Phase permeability improvers, fracturing fluid systems containing same, and respective methods of making and use

Abstract

The application belongs to the technical field of oil and gas field development, and provides a phase permeability improver, a fracturing fluid system containing the same, and respective preparation methods and applications. The phase permeability improver is obtained by copolymerization and hydrolysis of acrylamide AM, a functional monomer 2-acrylamido-2-methylpropanesulfonic acid AMPS, and cationic hydrophobic monomers A and B; the cationic hydrophobic monomer A is at least one of tetradecyl dimethyl allyl ammonium chloride, hexadecyl dimethyl allyl ammonium chloride, and octadecyl dimethyl allyl ammonium chloride; the cationic hydrophobic monomer B is at least one of methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, and acryloyloxyethyldimethyl benzyl ammonium chloride; the phase permeability improver and the fracturing fluid system containing the same can significantly reduce the water phase permeability after fracturing operation, while having a smaller influence on the oil phase permeability, and have a significant effect of stabilizing oil and controlling water, and can significantly improve the stable production effect of fracturing operation in a low-permeability oil reservoir.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil and gas field development, and relates to a relative permeability modifier, a fracturing fluid system containing the same, and respective preparation methods and applications. BACKGROUND

[0002] Low-permeability oilfields have large seepage resistance and low oil well development efficiency. Hydraulic fracturing is usually used to improve the development efficiency. However, for low-permeability oil reservoirs with high fracture development degree and complex oil-water relationship, the traditional hydraulic fracturing development method has poor effect, the water content rises rapidly after fracturing operation, and the oil production decreases, resulting in a sharp increase in the cost of crude oil dehydration and water treatment on the ground, and affecting the normal production of the oilfield. It is necessary to develop stable oil and water control fracturing technology to further improve the fracturing development efficiency of low-permeability oil reservoirs. In the research of stable oil and water control technology and stable oil and water control fracturing technology in low-permeability oil reservoirs, the conventional chemical water plugging technology not only plugs the formation water channel, but also plugs the oil flow channel, resulting in a significant decrease in oil production. The relative permeability modifier (relative permeability modifier) has the characteristics of water control without oil plugging, and has a greater reduction in water permeability than in oil permeability, so it has a wide application prospect. Therefore, the fracturing fluid system based on the relative permeability modifier is also a research hotspot and main direction.

[0003] The relative permeability modifier fracturing fluid system is composed of a relative permeability modifier and a traditional fracturing fluid. The core component of the system is the relative permeability modifier. The structure and performance of the relative permeability modifier and its compatibility with the fracturing fluid system directly affect the performance and effect of the relative permeability modifier fracturing fluid system.

[0004] Chinese patent application CN1614193A discloses a fracturing method for improving recovery by using a relative permeability modifier. The relative permeability modifier used in the method includes polyacrylamide and a crosslinking agent. The molecular weight of the polyacrylamide is 1-40 million, and the crosslinking agent is one or more of organic chromium, inorganic chromium, organic aluminum, and inorganic aluminum. Chinese patent CN113666686B discloses a preparation method of a selective water plugging system composed of cement, a modifier, a pore-forming agent, an additive, a solubilizing agent, etc. The system has strong oil stabilization and water control characteristics, can effectively reduce the water permeability, and has little effect on the oil permeability. However, the crosslinking system and cement used in the above oil stabilization and water control technology have certain damage to low-permeability oil reservoirs.

[0005] CN111574992B discloses a kind of nanometer phase permeability modifier for acidizing fracturing and its preparation method, polyacrylamide molecular chain is grafted on the surface of nanometer silicon dioxide particles by silane coupling agent, then the cationization of grafted polyacrylamide molecular chain is prepared, it has good acid resistance, water phase permeability reduction amplitude is greater than 60%; In the master's degree thesis of China University of Petroleum in 2020, Luoshuai studied a kind of nanometer phase permeability modifier water control fracturing fluid for low permeability carbonate reservoir in "carbonate reservoir phase permeability improvement fracturing fluid preparation technology application technology limit research", first surface modification is carried out to silicon dioxide by coupling grafting method, and on this basis, cationized KH570-SiO2-PAM phase permeability modifier is prepared, particle size is about 150nm, can reduce water phase permeability by more than 70%, further introduce surfactant and temperature stabilizer and form phase permeability improvement fracturing fluid system, which has obvious water control effect, wherein water phase permeability is reduced by about 70%, and oil phase permeability is reduced by about 13%; But the nanometer phase permeability modifier prepared by this method has complex process, high product cost, and is not conducive to industrialization and application.

[0006] CN102093880B discloses an oil well water control agent and its preparation method, which is a AM / AMPS / non-ionic hydrophobic monomer terpolymer prepared by inverse emulsion polymerization, and the water phase permeability reduction rate is 72.80-90.53% and the oil phase permeability reduction rate is 7.71-17.76% when the injection concentration is 0.12%; Gong Jun et al. studied a phase permeability improvement drag reduction agent emulsion in "preparation and field application of phase permeability improvement drag reduction agent emulsion", fault block oil and gas field, 2020, 27(04), which is polymerized from acrylamide, 2-acrylamido-2-methylpropane sulfonic acid and N,N-dimethyl acrylamide. The drag reduction rate of this system can reach 72.5%, and the water phase permeability can be reduced by more than 80%, and the oil phase permeability reduction rate is about 15%. The above-mentioned phase permeability improvement agent is synthesized by non-ionic monomer, and the adsorption capacity on core is weak. When used as fracturing fluid system, the water control performance and long-term effect of the broken gel are not studied, which is not conducive to understanding the effective period of fracturing water control.

[0007] In view of the above-mentioned shortcomings of phase permeability improvement agent and phase permeability improvement agent fracturing fluid system, a fracturing fluid system with strong adsorption capacity on rock pore surface, simple preparation process, low use concentration and stable oil control water function before and after gel breaking is needed. SUMMARY

[0008] The present application is directed to the low permeability reservoir with high fracture development degree and complex oil-water relationship, and the problems of difficult water control, rapid water cut increase after fracturing and the like are existed in the traditional fracturing operation, and a phase permeability improver, a fracturing fluid system containing the same and respective preparation methods and applications are provided, the fracturing fluid system can obviously reduce the permeability of water phase after fracturing operation, and has little influence on the oil phase permeability, and the effect of stabilizing oil and controlling water is obvious, and the long-acting property is good, and the stable production effect of the low permeability reservoir fracturing operation can be obviously improved.

[0009] One of the technical solutions of the present application is:

[0010] A phase permeability improver is provided, which is obtained by hydrolysis of acrylamide AM, functional monomer 2-acrylamido-2-methylpropanesulfonic acid AMPS, cationic hydrophobic monomer A and cationic hydrophobic monomer B through copolymerization; based on acrylamide AM, the dosages of the raw materials are as follows: functional monomer 2-acrylamido-2-methylpropanesulfonic acid AMPS 10-20 wt.%, cationic hydrophobic monomer A 5-10 wt.%, and cationic hydrophobic monomer B 1-3 wt.%.

[0011] The cationic hydrophobic monomer A is at least one of tetradecyl dimethyl allyl ammonium chloride, hexadecyl dimethyl allyl ammonium chloride and octadecyl dimethyl allyl ammonium chloride; preferably octadecyl dimethyl allyl ammonium chloride.

[0012] The cationic hydrophobic monomer B is at least one of methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride and acryloyloxyethyl dimethyl benzyl ammonium chloride; preferably methacryloyloxyethyl trimethyl ammonium chloride.

[0013] The particle size of the phase permeability improver is 100-120 mesh, and the viscosity average molecular weight is 0.5-5 million.

[0014] The mechanism of the phase permeability improver is as follows:

[0015] ① The cationic hydrophobic monomers A and B make the phase permeability improver have strong adsorption capacity on the rock surface, which is a necessary condition for successful water control;

[0016] The cationic hydrophobic monomer A used is a high-efficiency associating monomer, and the prepared phase permeability improver forms a supramolecular aggregate mainly by intermolecular association after the macromolecular chains are aggregated by hydrophobic association when the concentration of the phase permeability improver is higher than a critical concentration CAC, the solution network structure is more compact, the water binding capacity is enhanced, the water control performance of the phase permeability improver is further increased, meanwhile, the intermolecular association enhances the temperature resistance and salt resistance of the phase permeability improver, which is beneficial to reducing the use concentration; due to the presence of the cationic hydrophobic monomer, the supramolecular aggregate mainly by intermolecular association can still be formed after the solution is broken, so that the water control performance of the phase permeability improver after being broken is fully ensured.

[0017] The introduction of the temperature-resistant and salt-resistant functional monomer 2-acrylamido-2-methylpropanesulfonic acid AMPS can promote the association of the cationic hydrophobic monomer A in the phase permeability improver, so that the supramolecular aggregate structure of the solution is stronger, and the introduction of the 2-acrylamido-2-methylpropanesulfonic acid AMPS enables the polymer to have good water solubility and temperature resistance and salt resistance, so that the polymer can be dissolved in less than 1.5 min at room temperature and can be prepared by using oilfield sewage.

[0018] In general, the unique molecular structure of the phase permeability improver makes it have strong adsorption capacity on the pore surface of rocks, low use concentration and excellent oil stabilizing and water control functions before and after being broken.

[0019] The second technical scheme of the present application is:

[0020] The preparation method of the phase permeability improver is provided, and specifically includes the following steps:

[0021] (1) acrylamide AM and the functional monomer 2-acrylamido-2-methylpropanesulfonic acid AMPS are added to deionized water, and the pH value of the solution is adjusted to 7.0;

[0022] (2) the cationic hydrophobic monomer A and the cationic hydrophobic monomer B are further added and uniformly stirred;

[0023] (3) the temperature is increased, the initiator is added, and adiabatic polymerization is performed;

[0024] (4) after the end, the hydrolysis agent is added to perform hydrolysis reaction;

[0025] (5) drying, and the phase permeability improver is obtained.

[0026] The initiator includes an oxidizing agent and a reducing agent.

[0027] The oxidizing agent is at least one of potassium persulfate, ammonium persulfate, sodium persulfate and dibenzoyl peroxide; and the ammonium persulfate is preferred.

[0028] The reducing agent is at least one of sodium formaldehyde sulfoxylate, sodium sulfite, sodium bisulfite and urea, preferably sodium bisulfite.

[0029] That is, the initiator is preferably an ammonium sulfate-sodium bisulfite initiator system.

[0030] Further, the oxidizing agent is used in an amount of 0.1-0.4wt.% of acrylamide AM, preferably 0.25wt.%.

[0031] Further, the reducing agent is used in an amount of 0.2-0.6wt.% of acrylamide AM, preferably 0.4wt.%.

[0032] Further, the hydrolysis agent is at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate, preferably sodium hydroxide.

[0033] Further, the hydrolysis agent is used in an amount of 15-35% of the theoretical hydrolysis degree.

[0034] Further, the polymerization reaction temperature is 30-50℃, and the reaction time is 4-12h.

[0035] Preferably, the polymerization reaction temperature is 35-40℃, and the reaction time is 8-12h.

[0036] Further, the hydrolysis reaction temperature is 80-120℃, and the hydrolysis reaction time is 1-4h.

[0037] Preferably, the hydrolysis reaction temperature is 90-100℃, and the hydrolysis reaction time is 2-3h.

[0038] Further, the drying temperature is 80-140℃, and the drying time is 0.5-3h.

[0039] Preferably, the drying temperature is 100-110℃, and the drying time is 1-2h.

[0040] In the technical solution of the present application, the gelatinous product obtained after adiabatic polymerization is cut into particles with a particle size of 2-4mm before the hydrolysis reaction, so that the hydrolysis reaction is more complete and efficient; in addition, the dried product after hydrolysis needs to be crushed and sieved to obtain the phase permeability improver.

[0041] The third technical solution of the present application is:

[0042] The present application provides a fracturing fluid system, which comprises the phase permeability improver or the phase permeability improver prepared by the preparation method.

[0043] The fracturing fluid composition, by mass percentage, includes: 0.4-1.2% thickener, 0.1-0.5% clay stabilizer, 0.1-0.5% drainage aid, 0.1-0.5% demulsifier, 0.05-0.20% breaker, the above-mentioned interpenetration improver, or the interpenetration improver prepared by the above preparation method.

[0044] The thickener is water-soluble polyacrylamide and its derivatives.

[0045] Furthermore, the thickener is an emulsion or a 100-120 mesh powder.

[0046] The clay stabilizer is at least one of potassium chloride, ammonium chloride, and quaternary ammonium salt organic clay stabilizers.

[0047] The discharge aid is a fluorocarbon surfactant, including perfluorodecyl ether fluorocarbon surfactants and / or perfluorodecyl polyoxyethylene ether fluorocarbon surfactants.

[0048] The demulsifier is a polyether compound, including at least one of polyoxyethylene polyoxypropylene ether demulsifier, polyoxyethylene polyoxypropylene ether demulsifier, and polyoxyethylene polyoxypropylene ether demulsifier.

[0049] The decapsulating agent is at least one of ammonium persulfate, sodium persulfate, potassium persulfate, and capsule decapsulating agent.

[0050] The fourth technical solution of the present invention is:

[0051] The preparation method of the above-mentioned fracturing fluid system is provided. The specific operation is as follows: add thickener, phase permeability improver, clay stabilizer, drainage aid, demulsifier and breaker to water in sequence, and stir to obtain the solution.

[0052] Furthermore, the stirring process is carried out at a speed of 400-800 rad / min and the stirring time is 1-3 min.

[0053] The fifth technical solution of the present invention is:

[0054] The application of the above-mentioned phase permeability improver, the phase permeability improver prepared by the above-mentioned preparation method, the above-mentioned fracturing fluid system, or the fracturing fluid system prepared by the above-mentioned preparation method in hydraulic fracturing production in oil and gas fields is provided.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1. The relative permeability improver prepared in this invention possesses excellent performance due to the unique molecular structure: it has strong adsorption capacity on the surface of rock pores and requires low concentration; its water phase permeability is reduced by more than 90%, and its oil phase permeability is reduced by less than 10%, with a reduction ratio of 10.24, demonstrating excellent oil stabilization and water control functions; after 100 PV of water flushing, the ratio of the reduction in water phase permeability to oil phase permeability reaches 8.03, exhibiting excellent long-term effectiveness.

[0057] 2. The phase permeation improver of the present invention has excellent oil stabilization and water control functions in fracturing fluid systems before and after gel breaking, as well as in systems containing phase permeation improvers before and after gel breaking.

[0058] 3. The relative permeability improver and its fracturing fluid system prepared by this invention do not damage ultra-low permeability reservoirs. The preparation process is simple and easy to industrialize. The product has good water solubility, low concentration, and good compatibility with conventional fracturing fluid systems.

[0059] 4. This phase permeability improver and its fracturing fluid system can meet the existing fracturing preparation process (online preparation or continuous mixing, etc.) without adding other reagent addition equipment, and has wide adaptability. Detailed Implementation

[0060] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection of the present invention, and those skilled in the art can make various changes and modifications to the invention based on the disclosed content, which should also fall within the scope of protection of the present invention.

[0061] The relevant parameters and technical effects of this invention were tested according to the following standards:

[0062] I. The viscosity-average molecular weight test of the phase displacement improver should refer to section 6.5.3 of SY / T 5862-2020 "Technical Requirements for Polymers for Oil Displacement";

[0063] II. The evaluation method for the oil stabilization and water control effect of the phase penetration improver or its fracturing fluid system is based on section 7.7 of SY / T5107-2016 "Evaluation Method for Performance of Water-based Fracturing Fluids" with adjustments; the specific experimental steps are as follows:

[0064] (1) Simulated brine is injected into the core at a constant flow rate to fully saturate the core;

[0065] (2) Simulated crude oil was injected into the core at a constant flow rate, and the oil phase permeability under bound water saturation was measured. ;

[0066] (3) Inject simulated brine into the core at a constant flow rate to determine the water phase permeability at residual oil saturation ;

[0067] (4) Inject 1 PV of the oil control water agent system into the same core in the opposite direction, and keep the temperature constant in the thermostat for 24 h

[0068] (5) Inject simulated brine into the core at a constant flow rate until the pressure and flow rate are constant, to determine the water phase permeability ;

[0069] (6) Inject simulated crude oil into the core at a constant flow rate until the pressure and flow rate are constant, to determine the oil phase permeability ;

[0070] (7) Calculate the oil phase and water phase permeability reduction rates before and after injecting the oil control water agent system and , and calculate the ratio of the water phase permeability reduction rate to the oil phase permeability reduction rate (denoted as M 0 );

[0071] (8) Inject simulated brine into the core at a constant flow rate multiple times, with a single injection amount of 20 PV

[0072] (9) After the single injection of simulated brine is completed, inject simulated crude oil into the core at a constant flow rate to determine the oil phase permeability at the irreducible water saturation after the cumulative injection of simulated brine in step (8) ( n = 20, 60, 80, 100 );

[0073] (10) Inject simulated brine into the core at a constant flow rate to determine the water phase permeability at the residual oil saturation after the cumulative injection of simulated brine in step (8) ( n = 20, 60, 80, 100 );

[0074] (11) Calculate the oil phase and water phase permeability reduction rates before and after injecting the oil control water agent system and after water flushing n PV ( n = 20, 60, 80, 100 ) and ( n = 20, 60, 80, 100 ) and (n = 20, 60, 80, 100 ), and calculate the ratio of the water phase permeability reduction rate to the oil phase permeability reduction rate after water flushing n PV, denoted as M n ( n = 20, 60, 80, 100 );

[0075] (1) (2) (3)

[0076] (4) (4) (6)

[0077] ( n = 20, 60, 80, 100)

[0078] The ratio of the water phase permeability reduction rate to the oil phase permeability reduction rate M 0 as an oil control water effect evaluation index, M n as a long-acting index; M 0 is larger, the better the oil control water effect is, M n the larger, the better the long-acting is.

[0079] Example 1: Phase permeability modifier A - preparation of AM / octadecyl dimethyl allyl ammonium chloride / methacryloyloxyethyl trimethyl ammonium chloride / AMPS / NaAA copolymer

[0080] (1) Take 739.42 g of deionized water in a 1 L beaker, add 250 g of acrylamide AM, 37.5 g of 2-acrylamido-2-methylpropanesulfonic acid AMPS (15 wt.% of the amount of acrylamide AM), and stir until uniform, then add 7.25 g of sodium hydroxide to adjust the pH to 7.0;

[0081] (2) Add 18.75 g of octadecyl dimethyl allyl ammonium chloride (7.5 wt.% of the amount of acrylamide AM), 5.0 g of methacryloyloxyethyl trimethyl ammonium chloride (2 wt.% of the amount of acrylamide AM), and fully dissolve;

[0082] (3) Raise the polymerization system to 30°C, add 3.13 g of 20% ammonium persulfate solution, and add 5.0 g of 20% sodium bisulfite solution to initiate polymerization, and adiabatic polymerization for 8 h;

[0083] (4) After adiabatic polymerization is complete, remove the colloid and cut it into 2-4 mm particles, and add a hydrolysis agent, sodium hydroxide (2.64 g of sodium hydroxide per 100 g of colloid particles, i.e., the ratio of NaAA is 20%), to hydrolyze at 100°C for 3 h according to a theoretical hydrolysis degree of 20%;

[0084] (5) After hydrolysis is complete, dry the product at 100°C for 1 h, crush and sieve to obtain a phase permeability modifier A of 100-120 mesh, with a molecular weight of 2,255,200.

[0085] Example 2: Preparation of phase permeability modifier A-1 - AM / stearyl dimethyl allyl ammonium chloride / methacryloyloxyethyl trimethyl ammonium chloride / AMPS / NaAA copolymer

[0086] (1) Take 739.42 g of deionized water in a 1 L beaker, add 250 g of acrylamide AM, 50.0 g of 2-acrylamido-2-methylpropanesulfonic acid AMPS (20 wt.% of the amount of acrylamide AM), and stir until uniform, then add 9.66 g of sodium hydroxide to adjust the pH to 7.0;

[0087] (2) Add 25 g of stearyl dimethyl allyl ammonium chloride (10 wt.% of the amount of acrylamide AM), 7.5 g of methacryloyloxyethyl trimethyl ammonium chloride (3 wt.% of the amount of acrylamide AM), and fully dissolve;

[0088] (3) Raise the polymerization system to 30°C, add 3.13 g of 20% ammonium persulfate solution, and add 5.0 g of 20% sodium bisulfite solution to initiate polymerization, and adiabatic polymerize for 8 h;

[0089] (4) After the adiabatic polymerization is complete, remove the gel and cut it into 2-4 mm particles, and add a hydrolysis agent, sodium hydroxide (4.62 g of sodium hydroxide per 100 g of gel particles, i.e., the ratio of NaAA is 35%), to hydrolyze at 100°C for 3 h according to a theoretical hydrolysis degree of 35%;

[0090] (5) After the hydrolysis is complete, dry the product at 100°C for 1 h, crush and sieve to obtain 100-120 mesh phase permeability modifier A-1, with a molecular weight of 1.8094 million.

[0091] Example 3: Preparation of phase permeability modifier A-2 - AM / stearyl dimethyl allyl ammonium chloride / methacryloyloxyethyl trimethyl ammonium chloride / AMPS / NaAA copolymer

[0092] (1) Take 739.42 g of deionized water in a 1 L beaker, add 250 g of acrylamide AM, 25.0 g of 2-acrylamido-2-methylpropanesulfonic acid AMPS (10 wt.% of the amount of acrylamide AM), and stir until uniform, then add 4.83 g of sodium hydroxide to adjust the pH to 7.0;

[0093] (2) Add 12.5 g of stearyl dimethyl allyl ammonium chloride (5 wt.% of the amount of acrylamide AM), 2.5 g of methacryloyloxyethyl trimethyl ammonium chloride (1 wt.% of the amount of acrylamide AM), and fully dissolve;

[0094] (3) The polymerization system is warmed to 30°C, 3.13 g of 20% ammonium persulfate solution is added, 5.0 g of 20% sodium bisulfite solution is added to initiate polymerization, and adiabatic polymerization is carried out for 8 h;

[0095] (4) After the adiabatic polymerization is completed, the gel is taken out and cut into 2-4 mm particles, a hydrolysis agent, sodium hydroxide, is added at a theoretical hydrolysis degree of 15% (1.98 g of sodium hydroxide per 100 g of gel particles, i.e. the proportion of NaAA is 15%), and hydrolysis is carried out at 100°C for 3 h;

[0096] (5) After the hydrolysis is completed, the product is dried at 100°C for 1 h, and after crushing and sieving, phase permeability improving agent A-2 with a particle size of 100-120 mesh and a molecular weight of 3.8785 million is obtained.

[0097] Example 4: Preparation of phase permeability improving agent A-3 - AM / octadecyl dimethyl allyl ammonium chloride / methacryloyloxyethyl trimethyl ammonium chloride / AMPS / NaAA copolymer

[0098] (1) 739.42 g of deionized water is weighed into a 1 L beaker, 250 g of acrylamide AM and 75 g of 2-acrylamido-2-methylpropanesulfonic acid AMPS (30 wt.% of the amount of acrylamide AM) are added after stirring, and 14.49 g of sodium hydroxide is added to adjust the pH value to 7.0;

[0099] (2) 50 g of octadecyl dimethyl allyl ammonium chloride (20 wt.% of the amount of acrylamide AM) and 12.5 g of methacryloyloxyethyl trimethyl ammonium chloride (5 wt.% of the amount of acrylamide AM) are added and dissolved thoroughly;

[0100] (3) The polymerization system is warmed to 30°C, 3.13 g of 20% ammonium persulfate solution is added, 5.0 g of 20% sodium bisulfite solution is added to initiate polymerization, and adiabatic polymerization is carried out for 8 h;

[0101] (4) After the adiabatic polymerization is completed, the gel is taken out and cut into 2-4 mm particles, a hydrolysis agent, sodium hydroxide, is added at a theoretical hydrolysis degree of 50% (6.60 g of sodium hydroxide per 100 g of gel particles, i.e. the proportion of NaAA is 50%), and hydrolysis is carried out at 100°C for 3 h;

[0102] (5) After the hydrolysis is completed, the product is dried at 100°C for 1 h, and after crushing and sieving, phase permeability improving agent A-3 with a particle size of 100-120 mesh and a molecular weight of 0.8682 million is obtained.

[0103] Example 5: Preparation of phase permeability improving agent A-4 - AM / octadecyl dimethyl allyl ammonium chloride / methacryloyloxyethyl trimethyl ammonium chloride / AMPS / NaAA copolymer

[0104] (1) Take 739.42 g of deionized water in a 1 L beaker, add 250 g of acrylamide AM, 12.5 g of 2-acrylamido-2-methylpropanesulfonic acid AMPS (5 wt.% of acrylamide AM), and stir until uniform, then add 2.42 g of sodium hydroxide to adjust the pH to 7.0;

[0105] (2) Add 6.25 g of octadecyldimethylammonium allyl chloride (2.5 wt.% of acrylamide AM), 1.25 g of methacryloyloxyethyl trimethylammonium chloride (0.5 wt.% of acrylamide AM), and dissolve thoroughly;

[0106] (3) Warm the polymerization system to 30°C, add 3.13 g of 20% ammonium persulfate solution, and add 5.0 g of 20% sodium bisulfite solution to initiate polymerization, and adiabatic polymerize for 8 h;

[0107] (4) After the adiabatic polymerization is complete, remove the gel and cut it into 2-4 mm particles, and add a hydrolysis agent, sodium hydroxide (0.66 g of sodium hydroxide per 100 g of gel particles, i.e., the ratio of NaAA is 5%), to hydrolyze at 100°C for 3 h;

[0108] (5) After the hydrolysis is complete, dry the product at 100°C for 1 h, crush and sieve to obtain 100-120 mesh phase permeability improver A-4, with a molecular weight of 4.2678 million.

[0109] Example 6: Preparation of phase permeability improver B—AM / octadecyldimethylammonium allyl chloride / AMPS / NaAA copolymer

[0110] Compared with Example 1, the only difference is that no methacryloyloxyethyl trimethylammonium chloride is added, and the amount of octadecyldimethylammonium allyl chloride is 7.5 wt.% of acrylamide AM;

[0111] The molecular weight of phase permeability improver B is 2.9735 million.

[0112] Example 7: Preparation of phase permeability improver C—AM / methacryloyloxyethyl trimethylammonium chloride / AMPS / NaAA copolymer

[0113] Compared with Example 1, the only difference is that no octadecyldimethylammonium allyl chloride is added, and the amount of methacryloyloxyethyl trimethylammonium chloride is 2 wt.% of acrylamide AM;

[0114] The molecular weight of phase permeability improver C is 2.8463 million.

[0115] Example 8: Preparation of phase permeability improver D—AM / AMPS / NaAA copolymer

[0116] The difference compared with Example 1 is that 2.5 g of sodium formate is used instead of octadecyldimethylammonium allyl chloride and methacryloyloxyethyl trimethyl ammonium chloride.

[0117] The molecular weight of the phase permeability modifier D is 387.48 million.

[0118] Example 9:

[0119] Solutions of 0.04% phase permeability modifiers A-D were prepared with water as the solvent, 0.2% sodium persulfate was added to the solutions, and the solutions were placed in a 50°C water bath for sufficient gel breaking, with a gel breaking time of 24 h; the gel broken phase permeability modifiers A-D were obtained.

[0120] Example 10: Preparation of a fracturing fluid system containing a phase permeability modifier

[0121] The fracturing fluid system formulation: 0.4% thickener (water-soluble polyacrylamide with a viscosity average molecular weight of ≥ 25 million), 0.04% AM phase permeability modifier (the phase permeability modifiers of Examples 1, 6-8 were used respectively, and the obtained fracturing fluid systems were named fracturing fluid systems A, B, C, and D), 0.2% clay stabilizer (potassium chloride), 0.25% cleanup agent (perfluorodecyl ether fluorocarbon surfactant FHJ-601, Hebi Huajian Environmental Protection Technology Co., Ltd.), 0.25% demulsifier (polyoxyethylene polyoxypropylene ether demulsifier L35, Haian Petroleum Chemical Plant in Jiangsu Province), 0.20% gel breaker (potassium persulfate);

[0122] The fracturing fluid system preparation process: 350 mL of water was measured into a 500 mL beaker, a vertical constant speed stirrer was used for stirring, and the stirring speed was adjusted to 500 rad / min; the thickener, AM / octadecyldimethylammonium allyl chloride / methacryloyloxyethyl trimethyl ammonium chloride / AMPS / NaAA copolymer, clay stabilizer (potassium chloride), 0.25% cleanup agent (perfluorodecyl ether fluorocarbon surfactant FHJ-601, Hebi Huajian Environmental Protection Technology Co., Ltd.), 0.25% demulsifier (polyoxyethylene polyoxypropylene ether demulsifier L35, Haian Petroleum Chemical Plant in Jiangsu Province), and gel breaker (potassium persulfate) were added in the order of the formulation, and the stirring was continued for 1.5 min and then stopped, and the fracturing fluid system was obtained.

[0123] Example 11

[0124] The difference compared with Example 10 is that no phase permeability modifier was added, and the obtained fracturing fluid system was named fracturing fluid system E.

[0125] Example 12: Preparation of a fracturing fluid system containing a gel broken phase permeability modifier

[0126] The difference compared with Example 10 is only that the phase permeability modifier uses the broken gel phase permeability modifier A-D obtained from Example 9, and the obtained fracturing fluid system is named as fracturing fluid system F, G, H, I respectively.

[0127] Test example: oil control and water control effect evaluation

[0128] According to SY / T 5107-2016 “Water-based fracturing fluid performance evaluation method”, cores with a porosity in the range of 23-26% are selected to test the change of oil and water permeability in the reservoir rock pores before and after injecting the phase permeability modifier and the pressure also system of each embodiment of the application, and the oil and water permeability after injecting a certain amount of simulated brine, and the ratio M0 of the water phase permeability reduction rate to the oil phase permeability reduction rate is taken as the oil control and water control effect evaluation index, M n n = 20, 60, 80, 100) as the long-acting index; wherein the oil control and water control effect of the phase permeability modifier prepared in Examples 1-8 is shown in Table 1; the oil control and water control effect of the broken gel phase permeability modifier A-D in Example 9 is shown in Table 2; the oil control and water control effect of the fracturing fluid system E containing the phase permeability modifier A-D in Example 10 and the fracturing fluid system E not containing the phase permeability modifier in Example 11 is shown in Table 3; the oil control and water control effect of the fracturing fluid system containing the demulsified phase permeability modifier A-D in Example 12 is shown in Table 4.

[0129] Table 1: Oil control and water control effect of phase permeability modifier

[0130]

[0131] As can be seen from Table 1: the phase permeability modifier prepared in Examples 1-3 has good oil control and water control effect, wherein the phase permeability modifier A series prepared has the best oil control and water control effect, the water phase permeability reduction rate is greater than 90%, the oil phase permeability reduction rate is less than 10%, the reduction rate ratio reaches 10.24, and after 100 PV water flushing, the water phase permeability reduction rate to oil phase permeability reduction rate ratio reaches 8.03, which has good long-acting property; in Examples 4 and 5, due to the excessive or insufficient amount of APMS and hydrophobic functional monomers A and B, the water phase permeability reduction rate is reduced, and the oil phase permeability reduction rate is increased; in Examples 6 and 7, the copolymer containing only one kind of cationic hydrophobic monomer, i.e. phase permeability modifier B and C, has a water phase and oil phase permeability reduction ratio of about 3.0, and after 80 PV water flushing, the water phase permeability reduction rate to oil phase permeability reduction rate ratio is close to 1.0, and the long-acting property is poor; the AM / AMPS / NaAA copolymer prepared in Example 8, i.e. phase permeability modifier D, does not contain a cationic monomer, and has obviously poor oil control and water control effect, the water phase and oil phase permeability reduction ratio is only 1.37, and after 20 PV water flushing, the water phase permeability reduction rate to oil phase permeability reduction rate ratio is close to 1, and the long-acting property is worse.

[0132] ​Table 2 Oil control and water control effect of phase permeability modifier after gel breaking

[0133]

[0134] It can be seen from Table 2 that the phase permeability modifier A series prepared in Example 1 still has excellent oil control and water control performance after sufficient gel breaking, the water permeability reduction rate is greater than 90%, the oil permeability reduction rate is less than 10%, the reduction rate ratio is 10.03, the water permeability and oil permeability reduction rate ratio is 7.69 after 100 PV water flushing, and the long-acting property is good; the copolymer containing only one cationic hydrophobic monomer prepared in Example 6 and Example 7 and the phase permeability modifiers B and C have a water permeability and oil permeability reduction rate ratio of about 2.0 after gel breaking, the water permeability and oil permeability reduction rate ratio is close to 1 after 60 PV water flushing, and the long-acting property is poor; the AM / AMPS / NaAA copolymer prepared in Example 8 without cationic monomer, i.e., the phase permeability modifier D, has a water control and oil control effect that is obviously worse, the water permeability and oil permeability reduction rate ratio is only 1.09, the water permeability and oil permeability reduction rate ratio is close to 1 after 20 PV water flushing, and the long-acting property is worse.

[0135] It can be seen from Table 1 and Table 2 that the oil control and water control effect and the flushing resistance of the phase permeability modifiers prepared in Example 1, Example 2 and Example 3 are basically the same before and after gel breaking; the oil control and water control effect and the flushing resistance of Example 4 and Example 5 decrease; the oil control and water control effect of the phase permeability modifiers B, C and D prepared in Example 6, Example 7 and Example 8 decreases obviously after gel breaking, the water permeability and oil permeability reduction rate ratio rapidly approaches 1 after water flushing, and the long-acting property is poor.

[0136] Table 3 Oil control and water control effect of fracturing fluid systems A-E

[0137]

[0138] As can be seen from Table 3, the fracturing fluid system A containing phase permeability modifier A has a water phase permeability reduction rate of more than 80% and an oil phase permeability reduction rate of about 20%, has a significant water control effect, and has a water phase permeability to oil phase permeability reduction ratio of 3.57 after 100 PV water injection and scouring, and has good long-term effect. The fracturing fluid systems B and C containing phase permeability modifiers B and C have a water phase permeability reduction rate of less than 50% and an oil phase permeability reduction rate of about 30%, have poor oil stabilization and water control effect, and have a water phase permeability to oil phase permeability reduction ratio close to 1 after 60 PV water injection and scouring, and have poor long-term effect. The fracturing fluid system D containing phase permeability modifier D has a water phase permeability reduction rate of less than 50% and an oil phase permeability reduction rate of about 30%, has poor oil stabilization and water control effect, and has a water phase permeability to oil phase permeability reduction ratio close to 1 after 40 PV water injection and scouring, and has poor long-term effect. The fracturing fluid system E without any phase permeability modifier has poor oil stabilization and water control effect and long-term effect.

[0139] Table 4 Oil stabilization and water control effect of fracturing fluid system of fracturing fluid system F-I

[0140]

[0141] As can be seen from Table 4, the fracturing fluid system F containing post-gel breaking phase permeability modifier A has good oil stabilization and water control effect, has a water phase permeability reduction rate of more than 80% and an oil phase permeability reduction rate of more than 20%, has a water phase permeability to oil phase permeability reduction ratio of 2.88 after 100 PV water injection and scouring, and has good long-term effect. The fracturing fluid systems G and H containing post-gel breaking phase permeability modifiers B and C have poor oil stabilization and water control effect, have a water phase permeability reduction rate while also significantly reducing oil phase permeability, have a water phase permeability to oil phase permeability reduction ratio close to 1 after 60 PV water injection and scouring, and have poor long-term effect. The fracturing fluid system I containing post-gel breaking phase permeability modifier D has poor oil stabilization and water control effect, has a water phase permeability reduction rate while also significantly reducing oil phase permeability, has a water phase permeability to oil phase permeability reduction ratio close to 1 after 20 PV water injection and scouring, and has poorer long-term effect.

[0142] Finally, it should be noted that the above content is only used to illustrate the technical solutions of the present application, and is not a limitation on the protection scope of the present application. Simple modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A phase permeability improver characterized by comprising: obtained by hydrolysis after copolymerization of acrylamide AM, functional monomer 2-acrylamido-2-methylpropanesulfonic acid AMPS, cationic hydrophobic monomer A and cationic hydrophobic monomer B; the dosages of the raw materials are as follows, based on acrylamide AM: functional monomer 2-acrylamido-2-methylpropanesulfonic acid AMPS 10-20 wt.%, cationic hydrophobic monomer A 5-10 wt.%, cationic hydrophobic monomer B 1-3 wt.%; the cationic hydrophobic monomer A is at least one of tetradecyldimethylammonium allyl chloride, hexadecyldimethylammonium allyl chloride and octadecyldimethylammonium allyl chloride; the cationic hydrophobic monomer B is at least one of methacryloyloxyethyltrimethylammonium chloride, acryloyloxyethyltrimethylammonium chloride and acryloyloxyethyldimethylbenzylammonium chloride.

2. The phase-penetration improving agent according to claim 1, characterized by, the phase permeability improver has a particle size of 100-120 mesh and a viscosity average molecular weight of 5-5 million.

3. The method for producing a phase-separation improver according to claim 1 or 2, characterized by, comprising the following steps: (1) acrylamide AM and functional monomer 2-acrylamido-2-methylpropanesulfonic acid AMPS are added to deionized water, and the pH value of the solution is adjusted to 7.0; (2) cationic hydrophobic monomer A and cationic hydrophobic monomer B are added and stirred uniformly; (3) the temperature is raised, an initiator is added, and adiabatic polymerization is carried out; (4) after completion, a hydrolysis agent is added to carry out hydrolysis reaction; (5) drying, to obtain the phase permeability improver.

4. The production method according to claim 3, characterized by, the initiator comprises an oxidizing agent and a reducing agent; the oxidizing agent is at least one of potassium persulfate, ammonium persulfate, sodium persulfate and dibenzoyl peroxide; the reducing agent is at least one of sodium formaldehyde sulfoxylate, sodium sulfite, sodium bisulfite and urea.

5. The preparation method according to claim 4, characterized in that, the dosage of the oxidizing agent is 0.1-0.4 wt.% of acrylamide AM; the dosage of the reducing agent is 0.2-0.6 wt.% of acrylamide AM.

6. The preparation method according to claim 3, characterized in that, the hydrolysis agent is at least one of sodium hydroxide, sodium carbonate and sodium bicarbonate.

7. The preparation method according to claim 3, characterized in that, the dosage of the hydrolysis agent is calculated according to a theoretical hydrolysis degree of 15-35%.

8. The preparation method according to claim 3, characterized in that, the polymerization reaction temperature is 30-50℃, the reaction time is 4-12h; the hydrolysis reaction temperature is 80-120℃, the hydrolysis reaction time is 1-4h; the drying temperature is 80-140℃, and the drying time is 0.5-3h.

9. A fracturing fluid system characterized by, the phase permeability improver of claim 1 or 2 or the phase permeability improver prepared by the preparation method of any one of claims 3-8.

10. The fracturing fluid system of claim 9, wherein, by mass percentage, comprising: 0.4-1.2% thickening agent, 0.1-0.5% clay stabilizer, 0.1-0.5% cleanup aid, 0.1-0.5% demulsifier, 0.05-0.20% gel breaker and 0.03-0.05% phase permeability improver.

11. The fracturing fluid system of claim 10, wherein, The thickening agent is water-soluble polyacrylamide and its derivatives; the clay stabilizer is at least one of potassium chloride, ammonium chloride and quaternary ammonium salt organic clay stabilizer; the cleanup agent is fluorocarbon surfactant, including perfluorodecyl polyoxyethylene ether fluorocarbon surfactant; the demulsifier is polyether compound, including polyoxyethylene polyoxypropylene ether demulsifier; and the gel breaker is at least one of ammonium persulfate, sodium persulfate, potassium persulfate and capsule gel breaker.

12. The fracturing fluid system of claim 10, wherein, The thickening agent is in emulsion state or powder with 100-120 mesh.

13. The method of preparing a fracturing fluid system according to any one of claims 9-12, wherein, The thickening agent, phase permeability improving agent, clay stabilizer, cleanup agent, demulsifier and gel breaker are sequentially added into water, and stirred to obtain the fracturing fluid system.

14. The method of claim 13, wherein, The stirring speed is 400-800 rad / min, and the stirring time is 1-3 min.

15. Use of a phase permeability modifier or a fracturing fluid system in the hydraulic fracturing exploitation of an oil and gas field, characterized in that, The phase permeability improving agent is the phase permeability improving agent of claim 1 or 2 or the phase permeability improving agent prepared by the preparation method of any one of claims 3-8; and the fracturing fluid system is the fracturing fluid system of any one of claims 9-12 or the fracturing fluid system prepared by the preparation method of claim 13 or 14.

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