Cationic polymer acid-resistant thickening agent as well as preparation method and application thereof

Abstract

The invention discloses a cationic polymer acid-resistant thickening agent as well as a preparation method and application thereof, and belongs to the technical field of oil-gas field development. The polymer thickening agent is prepared from the following components in percentage by mass: 65 to 85 weight percent of acrylamide, 15 to 35 weight percent of methacryloyloxyethyl trimethyl ammonium chloride, 0.01 to 0.05 weight percent of dicationic functional monomer and 1 to 8 weight percent of cosolvent, the acid liquor system comprises the following components in percentage by mass: 5wt%-30wt% of solid acid, 0.01 wt%-0.6 wt% of a cationic polymer acid-resistant thickener, 0.5 wt%-5.0 wt% of a corrosion inhibitor, 0.3 wt%-1.0 wt% of an iron ion stabilizer and the balance of water; wherein the solid acid consists of 5wt%-15wt% of a solid metal catalyst and 85wt%-95wt% of solid particle acid; the acid liquid system has excellent slow release performance, is simple in formula, convenient to transport, low in cost and suitable for site construction, and has wide market prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field development, and particularly relates to a cationic polymer acid-resistant thickener and a preparation method and application thereof. Technical Background

[0002] With the large-scale exploitation and consumption of conventional oil and gas reservoirs, low-permeability, ultra-low-permeability, deep, high-temperature unconventional oil and gas resources such as tight sandstone gas, coalbed methane, and shale gas are in urgent need of development and utilization. Acid fracturing is currently one of the most important measures for transforming heterogeneous, low-permeability formations. In particular, many tight oil and gas reservoirs have been discovered in recent years. In the early stages of production, their production was very low or even non-existent, and they required acidification before they could achieve a certain level of production value. Currently, deep carbonate reservoirs often exhibit high or ultra-high temperature characteristics, making their acidification transformation a major challenge to the acid system. Specifically, high temperature accelerates the acid-rock reaction rate, shortening the effective action distance of the acid, making it difficult to achieve deep penetration of the reservoir.

[0003] At present, the existing acid system still has major safety hazards in transportation, storage, etc., and the acid-rock reaction rate is fast at high temperature, the pipe corrosion is serious, and it is impossible to achieve deep acidization at the far end of the reservoir and uneven etching of the fracture wall, which seriously restricts the efficient development of high-temperature and ultra-high-temperature carbonate reservoirs. Therefore, there is an urgent need for a solid acid system that can be slowly released at high temperature to solve the above problems. Summary of the Invention

[0004] In response to the problems existing in the current technology, the present invention provides a cationic polymer acid-resistant thickener and its preparation method and application, which can well meet the technical requirements of deep penetration and uneven etching of reservoir matrix acidizing / acid fracturing.

[0005] To achieve the above object, the technical solution adopted by the present invention is to provide a cationic polymer acid-resistant thickener, the chemical structure of which is as follows:

[0006]

[0007] x, y, z are the number of monomers in the cationic polymer acid-resistant thickener, R1 is an alkyl chain with 3-16 carbon atoms, R2 is C 21 H 41 (Erucic acid type) or C 17 H 33 (Oleic acid type), the molecular weight of the polymer ranges from 5 million to 9 million.

[0008] Furthermore, a method for preparing a cationic polymer acid-resistant thickener is provided: 65 wt% to 85 wt% of acrylamide, 15 wt% to 35 wt% of methacryloyloxyethyltrimethylammonium chloride, 1 wt% to 8 wt% of a solvent co-solvent, and 0.01 wt% to 0.05 wt% of a dicationic functional monomer are dissolved in deionized water (solid content is 40 wt%), and the pH is adjusted to 7.0 to 7.5 to obtain a reaction mixture; under nitrogen protection, an initiator is added to the reaction mixture, and polymerization is initiated at 5°C to 10°C. The reaction time is 6 to 9 hours. After the reaction is completed, the cationic polymer acid-resistant thickener is obtained by cutting, drying, and crushing.

[0009] Furthermore, the methacryloyloxyethyltrimethylammonium chloride in the cationic polymer acid-resistant thickener can also be replaced by diallyldimethylammonium chloride.

[0010] Furthermore, the initiator is composed of a redox initiator and / or an azo initiator, specifically one or more of ammonium persulfate, potassium persulfate, sodium sulfite, sodium bisulfite, sodium formaldehyde sulfoxylate, tert-butyl hydroperoxide, cyclohexanone peroxide, 2,2'-azobisisobutylamidine dihydrochloride, azobisisobutyronitrile, azobisisoheptonitrile, and azobisisobutylimidazoline hydrochloride.

[0011] Furthermore, the chemical structure of the dicationic functional monomer in the cationic polymer acid-resistant thickener is as follows:

[0012]

[0013] Another object of the present invention is to provide a preparation method and application of a cationic polymer acid solution system, which comprises, by weight percentage, 5wt% to 30wt% of a solid acid, 0.01wt% to 0.6wt% of a cationic polymer acid-resistant thickener, 0.5wt% to 5.0wt% of a corrosion inhibitor, 0.3wt% to 1.0wt% of an iron ion stabilizer, and the balance being water.

[0014] Furthermore, the solid acid is composed of 5wt% to 15wt% of a solid metal catalyst and 85wt% to 95wt% of a solid particle acid.

[0015] Furthermore, the solid catalyst in the solid acid is one or more of solid zirconium salts and titanium salts.

[0016] Furthermore, the solid particulate acid in the solid acid is one or more of citric acid, maleic anhydride, aminosulfonic acid, and polyhydrogen acid with or without capsules.

[0017] Furthermore, the solid acid is dissolved in dichloromethane and purified by rotary evaporation, so that the solid acid is covered with dichloromethane to form a capsule system. As the liquid system is pumped into the formation, the solid acid capsules gradually break under the action of formation pressure and shear, and the solid acid is released from the capsules, and then hydrolyzed in water, and hydrogen ions are gradually released.

[0018] Furthermore, the transition metal is one or more of organic zirconium and organic titanium. As the acid-rock reaction proceeds, the pH of the system gradually increases, reaching the crosslinking range of organic zirconium / organic titanium and cationic polymer acid-resistant thickener, increasing the viscosity of the system and reducing H + The diffusion rate inside the acid fluid can further reduce the acid-rock reaction rate, increase the acid-rock reaction distance, and achieve deep penetration of the reservoir.

[0019] In summary, the present invention has the following advantages:

[0020] 1. The present invention provides a method for producing a cationic polymer acid-resistant thickener. The method has the advantages of simple preparation process, high yield, simple post-processing, stable performance, low cost, and broad market prospects.

[0021] 2. The cationic polymer acid solution system prepared in the present invention has excellent performance of slowly releasing hydrogen ions.

[0022] 3. The acid liquid system provided by the present invention utilizes a capsule system. The solid acid capsules gradually break under the action of formation pressure and shear, achieving the first level of retarding. At the same time, the organic metal acts as a catalyst and cross-linking agent to cross-link with the polymer thickener, thereby improving the viscoelasticity of the system and achieving a double retarding effect.

[0023] 4. The polymer thickener used in the present invention contains dications in its molecular structure, which endows the system with excellent heat and acid resistance, thereby achieving the purpose of slowing down. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are described in detail below.

[0025] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] In the following examples, unless otherwise specified, all substances are commercially available and can be purchased directly from the market.

[0027] The method for preparing the cationic polymer acid-resistant thickener in the embodiment includes the following steps:

[0028] 1) adding acrylamide, methacryloyloxyethyltrimethylammonium chloride, a dicationic monomer, and a cosolvent to deionized water to prepare a uniform solution with a content of 40 wt %, adjusting the pH of the solution to 7.0-7.5, and introducing nitrogen to remove oxygen;

[0029] 2) After deoxygenation, an initiator is added to the solution and the reaction is continued for 8 hours. The polymer is then dried and granulated.

[0030] Comparative Examples and Examples 1-6 were set according to the raw materials of the cationic polymer acid-resistant thickener. The types and technical parameters of the raw materials in the comparative examples and examples are shown in Table 1.

[0031] Table 1 Types and technical parameters of raw materials in Examples and Comparative Examples

[0032]

[0033] Note: The amount of dicationic functional monomer added is the percentage of the total mass of acrylamide, methacryloyloxyethyl trimethyl ammonium chloride and cosolvent

[0034] Result analysis:

[0035] Cationic polymer acid-resistant thickener viscosity increasing performance test

[0036] This experimental example tests the viscosity-increasing performance of the cationic polymer acid-resistant thickeners obtained in Examples 1-6 and the comparative example.

[0037] The detection method is as follows: first, the cationic polymers obtained in Examples 1-6 and the comparative example are respectively prepared into 0.6 wt % polymer solutions with 15 wt % hydrochloric acid solution, and then the polymer solutions are measured using a Haake rheometer at 25°C and 170 s -1 Test the acid viscosity.

[0038] The viscosity increasing properties of the cationic polymer acid-resistant thickeners in the examples and comparative examples are shown in Table 2. The experimental results show that the cationic polymer acid-resistant thickener prepared in Example 5 has the best viscosity increasing property and was selected as the thickener for the cationic polymer acid solution system for the retarding performance test.

[0039] Table 2 Acid viscosity increasing properties of cationic polymers in Examples and Comparative Examples

[0040]

[0041] Note: “ / ” means insoluble in water.

[0042] Cationic polymer acid solution system sustained release performance test

[0043] The detection method is as follows: first, prepare 200 mL of a solid acid solution with a hydrochloric acid equivalent of 15 wt% and a hydrochloric acid solution with a 15 wt% concentration, and then prepare a solid acid retarding acid system and a hydrochloric acid retarding acid system according to the formula of 0.6 wt% cationic polymer acid-resistant thickener, 3.0 wt% corrosion inhibitor, and 1.0 wt% iron ion stabilizer. Then, referring to the SY / T6526-2019 industry standard, the acid-rock dynamic reaction rate of the above two acid solutions and 15 wt% hydrochloric acid solution with marble core at 140 ° C was tested. The experimental results are shown in Table 3. The results show that the acid-rock dynamic reaction rate of the solid acid retarding acid system is -8.25×10 - 4 mol / (cm 2 ·s) (negative value), indicating that the concentration of hydrogen ions generated at 140°C is higher than the hydrogen ions consumed by the acid-rock dynamic reaction, showing excellent retarding performance. The hydrochloric acid retarding acid system also shows good retarding performance, with the acid-rock dynamic reaction rate of 3.65×10 -5 mol / (cm 2 ·s), indicating that the cationic polymer acid-resistant thickener has excellent acid resistance and retarding performance.

[0044] Table 3 Different acid retarding performance test

[0045]

[0046] Note: “ / ” indicates that the core has been completely dissolved and the acid-rock dynamic reaction rate cannot be calculated.

[0047] Throughout this specification, references to "one embodiment" and the like indicate that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0048] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A cationic polymer acid-resistant thickener and its preparation method and application, characterized in that: The chemical formula of cationic polymer acid-resistant thickener is: Where: x, y, z are the number of monomers in the cationic polymer acid-resistant thickener; R1 is an alkyl chain with 3-16 carbon atoms, R2 is C 14 H 41 (Erucic acid type) or C 17 H 33 (Oleic acid type).

2. As claimed in claim 1, it is characterized in that The cationic polymer acid-resistant thickener has a molecular weight ranging from 5 million to 9 million.

3. As claimed in claim 1, it is characterized in that The cationic polymer acid-resistant thickener is prepared according to the following method: 65wt% to 85wt% of acrylamide, 15wt% to 35wt% of methacryloyloxyethyltrimethylammonium chloride, 1wt% to 8wt% of a solvent co-solvent, and 0.01wt% to 0.05wt% of a dicationic functional monomer are dissolved in deionized water (solid content is 40wt%), and the pH is adjusted to 7.0 to 7.5 to obtain a reaction mixture; under nitrogen protection, an initiator is added to the reaction mixture, polymerization is initiated at 5°C to 10°C, the reaction time is 6 to 9 hours, and after the reaction is completed, the cationic polymer acid-resistant thickener is obtained by cutting, drying and crushing.

4. As claimed in claim 3, it is characterized in that The initiator is one or more of ammonium persulfate, potassium persulfate, sodium sulfite, sodium bisulfite, sodium formaldehyde sulfoxylate, tert-butyl hydroperoxide, cyclohexanone peroxide, 2,2'-azobisisobutylamidine dihydrochloride, azobisisobutyronitrile, azobisisoheptonitrile, and azobisisobutylimidazoline hydrochloride.

5. As described in claim 3, the amount of initiator used is 0.03wt% to 0.06wt% of the mass of the reaction mixture.

6. A method for preparing a cationic polymer acid solution system using the cationic polymer acid-resistant thickener according to any one of claims 1 to 5 as an acid solution thickener, characterized in that: Calculated by weight percentage, the invention comprises: 5wt% to 30wt% of solid acid, 0.01wt% to 0.6wt% of cationic polymer acid-resistant thickener, 0.5wt% to 5.0wt% of corrosion inhibitor, 0.3wt% to 1.0wt% of iron ion stabilizer, and the balance is water.

7. A cationic polymer acid solution system as claimed in claim 6, characterized in that: The solid acid consists of 5wt% to 15wt% of a solid metal catalyst and 85wt% to 95wt% of a solid particle acid.

8. A cationic polymer acid solution system as claimed in claim 7, characterized in that: The solid catalyst in the solid acid is one or more of solid zirconium salt and titanium salt.

9. As described in claim 7, the solid particulate acid can be one or more of citric acid, maleic anhydride, sulfamic acid, and polyhydrogen acid with or without encapsulation.

10. According to claim 6, the cationic polymer acid system is used in water injection well unblocking, wellbore unstuck, reservoir matrix acidizing, acid fracturing, and pre-fracturing pressure reduction.

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