A broad-spectrum plugging oil-based drilling fluid and its application

Abstract

The present application relates to a broad-spectrum plugging oil-based drilling fluid, which comprises, by total mass, base oil, 25-35% calcium chloride solution, 4-6% emulsifier, 0.5-2% wetting agent, 2-4% organic soil, 2-4% fluid loss reducer, 1-2% reserve alkali, 4-6% plugging agent, and weighting material; the oil-water ratio (v / v) of the drilling fluid is 50 / 50-90 / 10; by optimizing the emulsifier system and the plugging agent system, the drilling fluid of the present application has excellent rheological properties, plugging properties, pollution resistance and high temperature resistance, and by compounding plugging materials of different particle sizes, it has a wide adaptability to different cracks, can effectively improve the stability of the wellbore wall, and reduce the risk of wellbore wall instability, and can be used in shale gas field drilling with harsh formation environments.

Description

Technical Field

[0001] The present application relates to the field of C09K8 / 03, and in particular to a broad-spectrum plugging oil-based drilling fluid and its application. Background Art

[0002] With the decrease of available reserves in oil fields, oil and gas reservoirs with high development difficulty, such as shale, mudstone, heavy oil layer, salt-gypsum layer, low permeability and ultra-low permeability reservoir and marine oil and gas, have become the focus of drilling and development. At the same time, more stringent requirements are put forward for the filtration, lubricity and high and low temperature resistance of drilling fluid. In drilling operations, in order to reduce the impact of drilling fluid entering the formation on the rock strength, plugging agents are usually required. The current plugging agents do not have a broad-spectrum plugging effect and can only plug cracks of specific widths. For example, the distribution of pores and fractures in Longmaxi is: D10 = 700nm, D50 = 2.29 microns, D90 = 8.91 microns, and the distribution of cracks is different. The plugging agent particle size in conventional drilling fluid is large, and it is difficult to form an effective plugging, which has a poor protection effect on the oil and gas layer and has a great impact on the performance of the drilling fluid. In addition, in the current drilling technology, the emulsification stability, rheological properties, well wall instability, and the risk of stuck drill of the drilling fluid are also key issues that need to be solved.

[0003] Patent CN2018105454935 discloses a low-density water-based drilling fluid that is resistant to ultra-high temperatures of 248°C, and a preparation method and application thereof. The drilling fluid has good applicability over a large temperature range, and is applicable to formation temperatures ranging from 180°C to 248°C. However, the water-based drilling fluid has a greater risk of drill sticking, a long drilling cycle, and a high construction safety risk. Patent CN2017800173074 discloses an oil-based drilling fluid containing an alkaline earth adamantane compound as a rheology modifier. The prepared oil-based drilling fluid has a more effective ability to remove drill cuttings, but the drilling fluid cannot adapt well to more complex oilfield systems, and has an insufficient reinforcement effect on the well wall. Summary of the invention

[0004] In order to solve the above technical problems, the present application provides a broad-spectrum plugging oil-based drilling fluid, which, by total mass, has a formula comprising: base oil, 25-35% calcium chloride solution, 4-6% emulsifier, 0.5-2% wetting agent, 2-4% organic soil, 2-4% filtration reducer, 1-2% reserve alkali, 4-6% plugging agent, and weighting material.

[0005] Furthermore, the oil-water ratio (v / v) of the drilling fluid is 50 / 50-90 / 10.

[0006] Furthermore, the base oil is selected from at least one of white oil, diesel and vegetable oil.

[0007] Preferably, the base oil is diesel.

[0008] Furthermore, the emulsifier is selected from at least one of nonionic emulsifiers, anionic emulsifiers, cationic emulsifiers, and zwitterionic emulsifiers.

[0009] Furthermore, the emulsifier is selected from at least one of polyoxyethylene ethers, polyester amines, fatty acids, and fatty acid salts.

[0010] Preferably, the emulsifier is polyester amine.

[0011] Furthermore, the emulsifier is SMEMUL-1 and / or SMEMUL-2, purchased from Sinopec.

[0012] Furthermore, the density of SMEMUL-1 is 0.92-0.98 g / cm 3 (25℃), pH value is 6-8.

[0013] Furthermore, the density of SMEMUL-2 is 0.90-1.02 g / cm 3 (25℃), pH value is 7-9.

[0014] Furthermore, the emulsifier is a combination of SMEMUL-1 and SMEMUL-2 in a weight ratio of (3-5): (1-3).

[0015] Preferably, the weight ratio of SMEMUL-1 to SMEMUL-2 is 3:2; SMEMUL series emulsifiers have a larger molecular extension volume and more hydrophilic groups, are directly connected to the water phase through chemical bonds, avoid electrostatic repulsion between adjacent hydrophilic groups, can be arranged more closely at the oil-water interface, and the lipophilic groups are more likely to entangle to form micelles, thereby improving the wrapping and stability of the oil phase to the water phase; however, SMEMUL-1 and SMEMUL-2 have different molecular weights, inconsistent surface amino group numbers and pH values, and large differences in the thickness of the wrapping structure and the stability of the micelles formed. Only when the weight ratio of SMEMUL-1 to SMEMUL-2 is 3:2, the high temperature resistance of the drilling fluid is the best and the filtration loss is small.

[0016] Although the emulsifier system of the present application is stable in practical applications and can be adapted to use in higher or lower temperature environments, it is still not suitable for complex shales, such as shales with well-developed fractures, weak gel structure, significant anisotropy, large fragmentation and instability.

[0017] Furthermore, the wetting agent includes at least one of a sulfonate wetting agent, a quaternary ammonium salt wetting agent, and an amide wetting agent.

[0018] Furthermore, the wetting agent is selected from at least one of hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium chloride, sodium lauryl sulfate, hexadecyldimethylamine oxide, octadecyldimethylamine oxide, stearyl dihydroxyethylammonium chloride, dodecyldimethylamine oxide, coconut trimethylammonium chloride, coconut trimethylamine oxide, and oleic acid diethanolamide.

[0019] Preferably, the wetting agent is cocotrimonium chloride (CAS: 61789-18-2).

[0020] Furthermore, the organic soil is modified organic soil, specifically quaternary ammonium salt modified organic soil, which can be HFGEL-136C.

[0021] Furthermore, the fluid loss reducer is at least one of humic acid amide, oxidized asphalt, sulfonated asphalt, sulfonated resin, Hi-FLO, organic lignite, modified rubber resin, and modified cellulose.

[0022] Preferably, the fluid loss reducer is modified cellulose, which may be one or a combination of modified CMC, HEC, and CMHEC.

[0023] Furthermore, the reserve alkali is CaO.

[0024] Furthermore, the plugging agent includes plugging agent A and plugging agent B, plugging agent A is selected from at least one of SiO2, modified SiO2, calcium carbonate, modified calcium carbonate, and calcite, and plugging agent B is selected from at least one of multi-vinyl polymer emulsion, elastic graphite, and asphalt resin.

[0025] Furthermore, the plugging agent A includes calcium carbonate and SiO2, and the mass ratio of the two is (2-3): (1-1.5).

[0026] Furthermore, the particle size of calcium carbonate is 800-1100 mesh, and the average particle diameter of SiO2 is 100-300nm; the present application utilizes the compound use of plugging agents with different particle sizes to improve the plugging effect of the plugging agent on cracks in different situations. Under the action of pressure difference, calcium carbonate with larger particle size enters the well seam to act as a bridging skeleton, plugging the micro-nano level cracks. Subsequently, silicon dioxide with smaller particle size can not only enter the bridging skeleton to improve the density, but also penetrate into smaller cracks. Although the plugging agent with smaller particle size can effectively plug micro-nano cracks, when the content of small particle size plugging material is too much, the bridging structure stability of the plugging agent is not good, and the reinforcement effect on the well wall is relatively poor. However, when the amount of plugging material with larger particle size is too much, the matching of the drilling fluid to special shale will be significantly reduced.

[0027] Furthermore, the plugging agent B includes elastic graphite and asphalt resin.

[0028] Furthermore, the elastic graphite is modified from a material having elasticity.

[0029] Furthermore, the amount of plugging agent B in the plugging agent is 0.5-2 times the amount of plugging agent A; calcium carbonate and SiO2 in the plugging agent have greater rigidity, and their ability to inhibit shale pressure transmission is still limited. Therefore, plugging agent B with elastic effect is compounded and used. Rigid materials are used to fill well seams. In addition to improving the density of cracks and strengthening plugging, elastic materials also effectively buffer the horizontal stress of the wellbore and rock.

[0030] Furthermore, the raw materials for preparing the elastic graphite include: by weight, 25-35 parts of graphite, 20-25 parts of monomers, and 0.3-0.5 parts of initiator.

[0031] Furthermore, the preparation method of the elastic graphite comprises: mixing the above-mentioned graphite, monomer, half the mass of initiator and solvent, heating to 80-90°C, stirring for 30min-1h, adding the remaining initiator to react for 1-2h, filtering and drying.

[0032] Furthermore, the monomers include acrylic monomers, vinyl monomers, amide monomers and sulfonic acid monomers.

[0033] Furthermore, the amide monomer includes at least one of acrylamide, N-methyl-N-vinylacetamide, N-methylacrylamide, and N-ethylacrylamide.

[0034] Furthermore, the acrylic monomer includes at least one of acrylic acid, methacrylic acid, hydroxyethyl acrylate phosphate, and isobornyl acrylate.

[0035] Furthermore, the sulfonic acid monomer is at least one of p-toluenesulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, propylenesulfonic acid, and sodium styrenesulfonate.

[0036] Furthermore, the vinyl monomer is at least one of styrene, acrylonitrile, polyethylene, and polystyrene-ethylene-styrene.

[0037] Furthermore, the initiator is one of ammonium persulfate, potassium persulfate and sodium persulfate.

[0038] The present invention connects different elastic materials on the graphite surface to modify the graphite, and uses different elastic materials in combination to better buffer the horizontal stress of the wellbore and rock, inhibit the generation of well wall cracks and delay the deepening of the cracks.

[0039] In one embodiment, the raw materials for preparing the elastic graphite A include: by weight, 30-35 parts of graphite, 20-25 parts of acrylic acid, 5-8 parts of styrene, 1-3 parts of acrylonitrile, and 0.3-0.5 parts of initiator.

[0040] In one embodiment, the raw materials for preparing the elastic graphite B include: by weight, 30-35 parts of graphite, 10-15 parts of acrylic acid, 5-8 parts of sodium styrene sulfonate, 1-3 parts of acrylonitrile, and 0.3-0.5 parts of initiator.

[0041] In one embodiment, the raw materials for preparing the elastic graphite C include: by weight, 30-35 parts of graphite, 5-7 parts of N-methyl acrylamide, 10-13 parts of acrylic acid, 5-8 parts of styrene, 1-3 parts of acrylonitrile, and 0.3-0.5 parts of initiator.

[0042] Furthermore, the elastic graphite is a compound of elastic graphite A, elastic graphite B and elastic graphite C. The present application has found in the research that when one elastic graphite is used alone, the reinforcement performance of the well wall is still insufficient. By using different elastic graphites, a better synergistic effect can be achieved. The possible reasons are: in the acrylic acid-styrene molecular chain formed on the surface of elastic graphite A, the content of acrylic acid is relatively high, the softness of the molecular chain is good, and the molecular chain can be better extended to adapt to external pressure; and the difference between the surface of elastic graphite B and elastic graphite A is that the hard segment chain of styrene is relatively large, which can enhance the mechanical strength of the plugging agent and also give the plugging agent a certain negative charge, to a certain extent, strengthen the encapsulation of the emulsifier and reduce the filtration loss; the intermolecular force between the amino group in elastic graphite C and the hydroxyl group, benzene ring, etc. in elastic graphite A and elastic graphite B can enhance the bonding effect between the plugging agents. In addition, the functional groups on the surface of elastic graphite can also generate force with the well wall, strengthen the bonding force between the system and the well wall, and reduce the phenomenon of plugging agent backseepage caused by mechanical disturbance of drilling.

[0043] Furthermore, the mass ratio of elastic graphite A, elastic graphite B, elastic graphite C and asphalt resin in the plugging agent B is (2-4): (3-4): (3-4): (4-6).

[0044] The present application unexpectedly discovered that when the mass ratio of elastic graphite A, elastic graphite B, elastic graphite C and asphalt resin is specified to be 3:3:3:5, the drilling fluid prepared at this ratio reduces friction resistance and avoids drill sticking. The possible reason is speculated to be: in addition to being able to generate intermolecular forces with the emulsifier, the elastic graphite at this ratio has a negative charge and the repulsion force on the emulsifier is greater than the intermolecular attraction, which makes the spherical wrapping structure of the emulsifier on the water phase more obvious, weakens the intermolecular effect between the emulsifier and the mud cake components, reduces the excessive adhesion of the mud cake on the well wall, and reduces friction and drill sticking; however, when the elastic graphite content is relatively high, it will cause an imbalance in the intermolecular effect with the emulsifier, reduce the stability of the emulsifier, and also change the rheological properties of the drilling fluid system.

[0045] Preferably, the particle size of the elastic graphite A is 20-40 mesh.

[0046] Preferably, the particle size of the elastic graphite B is 40-80 mesh.

[0047] Preferably, the particle size of the elastic graphite C is less than 120 mesh.

[0048] Furthermore, the weighting material is selected from at least one of calcium carbonate, barite, iron ore powder, limestone, ilmenite powder, galena powder, manganese tetroxide, and barium carbonate.

[0049] Preferably, the weighting material is barite.

[0050] Furthermore, the amount of weighting material added is determined according to the density of the drilling fluid.

[0051] Furthermore, the density of the drilling fluid is 1.7-2.2 g / cm 3 (20℃).

[0052] Secondly, the present invention also provides the application of the broad-spectrum plugging oil-based drilling fluid in shale gas field drilling.

[0053] Beneficial effects:

[0054] 1. The oil-based drilling fluid of the present application has excellent rheological properties, plugging properties, anti-pollution and high temperature resistance. By compounding plugging materials of different particle sizes, it has a wide adaptability to different cracks, can effectively improve the stability of the well wall, and reduce the risk of well wall instability.

[0055] 2. The oil-based drilling fluid of the present application improves the emulsification stability by optimizing the emulsifier system, and has a higher demulsification voltage, rheological properties and rock-carrying capacity.

[0056] 3. The oil-based drilling fluid of the present application uses different elastic plugging materials, which effectively buffers the extension of shale stress and improves the stability and structural strength of the well wall. In addition, the modified groups on the surface of the elastic material can enhance the emulsifier's encapsulation of the water phase and reduce the filtration loss.

[0057] 4. The oil-based drilling fluid of the present application can be used in the exploitation process of shale oil and gas in harsh formation environments due to its excellent performance. DETAILED DESCRIPTION

[0058] Example

[0059] Example 1

[0060] The present application provides a broad-spectrum plugging oil-based drilling fluid, which includes, by total mass, 0# diesel, 30% calcium chloride solution, 5% emulsifier, 1.5% wetting agent, 3% organic soil, 3% filtration reducer, 1.5% reserve alkali, 5% plugging agent, and barite.

[0061] The oil-water ratio (v / v) of the drilling fluid is 85 / 15; the emulsifier is a combination of SMEMUL-1 and SMEMUL-2, with a weight ratio of 3:2; the wetting agent is coconut trimethyl ammonium chloride; the organic soil is Fenghong HFGEL-136C; the fluid loss reducer is modified cellulose, Zhengzhou Jingyuan mud material HFLD-1, and the reserve alkali is CaO; the plugging agent includes plugging agent A and plugging agent B, plugging agent B The dosage is 1.2 times that of plugging agent A. Plugging agent A is calcium carbonate (particle size is 950 mesh) and SiO2 (average particle diameter is 200nm), and the mass ratio of the two is 2.5:1; plugging agent B is composed of elastic graphite A, elastic graphite B, elastic graphite C and asphalt resin, and the mass ratio is 3:3:3:5; the particle size of elastic graphite A is 30 mesh, the particle size of elastic graphite B is 60 mesh, and the particle size of elastic graphite C is 200 mesh.

[0062] The raw materials for preparing elastic graphite A include: by weight, 30 parts of graphite, 22 parts of acrylic acid, 6 parts of styrene, 2 parts of acrylonitrile, and 0.4 parts of potassium persulfate;

[0063] The raw materials for preparing elastic graphite B include: by weight, 30 parts of graphite, 15 parts of acrylic acid, 6 parts of sodium styrene sulfonate, 2 parts of acrylonitrile, and 0.4 parts of potassium persulfate.

[0064] The raw materials for preparing elastic graphite C include: by weight, 30 parts of graphite, 5 parts of N-methyl acrylamide, 12 parts of acrylic acid, 6 parts of styrene, 2 parts of acrylonitrile, and 0.4 parts of ammonium persulfate.

[0065] The preparation method of the elastic graphite is as follows: the above graphite, monomer, half the mass of the initiator and solvent are mixed, the temperature is raised to 85° C., stirred for 45 minutes, the remaining initiator is added and reacted for 1.5 hours, filtered and then dried.

[0066] The density of the drilling fluid is 2.2 g / cm 3 .

[0067] Example 2

[0068] The present application provides a broad-spectrum plugging oil-based drilling fluid, which comprises, by total mass, 0# diesel, 35% calcium chloride solution, 6% emulsifier, 2% wetting agent, 4% organic soil, 4% filtrate reducer, 2% reserve alkali, 6% plugging agent, and barite.

[0069] The oil-water ratio (v / v) of the drilling fluid is 90 / 10; the emulsifier is a combination of SMEMUL-1 and SMEMUL-2, with a weight ratio of 1:1, the wetting agent is coconut trimethyl ammonium chloride, the organic soil is Fenghong HFGEL-136C, the filtrate reducer is modified cellulose, Zhengzhou Jingyuan mud material HFLD-1, and the reserve alkali is CaO; the plugging agent includes plugging agent A and plugging agent B, the amount of plugging agent B is twice the amount of plugging agent A, plugging agent A is calcium carbonate (particle size is 800-1100 mesh) and SiO2 (average particle diameter is 100-300nm), the mass ratio of the two is 2:1.5, and plugging agent B is selected from at least one of multi-vinyl polymer emulsion, elastic graphite, and asphalt resin.

[0070] The plugging agent B is composed of elastic graphite A, elastic graphite B, elastic graphite C and asphalt resin in a mass ratio of 2:4:3:6; the particle size of the elastic graphite A is 40 meshes, the particle size of the elastic graphite B is 80 meshes, and the particle size of the elastic graphite C is 180 meshes.

[0071] The raw materials for preparing elastic graphite A include: by weight, 35 parts of graphite, 25 parts of acrylic acid, 8 parts of styrene, 3 parts of acrylonitrile, and 0.5 parts of potassium persulfate;

[0072] The raw materials for preparing elastic graphite B include: by weight, 35 parts of graphite, 15 parts of acrylic acid, 8 parts of sodium styrene sulfonate, 3 parts of acrylonitrile, and 0.5 parts of potassium persulfate.

[0073] The raw materials for preparing elastic graphite C include: by weight, 35 parts of graphite, 7 parts of N-methyl acrylamide, 13 parts of acrylic acid, 8 parts of styrene, 3 parts of acrylonitrile, and 0.5 parts of ammonium persulfate.

[0074] The preparation method of the elastic graphite is as follows: the above graphite, monomer, half the mass of the initiator and solvent are mixed, the temperature is raised to 90° C., stirred for 30 minh, the remaining initiator is added to react for 1 h, filtered and then dried.

[0075] The density of the drilling fluid is 1.98 g / cm 3 .

[0076] Example 3

[0077] The present application provides a broad-spectrum plugging oil-based drilling fluid, which, by total mass, comprises: 0# diesel, 25% calcium chloride solution, 4% emulsifier, 0.5% wetting agent, 2% organic soil, 2% fluid loss reducer, 1% reserve alkali, 4% plugging agent, and barite.

[0078] The oil-water ratio (v / v) of the drilling fluid is 50 / 50; the emulsifier is a combination of SMEMUL-1 and SMEMUL-2, with a weight ratio of 5:1; the wetting agent is coconut trimethyl ammonium chloride, the organic soil is Fenghong HFGEL-136C, the fluid loss reducer is modified cellulose, Zhengzhou Jingyuan mud material HFLD-1, and the reserve alkali is CaO; the plugging agent includes plugging agent A and plugging agent B, and the amount of plugging agent B is 0.5 times the amount of plugging agent A, plugging agent A is calcium carbonate (particle size is 800-1100 mesh) and SiO2 (average particle diameter is 100-300nm), and the mass ratio of the two is 3:1; plugging agent B is composed of elastic graphite A, elastic graphite B, elastic graphite C and asphalt resin, and the mass ratio is 4:4:3:3; the particle size of elastic graphite A is 20 mesh, the particle size of elastic graphite B is 40 mesh, and the particle size of elastic graphite C is 230 mesh.

[0079] The raw materials for preparing elastic graphite A include: by weight, 30 parts of graphite, 25 parts of acrylic acid, 5 parts of styrene, 1 part of acrylonitrile, and 0.3 parts of potassium persulfate;

[0080] The raw materials for preparing elastic graphite B include: by weight, 30 parts of graphite, 10 parts of acrylic acid, 5 parts of sodium styrene sulfonate, 1 part of acrylonitrile, and 0.3 parts of potassium persulfate.

[0081] The raw materials for preparing elastic graphite C include: by weight, 30 parts of graphite, 5 parts of N-methyl acrylamide, 10 parts of acrylic acid, 5 parts of styrene, 1 part of acrylonitrile, and 0.3 parts of ammonium persulfate.

[0082] The preparation method of the elastic graphite is as follows: the above graphite, monomer, half the mass of the initiator and solvent are mixed, the temperature is raised to 80° C., stirred for 1 hour, the remaining initiator is added and reacted for 2 hours, filtered and then dried.

[0083] The density of the drilling fluid is 1.79 g / cm3 .

[0084] Comparative Example 1

[0085] The same as Example 1, except that the emulsifier is a combination of SMEMUL-1 and SMEMUL-2, with a weight ratio of 0.5:1.

[0086] The density of the drilling fluid is 2.14 g / cm 3 .

[0087] Comparative Example 2

[0088] The same as Example 1, except that the emulsifier is a combination of SMEMUL-1 and SMEMUL-2, with a weight ratio of 6:1.

[0089] The density of the drilling fluid is 2.17 g / cm 3 .

[0090] Comparative Example 3

[0091] The same as Example 1, the difference is that the plugging agent A is calcium carbonate (particle size is 2000 mesh) and SiO2 (average particle diameter is 300nm), and the mass ratio of the two is 2.5:1.

[0092] The density of the drilling fluid is 2.21 g / cm 3 .

[0093] Comparative Example 4

[0094] The same as Example 1, except that the plugging agent B is composed of elastic graphite A, elastic graphite B, elastic graphite C and asphalt resin, and the mass ratio is 3:3:6:4.

[0095] The density of the drilling fluid is 2.15 g / cm 3 .

[0096] Comparative Example 5

[0097] The same as Example 1, except that: the particle size of the elastic graphite A is 60 mesh, the particle size of the elastic graphite B is 100 mesh, and the particle size of the elastic graphite C is 120 mesh.

[0098] The density of the drilling fluid is 2.22 g / cm 3 .

[0099] Performance testing method:

[0100] The drilling fluid was mixed according to the formula of the embodiment, stirred for 10 hours, sealed and allowed to stand for 14 hours, and the following test was performed.

[0101] 1. Water intrusion resistance: After adding contaminated water to the drilling fluid, the fluid was heated at 150° C. for 16 hours, with the amount of contaminated water added accounting for about 50% of the total mass, and the demulsification voltage value of the embodiment was tested.

[0102] 2. High temperature and high pressure rheology: The drilling fluid was heated at 150°C and 140 MPa for 16 h, cooled to room temperature, stirred at 10000 r / min for 10 min, and the rheological properties of the drilling fluid were tested (measurement temperature: 50°C);

[0103] 3. Sealing performance: The formula was hot-rolled at 150℃ for 16 hours, and the filtration loss after 30 minutes was measured at 10MPa using a 5μm sand disk.

[0104] The test results of the embodiment are shown in Table 1, where: demulsification voltage value: ES, V; plastic viscosity: PV, mPa·s;

[0105] Dynamic shear force: YP, Pa; filtration loss: APIFL, mL.

[0106] Performance test results:

[0107] Table 1

[0108]

[0109]

Claims

1. A broad-spectrum plugging oil-based drilling fluid, characterized in that: The formula includes, by total mass: base oil, 25-35% calcium chloride solution, 4-6% emulsifier, 0.5-2% wetting agent, 2-4% organic soil, 2-4% fluid loss reducer, 1-2% reserve alkali, 4-6% plugging agent, weighting material; The oil-water ratio (v / v) of the drilling fluid is 50 / 50-90 / 10; The emulsifier is a combination of SMEMUL-1 and SMEMUL-2, and the weight ratio of SMEMUL-1 to SMEMUL-2 is 3:2; The plugging agent includes a plugging agent A and a plugging agent B, wherein the plugging agent A includes calcium carbonate and SiO2, and the mass ratio of the calcium carbonate and SiO2 is (2-3): (1-1.5); the particle size of the calcium carbonate is 800-1100 mesh, and the average particle diameter of the SiO2 is 100-300nm; The plugging agent B includes elastic graphite and asphalt resin; the elastic graphite is a compound of elastic graphite A, elastic graphite B and elastic graphite C; The mass ratio of elastic graphite A, elastic graphite B, elastic graphite C and asphalt resin in the plugging agent B is (2-4): (3-4): (3-4): (4-6); The raw materials for preparing the elastic graphite A include: by weight, 30-35 parts of graphite, 20-25 parts of acrylic acid, 5-8 parts of styrene, 1-3 parts of acrylonitrile, and 0.3-0.5 parts of initiator; The raw materials for preparing the elastic graphite B include: by weight, 30-35 parts of graphite, 10-15 parts of acrylic acid, 5-8 parts of sodium styrene sulfonate, 1-3 parts of acrylonitrile, and 0.3-0.5 parts of initiator; The raw materials for preparing the elastic graphite C include: by weight, 30-35 parts of graphite, 5-7 parts of N-methyl acrylamide, 10-13 parts of acrylic acid, 5-8 parts of styrene, 1-3 parts of acrylonitrile, and 0.3-0.5 parts of initiator; The particle size of the elastic graphite A is 20-40 mesh; the particle size of the elastic graphite B is 40-80 mesh; the particle size of the elastic graphite C is less than 120 mesh; The density of the drilling fluid is 1.7-2.2 g / cm 3 ; The amount of plugging agent B in the plugging agent is 0.5-2 times the amount of plugging agent A.

2. Use of the broad-spectrum plugging oil-based drilling fluid according to claim 1 in shale gas field drilling.

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