Fracturing fluid acrylamide polymer thickener, preparation method thereof and fracturing fluid

Abstract

The present application relates to the field of oil field additives, and specifically discloses a kind of acrylamide polymer thickening agent for fracturing fluid and its preparation method and fracturing fluid.The acrylamide polymer thickening agent for fracturing fluid is prepared by reverse emulsion polymerization of aqueous phase mixture and oil phase mixture, wherein the aqueous phase mixture is mixed by acrylamide, hydrophilic acryl monomer, hydrophobic acryl monomer, aromatic ring or heterocyclic compound and water;The oil phase mixture is mixed by emulsifier and organic solvent.The acrylamide polymer thickening agent for fracturing fluid provided by the present application has the characteristics of low damage, variable viscosity, high sand carrying, strong desorption, settlement promotion, high efficiency anti-swelling and the like.

Description

Technical Field

[0001] This invention relates to the field of oilfield additives, specifically to an acrylamide polymer thickener for fracturing fluid, its preparation method, and the fracturing fluid itself. Background Technology

[0002] The national mandate to further expand the exploration, development, and utilization of unconventional resources presents a favorable opportunity for the large-scale development and utilization of deep coalbed methane. my country possesses abundant deep coalbed methane resources, making it a crucial replacement area for future natural gas reserve and production increases. Deep coalbed methane exploration and development are of great significance for ensuring regional energy demand, optimizing the regional energy structure, and achieving dual-carbon goals.

[0003] Research on deep coalbed methane (DBM) is still in its early stages both domestically and internationally, and key technologies for exploration and development are not yet mature. In particular, the properties of fracturing fluids, such as low damage, low adsorption, low friction, high efficiency in preventing swelling, and easy flowback, are not yet well-suited for deep coalbed methane operations, significantly hindering DBM development. Therefore, it is necessary to develop a fracturing fluid thickener for deep coalbed methane reservoir stimulation to meet the requirements of deep coalbed methane fracturing operations, thereby achieving efficient development of deep coalbed methane. Summary of the Invention

[0004] The purpose of this invention is to provide a thickener for fracturing fluid used in deep coalbed methane reservoir stimulation and its preparation method, in order to solve the problem of mismatch between current fracturing fluids and reservoir characteristics such as well-developed macroscopic cleavage of deep coal and rock, low matrix permeability, strong adsorption capacity, and high clay mineral content. It has the characteristics of low damage, variable viscosity, high sand carrying capacity, strong desorption, promoting sedimentation, and high efficiency in preventing swelling.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: According to a first aspect of the present invention, an acrylamide polymer thickener for fracturing fluid is provided, which is prepared by reverse emulsion polymerization of an aqueous phase mixture and an oil phase mixture, wherein the aqueous phase mixture is composed of acrylamide, a hydrophilic propylene monomer, a hydrophobic propylene monomer, an aromatic ring or heterocyclic compound and water; and the oil phase mixture is composed of an emulsifier and an organic solvent.

[0006] According to some embodiments of the present invention, the hydrophilic propylene monomer is one or more of methacrylamide, hydroxymethylacrylamide, acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid.

[0007] According to some embodiments of the present invention, the hydrophobic acrylic monomer is one or more of octadecyl acrylate, octadecyl methacrylate, methoxy polyethylene glycol methacrylate, and methacrylamide propyltrimethylammonium chloride.

[0008] According to some embodiments of the present invention, the aromatic ring or heterocyclic compound is one or more of p-butoxystyrene, styrene, 2-vinylthiophene, and 4-tert-butoxystyrene.

[0009] According to some embodiments of the present invention, the organic solvent is one or more of white oil, paraffin, and cyclohexane.

[0010] According to some embodiments of the present invention, the components in the aqueous phase mixture are used in the following amounts by weight: acrylamide: 18-22 parts, hydrophilic propylene monomer: 5-8 parts, hydrophobic propylene monomer: 4-6 parts, aromatic ring or heterocyclic compound: 3-5 parts, water: 40 parts; the components in the oil phase mixture are used in the following amounts by weight: emulsifier: 6-10 parts, organic solvent: 40-55 parts.

[0011] According to some embodiments of the present invention, the emulsifier is a mixture of SP-80 and OP-10.

[0012] According to some embodiments of the present invention, the weight ratio of SP-80 to OP-10 is (5.0-7.0):1.

[0013] According to some embodiments of the present invention, the aqueous phase mixture is composed of 18-22 parts acrylamide, 5-8 parts 2-acrylamido-2-methylpropanesulfonic acid, 4-6 parts methacrylamide propyltrimethylammonium chloride, 3-5 parts p-butoxystyrene and 40 parts water, by weight; the oil phase mixture is composed of 6-10 parts emulsifier and 40-55 parts white oil.

[0014] According to a second aspect of the present invention, a method for preparing the above-mentioned acrylamide polymer thickener for fracturing fluid is provided, comprising the following steps: S1: Mix acrylamide, hydrophilic propylene monomer, hydrophobic propylene monomer, aromatic ring or heterocyclic compound and water evenly, and adjust the pH of the system to 6.0-9.0 to obtain an aqueous phase mixture; S2: Mix the emulsifier and organic solvent evenly to obtain an oil phase mixture; S3: Mix the oil phase mixture and the aqueous phase mixture evenly, introduce inert gas to remove oxygen under stirring, add initiator after heating to 50℃-70℃, and continue to keep the temperature for 4h-6h to obtain acrylamide polymer thickener for fracturing fluid.

[0015] According to some embodiments of the present invention, in step S1, an alkaline solution is used to adjust the pH of the system.

[0016] According to some embodiments of the present invention, in step S3, the initiator is azobisisobutyronitrile, and the amount of initiator accounts for 0.03wt.%-0.05wt.% of the total weight of the monomer.

[0017] According to a third aspect of the present invention, a fracturing fluid is provided, comprising the aforementioned acrylamide polymer thickener for fracturing fluids.

[0018] By adopting the above technical solutions, the present invention has the following advantages compared with the prior art: The acrylamide polymer thickener for fracturing fluid provided by this invention has polyacrylamide molecules as the main chain and introduces different functional groups such as hydrophilic groups, hydrophobic groups, and rigid groups, which have the characteristics of low damage, variable viscosity, high sand carrying capacity, strong desorption, promoting sedimentation, and high efficiency in preventing swelling. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A flowchart illustrating the preparation method of the acrylamide polymer thickener for fracturing fluid provided by the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] Specific embodiments of the invention are disclosed herein as needed; however, it should be understood that the embodiments disclosed herein are merely examples of the invention that may be implemented in various alternative forms. In the following description, various operating parameters and components are described in several contemplated embodiments. These specific parameters and components are provided as examples only and are not intended to be limiting.

[0023] According to a first aspect of the present invention, an acrylamide polymer thickener for fracturing fluid is provided, which is prepared by reverse emulsion polymerization of an aqueous phase mixture and an oil phase mixture, wherein the aqueous phase mixture is composed of acrylamide, a hydrophilic propylene monomer, a hydrophobic propylene monomer, an aromatic ring or heterocyclic compound and water; and the oil phase mixture is composed of an emulsifier and an organic solvent.

[0024] The acrylamide polymer thickener for fracturing fluid provided by this invention uses polyacrylamide molecules as the main chain. By introducing different functional groups such as hydrophilic groups, hydrophobic groups, and rigid groups, it exhibits characteristics such as low damage, variable viscosity, high sand carrying capacity, strong desorption, promoting sedimentation, and efficient anti-swelling. Specifically, by using polyacrylamide molecules as the main chain and introducing hydrophilic and hydrophobic groups, the thickener polymer possesses good drag reduction properties, aids in drainage, thickens, and prevents swelling. By introducing rigid groups such as aromatic rings or heterocyclic rings, the stability, temperature resistance, and viscosity-enhancing properties of the aggregate are improved.

[0025] In some embodiments, the hydrophilic acrylic monomer is one or more selected from methacrylamide, hydroxymethylacrylamide, acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid. Preferably, the hydrophilic acrylic monomer is 2-acrylamido-2-methylpropanesulfonic acid.

[0026] In some embodiments, the hydrophobic acrylic monomer is one or more selected from octadecyl acrylate, octadecyl methacrylate, methoxy polyethylene glycol methacrylate, and methacrylamide propyltrimethylammonium chloride. Preferably, the hydrophobic acrylic monomer is methacrylamide propyltrimethylammonium chloride.

[0027] In some embodiments, the aromatic ring or heterocyclic compound is one or more of p-butoxystyrene, styrene, 2-vinylthiophene, and 4-tert-butoxystyrene. Preferably, the aromatic ring or heterocyclic compound is p-butoxystyrene.

[0028] In some embodiments, the organic solvent is one or more of white oil, paraffin, and cyclohexane. Preferably, the organic solvent is white oil.

[0029] In some embodiments, the amounts of each component in the aqueous phase mixture by weight are as follows: acrylamide: 18-22 parts, hydrophilic propylene monomer: 5-8 parts, hydrophobic propylene monomer: 4-6 parts, aromatic ring or heterocyclic compound: 3-5 parts, water: 40 parts; the amounts of each component in the oil phase mixture by weight are as follows: emulsifier: 6-10 parts, organic solvent: 40-55 parts.

[0030] In some embodiments, the emulsifier is a mixture of SP-80 and OP-10. Preferably, the weight ratio of SP-80 to OP-10 is (5.0-7.0):1.

[0031] In some embodiments, the aqueous phase mixture is composed of 18-22 parts acrylamide, 5-8 parts 2-acrylamido-2-methylpropanesulfonic acid, 4-6 parts methacrylamide propyltrimethylammonium chloride, 3-5 parts p-butoxystyrene and 40 parts water by weight; the oil phase mixture is composed of 6-10 parts emulsifier and 40-55 parts white oil.

[0032] According to a second aspect of the present invention, a method for preparing the above-mentioned acrylamide polymer thickener for fracturing fluid is provided, such as... Figure 1 As shown, the preparation method includes the following steps: S1: Mix acrylamide, hydrophilic propylene monomer, hydrophobic propylene monomer, aromatic ring or heterocyclic compound and water evenly, and adjust the pH of the system to 6.0-9.0 to obtain an aqueous phase mixture; S2: Mix the emulsifier and organic solvent evenly to obtain an oil phase mixture; S3: Mix the oil phase mixture and the aqueous phase mixture evenly, introduce inert gas to remove oxygen under stirring, add initiator after heating to 50℃-70℃, and continue to keep the temperature for 4h-6h to obtain acrylamide polymer thickener for fracturing fluid.

[0033] In step S1, the pH of the system is typically, but not limited to, adjusted to 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, and 9.0.

[0034] In step S1, an alkaline solution is used to adjust the pH of the system. In some embodiments, a sodium hydroxide solution is used to adjust the pH of the system. Preferably, a 12% sodium hydroxide solution is used to adjust the pH of the system.

[0035] In step S3, the heating temperature is typically, but not limited to, 50°C, 55°C, 60°C, 65°C, or 70°C, and the holding time is typically, but not limited to, 4h, 4.5h, 5h, 5.5h, or 6h.

[0036] In some embodiments, in step S3, the initiator is azobisisobutyronitrile (AIBN), and the amount of initiator accounts for 0.03 wt.% to 0.05 wt.% of the total monomer weight. Here, "total monomer weight" refers to the sum of the weights of acrylamide, hydrophilic propylene monomers, hydrophobic propylene monomers, and aromatic or heterocyclic compounds. The proportion of initiator to the total monomer weight is typically, but not limited to, 0.03 wt.%, 0.035 wt.%, 0.04 wt.%, 0.045 wt.%, and 0.05 wt.%.

[0037] According to a third aspect of the present invention, a fracturing fluid is provided, comprising the aforementioned acrylamide polymer thickener for fracturing fluids.

[0038] The present invention will be further described below with reference to specific embodiments, but the following embodiments are by no means intended to limit the present invention.

[0039] Example 1 A thickener for fracturing fluid used in deep coalbed methane reservoir stimulation is prepared by the following method: S1. Mix 20 parts by weight of acrylamide, 5 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 6 parts by weight of methacrylamide propyltrimethylammonium chloride, 3 parts by weight of p-butoxystyrene and 40 parts by weight of water until homogeneous. Adjust the pH to 7.0 with 12% sodium hydroxide solution to obtain an aqueous phase mixture. S2. Mix 6 parts by weight of emulsifier and 40 parts by weight of white oil evenly to obtain an oil phase mixture; wherein the emulsifier is a mixture of SP-80 and OP-10, with a weight ratio of 5:1. S3. Mix the oil phase mixture and the water phase mixture evenly, remove oxygen by purging with nitrogen under stirring, heat to 50°C, add 0.03 wt.% azobisisobutyronitrile, and continue to keep the reaction at the temperature for 5 hours to obtain the thickener.

[0040] Example 2 A thickener for fracturing fluid used in deep coalbed methane reservoir stimulation is prepared by the following method: S1. Mix 18 parts by weight of acrylamide, 5 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 4 parts by weight of methacrylamide propyltrimethylammonium chloride, 5 parts by weight of p-butoxystyrene and 40 parts by weight of water until homogeneous, and adjust the pH to 8.0 with 12% sodium hydroxide solution to obtain an aqueous phase mixture. S2. Mix 7 parts by weight of emulsifier and 50 parts by weight of white oil evenly to obtain an oil phase mixture; wherein the emulsifier is a mixture of SP-80 and OP-10, with a weight ratio of 5.5:1. S3. Mix the oil phase mixture and the water phase mixture evenly, remove oxygen by purging with nitrogen under stirring, heat to 55°C, add 0.05wt.% azobisisobutyronitrile, and continue to keep the reaction at the temperature for 4 hours to obtain the thickener.

[0041] Example 3 A thickener for fracturing fluid used in deep coalbed methane reservoir stimulation is prepared by the following method: S1. Mix 19 parts by weight of acrylamide, 6 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5 parts by weight of methacrylamide propyltrimethylammonium chloride, 4 parts by weight of p-butoxystyrene and 40 parts by weight of water until homogeneous, and adjust the pH to 7.5 with 12% sodium hydroxide solution to obtain an aqueous phase mixture. S2. Mix 8 parts by weight of emulsifier and 45 parts by weight of white oil evenly to obtain an oil phase mixture; wherein the emulsifier is a mixture of SP-80 and OP-10, with a weight ratio of 6:1. S3. Mix the oil phase mixture and the water phase mixture evenly, remove oxygen by purging with nitrogen under stirring, heat to 60°C, add 0.04 wt.% azobisisobutyronitrile, and continue to keep the reaction at the temperature for 5 hours to obtain the thickener.

[0042] Example 4 A thickener for fracturing fluid used in deep coalbed methane reservoir stimulation is prepared by the following method: S1. Mix 21 parts by weight of acrylamide, 7 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5 parts by weight of methacrylamide propyltrimethylammonium chloride, 4 parts by weight of p-butoxystyrene and 40 parts by weight of water until homogeneous, and adjust the pH to 9.0 with 12% sodium hydroxide solution to obtain an aqueous phase mixture. S2. Mix 9 parts by weight of emulsifier and 55 parts by weight of white oil evenly to obtain an oil phase mixture; wherein the emulsifier is a mixture of SP-80 and OP-10, with a weight ratio of 6.5:1. S3. Mix the oil phase mixture and the water phase mixture evenly, remove oxygen by purging with nitrogen under stirring, heat to 65°C, add 0.05wt.% azobisisobutyronitrile, and continue to keep the reaction at the temperature for 6 hours to obtain the thickener.

[0043] Example 5 A thickener for fracturing fluid used in deep coalbed methane reservoir stimulation is prepared by the following method: S1. Mix 22 parts by weight of acrylamide, 8 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 4 parts by weight of methacrylamide propyltrimethylammonium chloride, 3 parts by weight of p-butoxystyrene and 40 parts by weight of water until homogeneous, and adjust the pH to 8.0 with 12% sodium hydroxide solution to obtain an aqueous phase mixture. S2. Mix 10 parts by weight of emulsifier and 55 parts by weight of white oil evenly to obtain an oil phase mixture; wherein the emulsifier is a mixture of SP-80 and OP-10, with a weight ratio of 7:1. S3. Mix the oil phase mixture and the water phase mixture evenly, remove oxygen by purging with nitrogen under stirring, heat to 70°C, add 0.04 wt.% azobisisobutyronitrile, and continue to keep the reaction at the temperature for 4 hours to obtain the thickener.

[0044] Performance Evaluation 1. Viscosity and temperature and shear resistance of fracturing fluid The target materials prepared in Examples 1-5 were mixed with water in different proportions to prepare fracturing fluids, and their apparent viscosity and temperature and shear resistance (100℃, 100s) were tested. -1 ), as shown in Tables 1 and 2.

[0045] Table 1 Apparent viscosity at different concentrations

[0046] Table 2 Temperature and shear resistance at different concentrations

[0047] As shown in Tables 1 and 2, the target substances prepared in Examples 1-5, when configured into solutions according to different dosages, exhibit good viscosity-changing properties and temperature and shear resistance.

[0048] 2. Desorption and displacement capabilities The target materials prepared in Examples 1-5 were diluted to a 0.3% aqueous solution and then subjected to gel breaking. The surface tension, contact angle, and capillary force of the gel breaking solution were tested, and the results are shown in Table 3. Table 3 shows that the surface tension of Examples 1-5 was less than 28 mN / m, the contact angle was less than 21°, and the capillary pressure was less than 9 MPa. This indicates that the target materials of this invention have good desorption and displacement capabilities, can alter the wettability of coal and rock surfaces, resulting in lower surface tension and contact angle, reduced capillary resistance, enhanced aqueous solution permeability, minimized water-locking damage, improved desorption efficiency, and contribute to the long-term stable production of coal and rock gas.

[0049] Table 3 Desorption and displacement capabilities

[0050] 3. Core damage and swelling resistance Referring to the standard "SY / T 5107 Performance Evaluation Method of Water-Based Fracturing Fluid", 0.015% of capsule fracturing agent was added at 95℃, and the mixture was broken up for 120 minutes. The residue and core damage rate of the 0.5 wt.% fracturing fluid prepared in Examples 1-5 were then tested. The specific test results are shown in Table 4 below.

[0051] Table 4 Core damage and swelling resistance

[0052] As shown in Table 4, the anti-swelling rate of the fracturing fluids prepared in Examples 1-5 remained above 80% after gel breaking. This is because after gel breaking, the molecular chains break, and the positively charged cationic small molecular chains can be adsorbed and inserted between the clay mineral crystal layers through electrostatic attraction, thus inhibiting the hydration and swelling of the clay minerals. The core damage rate remained below 15%, indicating low damage performance.

[0053] The above descriptions are merely several preferred embodiments of the present invention, but the present invention is not limited to the specific embodiments described above. The specific embodiments described above are illustrative and not restrictive. Researchers in the art, under the guidance of the present invention and in accordance with the spirit and principles of the present invention, can make improvements and modifications, all of which fall within the protection scope of the present invention.

[0054] Matters not covered in this invention are common knowledge.

Claims

1. An acrylamide-based polymer thickener for fracturing fluid, characterized in that, It is prepared by reverse emulsion polymerization of an aqueous phase mixture and an oil phase mixture, wherein the aqueous phase mixture is composed of acrylamide, a hydrophilic propylene monomer, a hydrophobic propylene monomer, an aromatic ring or heterocyclic compound and water; and the oil phase mixture is composed of an emulsifier and an organic solvent.

2. The acrylamide polymer thickener for fracturing fluid according to claim 1, characterized in that, The hydrophilic propylene monomer is one or more of the following: methacrylamide, hydroxymethylacrylamide, acrylic acid, methacrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid.

3. The acrylamide polymer thickener for fracturing fluid according to claim 1, characterized in that, The hydrophobic acrylic monomer is one or more of octadecyl acrylate, octadecyl methacrylate, methoxy polyethylene glycol methacrylate, and methacrylamide propyltrimethylammonium chloride.

4. The acrylamide polymer thickener for fracturing fluid according to claim 1, characterized in that, The aromatic ring or heterocyclic compound is one or more of p-butoxystyrene, styrene, 2-vinylthiophene, and 4-tert-butoxystyrene.

5. The acrylamide polymer thickener for fracturing fluid according to claim 1, characterized in that, The organic solvent is one or more of white oil, paraffin, and cyclohexane.

6. The acrylamide polymer thickener for fracturing fluid according to claim 1, characterized in that, The aqueous phase mixture contains the following components by weight: acrylamide: 18-22 parts, hydrophilic propylene monomer: 5-8 parts, hydrophobic propylene monomer: 4-6 parts, aromatic ring or heterocyclic compound: 3-5 parts, and water: 40 parts; the oil phase mixture contains the following components by weight: emulsifier: 6-10 parts, and organic solvent: 40-55 parts.

7. The acrylamide polymer thickener for fracturing fluid according to claim 1, characterized in that, The emulsifier is a mixture of SP-80 and OP-10.

8. The acrylamide polymer thickener for fracturing fluid according to claim 7, characterized in that, The weight ratio of SP-80 to OP-10 is (5.0-7.0):

1.

9. The acrylamide polymer thickener for fracturing fluid according to claim 1, characterized in that, The aqueous phase mixture is composed of 18-22 parts acrylamide, 5-8 parts 2-acrylamido-2-methylpropanesulfonic acid, 4-6 parts methacrylamide propyltrimethylammonium chloride, 3-5 parts p-butoxystyrene and 40 parts water by weight, and the oil phase mixture is composed of 6-10 parts emulsifier and 40-55 parts white oil.

10. A method for preparing an acrylamide polymer thickener for fracturing fluid, characterized in that, The method for preparing the acrylamide polymer thickener for fracturing fluid according to any one of claims 1-9 comprises the following steps: S1: Mix acrylamide, hydrophilic propylene monomer, hydrophobic propylene monomer, aromatic ring or heterocyclic compound and water evenly, and adjust the pH of the system to 6.0-9.0 to obtain an aqueous phase mixture; S2: Mix the emulsifier and organic solvent evenly to obtain an oil phase mixture; S3: Mix the oil phase mixture and the aqueous phase mixture evenly, introduce inert gas to remove oxygen under stirring, add initiator after heating to 50℃-70℃, and continue to keep the temperature for 4h-6h to obtain acrylamide polymer thickener for fracturing fluid.

11. The method for preparing the acrylamide polymer thickener for fracturing fluid according to claim 10, characterized in that, In step S1, the pH of the system is adjusted using an alkaline solution of [Z2].

12. The method for preparing the acrylamide polymer thickener for fracturing fluid according to claim 10, characterized in that, In step S3, the initiator is azobisisobutyronitrile (AIBN), and the amount of initiator accounts for 0.03 wt.%-0.05 wt.% of the total weight of the monomer.

13. A fracturing fluid, characterized in that, Includes the acrylamide polymer thickener for fracturing fluid as described in any one of claims 1-9.

Images