A carbon dioxide scavenger for drilling fluids, its preparation method, and its application.

Abstract

This invention discloses a carbon dioxide eliminator for drilling fluids, its preparation method, and its application, comprising the following steps: S1, grinding walnut shells into powder; S2, hydrophilically modifying the walnut shell powder to obtain modified walnut shell powder; S3, adding the modified walnut shell powder to water, stirring, and adding calcium chloride and gluconic acid; S4, filtering and drying the mixture from step S3 to obtain a solid powder; S5, granulating the solid powder and drying it to obtain solid particles; S6, coating the surface of the solid particles obtained in step S5 to obtain the carbon dioxide eliminator for drilling fluids. This invention utilizes the porous structure of walnut shells as a support, enabling the storage of calcium ions, the main component for eliminating carbon dioxide, within it, thereby achieving a slow and continuous release of calcium ions in the drilling fluid; simultaneously, the hydrophilically modified walnut shell powder can disperse rapidly in water, increasing the release rate of calcium ions and thus improving the efficiency of carbon dioxide elimination.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field drilling technology, and more specifically, to a carbon dioxide eliminator for drilling fluids, its preparation method, and its application. Background Technology

[0002] Drilling fluids are widely used in the oil and gas drilling industry. When encountering formation fractures during drilling, carbon dioxide gas from the formation can enter the drilling fluid, severely affecting its performance. Specifically, this manifests as an increase in carbonate ions, causing low-density solids such as clay to disperse finely, leading to a significant increase in drilling fluid viscosity and reduced fluidity. The Southwest Oil and Gas Field has encountered the problem of carbon dioxide intrusion into drilling fluids in multiple exploration and development areas. During the treatment of acid gas contamination, the incremental treatment volume exceeded 4800 m³. 3 Using 230 tons of calcium treatment agent, several wells were forced to switch from water-based drilling fluid to oil-based drilling fluid. From 2022 to 2023, wells drilled in the southern Sichuan shale gas area were all affected by varying degrees of carbon dioxide contamination. Severe contamination resulted in the drilling mud losing its fluidity, leading to multiple drilling stoppages for mud adjustments. Currently, there are no effective means to address the problem of carbon dioxide intrusion.

[0003] The patent with publication number CN111927432A, entitled "A method for controlling carbon dioxide intrusion into wellbore in formation", provides a physical means to remove carbon dioxide from the wellbore, but the operation is complicated and costly.

[0004] The patent with publication number CN114292632A, entitled "A Carbon Dioxide Complexing Agent for Drilling Fluid and Its Preparation Method and Application", provides a carbon dioxide complexing agent whose main component is a macromolecular organic compound. It can be seen from the data of the examples that the complexing agent has little effect on the viscosity of the drilling fluid. However, the drilling fluid used in the experiment of this patent has a relatively simple composition, which is why the viscosity of the drilling fluid does not change much before and after the addition of the complexing agent. Drilling fluid is a mixture with many and complex components. The complexing agent composed of macromolecular organic compounds can easily react with other components in the drilling fluid and affect the viscosity of the drilling fluid.

[0005] Therefore, how to handle carbon dioxide in drilling fluid without affecting its viscosity remains a pressing problem in this field.

[0006] In view of the above, this application is hereby submitted. Summary of the Invention

[0007] To address the problems of the prior art, this invention provides a carbon dioxide eliminator for drilling fluids, its preparation method, and its application. By using walnut shells with a porous structure as a support, calcium ions, the main component for eliminating carbon dioxide, can be stored within them, thereby achieving a slow and continuous release of calcium ions in the drilling fluid without causing a sharp increase in the calcium ion content. Simultaneously, the walnut shell powder undergoes hydrophilic modification treatment, enabling it to disperse rapidly in water, increasing the release rate of calcium ions, thereby improving the efficiency of carbon dioxide elimination and preventing carbonate ions from affecting the performance of the drilling fluid.

[0008] This invention is achieved through the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a carbon dioxide eliminator for drilling fluids, comprising the following steps:

[0010] S1, grind walnut shells into powder to obtain walnut shell powder;

[0011] S2, walnut shell powder is subjected to hydrophilic modification treatment to obtain modified walnut shell powder;

[0012] S3, Pour the modified walnut shell powder into deionized water and stir. During the stirring process, add calcium chloride and gluconic acid respectively.

[0013] S4, the mixture from step S3 is filtered and dried to obtain a solid powder;

[0014] S5, granulate the solid powder and dry it to obtain solid particles;

[0015] S6. Coating the surface of the solid particles obtained in step S5 to obtain a carbon dioxide eliminator for drilling fluid.

[0016] In one specific embodiment, in step S1, the particle size of the walnut shell powder is 0.01 to 0.08 mm.

[0017] In a specific embodiment, the hydrophilic modification step S2 is as follows:

[0018] Prepare a modified mixed solution;

[0019] The modified mixed solution was sprayed onto the walnut shell powder obtained in S1.

[0020] In a specific embodiment, the specific steps of hydrophilic modification in step S2 are as follows:

[0021] S21, Prepare an aqueous solution of acrylic resin;

[0022] S22, add epoxy resin to the aqueous acrylic resin solution of step S21, stir, and obtain a mixed solution;

[0023] S23, add nano-silica to the mixed solution of step S22, stir, and obtain a modified mixed suspension;

[0024] S24, the modified mixed suspension is sprayed onto the walnut shell powder obtained in step S1, and the walnut shell powder is then heated to obtain the modified walnut shell powder.

[0025] The present invention improves walnut shell powder by using the above-mentioned components, which can effectively improve the hydrophilicity and internal porous loading capacity of walnut shell powder, thereby ensuring effective loading of calcium ions.

[0026] In one specific embodiment, in step S21, the concentration of the aqueous acrylic resin solution is 11-13 wt%.

[0027] In one specific embodiment, in step S22, the mass ratio of the aqueous acrylic resin solution to the epoxy resin is 1:0.02 to 0.04.

[0028] In one specific embodiment, in step S23, the mass ratio of the mixed solution to nano-silica is 1:0.09 to 0.11.

[0029] In one specific embodiment, in step S3, the mass ratio of deionized water, modified walnut shell powder, calcium chloride, and gluconic acid is 100:35-41:12-16:14-20.

[0030] In one specific embodiment, the preferred mass ratio of deionized water, modified walnut shell powder, calcium chloride, and gluconic acid is 100:41:16:20.

[0031] In one specific embodiment, in step S4, the baking temperature is 60-80°C and the baking time is 40-60 minutes.

[0032] In a specific embodiment, the specific method for preparing the solid particles in step S5 is as follows:

[0033] Water, solid powder, starch and water glass are mixed and granulated, and then dried with hot air to obtain solid particles.

[0034] This invention uses starch and water glass as auxiliary components for granulation. Water glass acts as a binder during the granulation process, allowing the solid powder to aggregate smoothly. In addition, when the carbon dioxide scavenger comes into contact with water, the added starch can quickly absorb water and swell, allowing the solid powder components to disperse rapidly.

[0035] In one specific embodiment, the mass ratio of solid powder, water, starch and water glass is 50:6~8:14~18:14~18.

[0036] In one specific embodiment, preferably, the mass ratio of solid powder, water, starch and water glass is 50:8:18:18.

[0037] In one specific embodiment, the particle size of the solid particles is 8–12 mm.

[0038] In a specific embodiment, the coating treatment in step S6 is as follows:

[0039] The solid particles are coated with sodium carboxymethyl cellulose by spraying.

[0040] In one specific embodiment, the mass ratio of sodium carboxymethyl cellulose to solid particles is 1:8 to 10.

[0041] In one specific embodiment, preferably, the mass ratio of sodium carboxymethyl cellulose to solid particles is 1:10.

[0042] Secondly, the present invention provides a carbon dioxide eliminator for drilling fluids, which is prepared by the aforementioned preparation method.

[0043] Thirdly, the present invention provides an application of the aforementioned carbon dioxide eliminator for drilling fluids, used to prepare drilling fluids resistant to carbon dioxide erosion.

[0044] Fourthly, the present invention provides a drilling fluid resistant to carbon dioxide erosion, comprising the prepared carbon dioxide scavenger.

[0045] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0046] 1. The present invention provides a carbon dioxide eliminator for drilling fluid, its preparation method, and its application. By using walnut shells with a porous structure as a support, calcium ions, the main component for eliminating carbon dioxide, can be stored therein, thereby achieving the slow and continuous release of calcium ions in the drilling fluid without causing a sharp increase in the calcium ion content in the drilling fluid, and without affecting the viscosity of the drilling fluid.

[0047] 2. The present invention provides a carbon dioxide eliminator for drilling fluid, its preparation method, and its application. The walnut shell powder used has undergone hydrophilic modification treatment. After being added to water, it can quickly disperse in the drilling fluid, improve the dispersibility of calcium ions, increase the release rate of calcium ions, and thus improve the efficiency of eliminating carbon dioxide.

[0048] 3. The present invention provides a carbon dioxide eliminator for drilling fluid, its preparation method, and its application. By using sodium carboxymethyl cellulose to coat walnut shell powder loaded with calcium ions, the carbon dioxide eliminator can be prevented from getting damp when not in use, thereby ensuring the effectiveness of calcium ions. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0050] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known materials or methods have not been specifically described in order to avoid obscuring the invention.

[0051] Throughout this specification, references to “an embodiment,” “an example,” or “an example” mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases “an embodiment,” “an example,” “an example,” or “an example” appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0052] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0054] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0055] Drilling fluid is a complex mixture with many components. Complexing agents composed of macromolecular organic compounds can easily react with other components in the drilling fluid, affecting its viscosity. Therefore, how to treat carbon dioxide in drilling fluid without affecting its viscosity remains a pressing problem in this field. To solve the above technical problems:

[0056] In a first aspect, the present invention provides a method for preparing a carbon dioxide eliminator for drilling fluids, comprising the following steps:

[0057] S1, grind walnut shells into powder to obtain walnut shell powder;

[0058] S2, walnut shell powder is subjected to hydrophilic modification treatment to obtain modified walnut shell powder;

[0059] S3, Pour the modified walnut shell powder into deionized water and stir. During the stirring process, add calcium chloride and gluconic acid respectively.

[0060] S4, the mixture from step S3 is filtered and dried to obtain a solid powder;

[0061] S5, granulate the solid powder and dry it to obtain solid particles;

[0062] S6. Coating the surface of the solid particles obtained in step S5 to obtain a carbon dioxide eliminator for drilling fluid.

[0063] In one specific embodiment, in step S1, the particle size of the walnut shell powder is 0.01 to 0.08 mm.

[0064] In a specific embodiment, the hydrophilic modification step S2 is as follows:

[0065] Prepare a modified mixed solution;

[0066] The modified mixed solution was sprayed onto the walnut shell powder obtained in S1.

[0067] In a specific embodiment, the specific steps of hydrophilic modification in step S2 are as follows:

[0068] S21, Prepare an aqueous solution of acrylic resin;

[0069] S22, add epoxy resin to the aqueous acrylic resin solution of step S21, stir, and obtain a mixed solution;

[0070] S23, add nano-silica to the mixed solution of step S22, stir, and obtain a modified mixed suspension;

[0071] S24, the modified mixed suspension is sprayed onto the walnut shell powder obtained in step S1, and the walnut shell powder is then heated to obtain the modified walnut shell powder.

[0072] The present invention improves walnut shell powder by using the above-mentioned components, which can effectively improve the hydrophilicity and internal porous loading capacity of walnut shell powder, thereby ensuring effective loading of calcium ions.

[0073] In one specific embodiment, in step S21, the concentration of the aqueous acrylic resin solution is 11-13 wt%.

[0074] In one specific embodiment, in step S22, the mass ratio of the aqueous acrylic resin solution to the epoxy resin is 1:0.02 to 0.04.

[0075] In one specific embodiment, in step S23, the mass ratio of the mixed solution to nano-silica is 1:0.09 to 0.11.

[0076] In one specific embodiment, in step S3, the mass ratio of deionized water, modified walnut shell powder, calcium chloride, and gluconic acid is 100:35-41:12-16:14-20.

[0077] In one specific embodiment, the preferred mass ratio of deionized water, modified walnut shell powder, calcium chloride, and gluconic acid is 100:41:16:20.

[0078] In one specific embodiment, in step S4, the baking temperature is 60-80°C and the baking time is 40-60 minutes.

[0079] In a specific embodiment, the specific method for preparing the solid particles in step S5 is as follows:

[0080] Water, solid powder, starch and water glass are mixed and granulated, and then dried with hot air to obtain solid particles.

[0081] This invention uses starch and water glass as auxiliary components for granulation. The water glass acts as a binder during granulation, allowing the solid powder to aggregate smoothly. Additionally, when the carbon dioxide scavenger comes into contact with water, the added starch rapidly absorbs the water and swells, enabling the solid powder components to disperse quickly. In one specific embodiment, the mass ratio of solid powder, water, starch, and water glass is 50:6–8:14–18:14–18.

[0082] In one specific embodiment, preferably, the mass ratio of solid powder, water, starch and water glass is 50:8:18:18.

[0083] In one specific embodiment, the particle size of the solid particles is 8–12 mm.

[0084] In a specific embodiment, the coating treatment in step S6 is as follows:

[0085] The solid particles are coated with sodium carboxymethyl cellulose by spraying.

[0086] In one specific embodiment, the mass ratio of sodium carboxymethyl cellulose to solid particles is 1:8 to 10.

[0087] In one specific embodiment, preferably, the mass ratio of sodium carboxymethyl cellulose to solid particles is 1:10.

[0088] Secondly, the present invention provides a carbon dioxide eliminator for drilling fluids, which is prepared by the aforementioned preparation method.

[0089] Thirdly, the present invention provides an application of the aforementioned carbon dioxide eliminator for drilling fluids, used to prepare drilling fluids resistant to carbon dioxide erosion.

[0090] Fourthly, the present invention provides a drilling fluid resistant to carbon dioxide erosion, comprising the prepared carbon dioxide scavenger.

[0091] Example 1

[0092] This invention provides a method for preparing a carbon dioxide eliminator for drilling fluids, comprising the following steps:

[0093] S1, walnut shell powder is obtained by grinding walnut shells into powder and then sieving it to obtain walnut shell powder with a particle size of 0.04 mm;

[0094] S2, walnut shell powder is subjected to hydrophilic modification treatment to obtain modified walnut shell powder;

[0095] S21, prepare an aqueous acrylic resin solution with a concentration of 12 wt%;

[0096] S22, Add epoxy resin to the aqueous acrylic resin solution from step S21, with a mass ratio of aqueous acrylic resin solution to epoxy resin of 1:0.03, stir to obtain a mixed solution;

[0097] S23, add nano-silica to the mixed solution from step S22, with a mass ratio of mixed solution to nano-silica of 1:0.1, stir, and obtain a mixed suspension;

[0098] S24, the mixed suspension is sprayed onto the walnut shell powder obtained in step S1, and the walnut shell powder is then heated to obtain modified walnut shell powder.

[0099] S3. Pour the modified walnut shell powder into deionized water and stir. During the stirring process, add calcium chloride and gluconic acid respectively. The mass ratio of deionized water: modified walnut shell powder: calcium chloride: gluconic acid is 100:38:14:16.

[0100] S4. After vacuum filtration of the mixture from step S3, it is placed in an oven for drying at a temperature of 70°C for 50 minutes to obtain a solid powder.

[0101] S5. After mixing water, solid powder, starch and water glass, the mixture is granulated. The mass ratio of solid powder: water: starch: water glass is 50:7:16:16. After hot air drying, solid particles with a particle size of 10 mm are obtained.

[0102] S6, the solid particles obtained in step S5 are coated with sodium carboxymethyl cellulose for coating treatment. The mass ratio of sodium carboxymethyl cellulose to solid particles is 1:9, thus obtaining carbon dioxide eliminator A1 for drilling fluid.

[0103] Example 2

[0104] This invention provides a method for preparing a carbon dioxide eliminator for drilling fluids, comprising the following steps:

[0105] S1, walnut shell powder is obtained by grinding walnut shells into powder and then sieving it to obtain walnut shell powder with a particle size of 0.01mm;

[0106] S2, walnut shell powder is subjected to hydrophilic modification treatment to obtain modified walnut shell powder;

[0107] S21, prepare an aqueous acrylic resin solution with a concentration of 11 wt%;

[0108] S22, Add epoxy resin to the aqueous acrylic resin solution from step S21, with a mass ratio of aqueous acrylic resin solution to epoxy resin of 1:0.02, stir to obtain a mixed solution;

[0109] S23, add nano-silica to the mixed solution in step S22, with a mass ratio of mixed solution: nano-silica = 1:0.09, stir, and obtain a mixed suspension;

[0110] S24, the mixed suspension is sprayed onto the walnut shell powder obtained in step S1, and the walnut shell powder is then heated to obtain modified walnut shell powder.

[0111] S3. Pour the modified walnut shell powder into deionized water and stir. During the stirring process, add calcium chloride and gluconic acid respectively. The mass ratio of deionized water: modified walnut shell powder: calcium chloride: gluconic acid is 100:35:12:14.

[0112] S4. After vacuum filtration of the mixture from step S3, it is placed in an oven for drying at a temperature of 60°C for 40 minutes to obtain a solid powder.

[0113] S5. After mixing water, solid powder, starch and water glass, the mixture is granulated. The mass ratio of solid powder: water: starch: water glass is 50:6:14:14. After hot air drying, solid particles with a particle size of 8 mm are obtained.

[0114] S6, the solid particles obtained in step S5 are coated with sodium carboxymethyl cellulose for coating treatment. The mass ratio of sodium carboxymethyl cellulose to solid particles is 1:8, thus obtaining carbon dioxide eliminator A2 for drilling fluid.

[0115] Example 3

[0116] This invention provides a method for preparing a carbon dioxide eliminator for drilling fluids, comprising the following steps:

[0117] S1, walnut shell powder is obtained by grinding walnut shells into powder and then sieving it to obtain walnut shell powder with a particle size of 0.08mm;

[0118] S2, walnut shell powder is subjected to hydrophilic modification treatment to obtain modified walnut shell powder;

[0119] S21, prepare an aqueous acrylic resin solution with a concentration of 13 wt%;

[0120] S22, Add epoxy resin to the aqueous acrylic resin solution from step S21, with a mass ratio of aqueous acrylic resin solution to epoxy resin of 1:0.04, stir to obtain a mixed solution;

[0121] S23, add nano-silica to the mixed solution from step S22, with a mass ratio of mixed solution to nano-silica of 1:0.11, stir, and obtain a mixed suspension;

[0122] S24, the mixed suspension is sprayed onto the walnut shell powder obtained in step S1, and the walnut shell powder is then heated to obtain modified walnut shell powder.

[0123] S3. Pour the modified walnut shell powder into deionized water and stir. During the stirring process, add calcium chloride and gluconic acid respectively. The mass ratio of deionized water: modified walnut shell powder: calcium chloride: gluconic acid is 100:41:16:20.

[0124] S4. After vacuum filtration of the mixture from step S3, it is placed in an oven for drying at 80°C for 60 minutes to obtain solid powder.

[0125] S5. After mixing water, solid powder, starch and water glass, the mixture is granulated. The mass ratio of solid powder: water: starch: water glass is 50:8:18:18. After hot air drying, solid particles with a particle size of 12 mm are obtained.

[0126] S6, the solid particles obtained in step S5 are coated with sodium carboxymethyl cellulose for coating treatment. The mass ratio of sodium carboxymethyl cellulose to solid particles is 1:10, thus obtaining carbon dioxide eliminator A3 for drilling fluid.

[0127] Preparation Example 1

[0128] This preparation example is used to formulate drilling fluid, and its purpose is to test the performance of the carbon dioxide scavenger in the drilling fluid. The specific preparation method is as follows:

[0129] Pour 100 parts of tap water into a measuring cup, and while stirring, add 5 parts of bentonite, 1.5 parts of sodium hydroxide, 4 parts of sodium carboxymethyl cellulose, 9 parts of xanthan gum, 22 parts of carbon dioxide scavenger A1 for drilling fluid prepared in Example 1, 65 parts of barite, and 6 parts of sulfonated phenolic resin into the measuring cup in sequence. Stir well to obtain drilling fluid B1.

[0130] Preparation Example 2

[0131] This preparation example is used to formulate drilling fluid, and its purpose is to test the performance of the carbon dioxide scavenger in the drilling fluid. The specific preparation method is as follows:

[0132] Pour 100 parts of tap water into a measuring cup, and while stirring, add 5 parts of bentonite, 1.5 parts of sodium hydroxide, 4 parts of sodium carboxymethyl cellulose, 9 parts of xanthan gum, 22 parts of carbon dioxide scavenger A2 for drilling fluid prepared in Example 2, 65 parts of barite, and 6 parts of sulfonated phenolic resin into the measuring cup in sequence. Stir well to obtain drilling fluid B2.

[0133] Preparation Example 3

[0134] Pour 100 parts of tap water into a measuring cup, and while stirring, add 5 parts of bentonite, 1.5 parts of sodium hydroxide, 4 parts of sodium carboxymethyl cellulose, 9 parts of xanthan gum, 22 parts of the carbon dioxide scavenger A3 for drilling fluid prepared in Example 3, 65 parts of barite, and 6 parts of sulfonated phenolic resin into the measuring cup in sequence. Stir well to obtain drilling fluid B3.

[0135] Comparative Example 1

[0136] The remaining characteristics are the same as those in Preparation Example 1, except that no carbon dioxide scavenger A1 for drilling fluid was added, and drilling fluid D1 was prepared.

[0137] Comparative Example 2

[0138] The remaining features are the same as in Preparation Example 1, except that the drilling fluid carbon dioxide scavenger A1 is replaced with calcium gluconate, and the calcium content of calcium gluconate is the same as the calcium content of the drilling fluid carbon dioxide scavenger A1 that was replaced, thus preparing drilling fluid D2.

[0139] Carbon dioxide was injected into the drilling fluids prepared in Examples 1-3 and Comparative Examples 1-2 using a high-pressure air pump (an additional cup of drilling fluid B1 was prepared as a blank group without air injection). The air injection time was 5 minutes, followed by stirring for 40 minutes to allow the air bubbles on the surface of the drilling fluid to dissipate. During this period, calcium ions could fully combine with carbonate ions. Viscosity performance was then tested, specifically according to the standard "Laboratory Testing of Drilling Fluids for Petroleum and Natural Gas Industry" (GB / T 29170 2012). The relevant data are shown in Table 1.

[0140] Table 1

[0141] experimental group Apparent viscosity (mPa·s) B1 48 B2 49 B3 48 D1 96 D2 21 Blank group 46

[0142] As shown in Table 1, compared with the blank group (without carbon dioxide gas injection), the viscosity of drilling fluids B1, B2, and B3 hardly increased, indicating that the slowly released calcium ions effectively eliminated carbonate ions in the drilling fluid, and the hydrophilically modified walnut shell powder was dispersed very evenly in the drilling fluid. However, the viscosity of drilling fluid D1 increased sharply due to the influence of carbon dioxide, while the viscosity of drilling fluid D2 decreased significantly due to the presence of a large number of calcium ions, which caused severe flocculation of clay.

[0143] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon dioxide scavenger for drilling fluids, characterized in that, Includes the following steps: S1, grind walnut shells into powder to obtain walnut shell powder; S2, walnut shell powder is subjected to hydrophilic modification treatment to obtain modified walnut shell powder; S3, Pour the modified walnut shell powder into deionized water, and add calcium chloride and gluconic acid while stirring; S4, the mixture from step S3 is filtered and dried to obtain a solid powder; S5, granulate the solid powder and dry it to obtain solid particles; S6. Coating the surface of the solid particles obtained in step S5 to obtain a carbon dioxide eliminator for drilling fluid.

2. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 1, characterized in that, In step S1, the particle size of the walnut shell powder is 0.01 to 0.08 mm.

3. The method for preparing a carbon dioxide eliminator for drilling fluid according to claim 1, characterized in that, In step S2, the hydrophilic modification process is as follows: Prepare a modified mixed solution; The modified mixed solution was sprayed onto the walnut shell powder obtained in S1.

4. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 3, characterized in that, In step S2, the specific steps of hydrophilic modification are as follows: S21, Prepare an aqueous solution of acrylic resin; S22, add epoxy resin to the aqueous acrylic resin solution of step S21, stir, and obtain a mixed solution; S23, add nano-silica to the mixed solution of step S22, stir, and obtain a modified mixed suspension; S24, the modified mixed suspension is sprayed onto the walnut shell powder obtained in step S1, and the walnut shell powder is then heated to obtain the modified walnut shell powder.

5. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 4, characterized in that, In step S21, the concentration of the aqueous acrylic resin solution is 11-13 wt%.

6. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 4, characterized in that, In step S22, the mass ratio of the aqueous acrylic resin solution to the epoxy resin is 1:0.02 to 0.

04.

7. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 4, characterized in that, In step S23, the mass ratio of the mixed solution to nano-silica is 1:0.09 to 0.

11.

8. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 1, characterized in that, In step S3, the mass ratio of deionized water, modified walnut shell powder, calcium chloride, and gluconic acid is 100:35-41:12-16:14-20.

9. A method for preparing a carbon dioxide scavenger for drilling fluid according to claim 8, characterized in that, The mass ratio of deionized water, modified walnut shell powder, calcium chloride, and gluconic acid is 100:41:16:

20.

10. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 1, characterized in that, In step S4, the baking temperature is 60-80℃ and the baking time is 40-60 minutes.

11. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 1, characterized in that, In step S5, the specific preparation method of the solid particles is as follows: Water, solid powder, starch and water glass are mixed and granulated, and then dried with hot air to obtain solid particles.

12. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 11, characterized in that, The mass ratio of solid powder, water, starch and water glass is 50:6~8:14~18:14~18.

13. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 12, characterized in that, The mass ratio of solid powder, water, starch and water glass is 50:8:18:

18.

14. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 11, characterized in that, The particle size of the solid particles is 8–12 mm.

15. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 1, characterized in that, In step S6, the specific method for the coating treatment is as follows: The solid particles are coated with sodium carboxymethyl cellulose by spraying.

16. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 15, characterized in that, The mass ratio of sodium carboxymethyl cellulose to solid particles is 1:8 to 10.

17. The method for preparing a carbon dioxide scavenger for drilling fluid according to claim 16, characterized in that, The mass ratio of sodium carboxymethyl cellulose to solid particles is 1:

10.

18. A carbon dioxide scavenger for drilling fluids, characterized in that, It is prepared by any of the preparation methods described in claims 1 to 17.

19. The application of the carbon dioxide scavenger for drilling fluids according to claim 18, characterized in that, Used to prepare drilling fluids resistant to carbon dioxide corrosion.

20. A drilling fluid resistant to carbon dioxide corrosion, characterized in that, Includes the carbon dioxide scavenger of claim 18.