Plugging agent, and oil-based drilling fluid and use thereof

Abstract

The present invention relates to the technical field of petroleum drilling. Disclosed are a plugging agent, and an oil-based drilling fluid and a use thereof. The plugging agent provided by the present invention has a multi-scale broad-spectrum strong plugging effect on formation micro-fractures, and the addition of the plugging agent into the oil-based drilling fluid can effectively solve the problem of wellbore instability and improve the safety of deep oil and gas exploration.

Description

Blocking agent, oil-based drilling fluid and application thereof

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Chinese Patent Application No. 202410760399.7, filed June 13, 2024, and Chinese Patent Application No. 202410785481.5, filed June 18, 2024, the contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of oil drilling technology, in particular to a blocking agent, an oil-based drilling fluid and application thereof. BACKGROUND

[0004] With the increasing intensity of unconventional oil and gas exploitation, the difficulty of drilling also increases. Oil-based drilling fluid plays an increasingly important role in deep and ultra-deep unconventional oil and gas exploration and development due to its better inhibitory and lubricating properties than water-based drilling fluid. In actual drilling operations, based on the need to balance the formation pressure and well control, when oil-based drilling fluid is used to drill micro-fractured formations, the oil-based drilling fluid or its filtrate will invade along the micro-fractures of the formation, transmitting pressure to the deep part of the wellbore formation, resulting in wellbore instability of the micro-fractured formation and affecting drilling safety. Therefore, how to effectively improve the micro-fracture sealing capacity of oil-based drilling fluid is the key way to solve the problem of wellbore instability of oil-based drilling fluid in complex formations.

[0005] Since oil-based drilling fluid is a thermodynamically unstable dispersion system with oil as the continuous phase, containing various additives, water, and solid phase (blocking material and weighting material) components, there are currently two industry problems in improving the sealing of oil-based drilling fluid: on the one hand, existing nano and micro sealing materials are mostly hydrophilic, which are suitable for use in water-based drilling fluid. The problem of the difficulty of dispersing nano and micro scale sealing particles with ultra-high specific surface area in oil phase has not been solved, which directly affects the sealing effect of multi-scale micro-fractures; on the other hand, the stability of existing sealing materials and other components of drilling fluid under high temperature and high pressure conditions in deep and ultra-deep formations also has certain problems, which affects the application under high temperature conditions. Therefore, there is currently no strong sealing oil-based drilling fluid that can be used on a large scale and effectively solve the problem of wellbore instability.

[0006] Therefore, it is urgent to develop a high-temperature oil-based drilling fluid multi-scale broad-spectrum sealing technology and related products that can achieve multi-scale, broad-spectrum, ultra-low filtration, and rigid-flexible synergy. SUMMARY

[0007] The application aims to overcome the problem that the oil-based drilling fluid lacks effective plugging of micro-fractures in the complex deep formation oil exploration work, thereby easily causing wellbore instability and the like, and provides a plugging agent, a base drilling fluid and application thereof.

[0008] To achieve the above-mentioned object, the application provides a plugging agent, which comprises an oil phase and a plugging material dispersed in the oil phase I, wherein the plugging material comprises expandable graphite, expanded graphite and silicon dioxide,

[0009] The particle size distribution of the plugging material is 1nm-50μm, and the D50 value of the plugging material increases by at least 10% after the plugging agent is heated at 240℃ for 16h compared with that before heating.

[0010] The application provides a drilling fluid, which comprises the plugging agent of the first aspect.

[0011] The application provides application of the plugging agent of the first aspect or the drilling fluid of the second aspect in improving the micro-fracture plugging effect in the drilling process, and / or reducing the filtration loss in the drilling process, and / or improving the wellbore stability in the drilling process.

[0012] Through the above technical solution, the application can at least achieve the following beneficial effects:

[0013] (1) The plugging agent provided by the application adopts a plugging agent material with specific composition and specific particle size distribution characteristics. The plugging agent can achieve broad-spectrum strong plugging of micro-fractures in the formation, and the oil-based drilling fluid prepared by using the plugging agent has good micro-fracture plugging effect and can effectively solve the problem of wellbore instability.

[0014] (2) The preparation method of the plugging agent provided by the application is simple, low in cost and safe and environmentally friendly. The plugging agent can exist in the form of an oil suspension with good stability, and the solid components in the plugging agent will not significantly float or settle during production and transportation.

[0015] (3) The plugging agent provided by the application has good compatibility with the common components of the oil-based drilling fluid, and when the oil-based drilling fluid is prepared by using the plugging agent, the flowability change range of the oil-based drilling fluid is small.

[0016] (4) In the preferred case, the plugging agent provided by the application is combined with a specific emulsifier to obtain an oil-based drilling fluid with good temperature resistance and plugging property. Through testing, it is found that the oil-based drilling fluid can effectively reduce the PPA filtration loss, which indicates that the oil-based drilling fluid has good plugging effect on micro-fractures in the formation. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a morphology diagram of individual particles of the plugging material according to the present application, wherein a is silicon dioxide, b is flake graphite, c is expandable graphite in a dry state, d is expandable graphite after absorbing oil in an oil phase, e is expanded graphite in a dry state, and f is expanded graphite after absorbing oil in an oil phase. DETAILED DESCRIPTION

[0018] The inventors of the present application found in research that the addition of a specific plugging material of multiple types and multiple scales to an oil-based drilling fluid used in deep oil and gas exploration can effectively improve the plugging of microfractures in the formation, thereby solving the problem of wellbore instability. Through extensive research, the inventors developed an emulsifier composition with good high-temperature resistance, prepared a key component of a plugging agent that can achieve multi-scale and broad-spectrum plugging of microfractures, and on this basis, formed an oil-based drilling fluid that can be used to prepare an oil-based drilling fluid with good temperature resistance and microfracture broad-spectrum plugging effect.

[0019] Based at least on the above findings, the first aspect of the present application provides a plugging agent, the plugging agent comprising an oil phase and a plugging material dispersed in the oil phase I, the plugging material comprising expandable graphite, expanded graphite, and silicon dioxide,

[0020] wherein the particle size distribution of the plugging material is 1 nm-50 μm, and after the plugging agent is heated at 240°C for 16 h, the D50 value of the plugging material increases by at least 10% compared to before heating.

[0021] In the present application, the numbering of the oil phase (such as "I", "II", etc. in oil phase I and oil phase II) is only used to describe the above for the convenience of distinguishing the oil phase in different formulations, but there is no limitation on the specific components, amount, etc. selected therefor.

[0022] In the present application, "D50" and "median particle size" in the particle size distribution are the same meaning, which can be used interchangeably herein. The median particle size refers to the particle size value corresponding to the cumulative percentage of 50wt% on the particle size distribution curve (also referred to as the particle size grading curve) of the sample, that is, under this particle size, 50wt% of the particles in the sample have a diameter less than or equal to this value, and another 50wt% of the particles have a diameter greater than or equal to this value. Similarly, the terms D10, D90, etc. in the present application are also particle size distribution characteristic values that can be obtained from the particle size distribution curve, which refer to the particle size values corresponding to the cumulative percentages of 10wt% and 90wt% on the particle size distribution curve, respectively. The particle size distribution can be detected by a laser particle size instrument or the like, and directly obtained by the computer software matched with the instrument; it can also be obtained by observing the sample by an electron microscope or the like, and statistically calculating the particle size in the field of view, and the computer software matched with certain electron microscopes also has the function of statistically calculating the particle size distribution of the particles in the field of view, in order to obtain more accurate results, the particle size in multiple fields of view can be statistically calculated to obtain the particle size distribution of the sample (for example, the particle size distribution is calculated by statistically calculating the particle size in at least 3 fields of view).

[0023] The plugging agent provided by the present application is used for the preparation of oil-based drilling fluid, which innovatively introduces a variety of carbon-based materials (different types of graphite materials). Among them, expandable graphite is natural graphite (usually flake graphite) treated under appropriate conditions by the action of oxidizing agents, intercalating agents and the like, so that the oxidizing agents, intercalating agents and the like are inserted between the graphite layers and combined with carbon atoms to form a new chemical phase-graphite intercalation compound (GIC for short). Under the action of high temperature (usually above 800°C), the oxidizing agents and intercalating agents inserted between the graphite layers "explode", causing the graphite to expand into a worm-like substance along the axial direction, which is expanded graphite. Natural flake graphite, expandable graphite and expanded graphite have obvious differences in macroscopic and / or microscopic morphology. For example, from a macroscopic point of view, natural flake graphite and expandable graphite are relatively similar, but expanded graphite exhibits a clear worm-like structure; from a microscopic point of view, due to the insertion of chemical substances (oxidizing agents and intercalating agents), expandable graphite has a "lamellar" structure, that is, compared with the "single-layer" structure of natural flake graphite, expandable graphite can be observed to have a "multi-layer" structure under a microscope, and expanded graphite has a loose and porous structure, which absorbs oil and presents a fluffy block shape when immersed in an oil phase.

[0024] The plugging agent provided by the present application is added to the oil-based drilling fluid, and can more tightly plug micro fissures in the process of oil and gas exploration and development of deep and ultra-deep layers. The inventors of the present application have long-term studied the morphology of the micro fissures of the formation and the operation environment of the micro fissure plugging of the complex formation, and selected inorganic particulate materials with different morphologies and characteristics according to their characteristics, and obtained the unique plugging agent formula of the present application through the cooperation of the inorganic particulate materials. For example, the nanometer silicon dioxide is a rigid spherical particle, which contains silicon dioxide particles with different sizes, and can directly enter the fissure and fill the fissure when plugging the micro fissure. The expanded graphite becomes fluffy after absorbing oil, and has good deformability. Under the action of the formation pressure, the expanded graphite can further build a network and consolidate the fissure. The expandable graphite itself has a sheet-like structure, can be inserted into the micro fissure and the fine gap of other plugging materials, and will expand to a certain extent at a temperature of 200-300 DEG C, so that the plugging of the micro fissure is more compact.

[0025] The plugging agent provided by the present application is directly provided in the form of an oil phase suspension, which can be more conveniently mixed with other components when the oil-based drilling fluid is prepared on site, and is also beneficial to obtaining a uniform oil-based drilling fluid, thereby avoiding the problem that the micro-nano-sized particulate plugging components are difficult to be uniformly dispersed when directly added to the drilling fluid in the form of a solid powder on site, and causing poor plugging effect.

[0026] In the plugging agent provided by the present application, the expandable graphite is used as one of the plugging materials, and the volume of the expandable graphite will expand under the action of a certain temperature (such as the temperature of an oil well). The volume of the expandable graphite and the silicon dioxide will not change obviously during the heating treatment process. Therefore, after the plugging agent provided by the present application is treated at a certain temperature for a period of time, the size of the expandable graphite will increase, so that the D50 of the plugging material in the plugging agent increases compared with that before the heating treatment.

[0027] In some preferred embodiments of the present application, the D50 of the plugging material in the plugging agent increases by 10-50% after the plugging agent is heated at 240 DEG C for 16h (the increase of the D50 of the plugging material after heating = (the D50 of the plugging material after heating-the D50 of the plugging material before heating) / the D50 of the plugging material before heating).

[0028] For example, the D50 of the plugging material in the plugging agent increases by 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% after the plugging agent is heated at 240 DEG C for 16h, or can also be a range formed by any two of the above values, or any intermediate value in the range.

[0029] Meanwhile, on the basis of the above detection, in combination with an environmental scanning electron microscope (ESEM), a scanning electron microscope (SEM), a transmission electron microscope (TEM), microbeam analysis and an energy dispersive spectrometer (EDS) energy spectrum scanning (also known as EDX spectrum, energy dispersive X-ray spectrum), etc., it can be further determined that the silica (containing Si-O bond) and graphite material (main component element is C) are contained therein. For example, by observing the morphology of the solid particles in the plugging agent sample through the microscopes such as ESEM, SEM and TEM, it can be preliminarily confirmed that the plugging material contains silica particles (usually spherical or spherical-like), and on this basis, in combination with the EDS energy spectrum scanning, the element composition of the solid particles is determined, so that the existence of silica and graphite material (such as expandable graphite and expanded graphite) is confirmed.

[0030] The EDS can be usually loaded on the aforementioned electron microscope, so that the particle morphology and element distribution of the plugging material in the same scanning field can be obtained at the same time, and in combination with the supporting computer software, the morphology and element composition of each plugging material particle observed in the field can be more conveniently compared, and then the composition of the plugging material is judged.

[0031] For example, the composition of the plugging material can be judged in the following manner: first, the particle morphology of the plugging material is observed under the electron microscope, and it is preliminarily confirmed that in a certain field, the silica particles (having spherical or spherical-like morphology), the expandable graphite (having a lamellar structure) and the expanded graphite (having a loose porous structure, which presents a morphology similar to "irregular sponge block" under the microscope) are contained, and the morphology of each particle is shown in FIG. 1; then, through the EDS energy spectrum scanning result of the field, the silica and graphite material can be further confirmed, and the expandable graphite and expanded graphite can be distinguished and confirmed by the C content in the graphite material shown by the scanning result. The basis for distinguishing the expandable graphite and expanded graphite according to the C content is as follows: since the chemical substances inserted between the graphite layers of the expanded graphite "explode and fly out" during the high-temperature treatment, the content of these inserted chemical substances in the expanded graphite is greatly reduced compared with the expandable graphite which is not subjected to high-temperature treatment. Usually, the particles with C content of 50-80 wt% are determined as expandable graphite, and the particles with C content of 90 wt% or more are determined as expanded graphite.

[0032] Generally, the plugging agent sample needs to be treated before ESEM, SEM, TEM and EDS spectrum scanning, for example, the plugging agent sample is diluted to make the effective solid content in the plugging agent sample less than 5% (mass / volume ratio, i.e. less than 5 g / 100 mL) or the plugging agent sample is dried to take out the plugging material for detection. The purpose of drying the plugging agent sample is to remove the oil phase in the plugging agent sample. For the convenience, the plugging agent sample can be treated by suction filtration and the obtained solid component (i.e. the plugging material) is washed (for example, washed by ethanol) and dried. In order to avoid the expandable graphite from expanding during the drying process, the drying is usually performed at room temperature without heating.

[0033] For example, 100 g of the plugging agent sample can be subjected to suction filtration. In order to reduce the loss of the plugging material, the collected filtrate is returned to the suction filtration for 5 times. Then the collected solid (i.e. the separated plugging material) is washed by ethanol. In order to improve the washing effect, the washing can be repeated for 5 times. The amount of ethanol used for each washing is about 10 times the volume of the solid. After each washing, the suction filtration is performed and the collected filtrate is returned to the suction filtration for 5 times. After the last washing, the solid obtained by the suction filtration is air-dried at room temperature, weighed and then subjected to ESEM, SEM, TEM and EDS spectrum scanning by the aforementioned method to observe the morphological characteristics and elemental composition of the plugging material in the plugging agent and thus determine the components contained therein.

[0034] For example, the plugging agent sample can also be diluted to reduce the content of the solid substance to 5% and then subjected to ESEM, SEM, TEM and EDS spectrum scanning to observe the morphological characteristics and elemental composition of the solid particles (i.e. the plugging material) in the plugging agent and thus determine the components contained therein.

[0035] In addition, in the case of known raw materials, the content of the plugging material can also be calculated according to the amount of the raw materials.

[0036] Through research, the inventors found that the plugging agent provided by the present application has excellent stability. During long-term storage, the plugging material in the plugging agent does not settle or float. Generally, the stability of the plugging agent can be detected by observing the distribution of the solid components in the plugging agent after standing for a period of time. However, the detection method of standing observation is time-consuming. In order to facilitate detection, the stability of the plugging agent can also be detected by the following method: a certain amount of the plugging agent sample is placed in a centrifuge tube and centrifuged at 10-100 g (i.e. 10-100 times the gravitational acceleration) for more than 5 min. The middle position of the liquid surface in the centrifuge tube after centrifugation is taken as the demarcation line. A certain amount of the liquid above the demarcation line (marked as "upper liquid") and an equal amount of the liquid below the demarcation line (marked as "lower liquid") are taken and weighed, respectively. The weight difference of the two is compared or the density (g / cm3) is calculated according to the weighing results.3 ), the density difference between the upper liquid and the lower liquid is compared. If the weight difference / density difference is large, it indicates poor stability, and if the weight difference / density difference is small or there is substantially no density difference, it indicates good stability.

[0037] In the above method, g can be converted into the centrifugal speed by the following formula I: G = 1.11 x 10 -5 x R x a 2 Formula I

[0038] In formula I, G is the centrifugal force, i.e., the multiple of the gravitational acceleration g; R is the centrifugal radius (cm); and a is the centrifugal speed (rpm). For example, the calculated centrifugal force G is ten times the gravitational acceleration g, which can be recorded as 10g.

[0039] In the above method, the density ratio of the upper liquid to the lower liquid can be calculated by the following formula II:

[0040] Density ratio (%) = upper liquid density / lower liquid density x 100% Formula II

[0041] According to a preferred embodiment of the present application, wherein the density of the upper liquid is 70-100% of the density of the lower liquid when the plugging agent is centrifuged at a centrifugal force of 100g (g is the gravitational acceleration, i.e., the centrifugal force is 100 times the gravitational acceleration) for 10 min.

[0042] Preferably, the density of the upper liquid is 80-100% of the density of the lower liquid when the plugging agent is centrifuged at a centrifugal force of 100g for 10 min. For example, it can be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, 100%, or a range formed by any two of the above values, or any intermediate value in the range.

[0043] According to a preferred embodiment of the present application, wherein the density difference between the upper liquid and the lower liquid in the centrifugation product is not more than 0.05 g / cm 3 , preferably not more than 0.03 g / cm 3 , when the plugging agent is centrifuged at a centrifugal force of 100g (g is the gravitational acceleration, i.e., the centrifugal force is 100 times the gravitational acceleration) for 10 min. 3 3 ​0.003 g / cm 3 0.004 g / cm 3 0.005 g / cm 3 0.01 g / cm 3 0.015 g / cm 3 0.02 g / cm 3 0.025 g / cm 3 0.03 g / cm 3 , or also can be any two of the above values or any intermediate value in the range.

[0044] According to a preferred embodiment of the present application, the particle size distribution of the plugging material in the plugging agent is D10 of 50-1500 nm, D50 of 1-10 μm, and D90 of 1-15 μm.

[0045] Preferably, the particle size distribution of the plugging material in the plugging agent is D10 of 300-1500 nm, D50 of 1-5 μm, and D90 of 5-15 μm.

[0046] In the present application, in order to improve the plugging effect, the silicon dioxide used in the plugging agent is nanometer-micron silicon dioxide. Unless otherwise specified, "nanometer-micron silicon dioxide" refers to a mixture of nanometer (level) and micron (level) silicon dioxide, which has the characteristics of rigid spherical structure, wide particle size distribution, and various sizes. Nanometer (level) silicon dioxide refers to silicon dioxide with a particle size of not more than 1 μm, and micron-level silicon dioxide refers to silicon dioxide with a particle size of greater than or equal to 1 μm and less than 1 mm. Since the particle size distribution of the plugging material in the plugging agent of the present application is 1 nm-50 μm, the nanometer-micron silicon dioxide used in the present application preferably has a particle size distribution of 1 nm-50 μm.

[0047] In the present application, there is no particular limitation on the source of the plugging material used in the plugging agent. Commercially available expandable graphite, expanded graphite, and silicon dioxide can be compounded according to the requirements of the present application to obtain the plugging material, or expandable graphite, expanded graphite, and silicon dioxide that meet the requirements of the present application can be prepared as the plugging material. In some preferred embodiments, the plugging agent provided by the present application can use a new material developed by the inventors in previous research. Among them, the nanometer-micron silicon dioxide can be provided by the high-temperature-resistant lipophilic nanometer-micron silicon dioxide plugging dispersion system prepared in CN202310894527.2; the expandable graphite can be the expandable graphite prepared in CN202410001951.4; and the expanded graphite can be the (ultra-fine) expanded graphite prepared in CN202410785481.5. The above applications are all incorporated by reference herein.

[0048] The inventors of the present application have ingeniously found in research that the plugging agent prepared by compounding the materials with the features described in the present application can achieve broad-spectrum strong plugging of micro-fractures in the formation. In addition, when the preferred formulation of the present application is used, the plugging agent provided by the present application can be provided in the form of a stable oil phase suspension. "Stable" means that the plugging agent provided by the present application can still maintain the characteristics of a suspension during long-term storage and transportation, and the fluidity thereof will not change significantly, and the solid substances therein will not or substantially not be precipitated or floated on the surface.

[0049] According to a preferred embodiment of the present application, the particle size distribution of the plugging material (i.e. the solid component in the plugging agent) is 5 nm-30 μm.

[0050] For example, the lower end point of the particle size of the plugging material can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 950 nm, 960 nm, 970 nm, 980 nm, 990 nm, 995 nm, 999 nm; and the upper end point of the particle size of the plugging material can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm. The particle size distribution of the nanometer-micron silicon dioxide can be a range formed by any lower end point and any upper end point described above.

[0051] In the present application, "particle size distribution" refers to the size range of the plugging material, i.e. the range between the minimum size and the maximum size of the plugging material, while "particle size distribution" refers to the characteristic value of the size of the plugging material, such as D10, D50, D90, etc. The particle size distribution can indicate the range of the maximum and minimum particle size of the plugging material in the plugging agent, while the particle size distribution can indicate the particle size characteristics of the plugging material in the plugging agent. Both the particle size distribution and the particle size distribution can be detected by a laser particle size analyzer.

[0052] According to a preferred embodiment of the present application, the particle size distribution of the nanometer-micron silicon dioxide is D10 of 20-40 nm, D50 of 230-280 nm, and D90 of 1200-1500 nm.

[0053] Preferably, the particle size distribution of the nanomicro silica is D10 of 25-40 nm, D50 of 240-275 nm, and D90 of 1200-1450 nm.

[0054] For example, the D10 of the nanomicro silica can be 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, or can also be a range formed by any two of the above values, or any intermediate value in the range.

[0055] For example, the D50 of the nanomicro silica can be 240 nm, 242 nm, 246 nm, 248 nm, 250 nm, 252 nm, 254 nm, 256 nm, 258 nm, 260 nm, 262 nm, 264 nm, 26 nm, 268 nm, 270 nm, 272 nm, 274 nm, 275 nm, or can also be a range formed by any two of the above values, or any intermediate value in the range.

[0056] For example, the D90 of the nanomicro silica can be 1200 nm, 1220 nm, 1240 nm, 1280 nm, 1300 nm, 1320 nm, 1340 nm, 1360 nm, 1380 nm, 1400 nm, 1420 nm, 1440 nm, 1450 nm, or can also be a range formed by any two of the above values, or any intermediate value in the range.

[0057] According to a preferred embodiment of the present application, the surface of the nanomicro silica has hydrophobicity. Preferably, the nanomicro silica has good hydrophobicity by hydrophobic surface modification (i.e., the surface of the nanomicro silica has a hydrophobic modifier).

[0058] Preferably, the hydrophobic surface modifier can be a silane coupling agent.

[0059] More preferably, the silane coupling agent is selected from at least one of 3-aminopropyltrimethoxysilane (KH540), 3-aminopropyltriethoxysilane (KH550), and γ-methacryloyloxypropyltrimethoxysilane (KH570).

[0060] In the present application, when formulating the plugging agent of the present application, the nanomicro silica can be provided in the form of a silica solid (powder) having the above characteristics, or can be provided in the form of an oil phase suspension. For example, it can be provided in the form of a liquid (oil phase suspension) of the nanomicro silica plugging dispersion system in CN202310894527.2.

[0061] According to a preferred embodiment of the present application, the nanomicro silica is provided in the form of an oil phase suspension (may also be referred to as "nanomicro silica dispersion system" in the present application).

[0062] Preferably, the nanomicro silica dispersion system comprises an oil phase and nanosilica and microsilica dispersed in the oil phase. The nanosilica and microsilica have the characteristics as described above, which will not be repeated here.

[0063] More preferably, the nanomicro silica dispersion system further comprises a dispersant. Preferably, the dispersant is selected from at least one of alkyl sulfonate, alkyl polyoxyethylene ether and alkyl amido propyl betaine.

[0064] According to a preferred embodiment of the present application, the expandable graphite has an expansion ratio of 1-10 times, preferably 1.5-3 times, after being heated at 240℃ for 16h. The "expansion ratio" refers to the ratio of the size of the expandable graphite after the heat treatment to the size before the heat treatment, which is usually compared by D50, i.e. expansion ratio = D50 value after being heated at 240℃ for 16h / D50 value before being heated at 240℃ for 16h. The D50 can usually be detected by a laser particle size analyzer. Generally, in addition to self-testing, the expandable graphite products obtained through commercial channels can also obtain product parameter information such as the expansion ratio after being heated at a specific temperature from the supplier.

[0065] For example, the expandable graphite can have an expansion ratio of 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2 times, 2.1 times, 2.2 times, 2.3 times, 2.4 times, 2.5 times, 2.6 times, 2.7 times, 2.8 times, 2.9 times, 3 times, or a range formed by any two of the above values, or any intermediate value in the range.

[0066] According to a preferred embodiment of the present application, the D50 (D50 before being heated at 240℃ for 16h, or initial D50 value, or D50 at room temperature) of the expandable graphite is 1-100 μm, preferably 1-20 μm, and more preferably 1-5 μm. Preferably, the D10 of the expandable graphite is 1-3 μm, the D50 is 1-5 μm, and the D90 is 4-7 μm.

[0067] In the present application, unless otherwise specified, the particle size distribution characteristic parameters such as "D10, D50, D90 of the expandable graphite" refer to the corresponding parameter values before the heat treatment and before the expansion.

[0068] According to a preferred embodiment of the present application, the expanded graphite has an expansion coefficient > 285 mL / g, preferably 290-400 mL / g, more preferably 290-350 mL / g. The "expansion coefficient" refers to the volume (mL) of the expanded graphite obtained after expansion treatment of a unit weight (g) of the expandable graphite before expansion. The expansion coefficient of the expanded graphite can be generally determined by the cylinder volume method. The cylinder volume method refers to a method in which a unit weight (e.g., 1 g) of the expandable graphite is weighed before expansion treatment, the obtained expanded graphite is placed in a cylinder after expansion treatment (the temperature of the expansion treatment is a temperature at which the expandable graphite can be rapidly expanded to the maximum volume, which is generally 800-1000°C, preferably 960±10°C), and the volume of the expanded graphite is measured to calculate the expansion coefficient of the expanded graphite. In the method, the expansion coefficient can be calculated using the following formula:

[0069] Expansion coefficient (mL / g) = Volume of the expanded graphite after expansion (mL) / Weight of the expandable graphite before expansion (g)

[0070] Generally, the expansion coefficient of the expanded graphite obtained by commercial purchase can be obtained from the product parameter information of the supplier, and the expansion coefficient of the expanded graphite prepared by oneself can be calculated according to the above method.

[0071] For example, the expansion coefficient of the expanded graphite can be 290 mL / g, 295 mL / g, 300 mL / g, 305 mL / g, 310 mL / g, 315 mL / g, 320 mL / g, 325 mL / g, 330 mL / g, 335 mL / g, 340 mL / g, 345 mL / g, 350 mL / g, or a range formed by any two of the above values, or any intermediate value in the range.

[0072] Preferably, the D50 of the expanded graphite is 1-5 μm, more preferably 1-3 μm.

[0073] For example, the D50 of the expanded graphite can be 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, or a range formed by any two of the above values, or any intermediate value in the range.

[0074] The oil phase I in the plugging agent of the present application can generally be provided by the base oil used for preparing the drilling fluid. The "base oil" refers to a conventional oil substance used for preparing the oil-based drilling fluid. Any oil that can be used for the configuration of the oil-based drilling fluid in the art can be suitable for the plugging agent of the present application.

[0075] According to some preferred embodiments of the present application, wherein the oil phase I is provided by at least one of diesel oil, white oil and linear or branched a-olefin with C atom number of 5 or more.

[0076] Preferably, the oil phase I is selected from at least one of diesel oil with freezing point of -30℃ to 0℃, white oil with freezing point of -30℃ to 0℃ and linear or branched a-olefin with C atom number of 6-30.

[0077] For example, the freezing point of the diesel oil can be -30℃, -28℃, -25℃, -22℃, -20℃, -18℃, -15℃, -12℃, -10℃, -8℃, -5℃, -2℃, 0℃, or can also be a range formed by any two of the above values, or any intermediate value in the range.

[0078] For example, the freezing point of the white oil can be -30℃, -28℃, -25℃, -22℃, -20℃, -18℃, -15℃, -12℃, -10℃, -8℃, -5℃, -2℃, 0℃, or can also be a range formed by any two of the above values, or any intermediate value in the range.

[0079] For example, the C atom number of the linear or branched a-olefin can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, or can also be a range formed by any two of the above values, or any intermediate value in the range.

[0080] According to some preferred embodiments of the present application, wherein the weight ratio of expandable graphite, expanded graphite, nanometer-sized silicon dioxide in the plugging agent is 1:0.1-5:0.1-5, preferably 1:0.2-2:0.2-2.

[0081] For example, the weight ratio of expandable graphite and expanded graphite in the plugging agent can be 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, or can also be a range formed by any two of the above values, or any intermediate value in the range.

[0082] For example, the weight ratio of expandable graphite and nanometer / micron-sized silicon dioxide in the plugging agent can be 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, or can also be a range formed by any two of the above values, or any intermediate value in the range.

[0083] Preferably, the content of plugging material in the plugging agent is 20-200 g relative to 100 mL of oil phase I. The "content of plugging material" refers to the total weight of various plugging materials (including silicon dioxide, expandable graphite, and expanded graphite) added in 100 mL of oil phase I.

[0084] For example, the content of plugging material in the plugging agent can be 20 g, 25 g, 30 g, 35 g, 40 g, 45 g, 50 g, 55 g, 60 g, 65 g, 70 g, 75 g, 80 g, 85 g, 90 g, 95 g, 100 g, 105 g, 110 g, 115 g, 120 g, 125 g, 130 g, 135 g, 140 g, 145 g, 150 g, 155 g, 160 g, 165 g, 170 g, 175 g, 180 g, 185 g, 190 g, 195 g, 200 g, or can also be a range formed by any two of the above values, or any intermediate value in the range, relative to 100 mL of oil phase.

[0085] Preferably, the content of plugging material in the plugging agent is 30-100 g relative to 100 mL of oil phase I.

[0086] According to a preferred embodiment of the present application, the plugging agent can further comprise flake graphite, preferably the flake graphite has a thickness of no more than 2 nm and a width of no more than 2 μm. The width of flake graphite refers to the length of its widest diagonal. Although the plugging agent of the present application can already achieve a relatively ideal micro-fracture plugging effect when the plugging material is only selected from the aforementioned silicon dioxide, expandable graphite, and expanded graphite, further adding flake graphite can further improve the plugging effect. The flake graphite and the aforementioned plugging material can cooperate with each other to achieve sheet-like deformation and bridging support, thereby improving the plugging effect. As described above, the presence and content of flake graphite can be determined by microscope observation and EDS energy spectrum scanning. Flake graphite appears in a sheet-like shape under a microscope, and the EDS energy spectrum scanning result shows that the element composition is completely or substantially entirely C, which is flake graphite.

[0087] For example, the flake graphite can have a thickness of 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm, 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1 nm, 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, 1.9 nm, 2 nm, or a range between any two of the above values, or any intermediate value in the range.

[0088] For example, the flake graphite can have a width of 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, or a range between any two of the above values, or any intermediate value in the range.

[0089] Preferably, the weight ratio of expandable graphite to flake graphite in the plugging agent is 1:0.1-5, preferably 1:0.2-2.

[0090] For example, the weight ratio of expandable graphite to flake graphite in the plugging agent can be 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, or a range between any two of the above values, or any intermediate value in the range.

[0091] According to some preferred embodiments of the present application, the content of flake graphite in the plugging agent is 0.5-150 g relative to 100 mL of the oil phase I.

[0092] For example, the content of flake graphite in the plugging agent can be 0.5 g, 1 g, 2 g, 3 g, 4 g, 5 g, 6 g, 7 g, 8 g, 9 g, 10 g, 11 g, 12 g, 13 g, 14 g, 15 g, 16 g, 17 g, 18 g, 19 g, 20 g, 25 g, 30 g, 35 g, 40 g, 45 g, 50 g, 60 g, 70 g, 80 g, 90 g, 100 g, 110 g, 120 g, 130 g, 140 g, 150 g relative to 100 mL of the oil phase I, or a range between any two of the above values, or any intermediate value in the range.

[0093] Preferably, the content of flake graphite in the plugging agent is 1-50 g relative to 100 mL of the oil phase I.

[0094] According to some preferred embodiments of the present application, the weight ratio of the expandable graphite, the expanded graphite, the nanometer silica, and the flake graphite in the plugging agent is 1:0.1-5:0.1-5:0.1-5, preferably 1:0.2-2:0.2-2:0.1-2.

[0095] The second aspect of the present application provides a drilling fluid, which comprises the plugging agent of the first aspect.

[0096] The drilling fluid provided by the present application can further comprise any component commonly used in oil-based drilling fluids in the art, in addition to the plugging agent. The present application does not have specific limitations on the specific selection and source of other components in the drilling fluid, which can be a conventional product obtained by commercial purchase.

[0097] The inventors of the present application have ingeniously found that the emulsifier containing both oligomeric fatty acid salt and alkyl-containing sulfonate salt has good temperature resistance, and is thus more suitable for use in deep and ultra-deep oil and gas exploration and development.

[0098] According to preferred embodiments of the present application, the drilling fluid further comprises an emulsifier. The present application does not have specific limitations on the specific selection of the emulsifier, and any emulsifier that can be used in oil-based drilling fluids, especially in the preparation of oil-based drilling fluids used in deep and ultra-deep oil and gas exploration and development, can be suitable for the present application. The present application also does not have specific limitations on the specific source of the emulsifier, which can be a commercially available finished emulsifier or a self-prepared related product.

[0099] According to some preferred embodiments of the present application, the emulsifier comprises an oligomeric fatty acid salt and an alkyl-containing sulfonate salt, and the total carbon number of the oligomeric fatty acid salt is not more than 108. In the present application, the "oligomeric fatty acid salt" refers to a polymeric fatty acid salt with a relatively low degree of polymerization (usually not more than 10, for example, 10, 9, 8, 7, 6, 5, 4, 3, 2).

[0100] The preferred emulsifier described above used in the drilling fluid provided by the present application has better high-temperature resistance than the fatty amide and fatty acid ester emulsifiers commonly used in the art, with a carbon-carbon bond and a carbon-sulfur bond in the molecule of the emulsifying system, and without a carbon-nitrogen bond of amide and a carbon-oxygen bond of acid ester, and the emulsifier has good emulsifying effect and can resist a temperature of up to 240℃, and is thus more suitable for use in deep exploration. The emulsifier can be a high-temperature-resistant emulsifier prepared according to the method of 202410760399.7, which is incorporated herein by reference in its entirety.

[0101] Preferably, the emulsifier further contains an oil phase II. Similar to the oil phase I in the aforementioned plugging agent, the oil phase II in the emulsifier can also be provided by the base oil commonly used in the preparation of oil-based drilling fluids, and the specific selection can refer to the aforementioned oil phase I, which will not be described here again. It should be noted that in the drilling fluid provided by the present application, the base oil can be selected from only one kind or multiple kinds. That is, the oil phase II contained in the emulsifier and the oil phase I contained in the plugging agent can be the same or different. In addition, further base oil can be added during the preparation of the drilling fluid. The base oil added during the preparation of the drilling fluid can be provided by the base oil commonly used in the preparation of oil-based drilling fluids, and the specific selection can also refer to the aforementioned oil phase I. Similarly, the base oil added during the preparation of the drilling fluid can be the same as or different from the oil phase I and the oil phase II in the emulsifier and the plugging agent.

[0102] According to the preferred embodiment of the present application, in the emulsifier, the content of the oligomeric fatty acid salt is 10-50% by weight, the content of the alkyl-containing sulfonate is 5-25% by weight, and the balance is base oil, based on the total weight of the emulsifier.

[0103] According to the preferred embodiment of the present application, the degree of polymerization of the oligomeric fatty acid salt is 2-5.

[0104] Preferably, the oligomeric fatty acid salt is selected from at least one of oligomeric oleic acid salt, oligomeric linoleic acid salt, oligomeric linolenic acid salt, and oligomeric tall oil fatty acid salt.

[0105] More preferably, the oligomeric fatty acid salt is selected from at least one of calcium oligomeric oleate, sodium oligomeric oleate, potassium oligomeric oleate, calcium oligomeric linoleate, sodium oligomeric linoleate, potassium oligomeric linoleate, calcium oligomeric linolenate, sodium oligomeric linolenate, potassium oligomeric linolenate, calcium oligomeric tall oil fatty acid salt, sodium oligomeric tall oil fatty acid salt, and potassium oligomeric tall oil fatty acid salt.

[0106] Further preferably, the fatty acid part of the oligomeric fatty acid salt is provided by at least one of dimer oleic acid, dimer linoleic acid, dimer tall oil acid, trimer oleic acid, trimer linolenic acid, trimer linoleic acid, trimer tall oil acid, tetramer linoleic acid, tetramer oleic acid, pentamer linoleic acid, and pentamer tall oil acid.

[0107] According to the preferred embodiment of the present application, the alkyl-containing sulfonate is selected from at least one of alkyl benzene sulfonate, alkyl sulfonate, and alkyl naphthalene sulfonate; preferably at least one of potassium alkyl benzene sulfonate, sodium alkyl benzene sulfonate, calcium alkyl benzene sulfonate, potassium alkyl sulfonate, calcium alkyl sulfonate, sodium alkyl sulfonate, potassium alkyl naphthalene sulfonate, sodium alkyl naphthalene sulfonate, and calcium alkyl naphthalene sulfonate.

[0108] Preferably, the alkyl in the alkyl-containing sulfonate is selected from C6-C 40The number of carbon atoms in the alkyl group of the alkyl-containing sulfonate salt can be, for example, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, or can also be a range formed by any two of the above values, or any intermediate value in the range.

[0109] More preferably, the alkyl-containing sulfonate salt is selected from at least one of sodium dodecyl sulfonate, calcium dodecyl sulfonate, calcium octadecyl benzene sulfonate, calcium octyl naphthalene sulfonate, calcium decyl naphthalene sulfonate, potassium cetyl benzene sulfonate, sodium eicosyl sulfonate, and calcium octadecyl sulfonate.

[0110] Preferably, the weight ratio of the oligomeric fatty acid salt to the alkyl-containing sulfonate salt in the emulsifier composition is 0.5-20:1, preferably 0.5-15:1.

[0111] For example, the weight ratio of the oligomeric fatty acid salt to the alkyl-containing sulfonate salt in the emulsifier composition can be 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, 10.5:1, 11:1, 11.5:1, 12:1, 12.5:1, 13:1, 13.5:1, 14:1, 14.5:1, 15:1, or can also be a range formed by any two of the above ratios, or any intermediate ratio in the range.

[0112] According to a preferred embodiment of the present application, the weight ratio of the emulsifier to the plugging agent in the drilling fluid is 1:0.5-5, preferably 1:0.6-3.

[0113] For example, the weight ratio of the emulsifier to the plugging agent in the drilling fluid can be 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, or can also be a range formed by any two of the above ratios, or any intermediate ratio in the range.

[0114] Preferably, the amount of the emulsifier used in the drilling fluid is 3-8g per 100mL, preferably 4-6g.

[0115] For example, the amount of the emulsifier used in the drilling fluid can be 4g, 4.2g, 4.4g, 4.6g, 4.8g, 5g, 5.2g, 5.4g, 5.6g, 5.8g, 6g per 100mL, or can also be a range formed by any two of the above values, or any intermediate value in the range.

[0116] Preferably, the amount of the plugging agent is 2-10 g, preferably 3-7 g, per 100 mL of the drilling fluid.

[0117] For example, the amount of the plugging agent can be 3 g, 3.1 g, 3.2 g, 3.3 g, 3.4 g, 3.5 g, 3.6 g, 3.7 g, 3.8 g, 3.9 g, 4 g, 4.2 g, 4.5 g, 4.8 g, 5 g, 5.2 g, 5.5 g, 5.8 g, 6 g, 6.2 g, 6.5 g, 6.8 g, 7 g, or a range formed by any two of the above values or any intermediate value in the range, per 100 mL of the drilling fluid.

[0118] The drilling fluid containing the plugging agent and the preferred emulsifier described above has good high-temperature resistance and can achieve multi-scale and broad-spectrum strong plugging of the bottom micro-fracture, thereby being more conducive to maintaining the stability of the well wall.

[0119] According to the preferred embodiment of the present application, the drilling fluid system contains expandable graphite, expanded graphite, hydrophobically modified nano-sized silica, hydrophobically modified micro-sized silica, oligomeric fatty acid salt and alkyl-containing sulfonate salt, and the weight ratio of the expandable graphite, expanded graphite, hydrophobically modified nano-sized silica, hydrophobically modified micro-sized silica, oligomeric fatty acid salt and alkyl-containing sulfonate salt is 1:0.1-5:0.1-5:0.1-5:0.5-4:0.1-2.

[0120] According to the preferred embodiment of the present application, the drilling fluid further contains at least one of base oil, dispersant, fluid loss additive, wetting agent, organic clay, weighting agent and viscosity builder. The above components can be the corresponding components commonly selected in the art, and the corresponding finished materials can be usually obtained through commercial channels.

[0121] Preferably, the dispersant is selected from at least one of alkyl sulfonate, alkyl polyoxyethylene ether and alkyl amido propyl betaine.

[0122] According to some preferred embodiments of the present application, the content of the expandable graphite in the drilling fluid is 0.5-8 wt.%, based on the total weight of the drilling fluid.

[0123] According to the preferred embodiment of the present application, the drilling fluid can further contain other plugging components commonly used in the art, such as hydrophobic supercalcium, oil-soluble resin and asphalt, etc.

[0124] Preferably, the particle size of the hydrophobic supercalcium is not less than 1 μm, preferably 5-50 μm.

[0125] For example, the hydrophobic supercalcium can have a particle size of 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or a range between any two of the above values, or any intermediate value in the range.

[0126] Preferably, the asphalt has a softening point of no less than 180 °C.

[0127] More preferably, the hydrophobic supercalcium can have a content of 0-3 g per 100 mL of the drilling fluid.

[0128] According to preferred embodiments of the present application, the drilling fluid can further comprise a flow pattern regulator, an alkali (preferably CaO), and calcium chloride. The above components can be the corresponding components commonly used in the art, and the corresponding finished materials can be obtained through commercial channels.

[0129] According to some preferred embodiments of the present application, the content of the wetting agent is 1-2 g, the content of the flow pattern regulator is 0.3-0.8 g, the content of the organic clay is 3-5 g, the content of the alkali is 3-5 g, and the content of the fluid loss additive is 4-6 g per 100 mL of the drilling fluid.

[0130] According to preferred embodiments of the present application, the components in the drilling fluid can be independently packaged and stored, and mixed when used. For example, the plugging agent, the emulsifier (as well as the base oil, the dispersant, the fluid loss additive, the wetting agent, the organic clay, the weighting agent, and the viscosifier, etc.) can be individually packaged according to the aforementioned amounts, and mixed in the base oil when used, so as to obtain the drilling fluid provided by the present application.

[0131] The present application further provides a preparation method of the drilling fluid, which can comprise mixing the plugging agent and the emulsifier in the presence of the base oil. The base oil, the plugging agent, and the emulsifier are characterized as described above, and will not be repeated here.

[0132] According to some preferred embodiments of the present application, the method further comprises the steps of preparing the expandable graphite, the expanded graphite, and the micro-nano silicon dioxide (dispersion system) used in the plugging agent.

[0133] According to preferred embodiments of the present application, the preparation of the expandable graphite can comprise: contacting flake graphite with a pre-oxidation agent to obtain pre-oxidized graphite, and contacting the pre-oxidized graphite with an intercalation agent and an oxidizing agent to obtain the expandable graphite. The preparation method of the expandable graphite can refer to CN202410001951.4, or the expandable graphite can be prepared by the method as described above.

[0134] According to the preferred embodiment of the present application, the preparation method of the expandable graphite comprises:

[0135] (1) mixing an oxidizing agent and an intercalating agent I to obtain a mixed solution;

[0136] (2) mixing flake graphite and a pre-oxidizing agent II to obtain pre-oxidized graphite;

[0137] (3) mixing the pre-oxidized graphite and the mixed solution III to occur oxidation intercalation, to obtain an oxidized intercalated graphite solution;

[0138] (4) mixing the oxidized intercalated graphite solution and an auxiliary intercalating agent IV to occur reinforced intercalation, to obtain the expandable graphite.

[0139] Preferably, in step (1), the oxidizing agent is selected from at least one of hydrogen peroxide, concentrated sulfuric acid, fuming nitric acid, sodium nitrate (acidic) and potassium permanganate.

[0140] Preferably, in step (1), the intercalating agent is selected from at least one of concentrated sulfuric acid, perchloric acid and concentrated nitric acid.

[0141] More preferably, the mass ratio of the oxidizing agent to the flake graphite is 0.1-2.

[0142] More preferably, the mass ratio of the intercalating agent to the flake graphite is 2-15.

[0143] Preferably, in step (2), the pre-oxidizing agent is hydrogen peroxide.

[0144] More preferably, the mass ratio of the pre-oxidizing agent to the flake graphite is 5-20.

[0145] Preferably, in step (4), the auxiliary intercalating agent is selected from at least one of glacial acetic acid, ammonium nitrate and acetic acid.

[0146] More preferably, the mass ratio of the auxiliary intercalating agent to the flake graphite is 1-15.

[0147] According to the preferred embodiment of the present application, the preparation of the expandable graphite comprises: contacting flake graphite with an oxidizing agent and an intercalating agent to obtain expandable graphite, and then expanding the expandable graphite. The preparation method of the expandable graphite can refer to CN202410785481.5.

[0148] According to the preferred embodiment of the present application, the preparation method of the expandable graphite comprises:

[0149] (1) mixing flake graphite with an oxidizing agent and an intercalating agent to obtain expandable graphite;

[0150] (2) expanding the expandable graphite to obtain expanded graphite.

[0151] Preferably, the oxidizing agent is selected from at least one of hydrogen peroxide, sulfuric acid, nitric acid, sodium nitrate, potassium permanganate, more preferably potassium permanganate.

[0152] Preferably, the intercalating agent is selected from at least one of sulfuric acid, perchloric acid, nitric acid, more preferably perchloric acid.

[0153] More preferably, the mass ratio of the oxidizing agent to the flake graphite is 0.2-0.5:1.

[0154] More preferably, the mass ratio of the intercalating agent to the flake graphite is 6-12:1.

[0155] Preferably, in step (1), the temperature of the oxidation intercalation is 30-50℃.

[0156] Preferably, in step (2), the temperature of the expansion is 900-1000℃, and the time is 30-180s.

[0157] Preferably, the method further comprises a step of crushing the expanded graphite obtained in step (2). Preferably, the crushing makes it have the aforementioned particle size characteristics.

[0158] According to a preferred embodiment of the present application, wherein the preparation of the nanometer-micron silica dispersion system comprises: sequentially mixing the nanometer silica and the micron silica with the dispersant and the dispersion medium. The preparation method of the nanometer-micron silica dispersion system can refer to CN202310894527.2.

[0159] According to some preferred embodiments of the present application, wherein the preparation method of the nanometer-micron silica dispersion system comprises:

[0160] (1) first mixing the dispersant and the dispersion medium to obtain a dispersion liquid phase;

[0161] (2) second mixing the nanometer silica with the dispersion liquid phase to obtain a nanometer silica dispersion liquid;

[0162] (3) third mixing the micron silica with the nanometer silica dispersion liquid to obtain a nanometer-micron silica dispersion system.

[0163] Preferably, in step (1), the dispersion medium is oil phase I. The specific characteristics of the oil phase I are as described above, which are not repeated here.

[0164] Preferably, in step (1), the dispersant is selected from at least one of alkyl sulfonate, alkyl polyoxyethylene ether, and alkyl amido propyl betaine.

[0165] Preferably, step (2) further comprises further classifying the hydrophobically modified nanoscale silica by D50 before the second mixing. Preferably, the nanoscale silica is divided into 2-5 sub-classes by D50. More preferably, the D50 of the nanoscale silica of two adjacent sub-classes differs by 30-500 nm. The D50 difference between the nanoscale silica of different sub-classes and its adjacent sub-class can be the same or different.

[0166] More preferably, step (2) comprises sequentially mixing the nanoscale silica of each sub-class with the dispersion liquid in the order of increasing D50.

[0167] For the convenience of understanding, taking the nanoscale silica divided into three sub-classes (named as first sub-class, second sub-class and third sub-class nanoscale silica in the order of increasing D50) as an example, step (2) can comprise:

[0168] (2-1) second mixing-1 of the first sub-class nanoscale silica with the dispersion liquid;

[0169] (2-2) second mixing-2 of the second sub-class nanoscale silica with the product of step (2-1);

[0170] (2-3) second mixing-3 of the third sub-class nanoscale silica with the product of step (2-2), to obtain the nanoscale silica dispersion liquid.

[0171] In some preferred embodiments, the D50 of the first sub-class, second sub-class and third sub-class nanoscale silica can be 20-40 nm, 80-150 nm and 500-600 nm, respectively.

[0172] Preferably, step (3) further comprises further classifying the hydrophobically modified microscale silica by D50 before the third mixing. Preferably, the microscale silica is divided into 2-4 sub-classes by D50. More preferably, the D50 of the microscale silica of two adjacent sub-classes differs by 2-20 μm. The D50 difference between the microscale silica of different sub-classes and its adjacent sub-class can be the same or different.

[0173] More preferably, step (3) comprises sequentially mixing the microscale silica of each sub-class with the nanoscale silica dispersion liquid in the order of increasing D50.

[0174] For the convenience of understanding, taking the microscale silica divided into two sub-classes (named as first sub-class and second sub-class microscale silica in the order of increasing D50) as an example, step (3) can comprise:

[0175] (3-1) third mixing-1 of the first sub-class microscale silica with the nanoscale silica dispersion liquid;

[0176] (3-2) mixing the second sub-grade micron-sized silica with the product of step (3-1) to obtain a nanometer-micron-sized silica dispersion.

[0177] In some preferred embodiments, the D50 of the first and second sub-grade micron-sized silica can be 2-5 μm and 6-10 μm, respectively.

[0178] According to a preferred embodiment of the present application, the method for preparing the drilling fluid provided by the present application comprises: providing the aforementioned plugging agent and emulsifier and other optional components (such as dispersing agent, fluid loss additive, wetting agent, organic clay, weighting agent, and viscosity builder, etc.) respectively; and mixing the plugging agent, emulsifier, and other optional components in the presence of base oil.

[0179] According to some preferred embodiments of the present application, the method for preparing the plugging agent comprises:

[0180] 1) providing a nanometer-micron-sized silica dispersion system;

[0181] 2) adding expandable graphite and expanded graphite into the nanometer-micron-sized silica dispersion system.

[0182] Step 1) can adopt the aforementioned method for preparing the nanometer-micron-sized silica dispersion system, the specific process of which is not repeated here.

[0183] In step 2), any method that can mix the expandable graphite and expanded graphite in the nanometer-micron-sized silica dispersion system can be suitable for the present application. For example, the expandable graphite and expanded graphite can be mixed in the nanometer-micron-sized silica dispersion system by stirring.

[0184] Preferably, step 2) further comprises adding flake graphite.

[0185] The specific characteristics of the expandable graphite, expanded graphite, and flake graphite used in the above method are as described above, which are not repeated here.

[0186] In the above method, the expandable graphite, expanded graphite, and flake graphite can be added into the nanometer-micron-sized silica dispersion system at the same time in step 2), or the expandable graphite, expanded graphite, and flake graphite can be added into the nanometer-micron-sized silica dispersion system step by step. The present application does not have special requirements for the specific adding method and order, etc., as long as the system is mixed after adding.

[0187] The aforementioned emulsifier can be prepared by the method of 202410760399.7, the content of which is incorporated into the present application by reference.

[0188] According to some preferred embodiments of the present application, the method for preparing the emulsifier comprises:

[0189] oligofatty acid and a basic substance are contacted and reacted in the presence of the oil phase II and the alkyl-containing sulfonate, the total carbon number of the oligofatty acid being no more than 108.

[0190] Preferably, the basic substance is selected from the group consisting of alkali metal hydroxides and / or alkaline earth metal hydroxides, preferably at least one of calcium oxide, sodium oxide, potassium oxide, calcium hydroxide, sodium hydroxide, potassium hydroxide and lithium hydroxide.

[0191] In the above method, the oligofatty acid salt in the emulsifier is formed by the reaction of the oligofatty acid and the basic substance. The person skilled in the art can select the types and amounts of the oligofatty acid and the basic substance used in the method according to the actual situation and the characteristics of the oligofatty acid salt in the aforementioned emulsifier, and the specific details are not described herein. The characteristics of the emulsifier prepared by the method are as described above, and are not described herein.

[0192] The third aspect of the present application provides the use of the plugging agent of the first aspect, or the drilling fluid of the second aspect, in improving the microfracture plugging effect in the drilling process, and / or reducing the filtration loss in the drilling process, and / or improving the wellbore stability in the drilling process.

[0193] According to a preferred embodiment of the present application, the drilling process is carried out in a high-temperature and high-pressure environment.

[0194] Preferably, the temperature of the high-temperature and high-pressure environment is no less than 180℃, preferably 200-260℃, and the pressure is no less than 100MPa.

[0195] Preferably, reducing the filtration loss includes reducing the high-temperature and high-pressure filtration loss and reducing the PPA filtration loss. The PPA filtration loss refers to the volume of filtrate that penetrates into the porous formation under the action of pressure difference within a certain time when tested by using a drilling fluid plugging performance evaluation instrument (PPA). The specific detection process and operation can be referred to the instruction manual provided by the PPA supplier.

[0196] The fourth aspect of the present application provides the use of the plugging agent of the first aspect, or the drilling fluid system of the second aspect, in improving the wellbore stability in the drilling process.

[0197] Examples

[0198] The content of the present application will be further explained and described below by way of examples. It should be understood that the following examples are only used to exemplarily further explain and describe the content of the present application, and are not used to limit the present application.

[0199] The thickness of the flake graphite (i.e. natural flake graphite) used in the following examples is 1.5 ± 0.5 nm, and the width is 1 ± 0.5 μm, unless otherwise specified. The freezing point of 0# diesel is 0℃; the freezing point of 3# white oil is -30℃, the freezing point of 5# white oil is -25℃, and the freezing point of 10# white oil is -10℃.

[0200] Preparation Example

[0201] (I) Preparation of expandable graphite

[0202] The expandable graphite was prepared according to the method of CN202410001951.4. The specific method is as follows:

[0203] (1) The flake graphite and hydrogen peroxide were weighed (A, B, and C were 10 g of flake graphite + 100 g of hydrogen peroxide; D was 10 g of flake graphite + 120 g of hydrogen peroxide), and pre-oxidation was carried out at 35℃ with 250 rpm stirring for 15 min;

[0204] (2) The potassium permanganate and perchloric acid weighed according to Table 1 were stirred and mixed uniformly, and then the pre-oxidation product was added. Oxidation intercalation was carried out at 35℃ with 350 rpm stirring for 10 min;

[0205] (3) The oxidation intercalation product was mixed with 50 g of ice acetic acid for intensive intercalation. After stirring at 40℃ with 150 rpm for 8 min, filtration, water washing, and drying were carried out in sequence. The water washing temperature was 25℃, the drying temperature was 65℃, and the drying time was 4.5 h. The expandable graphite was obtained.

[0206] An appropriate amount of the obtained expandable graphite was added to white oil No. 5 (the weight ratio of expandable graphite to white oil was 1:20), heated at 200℃ for 16 h, and the volume expansion ratio of the expandable graphite was detected. The particle size distribution of the expandable graphite before and after expansion was detected by a nano-laser particle size analyzer, and the results are shown in Table 1.

[0207] Table 1

[0208] (II) Preparation of expanded graphite

[0209] The expanded graphite was prepared according to the method of CN202410785481.5. The specific method is as follows:

[0210] (1) The potassium permanganate and perchloric acid were weighed according to the amount in Table 2, mixed uniformly, and then 10 g of natural flake graphite was added. Oxidation intercalation was carried out at 40℃ with 350 rpm stirring for 15 min;

[0211] (2) The oxidized intercalation product is sequentially subjected to suction filtration, water washing and drying, the water washing temperature is 25±5℃, the time is 1h, the drying temperature is 65±5℃, and the time is 6h, to obtain the expandable graphite;

[0212] (3) The expandable graphite is placed at 960±10℃ for expansion for 60s, and then the expansion product is subjected to gas crushing (crushing time 45min) to obtain the expanded graphite.

[0213] The expansion coefficient of the obtained expanded graphite is detected, and the particle size characteristics of the expanded graphite are detected by a nano laser particle size analyzer. The results are shown in Table 2.

[0214] Table 2

[0215] (Three) Preparation of nanometer-micron silica dispersion system

[0216] The preparation of the nanometer-micron silica dispersion system is carried out according to the method of CN202310894527.2. The specific method is as follows:

[0217] (1) Nanoscale silica and micron-sized silica are added to toluene, heated to 60℃, and nitrogen is passed for 25min. Continue to heat to 90℃, add hydrophobic modifier (0.75±0.25g of hydrophobic modifier is used for 10g of silica), react for 5h, and then sequentially perform distillation, washing, filtration and vacuum drying to obtain hydrophobic modified silica particles;

[0218] (2) The dispersant (sodium salt of pentadecyl sulfonate) is weighed according to the amount in Table 4 and added to the base oil (oil phase I) for first mixing (stirring speed 150rpm, temperature 30℃, time 15min) to obtain a dispersion liquid;

[0219] (3) Different D50 of nanoscale modified silica particles are taken from the modified nanoscale silica obtained in step (1) (see Table 3 for specific selection and amount of nanoscale silica), and are sequentially added to the dispersion liquid obtained in step (2) for second mixing (stirring for 25min at a stirring speed of 250rpm and a temperature of 30℃ after each addition of silica), to obtain a nanodispersion liquid;

[0220] (4) The micron-sized D50 modified silica particles obtained in step (1) are sequentially added to the nanodispersion liquid obtained in step (3) (see Table 3 for specific selection and amount of micron-sized silica), and are subjected to third mixing (stirring for 35min at a stirring speed of 350rpm and a temperature of 30℃ after each addition of silica), to obtain a nanometer-micron silica dispersion system.

[0221] Table 3

[0222] The obtained nanometer / micron silica dispersion system was detected for its characteristics by the following method, and its solubility was observed, and the results are shown in Table 4.

[0223] The particle size distribution and particle size distribution of the nanometer / micron silica in the dispersion system were detected by a laser particle size method.

[0224] The dispersion degree was calculated as follows: Dispersion degree (wt%) = (total weight of silica in the system / total weight of nanometer / micron silica dispersion system) x 100%

[0225] Table 4

[0226] The hydrophobic modifier used in the nanometer / micron silica dispersion systems 1# to 4# was KH540, KH550, KH570 and KH570, respectively; the density of the white oil in 3# was 0.86 g / cm 3 ; the density of the white oil in 5# was 0.82 g / cm 3 .

[0227] (Four) Preparation of emulsifier

[0228] The preparation of the emulsifier was carried out according to the method of 202410760399.7. The specific method is as follows:

[0229] After mixing the oligomeric fatty acid and the base oil (oil phase II) and heating to 60±5℃, stirring was carried out to fully dissolve, an alkaline compound (i.e. the hydroxide corresponding to the alkali metal contained in the oligomeric fatty acid salt) was added, and the reaction was carried out at 90±5℃ for about 2h, then an alkyl-containing sulfonate was added, and the reaction was continued at 90±5℃ for about 3h, and then the emulsifier was obtained after cooling.

[0230] The obtained emulsifier components are shown in Table 5. The content refers to the weight percentage of the component in the emulsifier (obtained according to the feeding calculation).

[0231] Table 5

[0232] Example 1

[0233] This example is used to illustrate the preparation of the plugging agent provided by the present application.

[0234] According to the formulation in Table 6, the nanometer / micron silica dispersion system, expandable graphite, expanded graphite and flake graphite obtained in the preparation examples were respectively measured or weighed. Under stirring conditions (stirring at 250 rpm for 15 min), the expandable graphite, expanded graphite and flake graphite were added together into the nanometer / micron silica dispersion system. After mixing the components, the obtained oil phase suspension was the plugging agent. Note: The amount of nanometer / micron silica dispersion system in Table 6 is calculated based on the oil phase content therein.

[0235] Table 6

[0236] *a9 is a plugging agent prepared by directly adding expandable graphite, expanded graphite and flaky graphite in base oil (3# white oil, 100 mL) according to the above method, without the silica component.

[0237] Each of the prepared plugging agents was sampled 1 mL, heated at 240°C for 16 h, and the D50 of the plugging material in the plugging agent before and after heating was measured by a laser particle size analyzer, and the increase value (%) of D50 after heating was calculated by the following formula III, and the results are shown in Table 7. D50 increase value (%) = (D50 after heating - D50 before heating) / D50 before heating x 100% Formula III

[0238] Table 7

[0239] Each of the prepared plugging agents was sampled 1 mL, and the particle size distribution and particle size distribution were detected by a laser particle size analyzer. The results are shown in Table 8.

[0240] Table 8

[0241] Example 2

[0242] This example is used to illustrate the preparation of the drilling fluid system provided by the present application.

[0243] Preparation method: according to the formula in Table 9, first take the base oil into the material cup of the high-speed stirrer, add the emulsifier and wetting agent, and stir at a speed of 12000 r / min for 15 min; take the calcium chloride solution into the material cup, continue to stir at a speed of 12000 r / min for 20 min; weigh the organic soil and slowly add it to the material cup, stir at a speed of 12000 r / min for 20 min; continue to weigh the fluid loss reducer and add it to the material cup, stir at a speed of 12000 r / min for 10 min; add the base to the material cup, stir at a speed of 12000 r / min for 10 min; then add the plugging agent to the material cup, stir for 10 min; finally add 270 g of weighting agent (barite), stir at a speed of 12000 r / min for 20 min.

[0244] Table 9 Drilling fluid formula Note: The commercial plugging agent components used in No. 22 and No. 24 are mixtures of hydrophobic supercalcium of different particle sizes (in the mixture, the weight ratio of hydrophobic supercalcium with D50 of 5 μm, 10 μm and 15 μm is 1:1:1)

[0245] Test Example 1

[0246] The test example is used to illustrate the uniformity, stability and compatibility of the plugging agent provided by the application.

[0247] (I) Uniformity and stability

[0248] The plugging agent prepared in Example 1 was taken respectively, and the stability test was carried out by using the following method, and the results are shown in Table 10.

[0249] 6g of the plugging agent sample was taken and placed in a 10mL centrifuge tube, centrifuged at a centrifugal force of 100g for 10min, and the middle position of the liquid surface in the centrifuge tube after centrifugation (1 / 2 liquid surface) was taken as the demarcation line, 1mL of the liquid above the demarcation line (marked as "upper liquid") and the liquid below the demarcation line (marked as "lower liquid") were taken by using a pipette, and their densities (g / cm 3 ) were calculated and compared.

[0250] The density ratio of the upper liquid and the lower liquid was calculated according to the following formula II: Density ratio (%) = upper liquid density / lower liquid density x 100% formula II

[0251] Table 10

[0252] (II) Compatibility

[0253] The plastic viscosity (PV) and yield point (YP) of the plugging agents a1, a6-a13 prepared in Example 1 and the drilling fluids No. 1 and No. 6-15 prepared in Example 2 were detected respectively, and the specific detection results are shown in Table 11.

[0254] The above parameters were detected by referring to the related methods described in the Chinese national standard GB / T16783.2-2012 "Petroleum and Natural Gas Industry Drilling Fluids Field Testing Part 2: Oil-based Drilling Fluids".

[0255] Table 11

[0256] Test Example 2

[0257] This example is used to test the rheological property and filtration loss of the drilling fluid prepared in the preparation example.

[0258] According to the Chinese national standard GB / T 16783.2-2012 "Oil and gas industry-drilling fluid field testing-part 2: oil-based drilling fluids", the drilling fluids obtained in the preparation examples were respectively heated at 240℃ for 16h, and after heating, the rheological property, fluid loss property and demulsification voltage were tested, and the experimental results are shown in Table 12. Among them, AV-apparent viscosity, unit mPa·s; PV-plastic viscosity, unit mPa·s; YP-yield point, unit Pa; API-medium pressure fluid loss, unit mL; HTHP-high temperature and high pressure fluid loss (240℃, 500psi), unit mL; ES-demulsification voltage, unit V.

[0259] Table 12

[0260] Test Example 3

[0261] This example is used to test the sealing performance of the drilling fluids prepared in the preparation examples.

[0262] The drilling fluids prepared in the preparation examples were respectively heated at 240℃ for 16h, and then the sand disc fluid loss (PPA fluid loss) of the heated drilling fluids at 180℃ was tested by a drilling fluid sealing performance evaluation experimental device (permeation sealing instrument (PAA), purchased from Fann, model: Model 389A). The test was carried out using a 20μm sand disc, the test pressure difference was 500psi, and the test time was 30min. The test results are shown in Table 13.

[0263] Table 13

Claims

1. A sealant, characterized by, The plugging agent comprises an oil phase and a plugging material dispersed in the oil phase I, the plugging material comprising expandable graphite, expanded graphite and silicon dioxide, The particle size distribution of the plugging material is 1 nm-50 μm, and the D50 value of the plugging material increases by at least 10% after the plugging agent is heated at 240 ℃ for 16 h compared with that before heating.

2. The occlusive agent of claim 1, wherein, The plugging agent is centrifuged under the action of a centrifugal force of 100 g for 10 min, and the density of the upper liquid is 70-100%, preferably 80-100%, of the density of the lower liquid. The particle size distribution of the plugging material in the plugging agent is D10 of 50-1500 nm, D50 of 1-10 μm, and D90 of 1-15 μm. Preferably, the particle size distribution of the plugging material in the plugging agent is D10 of 300-1500 nm, D50 of 1-5 μm, and D90 of 5-15 μm.

3. The occlusive agent of claim 1 or 2, wherein, The particle size distribution of the silicon dioxide is D10 of 20-40 nm, D50 of 230-280 nm, and D90 of 1200-1500 nm. Preferably, the particle size distribution of the silicon dioxide is D10 of 25-40 nm, D50 of 240-275 nm, and D90 of 1200-1450 nm. The expandable graphite has an expansion ratio of 1-10, preferably 1.5-3, after being heated at 240 ℃ for 16 h.

4. The occlusive agent of any one of claims 1-3, wherein, The expandable graphite has a D50 of 1-100 μm, preferably 1-20 μm, and more preferably 1-5 μm. Preferably, the expandable graphite has a D10 of 1-3 μm, a D50 of 1-5 μm, and a D90 of 4-7 μm. The expanded graphite has a D50 of 1-5 μm, preferably 1-3 μm.

5. The occlusive agent of any one of claims 1-4, wherein, The oil phase I is provided by at least one of diesel oil, white oil, a linear or branched α-olefin having a C atom number of 5 or more, and refined mineral oil.

6. The occlusive agent of any one of claims 1-5, wherein, The weight ratio of the expandable graphite, the expanded graphite and the silicon dioxide in the plugging agent is 1:0.1-5:0.1-5, preferably 1:0.2-2:0.2-2.

7. The occlusive agent of any one of claims 1-6, wherein, Preferably, the content of the plugging material in the plugging agent is 20-200 g, preferably 30-100 g, relative to 100 mL of the oil phase I. The plugging agent further comprises flake graphite, preferably the flake graphite has a thickness of not more than 2 nm and a width of not more than 2 μm.

8. The occlusive agent of any one of claims 1-7, wherein, Preferably, the content of the flake graphite in the plugging agent is 0.5-150 g, preferably 1-50 g, relative to 100 mL of the oil phase I. The drilling fluid comprises the plugging agent according to any one of claims 1-8.

9. A drilling fluid, characterized by, The drilling fluid further comprises an emulsifier, preferably the emulsifier comprises an oligomer fatty acid salt and an alkyl-containing sulfonate salt, the total carbon number of the oligomer fatty acid salt being not more than 108.

10. The drilling fluid of claim 9, wherein, Preferably, the emulsifier further comprises an oil phase II, preferably the oil phase II is provided by at least one of diesel oil, white oil, a linear or branched α-olefin having a C atom number of 5 or more, and refined mineral oil. ​ Preferably, the weight ratio of the oligomeric fatty acid salt to the alkyl-containing sulfonate in the emulsifier is 0.5-20:1, preferably 0.5-15:1; More preferably, in the emulsifier, the content of the oligomeric fatty acid salt is 10-50% by weight, the content of the alkyl-containing sulfonate is 5-25% by weight, and the rest is the oil phase II, based on the total weight of the emulsifier.

11. The drilling fluid of claim 9 or 10, wherein, The oligomeric fatty acid salt has a polymerization degree of 2-5; Preferably, the oligomeric fatty acid salt is at least one selected from oligomeric oleate, oligomeric linoleate, oligomeric linolenate, and oligomeric tall oil fatty acid salt; More preferably, the oligomeric fatty acid salt is at least one selected from calcium oligomeric oleate, sodium oligomeric oleate, potassium oligomeric oleate, calcium oligomeric linoleate, sodium oligomeric linoleate, potassium oligomeric linoleate, calcium oligomeric linolenate, sodium oligomeric linolenate, potassium oligomeric linolenate, calcium oligomeric tall oil fatty acid salt, sodium oligomeric tall oil fatty acid salt, and potassium oligomeric tall oil fatty acid salt; Further preferably, the fatty acid part of the oligomeric fatty acid salt is provided by at least one of dimer oleic acid, dimer linoleic acid, dimer tall oil acid, trimer oleic acid, trimer linolenic acid, trimer linoleic acid, trimer tall oil acid, tetramer linoleic acid, tetramer oleic acid, pentamer linoleic acid, and pentamer tall oil acid.

12. The drilling fluid of any one of claims 9-11, wherein, The alkyl-containing sulfonate is at least one selected from alkyl benzene sulfonate, alkyl sulfonate, and alkyl naphthalene sulfonate; preferably at least one selected from potassium alkyl benzene sulfonate, sodium alkyl benzene sulfonate, calcium alkyl benzene sulfonate, potassium alkyl sulfonate, calcium alkyl sulfonate, sodium alkyl sulfonate, potassium alkyl naphthalene sulfonate, sodium alkyl naphthalene sulfonate, and calcium alkyl naphthalene sulfonate; Preferably, the alkyl group in the alkyl-containing sulfonate is selected from C6-C 40 alkyl; More preferably, the alkyl-containing sulfonate is at least one selected from sodium dodecyl sulfonate, calcium dodecyl sulfonate, calcium octadecyl benzene sulfonate, calcium octyl naphthalene sulfonate, calcium decyl naphthalene sulfonate, potassium hexadecyl benzene sulfonate, sodium eicosyl sulfonate, and calcium octadecyl sulfonate.

13. The drilling fluid of any one of claims 9-12, wherein, The weight ratio of the emulsifier to the plugging agent in the drilling fluid is 1:0.5-5, preferably 1:0.6-3; Preferably, the amount of the emulsifier in the drilling fluid is 3-8g per 100mL, preferably 4-6g per 100mL; Preferably, the amount of the plugging agent in the drilling fluid is 2-10g per 100mL, preferably 3-7g per 100mL.

14. Use of the plugging agent of any one of claims 1-8, or the drilling fluid of any one of claims 9-13 in improving the plugging effect of microfractures during drilling, and / or reducing the filtration loss during drilling, and / or improving the wellbore stability during drilling.

15. Use according to claim 14, wherein, The drilling process is carried out in a high-temperature and high-pressure environment, preferably the high-temperature and high-pressure environment has a temperature of not less than 180℃ and a pressure of not less than 100MPa.

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