A long-lasting, temperature-resistant drilling fluid for plugging leaks during drilling, its preparation method and application

Abstract

This invention belongs to the field of oilfield chemical plugging technology, and discloses a long-lasting, temperature-resistant, drilling fluid for plugging leaks while drilling, its preparation method, and its application. The long-lasting, temperature-resistant, drilling fluid for plugging leaks while drilling includes a base drilling fluid and a plugging agent. The plugging agent includes granular materials, flake materials, fibrous materials, and elastic materials. The mass ratio of the granular materials, flake materials, fibrous materials, and elastic materials is (10-14):(4-7):(4-6):(3-5). The long-lasting, temperature-resistant, drilling fluid for plugging leaks while drilling of this invention has strong temperature resistance and a long pressure-bearing time under high temperature and high pressure conditions. It can be applied to both water-based and oil-based drilling fluids. Furthermore, the long-lasting, temperature-resistant, drilling fluid for plugging leaks while drilling can withstand pressure for 7 days at 230℃ and 12.0MPa, effectively solving the problems of permeability loss and leakage from micropores in high-temperature and high-pressure wells.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical plugging technology, specifically to a long-lasting, temperature-resistant drilling fluid for plugging while drilling, its preparation method, and its application. Background Technology

[0002] Loss in wells has always been a bottleneck restricting wellbore stability. Loss often causes a series of complex situations, ranging from the loss of large amounts of drilling fluid and significant financial and material losses to stuck drill pipe and even wellbore abandonment. With the continuous deepening of oil and gas resource exploration and development, the number of deep and ultra-deep wells is increasing, and high-temperature, high-pressure, and fractured formations are constantly being encountered. Statistics from drilled high-temperature, high-pressure, and lost-flow wells show that the leakage channels are mostly pores and micro-fractures. Therefore, the technology of plugging lost-flows while drilling at high temperatures is urgently needed.

[0003] Currently, there are three types of drilling-while-drilling plugging materials used in the field. One type is ultra-low permeability treatment agent, which is a synthetic polymer material that can form associated micelles. Under certain temperature and pressure conditions, it can soften and deform to form a tight seal against high-permeability formations. It has a significant effect on preventing and plugging lost circulation while drilling when encountering pressure-depleted formations, fractured formations, high-permeability formations, and long open-hole formations with multiple pressure zones. However, during field applications, it has been found that ultra-low permeability treatment agent particles are small and can only provide good sealing for nano- to micron-sized pores and fractures. The effect is poor when encountering larger-sized pores and fractures. In addition, ultra-low permeability treatment agents have poor temperature resistance, generally only able to withstand temperatures up to about 150°C. When the bottom hole temperature exceeds 160°C, the sealing effect on deep and ultra-deep well formations is significantly weakened. Furthermore, ultra-low permeability treatment agents are polymerized from organic polymers and are soluble in oil, so they can only be used in water-based drilling fluids, which limits their application range.

[0004] The second type is polymer gel-based plugging technology. Polymer gels are viscoelastic materials with a three-dimensional cage-like structure formed by the cross-linking of macromolecular polymers. These viscoelastic materials have strong deformability and can enter fractures and pores through compression deformation, unrestricted by leakage channels, and remain at the location of the leak. They then solidify or expand at the leak location to form a sealing layer. Currently, polymer gel plugging technology is not widely used in the field and is mostly in the experimental stage, mainly due to the following two reasons: First, the gelation of polymer gels is affected by many factors. The drilling fluid system is a complex liquid environment containing organic molecules, inorganic salts, and inert solids, all of which significantly affect the gelation time of the polymer gel, preventing the plugging material from accurately entering the leak location to form a gel. Second, the presence of metal ions in the formation, and the inability to guarantee the strength of the gel under high temperature and pressure conditions, and the different types and concentrations of ions in different formation blocks, mean that the gel plugging agent cannot adapt to the constantly changing downhole environment. These uncertainties easily lead to waste of plugging material. More seriously, premature solidification of large amounts of gel material can easily lead to complex accidents such as stuck pipe.

[0005] The third type is conventional composite plugging agent while drilling. This type of plugging agent is mostly composed of rigid particulate materials such as calcium carbonate and coke particles, fibrous materials (sawdust, walnut shells, cottonseed hulls, peanut shells, straw, rayon fiber, and reeds, etc.), and ordinary rubber flexible deformable materials. These plugging materials can play a good role in preventing and sealing leakage when the bottom hole temperature is below 150°C. However, when the bottom hole temperature is above 150°C, plant fiber materials such as sawdust, walnut shells, cottonseed hulls, peanut shells, and straw directly carbonize into powder; rayon fiber becomes brittle directly at temperatures above 150°C and turns into powder crystals with slight pressure; although ordinary rubber has good elasticity and toughness and high compression resistance at room temperature, its flexibility and strength decrease significantly when the temperature is above 160°C. Therefore, the pressure-bearing time of such composite plugging agents is short, requiring repeated plugging, prolonging the drilling cycle, reducing drilling efficiency, and failing to meet the requirements for long-term pressure-bearing plugging under high temperature and high pressure conditions. Conventional drilling plugging technology has a short pressure bearing time, especially in high-temperature and high-pressure formations, which cannot meet the needs of engineering drilling.

[0006] Chinese patent document CN113122202A discloses a high-temperature resistant drilling plugging agent and its preparation method, which is formulated from granular materials, flake materials, fibrous materials, and elastic materials in a mass ratio of 5:2:2:1. The granular materials are coke particles, diatomaceous earth, and calcium carbonate; the flake materials are mica flakes; the fibrous materials are glass fibers or asbestos fibers; and the elastic material is the product of low-phenyl silicone rubber vulcanization. Further analysis of this patent reveals that:

[0007] (1) The granular materials in this patent are calcium carbonate, diatomaceous earth, and coke particles; calcium carbonate particles are acidic substances with positive charges on their surface, while the drilling fluid system is an alkaline environment. In the alkaline medium, the positive charge on the surface of calcium carbonate is neutralized, and the calcium carbonate particles will gradually dissolve and release CO2 gas. Therefore, the morphology of calcium carbonate particles will change in the drilling fluid and cannot maintain a long-term pressure-bearing state; diatomaceous earth is an aggregate composed of tiny diatom remains with a large porosity, which easily absorbs water, giving diatomaceous earth a certain elasticity and reducing its hardness; secondly, diatomaceous earth has a certain solubility in alkaline solutions; thirdly, diatomaceous earth is an inorganic substance, and its shape begins to change under conditions above 150°C, resulting in cracking and deformation; coke particles are loose and porous, brittle, and their hardness decreases at high temperatures, making them unable to meet the requirements of long-term leak sealing under high temperature and high pressure.

[0008] (2) The elastic material in this patent is the product of low-phenyl silicone rubber vulcanization; low-phenyl silicone rubber vulcanization increases its elasticity, heat resistance and tensile strength, and has good temperature resistance. However, low-phenyl vulcanized silicone rubber has poor oil erosion resistance and cannot withstand pressure for a long time under high temperature and high pressure when oil-based drilling fluid is used for plugging construction; secondly, the density of low-phenyl vulcanized silicone rubber is 1.0 g / cm³. 3 ~1.30g / cm 3 Between, when using a density greater than 1.50 g / cm³ 3 When drilling fluid is used for plugging operations, low-phenyl silica gel will float on the surface of the drilling fluid. When the leaking layer is encountered, only a small amount of low-phenyl silica gel will enter the hole with the drilling fluid and will not be able to seal the hole.

[0009] (3) The plugging agent in this patent is made of granular material, flake material, fibrous material and elastic material in a mass ratio of 5:2:2:1, without limiting the total mass percentage of the plugging agent in the drilling fluid. As is well known, the plugging agent can only bridge, fill and seal the gaps in the lost layer when it reaches a certain concentration in the drilling fluid. Otherwise, if the concentration of the plugging agent is too low, it cannot form a tight accumulation at the bottom hole, and the sealing effect on the lost layer will be poor, resulting in a large loss of drilling fluid.

[0010] Comprehensive analysis shows that this patent can withstand high pressure for short-term plugging operations at a temperature of 220℃. However, because the hardness and brittleness of the particles in the plugging agent decrease over time, and the total mass concentration of the plugging agent is uncertain, the drilling fluid prepared from the plugging agent described in this patent cannot withstand pressure for a long time, resulting in a low plugging success rate and forcing repeated plugging operations. Summary of the Invention

[0011] The technical problem to be solved by this invention is to address the issues of leakage during high-temperature and high-pressure well construction, poor plugging effect of existing drilling fluid plugging agents, and limited application fields, and to provide a long-lasting temperature-resistant drilling fluid for plugging during drilling and its preparation method.

[0012] The long-lasting, temperature-resistant drilling fluid described in this invention exhibits strong temperature resistance and a long pressure-bearing time under high temperature and high pressure conditions. It can be used in both water-based and oil-based drilling fluids. Furthermore, the long-lasting, temperature-resistant drilling fluid can withstand pressure for 7 days at 230°C and 12MPa, effectively solving the problems of permeability loss and leakage from micropores in high-temperature and high-pressure wells.

[0013] To solve the above-mentioned technical problems, the first aspect of the present invention provides a long-lasting temperature-resistant drilling fluid for plugging leaks while drilling, comprising a base drilling fluid and a plugging agent, wherein the plugging agent comprises granular material, flake material, fibrous material and elastic material; the mass ratio of the granular material, flake material, fibrous material and elastic material is (10-14):(4-7):(4-6):(3-5).

[0014] According to some embodiments of the present invention, the granular material is selected from quartz sand or modified quartz sand.

[0015] According to some embodiments of the present invention, the preparation method of the modified quartz sand includes sequential physical modification and chemical modification; preferably, the physical modification is shot peening; the chemical modification is coating the surface of the quartz sand with bisphenol A epoxy resin using a thermal method. The specific process is as follows: Quartz sand is shot-peened using 40-60 mesh steel shot under compressed air power to achieve surface polishing; the shot-peening time is 120 seconds and the shot-peening frequency is 50 Hz; then the shot-peened quartz sand is heated to 180℃ and poured into a sand mixer, which is stirred at a speed of 300 r / min. Bisphenol A epoxy resin is added to the sand mixer, and stirring continues for 8 minutes to allow the Si-OH (silanol group), Si-O-Si (silyl ether group) functional groups on the surface of the quartz sand to fully react with the epoxy groups in the bisphenol A epoxy resin. Heating is then stopped, and a 25% hexamethylenetetramine aqueous solution is added and stirring continues for 5 minutes. After cooling, the mixture is sieved to obtain modified quartz sand; the mass ratio of quartz sand, bisphenol A epoxy resin, and hexamethylenetetramine is 250:5:1.

[0016] According to some embodiments of the present invention, the particle size of the granular material is 20 mesh to 100 mesh.

[0017] According to some embodiments of the present invention, the sheet material is a mica sheet.

[0018] According to some embodiments of the present invention, the particle size of the sheet material is 80 mesh to 150 mesh.

[0019] According to some embodiments of the present invention, the fibrous material is selected from at least one of glass fiber and asbestos fiber.

[0020] According to some embodiments of the present invention, the particle size of the fibrous material is 55 mesh to 80 mesh.

[0021] According to some embodiments of the present invention, the elastic material is fluorosilicone rubber.

[0022] According to some embodiments of the present invention, the particle size of the elastic material is 150 mesh to 300 mesh.

[0023] According to some embodiments of the present invention, the base drilling fluid is a water-based drilling fluid and / or an oil-based drilling fluid.

[0024] According to some embodiments of the present invention, the mass percentage of the plugging agent is 21% to 30%, based on the volume of the long-acting temperature-resistant drilling fluid used for plugging leaks while drilling, which is 100%.

[0025] The second aspect of the present invention provides a method for preparing the long-lasting temperature-resistant drilling fluid for plugging leaks provided in the first aspect above, comprising adding the granular material, the flake material, the fibrous material and the elastic material sequentially to a base drilling fluid.

[0026] According to some embodiments of the present invention, the preparation method includes:

[0027] (1) Add granular material to the basic drilling fluid through the feeding funnel and stir for 10 min to 15 min to make the granular material evenly dispersed in the drilling fluid system;

[0028] (2) Continue to add the flake material through the feeding funnel and stir for 10 min to 15 min to make the flake material evenly dispersed in the drilling fluid system;

[0029] (3) Continue to add fibrous material through the feeding funnel and stir for 15 min to 20 min to make the fibrous material evenly dispersed in the drilling fluid system;

[0030] (4) Continue to add elastic material through the feeding funnel and stir for 20 min to 30 min to make the elastic material evenly dispersed in the drilling fluid system to obtain a long-lasting temperature-resistant drilling fluid for plugging leaks while drilling.

[0031] According to some embodiments of the present invention, the preparation method includes:

[0032] (1) Add granular material to the basic drilling fluid through the feeding funnel and stir for 10 minutes to make the granular material evenly dispersed in the drilling fluid system;

[0033] (2) Continue to add the flake material through the feeding funnel and stir for 10 minutes to make the flake material evenly dispersed in the drilling fluid system;

[0034] (3) Continue to add fibrous material through the feeding funnel and stir for 20 minutes to make the fibrous material evenly dispersed in the drilling fluid system;

[0035] (4) Continue to add elastic material through the feeding funnel and stir for 25 minutes to make the elastic material evenly dispersed in the drilling fluid system to obtain a long-lasting temperature-resistant drilling fluid for plugging leaks while drilling.

[0036] The third aspect of the present invention provides the application of the long-acting temperature-resistant drilling fluid provided in the first aspect or the long-acting temperature-resistant drilling fluid prepared by the preparation method provided in the second aspect in drilling.

[0037] This invention addresses the leakage problem that occurs during high-temperature and high-pressure well construction. Based on the "one-third and one-half" bridging mechanism of granular and sheet-like materials, fibrous material winding, and elastic material sealing in leakage plugging technology, it provides a long-lasting, temperature-resistant, drilling fluid for leakage plugging during drilling. Compared with conventional drilling fluids for leakage plugging, the long-lasting, temperature-resistant, drilling fluid for leakage plugging during drilling of this invention has the following beneficial effects:

[0038] (1) Conventional plugging agents used in drilling are sawdust, walnut shells and conventional rubber, which are heat-resistant to no more than 150°C. However, the long-lasting heat-resistant plugging drilling fluid described in this invention can withstand temperatures above 230°C and has a long pressure-bearing time under high temperature and high pressure conditions.

[0039] (2) Since conventional lost circulation plugging agents use ordinary rubber as the elastic material, which is soluble in oil, they can only be used in water-based drilling fluids. However, the long-lasting, temperature-resistant lost circulation plugging drilling fluid of this invention uses fluorosilicone rubber as the elastic material, which is insoluble in oil. Therefore, the long-lasting, temperature-resistant lost circulation plugging drilling fluid of this invention can be used in both water-based and oil-based drilling fluids, and can be used for lost circulation plugging in deep wells, ultra-deep wells, and geothermal wells. In addition, the density of conventional rubber is 0.8 g / cm³. 3 ~1.3g / cm 3 Between, in densities higher than 1.30 g / cm³ 3 In conventional drilling fluids, the fluorosilicone rubber floats on the surface, resulting in a small amount reaching the lost circulation zone and thus a poor sealing effect. The fluorosilicone rubber used in this invention has a density of 1.90 g / cm³. 3 ~2.10g / cm 3 It can enter the drilling fluid and enter the formation pores along with the drilling fluid, thus sealing the lost circulation zone.

[0040] (3) Conventional drilling plugging agents are simply a combination of materials of various shapes, while the long-acting temperature-resistant drilling plugging fluid of the present invention contains silicon oxide bonds in the structure of materials of various shapes, which can undergo chemical reactions under high temperature and high pressure at the bottom of the well and be bonded together by silicon-oxygen-silicon chemical bonds.

[0041] (4) The long-lasting temperature-resistant drilling fluid described in this invention has long-lasting temperature resistance. The long-lasting temperature-resistant drilling fluid described in this invention can withstand pressure for 7 days at a high temperature of 230℃ and a pressure of 12MPa. It can be used for drilling and plugging during the construction of deep wells, ultra-deep wells and geothermal wells. It can quickly and effectively seal permeable leakage and leakage from small pores, avoiding repeated plugging operations. Detailed Implementation

[0042] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to these embodiments.

[0043] Unless otherwise specified, all raw materials and instruments used in the following embodiments and comparative examples of the present invention are commercially available and are commonly used reagents or instruments that can be purchased by those skilled in the art.

[0044] Unless otherwise specified, the high-temperature and high-pressure sand bed filter loss meter and the high-temperature and high-pressure microcrack plugging device used in the preparation examples of this invention are all commercially available.

[0045] In the examples and comparative examples, the percentage mentioned in the drilling fluid preparation process refers to the mass percentage of each component in the total volume of the prepared drilling fluid.

[0046] Experimental procedure for high temperature and high pressure sand bed filtration analyzer:

[0047] Step 1: Add the prepared drilling fluid for plugging while drilling to the high temperature and high pressure sand bed filter (the sand bed is composed of quartz sand with a particle size of 0.45mm to 1.5mm and a thickness of 25mm), tighten the sealing cap, and connect the high pressure manifold.

[0048] Step 2: Heat to 230℃ and hold at that temperature for 10 minutes;

[0049] Step 3: Open the high-pressure manifold and pressurize at a rate of 0.2 MPa every 5 minutes, gradually increasing the pressure to 12.0 MPa;

[0050] Step 4: During the pressurization process, if the sand bed is breached, record the pressure value at which the sand bed is breached, which is the pressure-bearing capacity of the drilling fluid used for plugging leaks while drilling.

[0051] Step 5: Stop pressurizing when the pressure reaches 12.0 MPa and stabilize the pressure at 12.0 MPa for 7 days; during the pressure stabilization period, if the sand bed is breached, record the pressure stabilization time, i.e. the pressure bearing time, and collect the drilling fluid volume that permeates the sand bed for 30 minutes under pressure.

[0052] Step 6: During the period of stabilizing the pressure at 12.0 MPa until 7 days, if the sand bed is not breached, collect the drilling fluid volume that permeates the sand bed after 30 minutes and 7 days of pressure, and calculate the leakage rate after 30 minutes and 7 days of pressure.

[0053] Among them, the 30-minute leakage rate = the volume of drilling fluid that permeates the sand bed under pressure for 30 minutes / the total volume of drilling fluid * 100%; the 7-day leakage rate = the volume of drilling fluid that permeates the sand bed under pressure for 7 days / the total volume of drilling fluid * 100%.

[0054] Experimental operation procedure of high temperature and high pressure microcrack sealing instrument:

[0055] Step 1: Add the prepared drilling fluid to the high-temperature and high-pressure micro-fracture plugging device, tighten the sealing cap, and connect the high-pressure manifold;

[0056] Step 2: Heat to 230℃ and hold at that temperature for 10 minutes;

[0057] Step 3: Open the high-pressure manifold and pressurize at a rate of 0.2 MPa every 5 minutes, gradually increasing the pressure to 12.0 MPa;

[0058] Step 4: During the pressurization process, if the joint plate is punctured, record the pressure value at which the joint plate is punctured, which is the pressure bearing capacity of the drilling fluid used for plugging leaks while drilling.

[0059] Step 5: Stop pressurizing when the pressure reaches 12.0 MPa and stabilize the pressure at 12.0 MPa for 7 days. During the pressure stabilization period, if the fracture plate is punctured, record the pressure stabilization time, i.e., the pressure bearing time, and collect the drilling fluid volume that permeates through the fracture plate after 30 minutes of pressure bearing.

[0060] Step 6: During the period of stabilizing the pressure at 12.0 MPa until 7 days, if the fracture plate is not broken, collect the drilling fluid volume that permeates through the fracture plate after 30 minutes and 7 days of pressure, and calculate the leakage rate after 30 minutes and 7 days of pressure.

[0061] Among them, the 30-minute leakage rate = the volume of drilling fluid that permeates the slotted plate under pressure for 30 minutes / the total volume of drilling fluid * 100%; the 7-day leakage rate = the volume of drilling fluid that permeates the slotted plate under pressure for 7 days / the total volume of drilling fluid * 100%.

[0062] In the examples and comparative examples, the preparation process of the modified quartz sand is as follows:

[0063] Quartz sand was shot-peened using 40-60 mesh steel shot under compressed air power to achieve surface polishing; the shot-peening time was 120 seconds and the shot-peening frequency was 50 Hz. The shot-peened quartz sand was then heated to 180℃ and poured into a sand mixer. The mixer was stirred at 300 r / min, and bisphenol A epoxy resin was added to the mixer. Stirring continued for 8 minutes to allow the Si-OH (silanol group), Si-O-Si (silyl ether group), and other functional groups on the quartz sand surface to fully react with the epoxy groups in the bisphenol A epoxy resin. Heating was then stopped, and a 25% hexamethylenetetramine aqueous solution was added and stirring continued for 5 minutes. After cooling, the mixture was sieved to obtain modified quartz sand. The mass ratio of quartz sand, bisphenol A epoxy resin, and hexamethylenetetramine was 250:5:1. After modification, the roughness of the quartz sand is improved, and its adhesion is strong at high temperatures, which increases the sealing effect of the sealing material at the pores and cracks.

[0064] Example 1

[0065] This embodiment is used to illustrate the long-acting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0066] The sealing agent comprises modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber; the mass ratio of the modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the modified quartz sand is 20 mesh to 100 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the asbestos fiber is 55 mesh to 80 mesh; and the particle size of the fluorosilicone rubber is 150 mesh to 300 mesh.

[0067] A long-lasting, temperature-resistant, water-based drilling fluid for plugging and sealing was prepared. The formula was: 400 mL water + 2.5% saline-resistant clay + 0.2% sodium hydroxide + 5.0% sulfonated phenolic resin SMP-3 + 3.0% organic lignite filtration reducer + 3.5% sulfonated asphalt plugging agent + 1.0% benzenesulfonate copolymer filtration reducer DSP-2, and then weighted to 1.50 g / cm³ with barite. 3 13.0% modified quartz sand was added through a feeding funnel and stirred for 10 minutes; 5.2% mica flakes were added and stirred for 10 minutes; 5.2% asbestos fiber was added and stirred for 20 minutes; 3.9% fluorosilicone rubber was added and stirred for 25 minutes. The mixture was then added to a high-temperature and high-pressure sand bed filter for testing. The pressure-bearing and leak-stopping effects are shown in Table 1.

[0068] Example 2

[0069] This embodiment is used to illustrate the long-acting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0070] The sealing agent comprises modified quartz sand, mica flakes, glass fiber, and fluorosilicone rubber; the mass ratio of the modified quartz sand, mica flakes, glass fiber, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the modified quartz sand is 20 mesh to 100 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the glass fiber is 55 mesh to 80 mesh; and the particle size of the fluorosilicone rubber is 150 mesh to 300 mesh.

[0071] A long-lasting, temperature-resistant, water-based drilling fluid for plugging and sealing was prepared. The formula was: 800 mL water + 2.5% saline-resistant clay + 0.2% sodium hydroxide + 5.0% sulfonated phenolic resin SMP-3 + 3.0% organic lignite filtration reducer + 3.5% sulfonated asphalt plugging agent + 1.0% benzenesulfonate copolymer filtration reducer DSP-2, and then weighted to 1.50 g / cm³ with barite. 3 13.0% modified quartz sand was added through a feeding funnel and stirred for 10 minutes; 5.2% mica flakes were added and stirred for 10 minutes; 5.2% glass fiber was added and stirred for 20 minutes; 3.9% fluorosilicone rubber was added and stirred for 25 minutes. The water-based drilling fluid used for plugging leaks while drilling was then divided into two equal portions and added to a high-temperature and high-pressure micro-fracture plugging instrument for testing. The pressure-bearing plugging effect is shown in Table 1.

[0072] Example 3

[0073] This embodiment is used to illustrate the long-acting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0074] The sealing agent comprises modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber; the mass ratio of the modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the modified quartz sand is 20 mesh to 100 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the asbestos fiber is 55 mesh to 80 mesh; and the particle size of the fluorosilicone rubber is 150 mesh to 300 mesh.

[0075] A long-lasting, temperature-resistant, water-based drilling fluid for plugging and sealing was prepared. The formula was: 400 mL water + 1.8% saline-resistant clay + 0.2% sodium hydroxide + 5.0% sulfonated phenolic resin SMP-3 + 3.0% organic lignite filtration reducer + 3.5% sulfonated asphalt plugging agent + 0.8% benzenesulfonate copolymer filtration reducer DSP-2, and then weighted with barite to 2.00 g / cm³. 3 12.0% modified quartz sand was added through a feeding funnel and stirred for 10 minutes; 4.8% mica flakes were added and stirred for 10 minutes; 4.8% asbestos fiber was added and stirred for 20 minutes; 3.6% fluorosilicone rubber was added and stirred for 25 minutes. The mixture was then added to a high-temperature and high-pressure sand bed filter for testing. The pressure-bearing and leak-stopping effects are shown in Table 1.

[0076] Example 4

[0077] This embodiment is used to illustrate the long-acting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0078] The sealing agent comprises modified quartz sand, mica flakes, glass fiber, and fluorosilicone rubber; the mass ratio of the modified quartz sand, mica flakes, glass fiber, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the modified quartz sand is 20 mesh to 100 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the glass fiber is 55 mesh to 80 mesh; and the particle size of the fluorosilicone rubber is 150 mesh to 300 mesh.

[0079] A long-lasting, temperature-resistant, water-based drilling fluid for plugging and sealing was prepared. The formula was: 800 mL water + 1.8% saline-resistant clay + 0.2% sodium hydroxide + 5.0% sulfonated phenolic resin SMP-3 + 3.0% organic lignite filtration reducer + 3.5% sulfonated asphalt plugging agent + 0.8% benzenesulfonate copolymer filtration reducer DSP-2, then weighted to 2.00 g / cm³. 3 12.0% modified quartz sand was added through a feeding funnel and stirred for 10 minutes; 4.8% mica flakes were added and stirred for 10 minutes; 4.8% glass fiber was added and stirred for 20 minutes; 3.6% fluorosilicone rubber was added and stirred for 25 minutes. The water-based drilling fluid used for plugging leaks while drilling was then divided into two equal parts and added to a high-temperature and high-pressure micro-fracture plugging instrument for testing. The pressure-bearing plugging effect is shown in Table 1.

[0080] Table 1. Pressure-bearing capacity of different embodiments in water-based drilling fluids for plugging leaks while drilling.

[0081]

[0082] As can be seen from Table 1 above, under the condition of 230℃, whether for 0.45mm to 1.5mm quartz sand beds or for cracks with widths of 0.5mm and 1.0mm, the long-lasting temperature-resistant water-based drilling fluid prepared in Examples 1-4 of this invention has good pressure-bearing and plugging capabilities, and the pressure-bearing and plugging time can be maintained for 7 days, which can plug the leakage layer for a long time.

[0083] Example 5

[0084] This embodiment is used to illustrate the long-acting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0085] The sealing agent comprises modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber; the mass ratio of the modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the modified quartz sand is 20 mesh to 100 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the asbestos fiber is 55 mesh to 80 mesh; and the particle size of the fluorosilicone rubber is 150 mesh to 300 mesh.

[0086] A long-lasting, high-temperature-resistant oil-based drilling fluid for plugging and sealing was prepared using the following formula: 400 mL (320 mL base oil + 80 mL calcium chloride aqueous solution, with a calcium chloride concentration of 25%) + 3.0% primary emulsifier + 2.0% secondary emulsifier + 3.5% organoclay + 2.0% wetting agent + 3.5% oil-based filtration reducer + 4.0% oil-based high-temperature-resistant plugging agent for drilling fluid + 2.0% lime, then weighted to 1.50 g / cm³ with barite. 3 14.0% modified quartz sand was added through a feeding funnel and stirred for 10 minutes; 5.6% mica flakes were added and stirred for 10 minutes; 5.6% asbestos fiber was added and stirred for 20 minutes; 4.2% fluorosilicone rubber was added and stirred for 25 minutes. The mixture was then added to a high-temperature and high-pressure sand bed filter for testing. The pressure-bearing and leak-stopping effects are shown in Table 2.

[0087] Example 6

[0088] This embodiment is used to illustrate the long-acting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0089] The sealing agent comprises modified quartz sand, mica flakes, glass fiber, and fluorosilicone rubber; the mass ratio of the modified quartz sand, mica flakes, glass fiber, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the modified quartz sand is 20 mesh to 100 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the glass fiber is 55 mesh to 80 mesh; and the particle size of the fluorosilicone rubber is 150 mesh to 300 mesh.

[0090] A long-lasting, high-temperature-resistant oil-based drilling fluid for plugging and sealing was prepared using the following formula: 800 mL (640 mL base oil + 160 mL calcium chloride aqueous solution, with a calcium chloride concentration of 25%) + 3.0% primary emulsifier + 2.0% secondary emulsifier + 3.5% organoclay + 2.0% wetting agent + 3.5% oil-based filtration reducer + 4.0% oil-based high-temperature-resistant plugging agent for drilling fluid + 2.0% lime, then weighted to 1.50 g / cm³ with barite. 314.0% modified quartz sand was added through a feeding funnel and stirred for 10 minutes; 5.6% mica flakes were added and stirred for 10 minutes; 5.6% glass fiber was added and stirred for 20 minutes; 4.2% fluorosilicone rubber was added and stirred for 25 minutes. The oil-based drilling fluid used for plugging leaks while drilling was then divided into two equal parts and added to a high-temperature and high-pressure micro-fracture plugging instrument for testing. The pressure-bearing plugging effect is shown in Table 2.

[0091] Example 7

[0092] This embodiment is used to illustrate the long-acting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0093] The sealing agent comprises modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber; the mass ratio of the modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the modified quartz sand is 20 mesh to 100 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the asbestos fiber is 55 mesh to 80 mesh; and the particle size of the fluorosilicone rubber is 150 mesh to 300 mesh.

[0094] A long-lasting, high-temperature-resistant oil-based drilling fluid for plugging and sealing was prepared using the following formula: 400 mL (350 mL base oil + 50 mL calcium chloride aqueous solution, with a calcium chloride concentration of 25%) + 3.5% primary emulsifier + 2.5% secondary emulsifier + 3.0% organoclay + 4.0% wetting agent + 3.5% oil-based filtration reducer + 3.0% oil-based high-temperature-resistant plugging agent for drilling fluid + 2.0% lime, then weighted to 2.00 g / cm³ with barite. 3 12.0% modified quartz sand was added through a feeding funnel and stirred for 10 minutes; 4.8% mica flakes were added and stirred for 10 minutes; 4.8% asbestos fiber was added and stirred for 20 minutes; 3.6% fluorosilicone rubber was added and stirred for 25 minutes. The mixture was then added to a high-temperature and high-pressure sand bed filter for testing. The pressure-bearing and leak-stopping effect is shown in Table 2.

[0095] Example 8

[0096] This embodiment is used to illustrate the long-acting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0097] The sealing agent comprises modified quartz sand, mica flakes, glass fiber, and fluorosilicone rubber; the mass ratio of the modified quartz sand, mica flakes, glass fiber, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the modified quartz sand is 20 mesh to 100 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the glass fiber is 55 mesh to 80 mesh; and the particle size of the fluorosilicone rubber is 150 mesh to 300 mesh.

[0098] A long-lasting, high-temperature-resistant oil-based drilling fluid for plugging and sealing was prepared using the following formula: 800 mL (640 mL base oil + 160 mL calcium chloride aqueous solution, with a calcium chloride concentration of 25%) + 3.5% primary emulsifier + 2.5% secondary emulsifier + 3.0% organoclay + 4.0% wetting agent + 3.5% oil-based filtration reducer + 3.0% oil-based high-temperature-resistant plugging agent for drilling fluid + 2.0% lime, then weighted to 2.00 g / cm³ with barite. 3 12.0% modified quartz sand was added through a feeding funnel and stirred for 10 minutes; 4.8% mica flakes were added and stirred for 10 minutes; 4.8% glass fiber was added and stirred for 20 minutes; 3.6% fluorosilicone rubber was added and stirred for 25 minutes. The oil-based drilling fluid used for plugging leaks while drilling was then divided into two equal parts and added to a high-temperature and high-pressure micro-fracture plugging instrument for testing. The pressure-bearing plugging effect is shown in Table 2.

[0099] Table 2. Pressure-bearing capacity of different embodiments in oil-based drilling fluids for plugging leaks while drilling.

[0100]

[0101]

[0102] As can be seen from Table 2 above, under the condition of 230℃, for the leakage caused by 0.45mm~1.5mm quartz sand beds and cracks with a width of 0.5mm or 1.0mm, the long-acting temperature-resistant oil-based drilling fluid described in Examples 5-8 of this invention has good pressure-bearing and plugging capabilities, and the pressure stabilization time reaches 7 days, which can achieve the purpose of long-term pressure-bearing and plugging of the leakage layer.

[0103] Comparative Example 1

[0104] This comparative example is used to illustrate the long-lasting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0105] The sealing agent comprises calcium carbonate, mica flakes, asbestos fibers, and fluorosilicone rubber; the mass ratio of calcium carbonate, mica flakes, asbestos fibers, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the calcium carbonate is 20 mesh to 100 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the asbestos fibers is 55 mesh to 80 mesh; and the particle size of the fluorosilicone rubber is 150 mesh to 300 mesh.

[0106] The water-based drilling fluid for plugging leaks while drilling was prepared with the following formula: 1200 mL water + 2.5% saline-resistant clay + 0.2% sodium hydroxide + 5.0% sulfonated phenolic resin SMP-3 + 3.0% organic lignite filtration reducer + 3.5% sulfonated bitumen plugging agent + 1.0% benzenesulfonate copolymer filtration reducer DSP-2, and then weighted to 1.50 g / cm³ with barite. 313.0% calcium carbonate was added through a feeding funnel and stirred for 10 minutes; 5.2% mica flakes were added and stirred for 10 minutes; 5.2% asbestos fiber was added and stirred for 20 minutes; 3.9% fluorosilicone rubber was added and stirred for 25 minutes. The water-based drilling fluid used for plugging leaks while drilling was then divided into three equal portions and added to a high-temperature and high-pressure sand bed filtration tester and a high-temperature and high-pressure micro-fracture plugging tester, respectively, for testing. The pressure-bearing plugging effect is shown in Table 3.

[0107] Comparative Example 2

[0108] This comparative example is used to illustrate the long-lasting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0109] The sealing agent comprises diatomaceous earth, mica flakes, asbestos fibers, and fluorosilicone rubber; the mass ratio of diatomaceous earth, mica flakes, asbestos fibers, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the diatomaceous earth is 20-100 mesh; the particle size of the mica flakes is 80-150 mesh; the particle size of the asbestos fibers is 55-80 mesh; and the particle size of the fluorosilicone rubber is 150-300 mesh.

[0110] The water-based drilling fluid for plugging leaks while drilling was prepared with the following formula: 1200 mL water + 2.5% saline-resistant clay + 0.2% sodium hydroxide + 5.0% sulfonated phenolic resin SMP-3 + 3.0% organic lignite filtration reducer + 3.5% sulfonated bitumen plugging agent + 1.0% benzenesulfonate copolymer filtration reducer DSP-2, and then weighted to 1.50 g / cm³ with barite. 3 13.0% diatomaceous earth was added through a feeding funnel and stirred for 10 minutes; 5.2% mica flakes were added and stirred for 10 minutes; 5.2% asbestos fiber was added and stirred for 20 minutes; 3.9% fluorosilicone rubber was added and stirred for 25 minutes. The water-based drilling fluid for plugging while drilling was then divided into three equal portions and added to a high-temperature and high-pressure sand bed filtration tester and a high-temperature and high-pressure micro-fracture plugging tester, respectively, for testing. The pressure-bearing plugging effect is shown in Table 3.

[0111] Comparative Example 3

[0112] This comparative example is used to illustrate the long-lasting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0113] The sealing agent comprises coke particles, mica flakes, asbestos fibers, and fluorosilicone rubber; the mass ratio of the coke particles, mica flakes, asbestos fibers, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the coke particles is 20 mesh to 100 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the asbestos fibers is 55 mesh to 80 mesh; and the particle size of the fluorosilicone rubber is 150 mesh to 300 mesh.

[0114] The water-based drilling fluid for plugging leaks while drilling was prepared with the following formula: 1200 mL water + 2.5% saline-resistant clay + 0.2% sodium hydroxide + 5.0% sulfonated phenolic resin SMP-3 + 3.0% organic lignite filtration reducer + 3.5% sulfonated bitumen plugging agent + 1.0% benzenesulfonate copolymer filtration reducer DSP-2, and then weighted to 1.50 g / cm³ with barite. 3 13.0% coke particles were added through a feeding funnel and stirred for 10 minutes; 5.2% mica flakes were added and stirred for 10 minutes; 5.2% asbestos fiber was added and stirred for 20 minutes; 3.9% fluorosilicone rubber was added and stirred for 25 minutes. The water-based drilling fluid used for plugging leaks while drilling was then divided into three equal portions and added to a high-temperature and high-pressure sand bed filtration tester and a high-temperature and high-pressure micro-fracture plugging tester, respectively, for testing. The pressure-bearing plugging effect is shown in Table 3.

[0115] Table 3. Pressure-bearing and plugging capabilities of different comparative samples in water-based drilling fluids.

[0116]

[0117]

[0118] As can be seen from Table 3 above, the drilling fluids used as particulate materials in Comparative Examples 1-3 for plugging leaks exhibit short pressure-bearing time, high leakage rate, and poor plugging effect when dealing with permeable leakage and micro-fracture leakage under high temperature of 230℃ and pressure of 12.0MPa, requiring repeated plugging operations.

[0119] Comparative Example 4

[0120] This comparative example is used to illustrate the long-lasting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0121] The sealing agent comprises modified quartz sand, mica flakes, glass fiber, and low-phenyl vulcanizing silica gel; the mass ratio of the modified quartz sand, mica flakes, glass fiber, and low-phenyl vulcanizing silica gel is 10:4:4:3; wherein the particle size of the modified quartz sand is 20 mesh to 100 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the glass fiber is 55 mesh to 80 mesh; and the particle size of the low-phenyl vulcanizing silica gel is 150 mesh to 300 mesh.

[0122] The formula for preparing the oil-based drilling fluid for plugging leaks while drilling is as follows: 1200 mL (960 mL base oil + 240 mL calcium chloride aqueous solution, with a calcium chloride concentration of 25%) + 3.0% primary emulsifier + 2.0% secondary emulsifier + 3.5% organoclay + 2.0% wetting agent + 3.5% oil-based filtration reducer + 4.0% oil-based high-temperature sealing agent for drilling fluid + 2.0% lime, then weighted to 1.50 g / cm³ with barite. 314.0% modified quartz sand was added through a feeding funnel and stirred for 10 minutes; 5.6% mica flakes were added and stirred for 10 minutes; 5.6% glass fiber was added and stirred for 20 minutes; then 4.2% low-phenyl vulcanized silica gel was added and stirred for 25 minutes. The oil-based drilling fluid used for plugging leaks while drilling was divided into three equal parts and added to a high-temperature and high-pressure sand bed filter loss meter and a high-temperature and high-pressure micro-fracture plugging meter, respectively, for testing. The pressure-bearing plugging effect is shown in Table 4.

[0123] Table 4. Pressure-bearing and plugging capabilities of different embodiments in oil-based drilling fluids

[0124]

[0125] As can be seen from Table 4 above, compared with Example 6, the other materials in the sealing agent used in Comparative Example 4 are the same as those in Example 6, except that the elastic material is replaced by low-phenyl vulcanized silicone rubber instead of fluorosilicone rubber. Due to the poor oil resistance of low-phenyl vulcanized silicone rubber, it gradually dissolves under high temperature and high pressure, resulting in insufficient pressure bearing time for 0.45mm to 1.5mm quartz sand beds and cracks with widths of 0.5mm and 1.0mm under high temperature and high pressure, and short sealing time for the holes and cracks.

[0126] Comparative Example 5

[0127] This comparative example is used to illustrate the long-lasting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0128] The sealing agent comprises modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber; the mass ratio of the modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the modified quartz sand is 150 mesh to 250 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the asbestos fiber is 55 mesh to 80 mesh; and the particle size of the fluorosilicone rubber is 150 mesh to 300 mesh.

[0129] The water-based drilling fluid for plugging leaks while drilling was prepared with the following formula: 1200 mL water + 2.5% saline-resistant clay + 0.2% sodium hydroxide + 5.0% sulfonated phenolic resin SMP-3 + 3.0% organic lignite filtration reducer + 3.5% sulfonated bitumen plugging agent + 1.0% benzenesulfonate copolymer filtration reducer DSP-2, and then weighted to 1.50 g / cm³ with barite. 3 13.0% modified quartz sand was added through a feeding funnel and stirred for 10 minutes; 5.2% mica flakes were added and stirred for 10 minutes; 5.2% asbestos fiber was added and stirred for 20 minutes; 3.9% fluorosilicone rubber was added and stirred for 25 minutes. The water-based drilling fluid used for plugging leaks while drilling was then divided into three equal portions and added to a high-temperature and high-pressure sand bed filtration tester and a high-temperature and high-pressure micro-fracture plugging tester, respectively, for testing. The pressure-bearing plugging effect is shown in Table 5.

[0130] Comparative Example 6

[0131] This comparative example is used to illustrate the long-lasting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0132] The sealing agent comprises modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber; the mass ratio of the modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the modified quartz sand is 250 mesh to 500 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the asbestos fiber is 55 mesh to 80 mesh; and the particle size of the fluorosilicone rubber is 150 mesh to 300 mesh.

[0133] The water-based drilling fluid for plugging leaks while drilling was prepared with the following formula: 1200 mL water + 2.5% saline-resistant clay + 0.2% sodium hydroxide + 5.0% sulfonated phenolic resin SMP-3 + 3.0% organic lignite filtration reducer + 3.5% sulfonated bitumen plugging agent + 1.0% benzenesulfonate copolymer filtration reducer DSP-2, and then weighted to 1.50 g / cm³ with barite. 3 13.0% modified quartz sand was added through a feeding funnel and stirred for 10 minutes; 5.2% mica flakes were added and stirred for 10 minutes; 5.2% asbestos fiber was added and stirred for 20 minutes; 3.9% fluorosilicone rubber was added and stirred for 25 minutes. The water-based drilling fluid used for plugging leaks while drilling was then divided into three equal portions and added to a high-temperature and high-pressure sand bed filtration tester and a high-temperature and high-pressure micro-fracture plugging tester, respectively, for testing. The pressure-bearing plugging effect is shown in Table 5.

[0134] Comparative Example 7

[0135] This comparative example is used to illustrate the long-lasting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0136] The sealing agent comprises modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber; the mass ratio of the modified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber is 10:4:4:3; wherein the particle size of the modified quartz sand is 20 mesh to 100 mesh; the particle size of the mica flakes is 80 mesh to 150 mesh; the particle size of the asbestos fiber is 150 mesh to 300 mesh; and the particle size of the fluorosilicone rubber is 150 mesh to 300 mesh.

[0137] The water-based drilling fluid for plugging leaks while drilling was prepared with the following formula: 1200 mL water + 2.5% saline-resistant clay + 0.2% sodium hydroxide + 5.0% sulfonated phenolic resin SMP-3 + 3.0% organic lignite filtration reducer + 3.5% sulfonated bitumen plugging agent + 1.0% benzenesulfonate copolymer filtration reducer DSP-2, and then weighted to 1.50 g / cm³ with barite. 313.0% modified quartz sand was added through a feeding funnel and stirred for 10 minutes; 5.2% mica flakes were added and stirred for 10 minutes; 5.2% asbestos fiber was added and stirred for 20 minutes; 3.9% fluorosilicone rubber was added and stirred for 25 minutes. The water-based drilling fluid used for plugging leaks while drilling was then divided into three equal portions and added to a high-temperature and high-pressure sand bed filtration tester and a high-temperature and high-pressure micro-fracture plugging tester, respectively, for testing. The pressure-bearing plugging effect is shown in Table 5.

[0138] Table 5. Pressure-bearing and plugging capabilities of different comparative samples in water-based drilling fluids.

[0139]

[0140] As can be seen from Table 5 above, when the particle size of the material in the plugging agent used for long-acting temperature-resistant drilling fluid changes, the pressure-bearing capacity of the prepared long-acting temperature-resistant drilling fluid for 0.45mm to 1.5mm quartz sand beds and fractures with widths of 0.5mm and 1.0mm is significantly insufficient, and the plugging effect is significantly reduced.

[0141] Comparative Example 8

[0142] This comparative example is used to illustrate the long-lasting temperature-resistant drilling fluid for plugging leaks during drilling and its preparation method as described in this invention.

[0143] The sealant comprises unmodified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber; the mass ratio of the unmodified quartz sand, mica flakes, asbestos fiber, and fluorosilicone rubber is 10:4:4:3.

[0144] The unmodified quartz sand has a particle size of 20-100 mesh; the mica flakes have a particle size of 80-150 mesh; the asbestos fiber has a particle size of 55-80 mesh; and the fluorosilicone rubber has a particle size of 150-300 mesh.

[0145] The water-based drilling fluid for plugging leaks while drilling was prepared with the following formula: 1200 mL water + 1.8% saline-resistant clay + 0.2% sodium hydroxide + 5.0% sulfonated phenolic resin SMP-3 + 3.0% organic lignite filtration reducer + 3.5% sulfonated asphalt plugging agent + 0.8% benzenesulfonate copolymer filtration reducer DSP-2, and then weighted with barite to 2.00 g / cm³. 3 12.0% unmodified quartz sand was added through a feeding funnel and stirred for 10 minutes; 4.8% mica flakes were added and stirred for 10 minutes; 4.8% asbestos fiber was added and stirred for 20 minutes; 3.6% fluorosilicone rubber was added and stirred for 25 minutes. The water-based drilling fluid used for plugging leaks while drilling was then divided into three equal portions and added to a high-temperature and high-pressure sand bed filtration tester and a high-temperature and high-pressure micro-fracture plugging tester, respectively, for testing. The pressure-bearing plugging effect is shown in Table 6.

[0146] Table 6. Pressure-bearing capacity of different embodiments in water-based drilling fluids for plugging leaks while drilling.

[0147]

[0148] As can be seen from Table 6 above, the quartz sand in the plugging agent used in the long-lasting temperature-resistant drilling fluid described in Comparative Example 8 is unmodified and can seal permeable leaks such as quartz sand beds with a particle size of 0.45mm to 1.5mm and fractures with a width of 0.5mm; however, it cannot provide long-term pressure-bearing sealing for slightly larger fracture-type leaks such as those with a width of 1.0mm.

[0149] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A long-lasting temperature-resistant lost circulation drilling fluid, the drilling fluid comprising a base drilling fluid and a lost circulation agent, characterized in that, The lost circulation material comprises granular material, sheet material, fibrous material and elastic material; the mass ratio of the granular material, sheet material, fibrous material and elastic material is (10-14):(4-7):(4-6):(3-5); the elastic material is fluorosilicone rubber; the granular material is selected from quartz sand or modified quartz sand.

2. The long-lasting temperature resistant lost circulation drilling fluid of claim 1, wherein, The particle size of the granular material is 20-100 mesh; And / or, the preparation method of the modified quartz sand comprises sequentially performing physical modification and chemical modification on the quartz sand.

3. The long-lasting temperature resistant lost circulation drilling fluid of claim 2, wherein, The physical modification is shot peening treatment; and / or, the chemical modification is coating bisphenol A epoxy resin on the surface of the quartz sand by using a thermal method.

4. The long-lasting anti-temperature thermal drilling leak sealing drilling fluid according to any one of claims 1-3, characterized in that, The sheet material is mica sheet; And / or, the particle size of the sheet material is 80-150 mesh.

5. The long-lasting anti-temperature thermal drilling leak sealing drilling fluid according to any one of claims 1-3, characterized in that, The fibrous material is selected from at least one of glass fiber and asbestos fiber; And / or, the particle size of the fibrous material is 55-80 mesh.

6. The long-lasting anti-temperature thermal drilling leak sealing drilling fluid according to any one of claims 1-3, characterized in that, The particle size of the elastic material is 150-300 mesh.

7. The long-lasting temperature-resistant lost circulation drilling fluid of any one of claims 1-3, wherein, The base drilling fluid is water-based drilling fluid and / or oil-based drilling fluid.

8. The long-lasting anti-temperature thermal drilling leak sealing drilling fluid of any one of claims 1-3, wherein, The mass percentage of the lost circulation material is 21-30% based on 100% of the volume of the long-acting temperature-resistant lost circulation drilling fluid while drilling.

9. A method of preparing the long-lasting temperature-resistant lost circulation drilling fluid according to any one of claims 1 to 8, characterized in that, The lost circulation material is sequentially added into the base drilling fluid.

10. The use of the long-acting temperature-resistant lost circulation drilling fluid of any one of claims 1-8 or the long-acting temperature-resistant lost circulation drilling fluid prepared by the preparation method of claim 9 in drilling.

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