Drilling fluid composition as well as preparation method and application thereof

Abstract

The invention relates to the field of treating agents for oilfield drilling, in particular to a drilling fluid composition as well as a preparation method and application thereof. The composition comprises an inhibitor, a foaming agent, a foam stabilizer, bentonite and water, on the basis of the total weight of the composition, in the composition, the content of the inhibitor is 0.1 wt%-1 wt%, the content of the foaming agent is 0.2 wt%-2 wt%, the content of the foam stabilizer is 0.1 wt%-0.7 wt%, the content of the bentonite is 1 wt%-5 wt%, and the content of the water is 85 wt%-97 wt%. The drilling fluid composition has relatively strong microfoam, high rock debris inhibition and good wall protection property, and enhances the stability of a well wall; meanwhile, hydration of the rock debris can be effectively inhibited, the suspension effect and migration capacity of the rock debris are improved, the influence of rock debris sedimentation is reduced or eliminated, the rock debris is smoothly migrated, abrasion of the rock debris to a drilling tool is reduced, and the drilling fluid is suitable for sand-mud rock strata.

Description

Technical Field

[0001] The invention relates to the field of treating agents for oilfield drilling, and in particular to a drilling fluid composition and a preparation method and application thereof. Background Art

[0002] Foam drilling is a drilling method that uses a honeycomb foam fluid formed by mixing air or nitrogen and other gases with a foaming agent base liquid as the drilling fluid. The foam fluid has a lower density than conventional mud drilling fluid and a smaller bottom hole clamping effect. It can not only effectively control the circulation loss of drilling fluid and increase the mechanical drilling speed, but also reduce reservoir damage and protect low-pressure oil and gas reservoirs.

[0003] At present, a lot of research has been conducted in China on various basic theories of foam application in oil fields, especially in oil field drilling. There are many research and applications of foam, but there are relatively few studies on efficient inhibitory microfoam. Since conventional foam base fluid contains water and foaming agents have a certain promoting effect on shale hydration, mudstone hydration causes the viscosity of the foam base fluid to increase rapidly, and excessive viscosity affects the generation of foam, requiring a large amount of supplementary water and drilling materials. In addition, when drilling long sections of mudstone formations or mudstone interlayers, due to the poor wall protection of the foam base fluid, insufficient inhibition is prone to complex blocking phenomena (block drop, mud bag), which increases the downhole safety risk and the difficulty of subsequent casing operations. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem of insufficient inhibition and wall protection of existing drilling fluids, and to provide a drilling fluid composition and its preparation method and application. The composition has strong micro-foam, good inhibition and wall protection for rock cuttings, and enhances the stability of the well wall; at the same time, it can smoothly transport rock cuttings and reduce the wear of rock cuttings on drilling tools.

[0005] In order to achieve the above object, the first aspect of the present invention provides a drilling fluid composition, wherein the composition comprises: an inhibitor, a foaming agent, a foam stabilizer, bentonite and water;

[0006] Based on the total weight of the composition, in the composition, the content of the inhibitor is 0.1wt%-1wt%, the content of the foaming agent is 0.2wt%-2wt%, the content of the foam stabilizer is 0.1wt%-0.7wt%, the content of the bentonite is 1wt%-5wt%, and the content of water is 85wt%-97wt%.

[0007] The second aspect of the present invention provides a method for preparing a drilling fluid composition, wherein the preparation method comprises: adding bentonite to water for stirring and curing, and then adding an inhibitor, a foaming agent, and a foam stabilizer to obtain the drilling fluid composition.

[0008] The third aspect of the present invention provides a drilling fluid composition prepared by the above-mentioned preparation method.

[0009] A fourth aspect of the present invention provides a use of the aforementioned drilling fluid composition in oil field treatment.

[0010] Through the above technical solution, the following beneficial effects are achieved.

[0011] (1) The drilling fluid composition of the present invention has strong micro-foam, good inhibition of rock cuttings, strong wall protection, and enhanced well wall stability; at the same time, it can effectively inhibit the hydration of rock cuttings, increase the suspension effect and migration capacity of rock cuttings, reduce or eliminate the influence of rock cuttings sedimentation, smoothly transport rock cuttings, reduce the wear of rock cuttings on drilling tools, is suitable for sandstone and mudstone layers, and can be used at high temperatures;

[0012] Furthermore, the specific components work synergistically to form micro-foams that are small in size, stable, and can be recycled.

[0013] (2) A specific preparation method, through the step-by-step operation of first adding bentonite and then adding other components, can be dissolved smoothly and is not easy to condense into lumps, which has the effect of effectively improving the uniformity of the system and making the system more stable. DETAILED DESCRIPTION

[0014] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0015] The first aspect of the present invention provides a drilling fluid composition, wherein the composition comprises: an inhibitor, a foaming agent, a foam stabilizer, bentonite and water;

[0016] Based on the total weight of the composition, in the composition, the content of the inhibitor is 0.1wt%-1wt%, the content of the foaming agent is 0.2wt%-2wt%, the content of the foam stabilizer is 0.1wt%-0.7wt%, the content of the bentonite is 1wt%-5wt%, and the content of water is 85wt%-97wt%.

[0017] In the present invention, the content of each component can be tested as follows: bentonite can be separated by centrifugation, the solid matter can be collected, dried and then weighed for quantitative determination; the inhibitor, foaming agent and foam stabilizer can be quantitatively determined by collecting the supernatant and performing liquid chromatography on the supernatant.

[0018] In the present invention, each component in the drilling fluid composition does not work alone, but works synergistically to form micro-foam, which has good inhibitory and wall protection properties for cuttings and enhances the stability of the well wall; at the same time, it can effectively inhibit the hydration of cuttings, increase the suspension effect of cuttings, reduce or eliminate the impact of cuttings sedimentation, can smoothly transport cuttings, reduce the wear of cuttings on drilling tools, and is suitable for sandstone and mudstone layers; the formed micro-foam is small in size, good in stability, and can be recycled.

[0019] In the present invention, the micro foam refers to foam with an average size of micrometer level or below.

[0020] Furthermore, based on the total weight of the composition, the content of the inhibitor is 0.3wt%-0.8wt%, the content of the foaming agent is 1wt%-1.5wt%, the content of the foam stabilizer is 0.2wt%-0.5wt%, the content of the bentonite is 2wt%-4wt%, and the content of water is 90wt%-96wt%.

[0021] According to the present invention, the inhibitor is a polymer having a structural unit shown in Formula I,

[0022] X is selected from halogen elements.

[0023] In the present invention, the specific inhibitor can increase the inhibitory and wall protection properties of the drilling fluid composition on rock cuttings, enhance the stability of the well wall, improve the ability of the composition to move rock cuttings, and reduce the wear of the drilling tool by the rock cuttings.

[0024] In the present invention, the rock cuttings inhibition and wall protection properties of the drilling fluid composition are characterized by the rock cuttings rolling recovery rate, which is a common test method in the art. One preferred test method for the rock cuttings rolling recovery rate is to put 300g of the drilling fluid composition into a roller heating furnace, add 20g of rock cuttings, roll at 140°C for 16h, and test the quality of the rock cuttings after rolling.

[0025] Further, X is Cl.

[0026] According to the present invention, the weight average molecular weight of the polymer is 8000-10000 g / mol, preferably 8500-9000 g / mol.

[0027] According to the present invention, the foaming agent is selected from polymer surfactants.

[0028] According to the present invention, the polymer surfactant is selected from polyoxyethylene-polyoxypropylene block polymers.

[0029] In the present invention, the specific high molecular surfactant can make the drilling fluid composition have strong micro foam, reduce the damage to the reservoir; at the same time, it can effectively inhibit the hydration of cuttings and can transport the cuttings well.

[0030] According to the present invention, in the polyoxyethylene-polyoxypropylene block polymer, based on the total weight of the polymer, the ratio of the total weight of the oxyethylene segments to the total weight of the oxypropylene segments is 1-2:1, preferably 1-1.2:1.

[0031] According to the present invention, the number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer is 2000-4000 g / mol, preferably 2400-2850 g / mol.

[0032] According to the present invention, the foam stabilizer is selected from at least one of carboxymethyl cellulose, starch, hydroxyethyl saponin, and sodium caseinate; preferably selected from at least one of carboxymethyl cellulose, starch, and hydroxyethyl saponin.

[0033] According to the present invention, the average size of the bubbles of the composition is 50-95 μm.

[0034] In the present invention, when the average foam size of the composition meets the above range, the stability is good, the rock cuttings can be suppressed and the wall protection is good, the well wall stability is enhanced, and the suspension effect and migration capacity of the rock cuttings are increased. In addition, after one use, because the rock cuttings content in the composition is small, it can be used again or even multiple times. In order to ensure that the effect is not reduced, the general use method is to mix the used composition with the original composition. The mixing ratio does not need to be limited, as long as it can achieve the performance of the original composition, and then it is recycled.

[0035] Furthermore, the average size of the bubbles in the composition is 65-85 μm.

[0036] The second aspect of the present invention provides a method for preparing a drilling fluid composition, wherein the preparation method comprises: stirring and curing water and bentonite, and then mixing the obtained product with an inhibitor, a foaming agent, and a foam stabilizer to obtain the drilling fluid composition.

[0037] In the present invention, the specific preparation method can be dissolved smoothly and not easily coagulated into blocks by adding bentonite first and then adding other components in a step-by-step operation, which has the effect of effectively improving the uniformity of the system and making the system more stable. The uniformity can be characterized by the average size of the foam of the composition. The better the uniformity, the smaller the average size of the foam.

[0038] The components and dosages of the composition of the second aspect of the present invention are the same as those of the first aspect and will not be described in detail herein.

[0039] According to the present invention, the stirring conditions include: the stirring temperature is 40-60° C.; and the stirring time is 1-2 h.

[0040] In the present invention, the specific stirring conditions can make the system mix more uniformly and less likely to separate.

[0041] Furthermore, the stirring conditions include: the stirring temperature is 48-55° C.; and the stirring time is 1.5-1.8 h.

[0042] According to the present invention, the curing conditions include: the curing temperature is 20-35°C; the curing time is 20-36h.

[0043] Furthermore, the curing conditions include: the curing temperature is 25-27°C; the curing time is 24-28h.

[0044] The third aspect of the present invention provides a drilling fluid composition prepared by the above-mentioned preparation method.

[0045] A fourth aspect of the present invention provides a use of the aforementioned drilling fluid composition in oil field treatment.

[0046] The present invention will be described in detail below through examples.

[0047] The test method for the average foam size of the drilling fluid composition is: take 100 mL of the drilling fluid composition, test its foam performance at room temperature and high-speed stirring conditions (12000±100 rpm), and measure its average foam size through an electron microscope.

[0048] The test method for the cuttings rolling recovery rate is as follows: 300 g of the drilling fluid composition is put into a roller heating furnace, 20 g of cuttings are added, and the cuttings are rolled at 140° C. for 16 hours, and the quality of the cuttings after rolling is tested.

[0049] Cuttings rolling recovery rate = cuttings mass after rolling / cuttings mass before rolling × 100%.

[0050] The number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer-1 is 2400 g / mol, wherein, based on the total weight of the polymer, the ratio of the total weight of the polyoxyethylene segment to the total weight of the polyoxypropylene segment is 1:1;

[0051] The number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer-2 is 4000 g / mol, wherein, based on the total weight of the polymer, the ratio of the total weight of the polyoxyethylene segment to the total weight of the polyoxypropylene segment is 1.2:1;

[0052] The number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer-3 is 2000 g / mol, wherein, based on the total weight of the polymer, the ratio of the total weight of the polyoxyethylene segment to the total weight of the polyoxypropylene segment is 1.2:1;

[0053] The number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer-4 is 2850 g / mol, wherein the ratio of the total weight of the polyoxyethylene chain segment to the total weight of the polyoxypropylene chain segment is 1:1 based on the total weight of the polymer;

[0054] The number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer-5 is 2500 g / mol, wherein, based on the total weight of the polymer, the ratio of the total weight of the polyoxyethylene segment to the total weight of the polyoxypropylene segment is 1.1:1;

[0055] The number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer-6 is 3000 g / mol, wherein, based on the total weight of the polymer, the ratio of the total weight of the polyoxyethylene segment to the total weight of the polyoxypropylene segment is 1.2:1;

[0056] The number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer-7 is 3000 g / mol, wherein the ratio of the total weight of the polyoxyethylene segments to the total weight of the polyoxypropylene segments is 2:1 based on the total weight of the polymer;

[0057] Bentonite, carboxymethyl cellulose, starch and hydroxyethyl saponin are all commercially available.

[0058] Example 1

[0059] Inhibitor-1, containing structural units The polymer has a weight average molecular weight of 8000 g / mol;

[0060] 15 g of bentonite was slowly added to 500 g of water, and stirred at a temperature of 50° C. for 2 h; then cured at a temperature of 25° C. for 24 h; then 2.5 g of polyoxyethylene-polyoxypropylene block polymer-1, 2.5 g of inhibitor-1 and 0.5 g of carboxymethyl cellulose were added and mixed to obtain a drilling fluid composition A1;

[0061] Based on the total weight of the drilling fluid composition A1, the content of the inhibitor is 0.3wt%, the content of the foaming agent is 1wt%, the content of the foam stabilizer is 0.2wt%, the content of the bentonite is 3wt%, and the content of water is 95.5wt%.

[0062] Example 2

[0063] Inhibitor-2, containing structural units The polymer has a weight average molecular weight of 9000 g / mol;

[0064] 20 g of bentonite was slowly added to 500 g of water, and stirred at 48° C. for 2 h. The mixture was then cured at 25° C. for 24 h. 5 g of polyoxyethylene-polyoxypropylene block polymer-2, 3 g of inhibitor-2 and 1 g of hydroxyethyl saponin were then added and mixed to obtain a drilling fluid composition A2.

[0065] Based on the total weight of the drilling fluid composition A2, the content of the inhibitor was 0.8wt%, the content of the foaming agent was 1.5wt%, the content of the foam stabilizer was 0.5wt%, the content of the bentonite was 4wt%, and the content of water was 93.2wt%.

[0066] Example 3

[0067] Inhibitor-3, containing structural units Polymer, weight average molecular weight 10000 g / mol;

[0068] 15 g of bentonite was slowly added to 500 g of water, and stirred at a temperature of 55° C. for 2 h; then cured at a temperature of 25° C. for 24 h; then 6 g of polyoxyethylene-polyoxypropylene block polymer-3, 4 g of inhibitor-3 and 2 g of carboxymethyl cellulose were added and mixed to obtain a drilling fluid composition A3;

[0069] Based on the total weight of the drilling fluid composition A3, the content of the inhibitor is 0.5wt%-, the content of the foaming agent is 1.5wt%, the content of the foam stabilizer is 0.7wt%, the content of the bentonite is 4wt%, and the content of water is 93.3wt%.

[0070] Example 4

[0071] Inhibitor-4, containing structural units The polymer has a weight average molecular weight of 9500 g / mol;

[0072] 20 g of bentonite was slowly added to 500 g of water, and stirred at a temperature of 50° C. for 2 h; then cured at a temperature of 25° C. for 24 h; then 4 g of polyoxyethylene-polyoxypropylene block polymer-4, 2.5 g of inhibitor-4 and 1 g of hydroxyethyl saponin were added and mixed to obtain a drilling fluid composition A4;

[0073] Based on the total weight of the drilling fluid composition A4, the content of the inhibitor was 0.5wt%, the content of the foaming agent was 0.8wt%, the content of the foam stabilizer was 0.1wt%, the content of the bentonite was 3.7wt%, and the content of water was 94.9wt%.

[0074] Example 5

[0075] Select inhibitor-3;

[0076] 25 g of bentonite was slowly added to 500 g of water, and stirred at 60° C. for 2 h; then cured at 25° C. for 24 h; then 10 g of polyoxyethylene-polyoxypropylene block polymer-5, 5 g of inhibitor-3 and 3 g of starch were added and mixed to obtain a drilling fluid composition A5;

[0077] Based on the total weight of the drilling fluid composition A5, the content of the inhibitor was 1 wt %, the content of the foaming agent was 0.68 wt %, the content of the foam stabilizer was 0.29 wt %, the content of the bentonite was 3.8 wt %, and the content of water was 94.23 wt %.

[0078] Example 6

[0079] Select inhibitor-3;

[0080] 10 g of bentonite was slowly added to 500 g of water, and stirred at 60° C. for 2 h. The mixture was then cured at 25° C. for 24 h. 2.5 g of polyoxyethylene-polyoxypropylene block polymer-1, 1 g of inhibitor-3 and 2 g of carboxymethyl cellulose were then added and mixed to obtain a drilling fluid composition A6.

[0081] Based on the total weight of the drilling fluid composition A6, the content of the inhibitor is 0.35wt%, the content of the foaming agent is 1.7wt%, the content of the foam stabilizer is 0.25wt%, the content of the bentonite is 2.5wt%, and the content of water is 95.2wt%.

[0082] Example 7

[0083] Inhibitor-7, containing structural units The polymer has a weight average molecular weight of 9000 g / mol;

[0084] 15 g of bentonite was slowly added to 500 g of water, and stirred at a temperature of 55° C. for 2 h; then cured at a temperature of 25° C. for 24 h; then 3 g of polyoxyethylene-polyoxypropylene block polymer-6, 2 g of inhibitor-7 and 1.5 g of starch were added and mixed to obtain a drilling fluid composition A7;

[0085] Based on the total weight of the drilling fluid composition A7, the content of the inhibitor is 0.5wt%, the content of the foaming agent is 2wt%, the content of the foam stabilizer is 0.5wt%, the content of the bentonite is 2wt%, and the content of water is 95wt%.

[0086] Example 8

[0087] In the same manner as in Example 1, except that "polyoxyethylene-polyoxypropylene block polymer-7" is used to replace "polyoxyethylene-polyoxypropylene block polymer-1", to obtain drilling fluid composition A8;

[0088] Based on the total weight of the drilling fluid composition A8, the content of the inhibitor is 0.3wt%, the content of the foaming agent is 1wt%, the content of the foam stabilizer is 0.2wt%, the content of the bentonite is 3wt%, and the content of water is 95.5wt%.

[0089] Example 9

[0090] In the manner of Example 1, except that "the stirring temperature is 48° C. and the stirring time is 1.5 h" is used instead of "the stirring temperature is 50° C. and the stirring time is 2 h", to obtain a drilling fluid composition A9;

[0091] Based on the total weight of the drilling fluid composition A9, the content of the inhibitor is 0.3wt%, the content of the foaming agent is 1wt%, the content of the foam stabilizer is 0.2wt%, the content of the bentonite is 3wt%, and the content of water is 95.5wt%.

[0092] Example 10

[0093] The method of Example 1 is the same, except that "the curing temperature is 25° C. and the curing time is 36 h" is used to replace "the curing temperature is 25° C. and the curing time is 24 h" to obtain a drilling fluid composition A10;

[0094] Based on the total weight of the drilling fluid composition A10, the content of the inhibitor is 0.3wt%, the content of the foaming agent is 1wt%, the content of the foam stabilizer is 0.2wt%, the content of the bentonite is 3wt%, and the content of water is 95.5wt%.

[0095] Comparative Example 1

[0096] The drilling fluid composition D1 was obtained in the same manner as in Example 1 except that the "inhibitor-1" was not added.

[0097] Comparative Example 2

[0098] The drilling fluid composition D2 was obtained in the same manner as in Example 1 except that the "polyoxyethylene-polyoxypropylene block polymer-1" was not added.

[0099] Comparative Example 3

[0100] The drilling fluid composition D3 was obtained in the same manner as in Example 1, except that the "inhibitor-1" and the "polyoxyethylene-polyoxypropylene block polymer-1" were not added.

[0101] Comparative Example 4

[0102] 15 g of bentonite, 500 mol of water, 2.5 g of polyoxyethylene-polyoxypropylene block polymer-1, 2.5 g of inhibitor-1 and 0.5 g of carboxymethyl cellulose were stirred at a temperature of 50° C. for 2 h; then cured at a temperature of 25° C. for 24 h to obtain a drilling fluid composition D4.

[0103] Comparative Example 5

[0104] A common drilling fluid commercially available drilling foaming agent in the art, code-named WD-12, was used as a control group and numbered D5.

[0105] Comparative Example 6

[0106] Water was used as a control group (ie, only water without the drilling fluid composition was used as the tested sample), and was numbered as D6.

[0107] The drilling fluid compositions and water in the examples and comparative examples were tested, and the results are shown in Table 1.

[0108] Table 1

[0109]

[0110]

[0111] The temperature of the roller heating furnace is as high as 140° C., which can prove that the drilling fluid composition of the present invention can be used in a high temperature environment.

[0112] It can be seen from the results in Table 1 that by comparing Example 1 with Comparative Examples 1-3, it can be seen that the average foam size of Comparative Example 3 in which two components are omitted is larger than that of Example 1, Comparative Example 1 and Comparative Example 2, while the cuttings rolling recovery rate is smaller than that of Example 1, Comparative Example 1 and Comparative Example 2; the drilling fluid composition acts synergistically, not simply combined.

[0113] By comparing Example 1 with Comparative Example 4, it can be seen that the specific step-by-step addition preparation steps in the present invention can dissolve smoothly and are not easy to coagulate into lumps, which has the effect of effectively improving the uniformity of the system and making the system more stable. Example 1 has a smaller average foam size of the composition and a higher rock cuttings rolling recovery rate.

[0114] Comparing Example 1 with Comparative Examples 5 and 6, it can be seen that the specific drilling machine composition in the present invention has a better effect than the drilling machine in the prior art.

[0115] Comparing Examples 1-8, it can be seen that the components and contents interact with each other and work synergistically, which will have a certain impact on the average foam size and rock cuttings rolling recovery rate of the composition, among which Examples 2, 5 and 6 have the best effects. Comparing Example 1 with Examples 9 and 10, it can be seen that when the stirring and curing reaction conditions are adjusted, the mixing degree of the system will be affected, which is ultimately reflected in the average foam size and rock cuttings rolling recovery rate of the composition.

[0116] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A drilling fluid composition, characterized in that: The composition comprises: an inhibitor, a foaming agent, a foam stabilizer, bentonite and water; Based on the total weight of the composition, in the composition, the content of the inhibitor is 0.1wt%-1wt%, the content of the foaming agent is 0.2wt%-2wt%, the content of the foam stabilizer is 0.1wt%-0.7wt%, the content of the bentonite is 1wt%-5wt%, and the content of water is 85wt%-97wt%.

2. The composition according to claim 1, wherein Based on the total weight of the composition, in the composition, the content of the inhibitor is 0.3wt%-0.8wt%, the content of the foaming agent is 1wt%-1.5wt%, the content of the foam stabilizer is 0.2wt%-0.5wt%, the content of the bentonite is 2wt%-4wt%, and the content of water is 90wt%-96wt%.

3. The composition according to claim 1 or 2, wherein The inhibitor is a polymer having a structural unit shown in Formula I, X is selected from halogen elements; Preferably, X is Cl; Preferably, the weight average molecular weight of the polymer is 8000-10000 g / mol, preferably 8500-9000 g / mol.

4. The composition according to any one of claims 1 to 3, wherein The foaming agent is selected from polymer surfactants; Preferably, the polymer surfactant is selected from polyoxyethylene-polyoxypropylene block polymers; Preferably, in the polyoxyethylene-polyoxypropylene block polymer, based on the total weight of the polymer, the ratio of the total weight of the polyoxyethylene segments to the total weight of the polyoxypropylene segments is 1-2:1, preferably 1-1.2:1; Preferably, the number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer is 2000-4000 g / mol, preferably 2400-2850 g / mol; Preferably, the foam stabilizer is selected from at least one of carboxymethyl cellulose, starch, hydroxyethyl saponin, and sodium caseinate; preferably selected from at least one of carboxymethyl cellulose, starch, and hydroxyethyl saponin.

5. The composition according to any one of claims 1 to 4, wherein The average size of the bubbles of the composition is 50-95 μm, preferably 65-85 μm.

6. A method for preparing a drilling fluid composition, characterized in that: The preparation method comprises: stirring and curing water and bentonite, and then mixing the obtained product with an inhibitor, a foaming agent and a foam stabilizer to obtain the drilling fluid composition.

7. The preparation method according to claim 6, wherein: Based on the total weight of the composition, the content of the inhibitor is 0.1wt%-1wt%, the content of the foaming agent is 0.2wt%-2wt%, the content of the foam stabilizer is 0.1wt%-0.7wt%, the content of the bentonite is 1wt%-5wt%, and the content of water is 85wt%-97wt%; Preferably, based on the total weight of the composition, the content of the inhibitor is 0.3wt%-0.8wt%, the content of the foaming agent is 1wt%-1.5wt%, the content of the foam stabilizer is 0.2wt%-0.5wt%, the content of the bentonite is 2wt%-4wt%, and the content of water is 90wt%-96wt%.

8. The composition according to claim 6 or 7, wherein The inhibitor is a polymer having a structural unit shown in Formula I, X is selected from halogen elements; Preferably, X is Cl; Preferably, the weight average molecular weight of the polymer represented by formula I is 8000-10000 g / mol, preferably 8500-9000 g / mol. Preferably, the foaming agent is selected from polymer surfactants; Preferably, the polymer surfactant is selected from polyoxyethylene-polyoxypropylene block polymers; Preferably, in the polyoxyethylene-polyoxypropylene block polymer, based on the total weight of the polymer, the ratio of the total weight of the oxyethylene segments to the total weight of the oxypropylene segments is 1-2:1, preferably 1-1.2:1; Preferably, the number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer is 2000-4000 g / mol, preferably 2400-2850 g / mol; Preferably, the foam stabilizer is selected from at least one of carboxymethyl cellulose, starch, hydroxyethyl saponin, and sodium caseinate; preferably selected from at least one of carboxymethyl cellulose, starch, and hydroxyethyl saponin.

9. The preparation method according to any one of claims 6 to 8, wherein: The stirring conditions include: the stirring temperature is 40-60°C, preferably 48-55°C; the stirring time is 1-2h, preferably 1.5-1.8h; Preferably, the curing conditions include: a curing temperature of 20-35°C, preferably 25-27°C; and a curing time of 20-36h, preferably 24-28h.

10. A drilling fluid composition obtained by the preparation method according to any one of claims 6 to 9.

11. Use of the drilling composition according to any one of claims 1 to 5 and claim 10 in oil field treatment.

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