Drilling fluid composition, method of making and use thereof

Abstract

The present application relates to the field of oilfield drilling treatment agent, and particularly relates to a drilling fluid composition and a preparation method and application thereof. The composition comprises an inhibitor, a foaming agent, a foam stabilizer, bentonite and water; the content of the inhibitor in the composition is 0.1wt%-1wt% based on the total weight of the composition, 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 the water is 85wt%-97wt%. The drilling fluid composition has strong micro-foam, high inhibition of cuttings and good wall protection, and the well wall stability is enhanced; meanwhile, the drilling fluid composition can effectively inhibit the hydration of cuttings, increase the suspension and migration capacity of cuttings, reduce or eliminate the influence of cuttings settlement, smoothly migrate the cuttings, reduce the abrasion of cuttings on drilling tools, and is suitable for sand and mudstone layers.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oilfield drilling treatment agent, in particular to a drilling fluid composition and a preparation method and application thereof. BACKGROUND

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

[0003] At present, a large amount of research on various basic theories of foam applied to oilfields has been carried out in China, especially in the field of oilfield drilling. The research and application of foam are more, but the research on efficient inhibitory micro-foam is less. Because the conventional foam base fluid contains water and the foaming agent has a certain promoting effect on shale hydration, shale hydration promotes the rapid increase of foam base fluid viscosity, and the excessive viscosity affects the generation of foam. A large amount of water and drilling materials need to be supplemented. In addition, when drilling long section of mudstone formation or mudstone interlayer, due to the poor inhibitory and wall protection of foam base fluid, the inhibitory is insufficient, and the blocking and complex phenomena (block dropping, mud packing) are prone to occur, which increases the downhole safety risk and the difficulty of subsequent casing operation. SUMMARY

[0004] The purpose of the present application is to overcome the problems of insufficient inhibition and wall protection of the existing drilling fluid. The present application provides a drilling fluid composition and a preparation method and application thereof. The composition has strong micro-foam, good inhibition and wall protection of cuttings, and enhances the stability of well wall. At the same time, it can smoothly transport cuttings and reduce the wear of cuttings on drilling tools.

[0005] In order to achieve the above purpose, the first aspect of the present application 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, the content of the inhibitor in the composition 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 the water is 85wt%-97wt%.

[0007] The second aspect of the present application provides a preparation method of 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 application provides a drilling fluid composition prepared by the aforementioned preparation method.

[0009] The fourth aspect of the present application provides an application of the aforementioned drilling fluid composition in oilfield treatment.

[0010] The above technical solution achieves the following beneficial effects.

[0011] (1) The drilling fluid composition in the present application has strong microfoam, good cutting inhibition and strong wall protection, thereby enhancing the stability of the well wall; at the same time, the drilling fluid composition can effectively inhibit the hydration of cuttings, increase the suspension and migration capacity of the cuttings, reduce or eliminate the influence of the cuttings settlement, smoothly migrate the cuttings, reduce the wear of the drilling tools by the cuttings, and is suitable for sand and mudstone layers and can be applied at high temperatures.

[0012] Further, the specific components synergistically form microfoam with small size and good stability, which can be recycled.

[0013] (2) The specific preparation method can smoothly dissolve the bentonite which is not easy to coagulate into blocks, effectively improve the uniformity of the system, and make the system more stable. DETAILED DESCRIPTION

[0014] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not considered critical for the present application. The endpoints of the ranges and any values are only approximations. The range values are only approximations since the variations of values are expected as component values are expected to vary slightly when made commercially. Variations are to be expected by virtue of the standard variability of the components or the process. A new range or value can be derived from the endpoints if desired or necessary.

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

[0016] 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 the water is 85wt%-97wt%, based on the total weight of the composition.

[0017] In the present application, the testing method of the content of each component is as follows: the bentonite can be separated by centrifugation, the solid material is collected, dried and weighed for quantitative determination; the inhibitor, the foaming agent and the foam stabilizer can be collected by collecting the supernatant, and the supernatant is subjected to liquid chromatography quantitative determination.

[0018] In the present application, the components in the drilling fluid composition do not work alone, and the components work synergistically to form microfoam, which has good inhibition and wall protection on cuttings and enhances the stability of the well wall; at the same time, can effectively inhibit the hydration of cuttings, increase the suspension of cuttings, reduce or eliminate the influence of cuttings settlement, can smoothly transport cuttings, reduce the wear of cuttings on drilling tools, and is suitable for sandstone and mudstone layers; the microfoam formed has small size and good stability, and can be recycled.

[0019] In the present application, the microfoam refers to a foam with an average size of micron level or below.

[0020] Further, 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 the water is 90wt%-96wt%, based on the total weight of the composition.

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

[0022] X is selected from halogen elements.

[0023] In the present application, the specific inhibitor can increase the inhibition and wall protection of the drilling fluid composition on cuttings, enhance the stability of the well wall, and improve the transport capacity of the composition on cuttings and reduce the wear of cuttings on drilling tools.

[0024] In the present application, the inhibition and wall protection of the drilling fluid composition on cuttings are characterized by the rolling recovery rate of cuttings, which is a common test method in the art, and one preferred test method for the rolling recovery rate of cuttings is to put 300g of drilling fluid composition into a roller heating furnace, add 20g of cuttings, roll at 140℃ for 16h, and test the mass of the rolled cuttings.

[0025] Further, X is Cl.

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

[0027] According to the present application, the foaming agent is selected from high molecular surfactants.

[0028] According to the present application, the high molecular surfactant is selected from polyoxyethylene-polyoxypropylene block polymers.

[0029] In the present application, the specific high molecular surfactant can make the drilling fluid composition have strong microfoam, reduce the damage to the reservoir; at the same time, effectively inhibit the hydration of the cuttings can be well transported.

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

[0031] According to the present application, 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 application, the foam stabilizer is selected from at least one of carboxymethyl cellulose, starch and hydroxyethyl soap husk gum, and sodium caseinate; preferably at least one of carboxymethyl cellulose, starch and hydroxyethyl soap husk gum.

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

[0034] In the present application, when the average size of the foam of the composition meets the above range, the stability is good, the inhibition and wall protection of the cuttings are good, the well wall stability is enhanced, and the suspension and migration ability of the cuttings is increased. In addition, after one use, the composition can be used again or even multiple times because of the small amount of cuttings in the composition. In order to not reduce the effect, the general use method is to mix the used composition with the original composition, the mixing ratio does not need to be limited, and the performance of the original composition can be achieved for recycling.

[0035] Further, the average size of the foam of the composition is 65-85 μm.

[0036] The second aspect of the present application provides a preparation method of 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 application, the specific preparation method can smoothly dissolve the bentonite which is not easy to coagulate into blocks, has the effect of effectively improving the uniformity of the system, makes the system more stable, and the uniformity can be characterized by the average size of the foam of the composition. The uniformity is good, and the average size of the foam is small.

[0038] In the present application, the components and amounts of the composition of the second aspect are the same as those of the first aspect, which will not be repeated here.

[0039] According to the present application, the stirring condition comprises that the temperature of stirring is 40-60℃, and the time of stirring is 1-2h.

[0040] In the present application, the specific stirring condition can make the system mixing more uniform and not easy to stratify.

[0041] Further, the stirring condition comprises that the temperature of stirring is 48-55℃, and the time of stirring is 1.5-1.8h.

[0042] According to the present application, the curing condition comprises that the temperature of curing is 20-35℃, and the time of curing is 20-36h.

[0043] Further, the curing condition comprises that the temperature of curing is 25-27℃, and the time of curing is 24-28h.

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

[0045] The fourth aspect of the present application provides an application of the above drilling fluid composition in oil field treatment.

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

[0047] The test method of the average size of the foam of the drilling fluid composition is as follows: 100mL of the drilling fluid composition is taken, and the foam performance thereof is measured under the conditions of room temperature and high-speed stirring (12000±100rpm), and the average size of the foam is measured by an electron microscope.

[0048] The test method of the rolling recovery rate of the cuttings is as follows: 300g of the drilling fluid composition is taken and put into a roller heating furnace, 20g of the cuttings is added, and the cuttings is rolled at 140℃ for 16h, and the mass of the rolled cuttings is tested.

[0049] The rolling recovery rate of the cuttings = the mass of the rolled cuttings / the mass of the cuttings before rolling × 100%.

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

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

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

[0053] Polyoxyethylene-polyoxypropylene block polymer-4 has a number average molecular weight of 2850 g / mol, wherein the total weight of the polyoxyethylene segments to the total weight of the polyoxypropylene segments is 1:1 based on the total weight of the polymer;

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

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

[0056] Polyoxyethylene-polyoxypropylene block polymer-7 has a number average molecular weight of 3000 g / mol, wherein 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 tamarind gum are commercially available.

[0058] Example 1

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

[0060] 15 g of bentonite was slowly added into 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; and then mixed with 2.5 g of polyoxyethylene-polyoxypropylene block polymer-1, 2.5 g of inhibitor-1 and 0.5 g of carboxymethyl cellulose to obtain drilling fluid composition Al;

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

[0062] Example 2

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

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

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

[0066] Example 3

[0067] Inhibitor-3, containing the structural unit a polymer having a weight average molecular weight of 10000 g / mol;

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

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

[0070] Example 4

[0071] Inhibitor-4, containing the structural unit a polymer having a weight average molecular weight of 9500 g / mol;

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

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

[0074] Example 5

[0075] The inhibitor-3 is selected;

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

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

[0078] Example 6

[0079] The inhibitor-3 is selected;

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

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

[0082] Example 7

[0083] The inhibitor-7 contains a polymer having the structural unit with a weight average molecular weight of 9000 g / mol;

[0084] Slowly add 15 g of bentonite into 500 g of water, stir, the stirring temperature is 55 °C, the stirring time is 2 h; then maintain, the maintaining temperature is 25 °C, the maintaining time is 24 h; then add 3 g of polyoxyethylene-polyoxypropylene block polymer-6, 2 g of inhibitor-7 and 1.5 g of starch to mix, to obtain a drilling fluid composition A7;

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

[0086] Example 8

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

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

[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 to replace "the stirring temperature is 50 °C, and the stirring time is 2 h", to obtain a drilling fluid composition A9;

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

[0092] Example 10

[0093] In the manner of Example 1, except that "the maintaining temperature is 25 °C, and the maintaining time is 36 h" is used to replace "the maintaining temperature is 25 °C, and the maintaining time is 24 h", to obtain a drilling fluid composition A10;

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

[0095] Comparative Example 1

[0096] In the same manner as in Example 1, except that "Inhibitor-1" was not added, to obtain a drilling fluid composition D1.

[0097] Comparative Example 2

[0098] In the same manner as in Example 1, except that "Polyoxyethylene-polyoxypropylene block polymer-1" was not added, to obtain a drilling fluid composition D2.

[0099] Comparative Example 3

[0100] In the same manner as in Example 1, except that "Inhibitor-1" was not added, "Polyoxyethylene-polyoxypropylene block polymer-1" was not added, to obtain a drilling fluid composition D3.

[0101] Comparative Example 4

[0102] 15 g of bentonite, 500 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; and then cured at a temperature of 25 °C for 24 h to obtain a drilling fluid composition D4.

[0103] Comparative Example 5

[0104] A commercially available drilling fluid foaming agent commonly used in the art, which is designated as WD-12, was used as a control group, and was designated as D5.

[0105] Comparative Example 6

[0106] Water was used as a control group (i.e., only water was used without the drilling fluid composition as a sample for testing), and was designated as D6.

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

[0108] Table 1

[0109]

[0110]

[0111] The roller heating furnace has a high temperature of 140 °C, and it can be proved that the drilling fluid composition in the present application can be applied in a high temperature environment.

[0112] From the results of Table 1, it can be seen that, by comparing Example 1 with Comparative Examples 1-3, the average size of the foam of Comparative Example 3, in which two components were 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 synergistically acts, and is not simply combined.

[0113] By comparing Example 1 with Comparative Example 4, it can be seen that, in the present application, the specific preparation step of step-by-step addition can successfully dissolve the substance which is not easy to coagulate into blocks, has the effect of effectively improving the uniformity of the system, and makes the system more stable, and Example 1 has smaller average size of the foam of the composition and higher cuttings rolling recovery rate.

[0114] By comparing Example 1 with Comparative Examples 5 and 6, it can be seen that, in the present application, the specific drilling machine composition is superior to the drilling machine in the prior art.

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

[0116] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all belong to the protection scope of the present application.

Claims

1. A drilling fluid composition, characterized in that, The composition comprises: an inhibitor, a foaming agent, a foam stabilizer, bentonite, and water; The inhibitor is a polymer having the structural unit shown in Formula I. Formula I, X is selected from halogen elements; The weight-average molecular weight of the polymer is 8000-10000 g / mol; The foaming agent is selected from high molecular surfactants; The polymeric surfactant is selected from polyoxyethylene-polyoxypropylene block polymers; The foam stabilizer is selected from at least one of carboxymethyl cellulose, starch and hydroxyethyl saponin, and sodium caseinate; Based on the total weight of the composition, the composition contains 0.1wt%-1wt% of the inhibitor, 0.2wt%-2wt% of the foaming agent, 0.1wt%-0.7wt% of the foam stabilizer, 1wt%-5wt% of the bentonite, and 85wt%-97wt% of the water.

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

3. The composition according to claim 1 or 2, wherein, X is Cl; And / or, the weight-average molecular weight of the polymer is 8500-9000 g / mol.

4. The composition according to claim 1 or 2, wherein, 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. And / or, the number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer is 2000-4000 g / mol; And / or, the foam stabilizer is selected from at least one of carboxymethyl cellulose, starch and hydroxyethyl saponin.

5. The composition according to claim 4, wherein, 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 1-1.2:

1. And / or, the number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer is 2400-2850 g / mol.

6. The composition according to claim 3, wherein, 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. And / or, the number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer is 2000-4000 g / mol; And / or, the foam stabilizer is selected from at least one of carboxymethyl cellulose, starch and hydroxyethyl saponin.

7. The composition according to claim 6, wherein, 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 1-1.2:

1. And / or, the number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer is 2400-2850 g / mol.

8. The composition according to any one of claims 1, 2, 5-7, wherein, The average foam size of the composition is 50-95 μm.

9. The composition according to claim 8, wherein, The average foam size of the composition is 65-85 μm.

10. The composition according to claim 3, wherein, The average foam size of the composition is 50-95 μm.

11. The composition according to claim 10, wherein, The average foam size of the composition is 65-85 μm.

12. The composition according to claim 4, wherein, The average foam size of the composition is 50-95 μm.

13. The composition according to claim 12, wherein, The average foam size of the composition is 65-85 μm.

14. A method for preparing the drilling fluid composition according to any one of claims 1-13, characterized in that, The preparation method includes: stirring and curing water and bentonite, and then mixing the resulting product with an inhibitor, a foaming agent, and a foam stabilizer to obtain the drilling fluid composition.

15. The preparation method according to claim 14, 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 the water is 85wt%-97wt%.

16. The preparation method according to claim 14, wherein, 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%.

17. The composition according to any one of claims 14-16, wherein, The inhibitor is a polymer having the structural unit shown in Formula I. Formula I, X is selected from halogen elements; And / or, the weight-average molecular weight of the polymer shown in Formula I is 8000-10000 g / mol; And / or, the foaming agent is selected from polymeric surfactants; And / or, the foam stabilizer is selected from at least one of carboxymethyl cellulose, starch and hydroxyethyl saponin, and sodium caseinate.

18. The preparation method according to claim 17, wherein, X is Cl; And / or, the weight-average molecular weight of the polymer shown in Formula I is 8500-9000 g / mol; And / or, the polymeric surfactant is selected from polyoxyethylene-polyoxypropylene block polymers; And / or, the foam stabilizer is selected from at least one of carboxymethyl cellulose, starch and hydroxyethyl saponin.

19. The preparation method according to claim 18, wherein, In the polyoxyethylene-polyoxypropylene block polymer, based on the total weight of the polymer, the ratio of the total weight of the ethylene oxide segments to the total weight of the propylene oxide segments is 1-2:

1. And / or, the number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer is 2000-4000 g / mol.

20. The preparation method according to claim 19, wherein, In the polyoxyethylene-polyoxypropylene block polymer, based on the total weight of the polymer, the ratio of the total weight of the ethylene oxide segments to the total weight of the propylene oxide segments is 1-1.2:

1. And / or, the number average molecular weight of the polyoxyethylene-polyoxypropylene block polymer is 2400-2850 g / mol.

21. The preparation method according to any one of claims 14-16 and 18-20, wherein, The stirring conditions include: a stirring temperature of 40-60℃; and a stirring time of 1-2 hours. And / or, the conditions for maintenance include: a maintenance temperature of 20-35℃; and a maintenance time of 20-36 hours.

22. The preparation method according to claim 21, wherein, The stirring conditions include: a stirring temperature of 48-55℃; and a stirring time of 1.5-1.8 hours. And / or, the conditions for maintenance include: a maintenance temperature of 25-27°C; and a maintenance time of 24-28 hours.

23. The preparation method according to claim 17, wherein, The stirring conditions include: a stirring temperature of 40-60℃; and a stirring time of 1-2 hours. And / or, the conditions for maintenance include: a maintenance temperature of 20-35℃; and a maintenance time of 20-36 hours.

24. The preparation method according to claim 23, wherein, The stirring conditions include: a stirring temperature of 48-55℃; and a stirring time of 1.5-1.8 hours. And / or, the conditions for maintenance include: a maintenance temperature of 25-27°C; and a maintenance time of 24-28 hours.

25. A drilling fluid composition prepared by the method according to any one of claims 14-24.

26. The use of the drilling fluid composition according to any one of claims 1-13 and 25 in oilfield treatment.

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