Shear improving agent for water-based drilling fluid and preparation method of shear improving agent

Abstract

The invention discloses a shear strength improving agent for water-based drilling fluid, which comprises a structural monomer A. The structural monomer A has the following structural formula: in the formula, R1 is selected from H or C1-C6 alkyl, R2 is selected from H or C1-C6 alkyl, M is selected from H or an alkali metal element, and R3 is selected from C1-C6 alkylene; the invention also discloses a preparation method of the shear strength improving agent for the water-based drilling fluid. The prepared water-based drilling fluid shear strength improving agent is a zwitterionic copolymer, a molecular chain contains an anionic group and a cationic group at the same time, good coalescence stability and temperature resistance are achieved, meanwhile, the water-based drilling fluid shear strength improving agent is a block polymer with several different structures, and the water-based drilling fluid shear strength improving agent is suitable for being used as a water-based drilling fluid shear strength improving agent. The shear strength improving effect of the drilling fluid is remarkably achieved, and the rheological property and the filtrate loss reduction performance of the water-based drilling fluid are not affected or have a synergistic effect.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid technology, specifically to a cutting agent for water-based drilling fluid and its preparation method. Background Technology

[0002] Drilling fluid plays a crucial role in oil and gas exploration and development; it is the "blood" of drilling, requiring excellent rheological properties to ensure smooth and efficient drilling operations. With the continuous development of deep, ultra-deep, and extended-reach wells in the petroleum industry, some properties of drilling fluids are no longer sufficient to meet drilling needs, requiring optimization and adjustment. As well depth increases, or the horizontal displacement of directional wells increases, improving wellbore cleaning becomes a key challenge in the drilling process. The degree of cuttings removal from the bottom of the well directly affects the rate of penetration (RLP) during drilling. The most direct and effective way to improve wellbore cleaning is to enhance the cuttings-carrying capacity of the drilling fluid, or in other words, to increase the dynamic plasticity ratio and dynamic shear strength of the drilling mud. While maintaining an appropriate apparent viscosity range, increasing the dynamic plasticity ratio and dynamic shear strength results in good cuttings-carrying capacity and good shear dilution properties, efficiently bringing cuttings from the bottom of the well to the surface. By adding drilling fluid cutting enhancers to improve the performance of the drilling fluid system, the drilling fluid and its components work synergistically to increase the viscosity and shear force of the drilling fluid system. It has suitable low shear rate viscosity, excellent shear dilution properties and other characteristics, which effectively enhance the suspension and removal of drill cuttings by the drilling fluid.

[0003] Adjusting polymer structure is an important way to improve rheological regulation. To achieve diverse copolymer structures and ensure structural uniformity, numerous methods exist for polymer preparation, among which free radical polymerization has attracted much attention due to its mild reaction conditions and wide range of applicable monomers. However, in traditional free radical polymerization systems, the high concentration of free radicals easily leads to free radical termination reactions, resulting in uncontrollable reactions and polymers with wide molecular weight distributions and difficult-to-control molecular structures, significantly impacting their application performance. Controlled / living radical polymerization, as an emerging polymerization method, can achieve dynamic equilibrium by adding special chain transfer agents with high chain transfer constants to the polymerization system. This allows for degenerative transfer between the growing free radicals and the chain transfer agent, reducing the free radical concentration in the reaction system and suppressing bimolecular termination, thereby controlling the polymer molecular weight and its distribution. It is widely used in polymer synthesis. Based on existing research, a zwitterionic copolymer sizing agent was prepared. Zwitterionic polymers contain both anionic and cationic groups in their molecular chains. The cationic groups adsorb onto clay particles via electrostatic interactions, while the neutral groups form a hydration film around them. The anionic groups enhance repulsive forces, thus comprehensively improving the system's aggregation stability. Therefore, zwitterionic polymers can both inhibit the hydration and dispersion of clay particles and reduce drilling fluid filtration loss, making them widely used as polymeric chemical agents in petroleum engineering. Utilizing the charge interactions between anionic and cationic monomers and their excellent thermal stability, bentonite can be stably dispersed, and drilling fluids can exhibit excellent shear-dilution properties. Further research into developing highly efficient drilling fluid shear-reducing agents to fully utilize the functions of these monomers is a pressing area of ​​research in the field of drilling fluid treatment agents. Summary of the Invention

[0004] The purpose of this invention is to provide a block polymer, its preparation method, and its application, to solve the technical problems of poor rock-carrying performance of drilling fluids and poor dynamic plasticity ratio and dynamic shear force of drilling mud in the prior art.

[0005] To achieve the above objectives, one embodiment of the present invention provides a cutting agent for water-based drilling fluids, comprising structural monomer A, which has the following structural formula:

[0006]

[0007] In the formula, R1 is selected from H or C1-C6 alkyl groups, R2 is selected from H or C1-C6 alkyl groups, M is selected from H or alkali metal elements, and R3 is selected from C1-C6 alkylene groups.

[0008] In one preferred embodiment of the present invention, the cutting agent further includes structural monomer B and structural monomer C, wherein the molar ratio of structural monomer A, structural monomer B and structural monomer C is 2-4:3-5:0.5-2;

[0009] Structural monomer B has the following structural formula:

[0010]

[0011] In the formula, R4 is selected from H or C1-C6 alkyl groups, and R5 is selected from -OH or -NH2;

[0012] Structural monomer C has the following structural formula:

[0013]

[0014] In the formula, R6, R7, and R8 are each independently selected from H or C1-C6 alkyl groups, and X... - Selected from Cl - ,Br - Or I - .

[0015] Based on the cutting agent for water-based drilling fluid disclosed in this invention, this invention also discloses a method for preparing the cutting agent for water-based drilling fluid, which is prepared by atom transfer radical polymerization.

[0016] In one preferred embodiment of the present invention, during the preparation process, the mass ratio of initiator to monomer is 1-2:1000, and the mass ratio of catalyst to monomer is 2-3:500.

[0017] In one preferred embodiment of the present invention, the initiator is trithiocarbonate and the catalyst is azobisisobutyronitrile.

[0018] In one preferred embodiment of the present invention, the reaction temperature during the preparation process is 50℃-100℃ and the reaction time is 5h-10h.

[0019] In one preferred embodiment of the present invention, the reaction temperature is 70℃-75℃ and the reaction time is 6h during the preparation process.

[0020] One preferred embodiment of the present invention is prepared by:

[0021] Add structural monomer A to the dissolved initiator, stir well, and then add structural monomer B to obtain solution 1;

[0022] Dissolve the structural monomer C in water to obtain solution 2;

[0023] After freezing, vacuuming, and thawing, solutions 1 and 2 were mixed. A catalyst was added to solution 1 to carry out a polymerization reaction. After 4 hours of polymerization reaction in solution 1, solution 2 was added and reacted for 2 hours. The mixture was then dried to obtain the cutting agent.

[0024] One preferred embodiment of the present invention is prepared by:

[0025] Structural monomer A was added to the dissolved initiator to obtain solution 1;

[0026] Dissolve structural monomer B in water to obtain solution 2;

[0027] Dissolve the structural monomer C in water to obtain solution 3;

[0028] After freezing, vacuuming, and thawing, solutions 1, 2, and 3 are subjected to a polymerization reaction. A catalyst is added to solution 1 to carry out the polymerization reaction. After solution 1 has been polymerized for 2 hours, solution 2 is added and reacted for 2 hours. Then solution 3 is added and reacted for 2 hours. The mixture is then dried to obtain the cutting agent.

[0029] One preferred embodiment of the present invention is prepared by dissolving structural monomer A in water, stirring until homogeneous, then sequentially adding structural monomer B, structural monomer C, initiator, and catalyst, stirring until homogeneous, placing in a reaction flask, and subjecting it to freezing, vacuuming, and thawing treatments, followed by polymerization reaction for 6 hours, and drying to obtain the cutting agent.

[0030] In summary, the beneficial effects of the present invention are as follows:

[0031] 1. The water-based drilling fluid skimmer prepared by this invention is an amphoteric copolymer, which contains both anionic and cationic groups in its molecular chain, and has good aggregation stability and temperature resistance.

[0032] 2. The water-based drilling fluid shearing agent of the present invention is a block polymer with several different structures, which significantly achieves the shearing effect of drilling fluid, and has no effect on the rheological properties and filtration loss reduction properties of water-based drilling fluid or has an synergistic effect.

[0033] 3. The preparation method of the water-based drilling fluid cutting agent used in this invention is the ATRP polymerization method. As a type of free radical polymerization method, it has the advantages of a wide range of applicable monomers, mild polymerization conditions, and the ability to ensure the uniformity of polymer structure. Furthermore, the preparation method of the water-based drilling fluid cutting agent of this invention has simple procedures, low cost, and can be industrially applied.

[0034] 4. This invention proposes to introduce the influence of polymer sequence structure characteristics on solution rheological properties into the research of drilling fluid cutting agents, and analyzes the microscopic mechanism of action. It provides a method for preparing polymers with different structures by ATRP polymerization, which is a new idea for the research and development of key treatment agents such as drilling fluid cutting agents. It aims to produce a good maintenance effect on the problem of drilling fluid performance damage during drilling operations, and form a scientific and efficient water-based drilling fluid cutting agent.

[0035] 5. The water-based drilling fluid cutting agent of this invention contains structural monomers A, B, and C. Structural monomer A contains unsaturated carbon-carbon double bonds, facilitating copolymerization with other monomers. The addition of sulfonic acid groups with good temperature and salt resistance to the molecular chain imparts strong rigidity, enhancing the temperature and salt resistance of the synthesized cutting agent and ensuring its performance. Structural monomer B has an allyl functional group. This functional group achieves its cutting effect primarily through polymerization to form polyacrylic acid. When acrylic acid molecules undergo polymerization, the allyl functional group reacts with other acrylic acid molecules or other monomers. Conjugate addition reactions form high molecular weight polymers with high molecular weight and molecular weight distribution, enabling them to form three-dimensional network structures in aqueous solutions. The structural monomer C has alkyl chains and halogen anions. The alkyl chains can increase the hydrophobicity of surfactant molecules in solution, thereby enhancing their dispersibility and wettability in water. This helps the surfactant to contact solid surfaces and form a uniform film. The halogen element is an anion that can form ion pairs with the cations in cationic surfactants, improving the solubility and dispersibility of the surfactant. This helps the surfactant to form stable emulsions and colloids in water. Detailed Implementation

[0036] A water-based drilling fluid lifting agent includes structural monomer A, structural monomer B and structural monomer C, wherein the molar ratio of structural monomer A, structural monomer B and structural monomer C is 2-4:3-5:0.5-2.

[0037] Structural unit A has the following structural formula:

[0038]

[0039] In the formula, R1 is selected from H or C1-C6 alkyl, R2 is selected from H or C1-C6 alkyl, M is selected from H or an alkali metal element, and R3 is selected from C1-C6 alkylene.

[0040] Structural monomer B has the following structural formula:

[0041]

[0042] In the formula, R4 is selected from H or C1-C6 alkyl groups, and R5 is selected from -OH or -NH2;

[0043] Structural monomer C has the following structural formula:

[0044]

[0045] In the formula, R6, R7, and R8 are each independently selected from H or C1-C6 alkyl groups, and X... - Selected from Cl - ,Br- Or I - The alkyl groups of C1-C6 are selected from one of -CH3, -CH2CH3 and -CH2CH2CH3.

[0046] A method for preparing a cutting agent for water-based drilling fluid is disclosed, which employs atom transfer radical polymerization. During the preparation process, the mass ratio of initiator to monomer is 1-2:1000, and the mass ratio of catalyst to monomer is 2-3:500. Further, the initiator is trithiocarbonate, and the catalyst is azobisisobutyronitrile.

[0047] During the preparation process, the reaction temperature is 50-100℃ and the reaction time is 5h-10h. Preferably, the reaction temperature is 70-75℃ and the reaction time is 6h.

[0048] A method for preparing a cutting agent for water-based drilling fluid, the preparation method being as follows:

[0049] Add structural monomer A to the dissolved initiator, stir well, and then add structural monomer B to obtain solution 1;

[0050] Dissolve the structural monomer C in water to obtain solution 2;

[0051] After freezing, vacuuming, and thawing, solutions 1 and 2 were mixed. A catalyst was added to solution 1 to carry out a polymerization reaction. After 4 hours of polymerization reaction in solution 1, solution 2 was added and reacted for 2 hours. The mixture was then dried to obtain the cutting agent.

[0052] A method for preparing a cutting agent for water-based drilling fluid, the preparation method being as follows:

[0053] Structural monomer A was added to the dissolved initiator to obtain solution 1;

[0054] Dissolve structural monomer B in water to obtain solution 2;

[0055] Dissolve the structural monomer C in water to obtain solution 3;

[0056] After freezing, vacuuming, and thawing, solutions 1, 2, and 3 are subjected to a polymerization reaction. A catalyst is added to solution 1 to carry out the polymerization reaction. After solution 1 has been polymerized for 2 hours, solution 2 is added and reacted for 2 hours. Then solution 3 is added and reacted for 2 hours. The mixture is then dried to obtain the cutting agent.

[0057] A method for preparing a cutting agent for water-based drilling fluid is as follows: add water to dissolve structural monomer A, stir evenly, then add structural monomer B, structural monomer C, initiator and catalyst in sequence, stir evenly, place in a reaction bottle, freeze, vacuum, thaw, polymerize for 6 hours, and dry to obtain the cutting agent.

[0058] The cutting agent for water-based drilling fluid of this invention is synthesized from polymers with the same composition by chemical substances having the above three structures. However, the order of monomer addition is adjusted by atom transfer radical polymerization (ATRP) to make the synthesized polymers have different structures. Experiments are conducted to explore the cutting ability of different polymer structures on the drilling fluid system.

[0059] In this invention, the synthesis of polymers in water-based drilling fluids is studied and evaluated from multiple perspectives, including additive dosage, polymer structure, polymer molecular weight, and polymer action mechanism.

[0060] In this invention, the additives can be commercially available products or can be prepared according to methods known in the art, which will not be elaborated further in this invention.

[0061] In this invention, the drilling fluid polymer is prepared using the ATRP polymerization method well known to those skilled in the art, which will not be elaborated further here. Specific operations are listed below and should not be construed as limitations on this invention.

[0062] The present invention will be described in detail below through embodiments. Unless otherwise specified, all raw materials used in the following embodiments are commercially available products.

[0063] Experimental protocol

[0064] Scheme 1: Weigh 0.15% (by weight) of initiator trithiocarbonate, dissolve in distilled water, then add a certain amount of structural monomer A to a beaker. Adjust the pH to 7 with NaOH, stir well, and then add structural monomer B sequentially, stirring until the system is homogeneous and stable. Place the beaker in vacuum reaction flask 1. Add structural monomer C to the beaker, dissolve in distilled water, stir well, and place in vacuum reaction flask 2. Seal 1 and 2 and freeze in liquid nitrogen for 5-10 minutes. After the polymer is completely frozen, vacuum for 5 minutes, then purge with dry nitrogen or inert gas to eliminate oxygen interference. Repeat 2-3 times to ensure a pure reaction environment. Finally, thaw the polymer in a water bath at room temperature for 5 minutes, then add 0.5% (by weight) of catalyst azobisisobutyronitrile to 1. Place the beaker on a magnet and stir, initiating the polymerization reaction. After 4 hours of reaction 1, add 2 and react for 2 hours. The reaction is carried out at 70-75℃. After the reaction was completed, the sample was retrieved, rotary evaporated in a round-bottom flask, and then dried. The product obtained was X.

[0065] Option 2: Weigh 0.15% (by weight) of initiator trithiocarbonate, dissolve in distilled water, then add a certain amount of structural monomer A to a beaker, adjust the pH to 7 with NaOH, stir well, and place in vacuum reaction flask 1; add structural monomer B to a beaker, dissolve in distilled water, stir well, and place in vacuum reaction flask 2; add structural monomer C to a beaker, dissolve in distilled water, stir well, and place in vacuum reaction flask 3; seal and freeze in liquid nitrogen for 5-10 minutes. After the polymer is completely frozen, vacuum for 5 minutes, then purge with dry nitrogen or inert gas to eliminate oxygen interference. Repeat 2-3 times to ensure a pure reaction environment. Finally, thaw the polymer in a water bath at room temperature for 5 minutes, then add 0.5% (by weight) of catalyst azobisisobutyronitrile to option 1. Place the beaker on a magnet and stir, and the polymerization reaction will begin. After option 1 reacts for 2 hours, add option 2 and react for 2 hours, then add option 3 and react for 2 hours. The reaction is carried out at 70-75℃. After the reaction was completed, the sample was retrieved, rotary evaporated in a round-bottom flask, and then dried. The product obtained was Y.

[0066] Option 3: Add structural monomer A to a beaker, dissolve and stir in distilled water until homogeneous. Adjust the pH to 7 with NaOH. Then, add structural monomers B and C, initiator trithiocarbonate, and catalyst azobisisobutyronitrile in sequence, stir until homogeneous, place in a vacuum reaction flask, seal, and freeze in liquid nitrogen for 5-10 minutes. After the polymer is completely frozen, evacuate for 5 minutes, then purge with dry nitrogen or inert gas to eliminate oxygen interference. Repeat 2-3 times to ensure a pure reaction environment. Finally, thaw the polymer in a water bath at room temperature for 5 minutes, place the beaker on a magnet and stir. The polymerization reaction will begin simultaneously. Continue the reaction for 6 hours at 70-75℃. After the reaction is complete, retrieve the sample, rotary evaporate in a round-bottom flask, and then dry. The obtained product is Z.

[0067] Example 1

[0068] According to the method described in Scheme 1, polymer X1 is prepared, wherein the product obtained after a complete reaction process according to the molar ratio of structural monomer A: structural monomer B: structural monomer C = 3:4:1 is polymer X1.

[0069] Example 2

[0070] According to the method described in Scheme 2, polymer Y1 is prepared, wherein the product obtained after a complete reaction process according to the molar ratio of structural monomer A: structural monomer B: structural monomer C = 3:4:1 is polymer Y1.

[0071] Example 3

[0072] According to the method described in Scheme 3, polymer Z1 is prepared, wherein the product obtained after a complete reaction process according to the molar ratio of structural monomer A: structural monomer B: structural monomer C = 3:4:1 is polymer Z1.

[0073] Example 4

[0074] According to the method described in Scheme 1, polymer X2 is prepared, wherein the product obtained after a complete reaction process is polymer X2, wherein the molar ratio of structural monomer A: structural monomer B: structural monomer C is 3.2: 3.6: 1.2.

[0075] Example 5

[0076] According to the method described in Scheme 2, polymer Y2 is prepared, wherein the product obtained after a complete reaction process is polymer Y2, wherein the molar ratio of structural monomer A: structural monomer B: structural monomer C is 3.2: 3.6: 1.2.

[0077] Example 6

[0078] According to the method described in Scheme 3, polymer Z2 is prepared, wherein the product obtained after a complete reaction process is polymer Z2, wherein the molar ratio of structural monomer A: structural monomer B: structural monomer C is 3.2: 3.6: 1.2.

[0079] Example 7

[0080] According to the method described in Scheme 1, polymer X3 is prepared, wherein the product obtained after a complete reaction process is polymer X3, wherein the molar ratio of structural monomer A: structural monomer B: structural monomer C is 2.8: 3.8: 1.4.

[0081] Example 8

[0082] According to the method described in Scheme 2, polymer Y3 is prepared, wherein the product obtained after a complete reaction process is polymer Y3, wherein the molar ratio of structural monomer A: structural monomer B: structural monomer C is 2.8: 3.8: 1.4.

[0083] Example 9

[0084] According to the method described in Scheme 3, polymer Z3 is prepared, wherein the product obtained after a complete reaction process is polymer Z3, wherein the molar ratio of structural monomer A: structural monomer B: structural monomer C is 2.8: 3.8: 1.4.

[0085] (Note: Polymer X has a partially block structure, polymer Y has a fully block structure, and polymer Z has a random structure. The same applies below, and will not be described in detail again.)

[0086] The above-mentioned X1, X2, X3, Y1, Y2, Y3, Z1, Z2 and Z3 are all cutting agents for water-based drilling fluids.

[0087] Testing and Inspection

[0088] The performance testing methods involved in Examples 1-9 are as follows:

[0089] 1. Evaluation of the filtration performance of water-based drilling fluid: The filtration volume of water-based drilling fluid containing polymer cutting agent prepared by the ATRP method was determined using a medium-pressure filtration analyzer. The specific process is as follows:

[0090] Pour 150 mL of the prepared drilling fluid into the medium-pressure filtration analyzer, place the gasket and special filter paper, close the lid and tighten the seal. Record the volume of filtrate over 30 minutes at an output pressure of 0.7 MPa. This volume is the medium-pressure API filtration loss of the drilling fluid, in mL.

[0091] 2. Evaluation of the rheological properties of water-based drilling fluids: Reference data for drilling fluid rheological properties include apparent viscosity, plastic viscosity, and dynamic shear force. After stirring the water-based drilling fluid at a high-frequency speed of 12000 rpm for 20 minutes, the values ​​for Φ600 and Φ300 were measured using a six-speed rotational viscometer according to standard GB / T16782-1997. The apparent viscosity (AV), plastic viscosity (PV), and dynamic shear force (YP) of the water-based drilling fluid were calculated using the following formulas.

[0092] (1) Apparent viscosity AV (unit mPa·s) = 1 / 2 * Φ600

[0093] (2) Plastic viscosity PV (unit mPa·s) = Φ600 - Φ300

[0094] (3) Dynamic shear force (unit Pa) YP=AV-PV

[0095] Following the above method, water-based drilling fluids formulated with the polymers obtained in Examples 1-9 were used, with a polymer addition of 1% in each case. The molecular weight, filtration loss, and rheological properties of each water-based drilling fluid containing a shearing agent were tested. Performance evaluations were conducted on Examples 1-3, yielding the first set of data, as shown in Table 1; performance evaluations were conducted on Examples 4-6, yielding the second set of data, as shown in Table 2; and performance evaluations were conducted on Examples 7-9, yielding the third set of data, as shown in Table 3.

[0096] Table 1: Effects of polymers on rheological properties and filtration properties (Group 1)

[0097]

[0098] Table 2: Effects of polymers on rheological properties and filtration properties (Group 2)

[0099]

[0100] Table 3: Effects of polymers on rheological properties and filtration properties (Group 3)

[0101]

[0102] Comparing the data in Tables 1-3, the test results show that the synthetic polymer water-based drilling fluid shearing agent provided by this invention has a certain regulating effect on the rheology of drilling fluid, and the different sequence structures and molecular weights of the prepared polymers have different degrees of influence on the drilling fluid.

[0103] A comprehensive comparison of the data in Tables 1-3 shows that polymer molecular weight has a more significant impact on the apparent viscosity of drilling fluid. Table 2 indicates that the apparent viscosity of the drilling fluid is highest when the polymer molecular weight is around 90,000, suggesting that polymers at this molecular weight can be effective in the system. Partial block polymers X1, X2, and X3 generally have high dynamic plasticity ratios, reaching 0.93 Pa / mPa·s, while fully block polymers and randomly distributed polymers have lower dynamic plasticity ratios.

[0104] Analyzing the data in Tables 1, 2, and 3 separately reveals that for polymers with similar molecular weights but different sequence structures, their effects on the apparent viscosity of drilling fluid are not significantly different, while the plastic viscosity fluctuates considerably, resulting in large variations in dynamic shear force. Specifically, with the appearance of block structures, the plastic viscosity of the drilling fluid decreases, but the dynamic shear force increases, thus manifesting as a significant increase in the dynamic-to-plastic ratio.

[0105] Polymer sequence structure and molecular weight also significantly influence polymer filtration loss reduction. For polymers with similar molecular weights but different structures, partially block copolymers exhibit the best filtration loss reduction, while randomly distributed partially block and fully block copolymers show increased filtration loss. The filtration loss reduction of partially block copolymers is not significantly different from that of randomly distributed copolymers, and both are much lower than that of fully block copolymers. It can also be seen that for fully block copolymers, molecular weight has a relatively small impact on filtration loss.

[0106] To verify the effect of the polymer prepared in this invention, polymer X2, which showed the best experimental results, was selected for addition experiments. The rheological properties and filtration loss of drilling fluid were measured at addition rates of 0%, 1%, and 2%, respectively. The experimental data are shown in Table 4.

[0107] Table 4: Effects of polymer X2 on rheological properties and filtration properties

[0108]

[0109]

[0110] As can be seen from Table 4, with the continuous increase of X2 dosage, the viscosity increases significantly and the dynamic shear force is significantly improved. Polymer X2 can play a good role as a shearing agent in the system and achieve the effect of improving the flow pattern.

[0111] Comparative Example

[0112] Commonly used drilling fluid cutting agents, including HIRHEO, BT, RM-60, and PAC-50, were screened out. Their rheological properties and filtration loss were measured to evaluate their cutting effect and to compare them with the block polymer synthesized by the ATRP polymerization method provided in this invention.

[0113] Comparative Example 1: HIRHEO

[0114] The HIRHEO rheological properties and filtration loss measurements are shown in Table 5.

[0115] Table 5: Effects of Comparative Example 1 on rheological properties and filtration properties

[0116]

[0117] As can be seen from Table 5, as the amount of HIRHEO increases, the viscosity increases significantly, while the dynamic shear force changes very little. The shearing agent HIRHEO can play a good role in the system, but it cannot change the shear force.

[0118] Comparative Example 2: BT

[0119] The BT rheological properties and filtration loss measurements are shown in Table 6.

[0120] Table 6: Effects of Comparative Example 2 on rheological properties and filtration properties

[0121]

[0122]

[0123] As shown in Table 6, the viscosity and dynamic shear force increase significantly with the continuous increase of BT dosage. This indicates that BT can play a good role in improving shear strength.

[0124] Comparative Example 3: RM-60

[0125] The rheological properties and filtration loss of RM-60 are shown in Table 7.

[0126] Table 7: Effects of Comparative Example 3 on rheological properties and filtration efficiency

[0127]

[0128] As shown in Table 7, both viscosity and dynamic shear force increase with the continuous increase of RM-60 dosage. This indicates that RM-60 can improve shear strength.

[0129] Comparative Example 4: PAC-50

[0130] Table 8 shows the rheological properties and filtration loss of PAC-50.

[0131] Table 8: Effects of Comparative Example 4 on rheological properties and filtration efficiency

[0132]

[0133] As shown in Table 8, with the continuous increase of PAC-50 dosage, the increase in viscosity far exceeds the increase in dynamic shear force. This indicates that the rheological properties of the system have not been significantly improved.

[0134] In summary, while Comparative Examples 2 and 3 can achieve good shearing effects, compared with the embodiments of the present invention, the shearing effect of the embodiments of the present invention is higher than that of Comparative Examples 2 and 3. Therefore, the block polymer synthesized by the ATRP atom transfer radical polymerization method provided by the present invention has a very significant effect as a shearing agent. When applied to water-based drilling fluids, it can greatly improve the rheological properties of drilling fluids. Moreover, the preparation method is simple and the cost is low. Therefore, the present invention has a very broad application prospect and can effectively regulate the rheological problems of drilling fluids during the drilling process, bringing huge economic benefits.

[0135] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A cutting agent for water-based drilling fluids, characterized in that: Includes structural unit A, which has the following structural formula: In the formula, R1 is selected from H or C1-C6 alkyl groups, R2 is selected from H or C1-C6 alkyl groups, M is selected from H or alkali metal elements, and R3 is selected from C1-C6 alkylene groups.

2. The cutting agent for water-based drilling fluid as described in claim 1, characterized in that: The cutting agent further includes structural monomer B and structural monomer C, wherein the molar ratio of structural monomer A, structural monomer B and structural monomer C is 2-4:3-5:0.5-2; The structural unit B has the following structural formula: In the formula, R4 is selected from H or C1-C6 alkyl groups, and R5 is selected from -OH or -NH2; The structural unit C has the following structural formula: In the formula, R6, R7, and R8 are each independently selected from H or C1-C6 alkyl groups, and X... - Selected from Cl - ,Br - Or I - .

3. A method for preparing a cutting agent for water-based drilling fluid according to any one of claims 1-2, characterized in that: It was prepared using atom transfer radical polymerization.

4. The method for preparing a cutting agent for water-based drilling fluid as described in claim 3, characterized in that: During the preparation process, the mass ratio of initiator to monomer is 1-2:1000, and the mass ratio of catalyst to monomer is 2-3:

500.

5. The method for preparing a cutting agent for water-based drilling fluid as described in claim 4, characterized in that: The initiator is trithiocarbonate, and the catalyst is azobisisobutyronitrile.

6. A method for preparing a cutting agent for water-based drilling fluid as described in claim 3 or 4, characterized in that: During the preparation process, the reaction temperature is 50℃-100℃ and the reaction time is 5h-10h.

7. The method for preparing a cutting agent for water-based drilling fluid as described in claim 6, characterized in that: During the preparation process, the reaction temperature is 70℃-75℃ and the reaction time is 6h.

8. A method for preparing a cutting agent for water-based drilling fluid as described in any one of claims 3-7, characterized in that, The preparation method is as follows: Add structural monomer A to the dissolved initiator, stir well, and then add structural monomer B to obtain solution 1; Dissolve the structural monomer C in water to obtain solution 2; After freezing, vacuuming, and thawing, solutions 1 and 2 were mixed. A catalyst was added to solution 1 to carry out a polymerization reaction. After 4 hours of polymerization reaction in solution 1, solution 2 was added and reacted for 2 hours. The mixture was then dried to obtain the cutting agent.

9. A method for preparing a cutting agent for water-based drilling fluid as described in any one of claims 3-7, characterized in that, The preparation method is as follows: Structural monomer A was added to the dissolved initiator to obtain solution 1; Dissolve structural monomer B in water to obtain solution 2; Dissolve the structural monomer C in water to obtain solution 3; After freezing, vacuuming, and thawing, solutions 1, 2, and 3 are subjected to a polymerization reaction. A catalyst is added to solution 1 to carry out the polymerization reaction. After solution 1 has been polymerized for 2 hours, solution 2 is added and reacted for 2 hours. Then solution 3 is added and reacted for 2 hours. The mixture is then dried to obtain the cutting agent.

10. A method for preparing a cutting agent for water-based drilling fluid as described in any one of claims 3-7, characterized in that, The preparation method is as follows: add water to dissolve structural monomer A, stir evenly, then add structural monomer B, structural monomer C, initiator and catalyst in sequence, stir evenly, place in a reaction flask, freeze, vacuum, thaw and polymerize for 6 hours, and dry to obtain the cutting agent.

Images