 g of VA-044 initiator and 260 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature, and 4130 g of water was added to dilute it to a mass concentration of 5% aqueous solution containing a binary mixture of cationic copolymer and polyethylene oxide, i.e., stabilizer A2.

[0056] This preparation example further provides an aqueous dispersion of polyacrylamide.

[0057] At room temperature, 36 g of acrylamide, 7.2 g of an aqueous solution of methacryloyloxyethyl trimethyl ammonium chloride with a mass concentration of 80%, the above-mentioned 275 g of stabilizer A2 (a 5% aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene with a mass concentration) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. Then, nitrogen was charged after degassing and deoxygenation, and the temperature was raised to 30° C., and 0.60 mL of a degassed aqueous solution of ammonium persulfate (the concentration of the aqueous solution of ammonium persulfate was 40 mg / mL) and 0.40 mL of an aqueous solution of sodium bisulfite (the concentration of the aqueous solution of sodium bisulfite was 40 mg / mL) were added respectively, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B4.

[0058] Preparation Example 5

[0059] This preparation example provides a binary mixture containing a cationic copolymer and polyoxyethylene.

[0060] In a three-necked flask, 90 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 200 g of polyethylene glycol (PEG20000, molecular weight 20000 Da), 0.10 g of VA-044 initiator and 260 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature, and 6362 g of water was added to dilute it to a mass concentration of 5% aqueous solution containing a binary mixture of cationic copolymer and polyethylene oxide, i.e., stabilizer A3.

[0061] This preparation example further provides an aqueous dispersion of polyacrylamide.

[0062] At room temperature, 36 g of acrylamide, 5.4 g of an aqueous solution of 80% methacryloyloxyethyltrimethylammonium chloride, 270 g of the stabilizer A3 (a 5% aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. The mixture was then degassed and deoxygenated and filled with nitrogen. The temperature was raised to 45° C., 1 mL of a degassed and deoxygenated VA-044 aqueous solution (the concentration of the VA-044 aqueous solution was 40 mg / mL) was added, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B5.

[0063] Preparation Example 6

[0064] This preparation example provides a binary mixture containing a cationic copolymer and polyoxyethylene.

[0065] In a three-necked flask, 90 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 200 g of polyethylene glycol (PEG20000, molecular weight 20000 Da), 0.10 g of VA-044 initiator and 260 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature, and 6362 g of water was added to dilute it to a mass concentration of 5% aqueous solution containing a binary mixture of cationic copolymer and polyethylene oxide, i.e., stabilizer A3.

[0066] This preparation example further provides an aqueous dispersion of polyacrylamide.

[0067] At room temperature, 36 g of acrylamide, 7.2 g of an aqueous solution of methacryloyloxyethyl trimethyl ammonium chloride with a mass concentration of 80%, the above-mentioned 275 g of stabilizer A3 (a 5% aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene with a mass concentration) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. Then, nitrogen was charged after degassing and deoxygenation, and the temperature was raised to 30° C., and 0.60 mL of a degassed aqueous solution of ammonium persulfate (the concentration of the aqueous solution of ammonium persulfate was 40 mg / mL) and 0.40 mL of an aqueous solution of sodium bisulfite (the concentration of the aqueous solution of sodium bisulfite was 40 mg / mL) were added respectively, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B6.

[0068] Comparative Preparation Example 1

[0069] This comparative preparation example provides a cationic copolymer.

[0070] The method described in Preparation Example 2 was followed, except that PEG20000 was not added to the raw materials; the details are as follows:

[0071] In a three-necked flask, 90 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 0.10 g of VA-044 initiator and 160 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature, and 2330 g of water was added to dilute it to an aqueous solution of a cationic copolymer with a mass concentration of 5%, i.e., stabilizer A4.

[0072] This comparative preparation example further provides an aqueous dispersion of polyacrylamide.

[0073] At room temperature, 36 g of acrylamide, 5.4 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 270 g of the above-mentioned stabilizer A4 (an aqueous solution of a cationic copolymer with a mass concentration of 5%) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. Then, nitrogen was introduced after degassing and deoxygenation, the temperature was raised to 45°C, 1 mL of a degassed and deoxygenated VA-044 aqueous solution (the concentration of the VA-044 aqueous solution was 40 mg / mL) was added, the reaction was continued for 6 hours, the heating source was removed, the reaction was stopped, and a polyacrylamide aqueous dispersion B7 was obtained.

[0074] Comparative Preparation Example 2

[0075] This comparative preparation example provides a cationic copolymer.

[0076] The method described in Preparation Example 2 was followed, except that PEG20000 was not added to the raw materials; the details are as follows:

[0077] In a three-necked flask, 90 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 0.10 g of VA-044 initiator and 160 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at 45° C. for 7 hours, and then cooled to room temperature, and 2330 g of water was added to dilute it to a cationic copolymer aqueous solution with a mass concentration of 5%, i.e., stabilizer A4.

[0078] This comparative preparation example further provides an aqueous dispersion of polyacrylamide.

[0079] At room temperature, 36 g of acrylamide, 7.2 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, the above-mentioned 280 g of stabilizer A4 (aqueous solution of a cationic copolymer with a mass concentration of 5%) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. Then, nitrogen was charged after degassing and deoxygenation, and the temperature was raised to 30° C., and 0.60 mL of a degassed and deoxygenated aqueous solution of ammonium persulfate (the concentration of the aqueous solution of ammonium persulfate was 40 mg / mL) and 0.40 mL of an aqueous solution of sodium bisulfite (the concentration of the aqueous solution of sodium bisulfite was 40 mg / mL) were added respectively, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B8.

[0080] Comparative Preparation Example 3

[0081] This comparative preparation example uses a polyoxyethylene (PEG20000) aqueous solution with a mass concentration of 5% as stabilizer A5.

[0082] This comparative preparation example further provides an aqueous dispersion of polyacrylamide.

[0083] At room temperature, 36 g of acrylamide, 5.4 g of an aqueous solution of 80% methacryloyloxyethyltrimethylammonium chloride, 270 g of the above-mentioned stabilizer A5 (aqueous solution of 5% polyoxyethylene) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. The mixture was then degassed and deoxygenated and filled with nitrogen. The temperature was raised to 45° C., 1 mL of a degassed and deoxygenated VA-044 aqueous solution (the concentration of the VA-044 aqueous solution was 40 mg / mL) was added, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B9.

[0084] Test (I) Stabilizer parameters

[0085] The basic parameters of stabilizers A1-A3 prepared in Preparation Examples 1-6 of the present invention are shown in Table 1.

[0086] Among them, the binary mixture containing cationic copolymer and polyoxyethylene prepared and used in Preparation Examples 1-6, namely stabilizers A1, A2 and A3, have different weight ratios of cationic copolymer to polyoxyethylene. The ratio in A1 is 4.4 / 1 ((mass of cationic monomer II in the raw material + mass of acrylamide) / mass of PEG20000), that is, the cationic copolymer is the main component; in A2, the content of polyoxyethylene is increased, the ratio is 1.3 / 1; in A3, the content of polyoxyethylene is further increased, the ratio is 0.66 / 1, that is, PEG20000 is the main component;

[0087] Comparative Preparation Examples 1-3 prepared and used a single cationic copolymer aqueous solution or a PEG20000 aqueous solution as a stabilizer.

[0088] In Table 1, the appearance, solid content, and viscosity of stabilizers A1-A3 were tested with reference to GB / T 11175-2002;

[0089] The viscosity test instrument is Brookfield viscometer DV1, and the viscosity determination method is: direct testing at a temperature of 25°C.

[0090] Table 1 Comparison of basic parameters of the stabilizers prepared in Preparation Examples 1-6 and the stabilizers described in Comparative Preparation Examples 1-2

[0091]

[0092] In Table 1, PEG content (taking Example 1 as an example): 30g / (60g+30g+60g+30g+160g+2900g)×100%=0.92%.

[0093] The results in Table 1 show that the stabilizers A1, A2 and A3 prepared in Preparation Examples 1-6 have slightly lower viscosities than the cationic copolymer stabilizer A4 prepared in Comparative Preparation Example 1-2 due to the presence of nonionic polymer PEG. The viscosities of the stabilizers A1, A2 and A3 prepared in Preparation Examples 1-6 decrease as the content of PEG20000 increases.

[0094] Test (II) Parameters of polyacrylamide aqueous dispersion

[0095] The basic parameters of the aqueous polyacrylamide dispersions prepared in Preparation Examples 1-6 of the present invention and Comparative Preparation Examples 1-3 are shown in Table 2.

[0096] The polymer concentration is measured by diluting a polyacrylamide aqueous dispersion of weight C1 with water to a concentration of 1% of the polyacrylamide aqueous dispersion, placing it in a dialysis bag (molecular weight cutoff size: 1000 Da) and dialyzing it in water for three days, and then freeze-drying the sample to obtain a dry sample weight C2, and the polymer concentration is the percentage of the ratio of C2 to CI;

[0097] Among them, the apparent viscosity is the viscosity of the aqueous dispersion of polyacrylamide prepared in Preparation Examples 1-6 and Comparative Preparation Examples 1-3 directly tested without dilution with water; the viscosity of the polymer solution with a mass concentration of 1% refers to the viscosity of the solution when the aqueous dispersion of polyacrylamide is diluted with water to a mass concentration of polyacrylamide and its copolymer of 1%;

[0098] The stability of the aqueous dispersions of polyacrylamide prepared in Preparation Examples 1-6 of the present invention and Comparative Preparation Examples 1-3 at room temperature is visually observed. The dispersions are stable if they are not stratified, and unstable if they are stratified.

[0099] Among them, freeze-thaw stability: take 50mL of polyacrylamide dispersion and place it in a low-temperature box with a temperature of -5±2℃, take it out after 18 hours, and place it at a temperature of 23±2℃ for 6 hours. Repeat the operation to observe whether there is precipitation.

[0100] Table 2 Parameters of the aqueous dispersion of polyacrylamide described in Preparation Examples 1-6 of the present invention and Comparative Preparation Examples 1-3

[0101]

[0102]

[0103] The results in Table 2 show that the polyacrylamide aqueous dispersions prepared in Preparation Examples 1-6 have suitable apparent viscosity and relatively high viscosity of 1% polymer solution, and the stability is more than 6 months, even up to 1 year; while the viscosity of 1% polymer solution of the polyacrylamide aqueous dispersion prepared in Comparative Example 1-3 is significantly lower, and the stability is less than 1 month; this shows that the present invention is an effective method for preparing highly stable and highly viscous polyacrylamide aqueous dispersions by using cationic copolymers and polyoxyethylene binary as stabilizers for dispersion polymerization.

[0104] Example 1

[0105] This embodiment provides a salt-resistant and anti-swelling slippery water.

[0106] Taking the total mass of the salt-resistant and anti-swelling slippery water as 100%, the mass percentage of the drag reducing agent (the aqueous dispersion of polyacrylamide prepared in Preparation Example 2) is 1.0%, and the remainder is water.

[0107] Example 2

[0108] This embodiment provides a salt-resistant and anti-swelling slippery water.

[0109] Taking the total mass of the salt-resistant and anti-swelling slippery water as 100%, the mass percentage of the drag reducing agent (the aqueous dispersion of polyacrylamide prepared in Preparation Example 2) is 2.0%, and the remainder is water.

[0110] Example 3

[0111] This embodiment provides a salt-resistant and anti-swelling slippery water.

[0112] Taking the total mass of the salt-resistant and anti-swelling slippery water as 100%, the mass percentage of the drag reducing agent (the aqueous dispersion of polyacrylamide prepared in Preparation Example 2) is 3.0%, and the remainder is water.

[0113] Example 4

[0114] This embodiment provides a salt-resistant and anti-swelling slippery water.

[0115] Taking the total mass of the salt-resistant and anti-swelling slippery water as 100%, the mass percentage of the drag reducing agent (the aqueous dispersion of polyacrylamide prepared in Preparation Example 2) is 4.0%, and the remainder is water.

[0116] Example 5

[0117] This embodiment provides a salt-resistant and anti-swelling slippery water.

[0118] Taking the total mass of the salt-resistant and anti-swelling slippery water as 100%, the mass percentage of the drag reducing agent (the aqueous dispersion of polyacrylamide prepared in Preparation Example 2) is 5.0%, and the remainder is water.

[0119] Example 6

[0120] This embodiment provides a salt-resistant and anti-swelling slippery water.

[0121] Taking the total mass of the salt-resistant and anti-swelling slippery water as 100%, the mass percentage of the drag reducing agent (the aqueous dispersion of polyacrylamide prepared in Preparation Example 2) is 0.1%, and the remainder is water.

[0122] Comparative Example 1

[0123] This comparative example provides a kind of slippery water.

[0124] Taking the total mass of salt-resistant and anti-swelling slippery water as 100%, the mass percentage of conventional drag reducer (integrated emulsion drag reducer SFFRE-3 independently developed by Sinopec Petroleum Engineering Technology Research Institute) is 1.0%, and the balance is water.

[0125] In order to further illustrate the advancement of the salt-resistant and anti-swelling slippery water prepared in Examples 1-6 of the present invention, the performance of the salt-resistant and anti-swelling slippery water prepared in Examples 1-6 and the slippery water prepared in Comparative Example 1 was tested, and the results are summarized in Table 3; wherein, the anti-swelling rate evaluation method standard SY / T 5971-2016 Performance evaluation method of clay stabilizer for oil and gas field fracturing acidification and water injection was implemented;

[0126] Table 3

[0127]

[0128]

[0129] In the above Table 3, the anti-swelling rate (B) is calculated according to the following formula:

[0130] Wherein, B is the anti-swelling rate, expressed as a percentage; V0 is the volume of bentonite after expansion in kerosene, in milliliters (mL); V1 is the volume of bentonite after expansion in slippery water, in milliliters (mL); V2 is the volume of bentonite after expansion in distilled water, in milliliters (mL).

[0131] Application Example 1:

[0132] In this application example, clean water and 300,000 mg / L saline with a mineralization degree were used to prepare temperature-resistant and anti-swelling slippery water containing different concentrations (0.1% to 5.0%) of drag reducing agent (polyacrylamide aqueous dispersion prepared in Preparation Example 2), without adding anti-swelling agent. The viscosity change was tested as shown in FIG. Figure 1 ;

[0133] The test results are as follows: when the amount of the drag reducing agent (the aqueous dispersion of polyacrylamide prepared in Preparation Example 2) is within the range of 0.1% to 1.0%, it belongs to a low-viscosity slippery water system, and can be used as a slippery water system in large-volume dense cutting and fracture-making working fluids in shale gas reservoirs and tight gas reservoirs; when the amount of the drag reducing agent (the aqueous dispersion of polyacrylamide prepared in Preparation Example 2) is increased to the range of 1.0% to 2.0%, it belongs to a medium-viscosity slippery water system, which is suitable for sand-carrying operations; when the amount of the drag reducing agent (the aqueous dispersion of polyacrylamide prepared in Preparation Example 2) is increased to more than 2.0%, the apparent viscosity of the slippery water system increases significantly, and it belongs to a high-viscosity slippery water system, which can be used as a glue for sand addition;

[0134] Depend on Figure 1 It can also be seen that the temperature-resistant and anti-swelling slippery water prepared with 300,000 mg / L mineralization brine still maintains viscosity compared to the temperature-resistant and anti-swelling slippery water prepared with clean water, indicating that it has good salt resistance and meets the needs of on-site return water preparation.

[0135] In this application example, clean water and salt water with a mineralization degree of 300,000 mg / L are used to prepare heat-resistant and anti-swelling slippery water containing different concentrations (0.1% to 5.0%) of drag reducing agent (aqueous dispersion of polyacrylamide prepared in Preparation Example 2). The heat-resistant and shear-resistant properties of the heat-resistant and anti-swelling slippery water system are tested using a high-temperature and high-pressure rotational rheometer. The test temperature is maintained at 120°C and the shear rate is 170s. -1 , shear 2h; test results see Figure 2 , Figure 3 ;

[0136] Figure 2 , Figure 3 It shows that the temperature-resistant and anti-swelling slippery water system, whether prepared with clean water or salt water, can withstand 120℃ and 170s -1 After shearing for 2 hours under the conditions, the viscosity is maintained above 50mPa.s, demonstrating that the temperature-resistant and anti-swelling slippery water can maintain good sand-carrying properties in high-temperature reservoirs at 120℃.

[0137] Application Example 2:

[0138] This application example uses the salt-resistant and anti-swelling slippery water prepared by the present invention to carry out fracturing construction. The construction curve is shown in FIG. Figure 4 The specific operation is as follows: In this application example, the salt-resistant and anti-swelling slippery water prepared by the present invention is used in a well of a shale gas platform in Sichuan and Chongqing to mix and transform into a viscous slippery water system, and the water used for liquid preparation is the return fluid with a total mineralization of 38475 mg / L.

[0139] In this application example, during the fracturing construction of a certain section of the well, hydrochloric acid was used for acidification from the beginning of the fracturing construction to 50 minutes. From 55 minutes on, high-viscosity slippery water was used for fracturing construction, and the amount of drag reducing agent (polyacrylamide aqueous dispersion prepared in Preparation Example 2) was 5%. Until 75 minutes, 148m of glue was used.3 ; Then use low viscosity slippery water, drag reducing agent (polyacrylamide aqueous dispersion prepared in Preparation Example 2) added in an amount of 0.6%, to 165 minutes, low viscosity slippery water dosage 1352m 3 Then the drag reducing agent (polyacrylamide aqueous dispersion prepared in Preparation Example 2) was added to 2.0% to form medium-viscous slippery water until 275 minutes, and the amount of medium-viscous slippery water was 1320m 3 , carrying a total of 37.9m of 80 / 120 mesh proppant 3 .

[0140] The compliance rate of sand addition in this section reached 97.4%, and the on-site drag reduction rate in this section reached 83%. The slippery water system showed excellent results in construction applications.

[0141] Application Example 3:

[0142] This application example uses the salt-resistant and anti-swelling slippery water prepared by the present invention to carry out fracturing construction. The construction curve is shown in FIG. Figure 5 The specific operation is as follows: In this application example, the salt-resistant and anti-swelling slippery water prepared by the present invention is used in a well of a certain shale gas platform to mix and transform into a viscous slippery water system, and the water used for liquid preparation is the return fluid with a total mineralization of 36984 mg / L.

[0143] In this application example, during the fracturing construction of a certain section of the well, hydrochloric acid acidification was used from the beginning of the fracturing construction to 30 minutes. From 30 minutes on, the fracturing construction used low-viscosity slippery water, and the drag reducing agent (polyacrylamide aqueous dispersion prepared in Preparation Example 2) was added in an amount of 0.6%. Until 210 minutes, the amount of low-viscosity slippery water was 2225m 3 ; Then the amount of drag reducing agent (polyacrylamide aqueous dispersion prepared in Preparation Example 2) in slippery water was increased to 2.0%, forming medium viscous slippery water until 270 minutes, the amount of medium viscous slippery water was 640m 3 , carrying a total of 56m of 80 / 120 mesh proppant 3 .

[0144] The on-site drag reduction rate of this section reached 80%, and the sand addition compliance rate was 97.1%. The slippery water system showed excellent results in construction applications.

[0145] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A salt-resistant and anti-swelling slippery water, comprising a drag reducing agent, characterized in that: The drag reducing agent is a polyacrylamide aqueous dispersion; the synthesis method of the polyacrylamide aqueous dispersion comprises reacting a reaction system of acrylamide I, a cationic monomer I, an inorganic salt, a stabilizer and an initiator I to obtain the polyacrylamide aqueous dispersion; wherein the stabilizer is a binary mixture of a cationic copolymer containing a polyacrylamide segment and polyethylene oxide.

2. The salt-resistant and anti-swelling slippery water according to claim 1, characterized in that: Taking the total mass of the salt-resistant and anti-swelling slippery water as 100%, the mass percentage of the drag reducing agent is 0.1% to 6.7%, and the remainder is water.

3. The salt-resistant and anti-swelling slippery water according to claim 1 or 2, characterized in that: The mass ratio of the acrylamide I, the cationic monomer I, the inorganic salt and the stabilizer is 36: (4.32-5.76); 10：(270～275)； And / or, the added amount of the initiator I is 0.1% to 0.5% of the mass of the acrylamide I.

4. The salt-resistant and anti-swelling slippery water according to any one of claims 1 to 3, characterized in that: The cationic monomer I is selected from one or more of acryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl dimethyl benzyl ammonium chloride, and 2-acrylamido-2-methylpropyl trimethyl ammonium chloride; And / or, the inorganic salt is selected from ammonium salt; preferably, the ammonium salt is selected from at least one of ammonium sulfate and ammonium persulfate; And / or, the initiator I is selected from aqueous initiator I and / or thermal initiator I; preferably, the aqueous initiator I is selected from at least one of V-50 and VA-044; the thermal initiator I is selected from at least two of ammonium persulfate, sodium bisulfite, and potassium persulfate.

5. The salt-resistant and anti-swelling slippery water according to any one of claims 1 to 4, characterized in that: The conditions of the reaction I include: a temperature of 25° C. to 45° C. and a time of 1 hour to 6 hours.

6. The salt-resistant and anti-swelling slippery water according to any one of claims 1 to 5, characterized in that: The preparation of the stabilizer comprises: mixing cationic monomer II, acrylamide II and polyethylene oxide in water under the conditions of initiator II and inactive atmosphere, and carrying out reaction II to obtain the stabilizer.

7. The salt-resistant and anti-swelling slippery water according to claim 6, characterized in that: The mass ratio of the cationic monomer II, acrylamide II, polyethylene oxide and water is 72:60:(30-100):(160-260); And / or, the added amount of the initiator II is 0.1% to 0.5% of the mass of the cationic monomer II.

8. The salt-resistant and anti-swelling slippery water according to claim 6 or 7, characterized in that: The cationic monomer II is selected from one or more of acryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl dimethyl benzyl ammonium chloride, and 2-acrylamido-2-methylpropyl trimethyl ammonium chloride; And / or, the polyoxyethylene is selected from polyoxyethylene with or without end-capping; preferably, the molecular weight of the polyoxyethylene is 2000Da to 200000Da; further preferably, the polyoxyethylene with end-capping includes single-end-capped polyoxyethylene and double-end-capped polyoxyethylene; further preferably, the single-end-capped polyoxyethylene is selected from polyoxyethylene monomethyl ether; the double-end-capped polyoxyethylene is selected from polyoxyethylene dimethyl ether; And / or, the initiator II is selected from aqueous initiator II and / or thermal initiator II; preferably, the aqueous initiator II is selected from at least one of V-50 and VA-044; the thermal initiator II is selected from at least two of ammonium persulfate, sodium bisulfite and potassium persulfate; And / or, the inactive atmosphere is selected from at least one of nitrogen and argon.

9. The salt-resistant and anti-swelling slippery water according to any one of claims 6 to 8, characterized in that: The conditions of the reaction II include: a temperature of 30°C to 80°C, and a reaction time of 5 hours to 10 hours; And / or, the reaction II further comprises dilution.

10. Use of the salt-resistant and anti-swelling slippery water according to any one of claims 1 to 9 in hydraulic fracturing of oil and gas fields.

Images