Capsule activator, strong plugging slurry and preparation method and application thereof

Abstract

The present invention proposes a capsule activator, a strong plugging plugging slurry, and a preparation method and application thereof. The strong plugging plugging slurry comprises mineral oil, a strong plugging plugging agent and a capsule activator; wherein the capsule activator is a polyvinyl alcohol-coated water and strong water-absorbing sponge particle capsule; by coating the capsule, the water and the components in the strong plugging plugging agent react rapidly near the bottom leaking layer of the well to form a dense, high-strength pressure-bearing plugging layer; the method described in the present invention causes the capsule activator to rupture at the bottom of the well after passing through the nozzle, and the components of the capsule activator and the strong plugging plugging agent react rapidly to form a dense plugging layer, avoiding the problem that the two substances cannot react precisely at a fixed point and cannot be effectively retained in the double liquid method, and the plugging effect is good.

Description

Technical Field

[0001] The invention relates to the technical field of drilling fluid, and in particular to a capsule activator, a strong plugging slurry, and a preparation method and application thereof. Background Art

[0002] In recent years, as oil and gas exploration and development have deepened into shale oil and gas, well leakage has become more prominent. For example, in the Weiyuan-Changning block in Sichuan and Chongqing, well leakage has become a major problem that restricts speed and efficiency. Shale oil and gas drilling usually uses oil-based / synthetic-based drilling fluids, which are expensive and will cause serious economic losses once leakage occurs. According to statistics, leakage in shale oil reservoir formations is related to fractures. At present, the plugging agents for fracture leakage mainly include bridging plugging agents, high water loss plugging agents, temporary plugging plugging agents, expansion plugging agents, cement quick-setting plugging agents, curable plugging agents, composite plugging agents and other types. Among them, the most commonly used is the bridging plugging agent, which is easy to use and has a lower cost than other products. However, conventional bridge plugging materials are mostly hydrophilic materials, which have poor compatibility with oil-based drilling fluids and a small friction coefficient under oil-based wetting conditions, resulting in poor plugging effect and a low success rate of one-time plugging.

[0003] Patent 201010502698.9 provides a double-liquid plugging construction method for drilling. The disadvantage of this solution is that two plugging liquids will mix and react quickly in the high-pressure pipeline when two mud pumps are used to inject the mud into the high-pressure pipeline at the same time, making it difficult to achieve the effect of the two plugging liquids reaching the bottom of the well to react and plug the leaking layer.

[0004] Another existing technical solution: diesel oil-soil slurry is made by mixing diesel oil and soil in a certain proportion. Soil is an oil-repellent material, so it can be made into an oil-based soil mixture with a high solid content. When the mixture is pumped into the leaking layer and contacts water, the suspended soil particles begin to hydrate and separate from the oil to form a tough oil mud block, thereby achieving the purpose of plugging the leak. This solution is mainly used for plugging water-based drilling fluid leakage, and the process scheme described cannot be implemented in plugging oil-based drilling fluid leakage. Summary of the invention

[0005] In order to solve the above problems in the prior art, the present invention proposes a capsule activator, a strong plugging slurry and a preparation method and application thereof.

[0006] In a first aspect, the present invention provides a capsule activator, which is a coated capsule, wherein the coated capsule comprises an inner coating and an outer capsule shell; the capsule shell comprises a toughening agent and polyvinyl alcohol, and the coating comprises water and sponge particles.

[0007] In a second aspect, the present invention provides a method for preparing the activator, comprising the following steps:

[0008] S1: dispersing a toughening agent in a polyvinyl alcohol aqueous solution to obtain a first mixture;

[0009] S2: dispersing the highly absorbent sponge particles in a calcium chloride solution to obtain a second mixture;

[0010] S3: mixing the first mixture obtained in step S1 and the second mixture obtained in step S2 to perform a first reaction to obtain a first reaction product;

[0011] S4: adding paraffin emulsion to the first reaction product obtained in step S3 to carry out a second reaction, cooling, filtering, washing, and freeze-drying to obtain polyvinyl alcohol-coated water and highly absorbent sponge particle capsules, i.e., capsule activator.

[0012] As a specific embodiment of the present invention, in the step S1, the number average molecular weight of the polyvinyl alcohol is 170,000-220,000, and the degree of alcoholysis is 85-89%; and / or the concentration of the polyvinyl alcohol aqueous solution is 3-15wt%; and / or the toughening agent is a fiber with a length of 0.2-2mm, preferably including at least one of sisal fiber, palm fiber, coconut shell fiber, and jute fiber; and / or the amount of the toughening agent added is 0.5-3wt% of the polyvinyl alcohol aqueous solution by mass ratio.

[0013] As a specific embodiment of the present invention, in step S2, the particle size of the highly absorbent sponge particles is 2-8 mm; and / or the volume water absorption rate of the highly absorbent sponge particles is 40-70%; and / or the added amount of the highly absorbent sponge particles is 50-75% of the calcium chloride solution by volume; and / or the mass fraction of the calcium chloride solution is 10-20wt%.

[0014] As a specific embodiment of the present invention, in the step S3, the first mixture and the second mixture are mixed in a volume ratio of 4:3; the first reaction conditions include: air atmosphere, the reaction temperature is 40 to 60° C., and the reaction time is 0.3 to 0.6 h.

[0015] As a specific embodiment of the present invention, in step S4, the mass fraction of the paraffin emulsion is 5-10wt%, preferably, the paraffin emulsion contains 0.5% of emulsifier SP80; the second reaction conditions include: inert atmosphere, preferably nitrogen atmosphere; the reaction temperature is 80-90°C; the reaction time is 1-2h; the washing includes washing with anhydrous ethanol. The addition of paraffin wax mainly improves the emulsification coating performance.

[0016] In a third aspect, the present invention provides a strong plugging and plugging slurry, the components of which include: mineral oil, the capsule activator and a strong plugging and plugging agent.

[0017] As a specific embodiment of the present invention, the strong plugging agent comprises, by mass ratio, 60-80wt% sodium bentonite, 10-30wt% red mud, 3-5wt% accelerator, and 2-5wt% enhancer.

[0018] As a specific embodiment of the present invention, the sodium bentonite is at least one of Xiazijie sodium soil or Wyoming sodium soil; the sodium bentonite has a montmorillonite content of 75-90wt%, a attapulgite content of 3-8wt%, a feldspar content of 2-5wt%, and a slurry rate of 16-25m 3 / t;

[0019] As a specific embodiment of the present invention, the red mud is preferably the polluted waste residue discharged when the aluminum industry extracts alumina; the red mud particle size is 0.09-0.13 mm; the red mud contains 18-30wt% Al2O3, 15-25wt% SiO2, 12-17wt% CaO and 8-15wt% Na2O;

[0020] As a specific embodiment of the present invention, the accelerator is at least one of CaO, MgO and ZnO;

[0021] As a specific embodiment of the present invention, the reinforcing agent is at least one of lithium magnesium silicate or aluminum magnesium silicate.

[0022] As a specific embodiment of the present invention, the mineral oil includes white oil or diesel;

[0023] As a specific implementation of the present invention, the mass ratio of the mineral oil, the capsule activator and the strong plugging agent is 1: (0.8-1.5): (0.2-0.5).

[0024] In a fourth aspect, the present invention provides a method for preparing the strong plugging slurry, comprising the following steps:

[0025] A: Add the strong plugging agent into the mineral oil and fully disperse it to obtain the first mixture;

[0026] B: Add capsule activator to the first mixture obtained in step A and fully disperse it to obtain strong plugging slurry.

[0027] As a specific embodiment of the present invention, in step A, the amount of the strong plugging agent added is 80-150wt% of the mineral oil;

[0028] The sufficient dispersion is preferably carried out by high-speed stirring; the stirring rate is 8000-11000 rpm; and the stirring time is 20-40 min.

[0029] As a specific embodiment of the present invention, in step B, the amount of the capsule activator added is 20-50wt% of the mineral oil;

[0030] The sufficient dispersion is preferably performed by low-speed stirring; the stirring rate is 300 to 500 rpm; and the stirring time is 10 to 30 min.

[0031] The above raw materials in the present invention can be prepared in-house or commercially available, and the present invention is not particularly limited thereto.

[0032] In a fifth aspect, the present invention provides application of the strong plugging slurry in the field of oil-based drilling fluid.

[0033] As a specific embodiment of the present invention, the strong plugging slurry is used as a plugging section plug and injected into the leaking layer to plug the leak.

[0034] The technical principle of the present invention is: after the oil-based drilling fluid is injected into the wellbore with a strong plugging slurry, the capsule activator will break and release free water after passing through the drill bit water hole under the action of high temperature, shear, extrusion and alkalinity, causing the components in the strong plugging agent to react with the water phase. First, the sodium-based bentonite, which accounts for the main component, absorbs water and hydrates and swells when it encounters water, gelling and precipitating to form a gel layer with a certain structural strength. Red mud, silicate inorganic gel enhancers, promoters, toughening agents, etc. synergistically improve the plugging strength of the gel layer.

[0035] The condition for the capsule activator to release water is that the shear rate is greater than 4000s at room temperature. -1 When the capsule outer wall is broken quickly, the free water contained in it is released. Under the action of pressure, the free water absorbed by the strong water-absorbing sponge can be released in large quantities. At the same time, the increase in temperature and alkaline conditions can significantly increase the degree of breakage of the capsule activator. According to drilling fluid mechanics, the shear rate in the drill pipe during the circulation of drilling fluid is usually 100 to 1000 s -1 , the annular space is usually 50~250s -1 , the highest point is at the drill nozzle, about 10000~100000s -1 Therefore, the capsule shell can only be broken when the capsule activator passes through the drill bit nozzle, thereby ensuring that the leakage layer at the bottom of the well is broken to release free water and react with other components to form a gelled precipitate.

[0036] The reinforcing agent is a silicate inorganic gel. This type of material is composed of a large number of silicate platelets. The crystal structure of silicate platelets is unique. The ideal structure of its molecule can be divided into three layers: two layers of silicon dioxide (silicon oxygen tetrahedron) with a layer of metal oxide (octahedron) embedded in the middle. The metal oxide middle layer can be mainly composed of Al 3+ Composition, partly Mg 2+The interlayers are negatively charged due to insufficient cation charge. In order to balance these negative charges, Ca is adsorbed between the layers. 2+ Mg 2+ , K + 、Na + Such inorganic gel is called magnesium aluminum silicate inorganic gel; in addition, the metal oxide layer can also be mainly composed of Mg 2+ Composition, partly by Li + The negative charge between the layers is replaced by the insufficient cationic charge, which requires the adsorption of cations to balance the charge, thus forming an inorganic magnesium silicate lithium gel.

[0037] The powder form of inorganic gel contains a large number of regular flake structure aggregates. The activator in the plugging slurry will break and release a large amount of free water under the high shear rate of the drill bit water hole. The agent-free gel dispersed in the oil phase will be hydrated when it meets water and passes through the high-speed shear of the drill bit water hole. The cationic charge adsorbed between the flake structure layers will be dragged to the surface of the chip by electrostatic attraction. At this time, a large amount of water penetrates into the interlayer and swells to cause the flake structure to depolymerize. A new balance begins to be established between the chips. Finally, the chips overlap each other to form a three-dimensional network structure, also known as a "card house" structure. At this time, the inorganic gel is dissolved in water into a highly thixotropic gel in the macroscopic view. The gel has good suspension and thixotropic properties. It can not only suspend the solid phase material in the plugging slurry, but also as the plugging slurry leaks into the formation, the leakage rate decreases and the viscosity increases rapidly, which is conducive to the rapid formation of the plugging layer.

[0038] Red mud is a byproduct of the aluminum industry when extracting alumina. Its main mineral components are alumina, silicon dioxide and alkali. The oxides in the red mud undergo a "depolymerization-condensation" reaction in an alkaline environment, and then form a hydrate with a gelled structure through further stimulation by accelerators such as calcium oxide. At the same time, red mud and silicate inorganic gels can also synergize. The metal ions in the two interact with silicon-containing compounds to enhance the curing ability and further improve the strength of the plugging layer.

[0039] The toughening agent not only increases the strength of the coated capsule, but also breaks the capsule into pieces and disperses them into the gel through the nozzle, which improves the toughness and tensile resistance of the gelled precipitate through its high friction surface. The highly absorbent sponge in the capsule activator is an elastic mesh compressible material. Under the action of pressure difference, it can be compressed and deformed in advance to enter the crack to form a retention, providing a bridge for the later formation of a dense pressure-bearing plugging layer. The synergistic effect of the two greatly improves the retention capacity.

[0040] The capsule activator and strong plugging slurry of the present invention are mainly used for plugging the leakage of oil-based drilling fluid in formations with large fractures. The on-site application process is as follows: first, prepare 10m3 of 3Mineral oil (white oil or diesel), then add 80-150% by mass of oil-based drilling fluid strong plugging agent, stir at high speed for 30 minutes, then continue to add 20-50% by mass of capsule activator, stir at low speed for 20 minutes to make it evenly dispersed; then, simplify the drilling tool structure and drill down to 50-100m above the leaking layer; use a mud pump to pump the prepared strong plugging slurry into the wellbore, use the oil-based drilling fluid in the circulation tank to replace the slurry, and calculate that the strong plugging slurry replaces the drill bit water hole for about 5m 3 After that, drill 200m, close the wellbore plugging device, and start squeezing. For every 1MPa increase in pressure, maintain the pressure for 3min, repeat squeezing 3-5 times, and start the pump circulation after 2h of rest to verify the plugging effect.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. Compared with simple bridging plugging, the capsule activator and strong plugging plugging slurry of the present invention have strong adaptability to cracks and have a wide range of plugging capabilities. The formed gel precipitate is dense, has high toughness, strong plugging ability, and is not easy to leak again. It solves the problem of lack of existing plugging materials for oil-based drilling fluids and the difficulty of oil-based plugging.

[0043] 2. The capsule activator and strong plugging slurry of the present invention cause the capsule to rupture at the bottom of the well after passing through the nozzle. The components of the capsule activator and the strong plugging slurry react rapidly to form a dense plugging layer, thus avoiding the problem of being unable to achieve precise point-to-point reaction of the two substances and being unable to effectively retain them in the double-liquid method, and achieving a good plugging effect.

[0044] 3. The strong plugging slurry of the present invention has good plugging effect and significantly reduces the intrusion depth of the sand bed. In the field application example, the traditional bridge slurry plugging was ineffective twice, delaying the construction period by 28 hours. The strong plugging slurry of the present invention was used to successfully plug the leak once in 6 hours, and the plugging period was shortened by 78.6% on average.

[0045] 4. The strong plugging agent described in the present invention uses industrial waste red mud, which realizes the resource utilization of solid waste from the aluminum industry and reduces environmental pollution. Other raw materials used are green and environmentally friendly and do not pollute the environment. At the same time, this method has a high plugging success rate, greatly shortens the plugging time, reduces the time efficiency of complex plugging treatment, and saves the comprehensive drilling cost. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with specific embodiments, but they do not constitute any limitation to the present invention.

[0047] In each embodiment of the present invention, the specific information of the reagents used is as follows:

[0048] Polyvinyl alcohol, number average molecular weights of 215,000, 174,000, 190,000, 205,000 and 180,000, respectively, alcoholysis degrees of 86.5%, 89%, 87.6% and 85%, respectively, Shanghai trial, Sinopharm Chemical Reagent Co., Ltd.;

[0049] Lithium magnesium silicate, Hemmings, purity 90%, Shandong Yousuo Chemical Technology Co., Ltd.;

[0050] Magnesium aluminum silicate, Ecosol, PT-XL58F, purity 90%, Shandong Yousuo Chemical Technology Co., Ltd.;

[0051] CaO, analytical grade, Wuxi Yatai United Chemical Co., Ltd.;

[0052] MgO, analytical grade, Wuxi Yatai United Chemical Co., Ltd.;

[0053] ZnO, analytical grade, Wuxi Yatai United Chemical Co., Ltd.;

[0054] Sodium bentonite, drilling soil, Shengli Oilfield Boyu Mud Technology Co., Ltd.;

[0055] Red mud, Shandong Weiqiao Aluminum & Electricity Co., Ltd., Al2O3 content is 25.6%, SiO2 content is 19.8%, CaO content is 13.8%, and Na2O content is 13.7%;

[0056] Sisal fiber, fiber length 0.2-2 mm, Jinan Derun Hemp Industry Co., Ltd.;

[0057] Palm fiber, fiber length 0.2-2 mm, Jinan Derun Hemp Industry Co., Ltd.;

[0058] Coconut shell fiber, fiber length 0.2-2 mm, Jinan Derun Hemp Industry Co., Ltd.;

[0059] Jute fiber, fiber length 0.2-2 mm, Jinan Derun Hemp Industry Co., Ltd.;

[0060] White oil, 5#, Jingmen Petrochemical;

[0061] Diesel, 92#, Kenli Refinery;

[0062] Calcium chloride, analytical grade, Sinopharm Chemical Reagent Co., Ltd.;

[0063] Strong water-absorbent sponge particles, volume water absorption rate 65%, Dongguan Tengyue Sponge Products Co., Ltd.;

[0064] Paraffin wax, analytical grade, purity 99%, Wuxi Yatai United Chemical Co., Ltd.

[0065] Example 1

[0066] This embodiment provides a capsule activator and a preparation method thereof, the specific details of which are as follows:

[0067] S1: Dissolve polyvinyl alcohol with a molecular weight of 215,000 (high degree of polymerization) and a degree of alcoholysis of 86.5% in hot water at 75°C to obtain a polyvinyl alcohol aqueous solution with a mass fraction of 4%.

[0068] S2: Add 2% by mass of coconut shell fiber to the polyvinyl alcohol solution, stir to fully disperse it, and disperse 75% by volume of highly absorbent sponge particles with a particle size of 6 mm in a 15wt% calcium chloride solution.

[0069] S3: Mix the calcium chloride solution containing the highly absorbent sponge particles and the polyvinyl alcohol solution in a volume ratio of 3:4 in the air atmosphere of the reactor, and heat the reactor to 50°C.

[0070] S4: Add 10wt% paraffin emulsion, wherein the paraffin emulsion contains 0.5wt% emulsifier SP80, place it in a high-speed stirrer at a stirring rate of 10000rpm and stir it evenly, heat it to 85°C, react for 1.5 hours, and finally cool it to room temperature, filter, wash with anhydrous ethanol, and freeze-dry to obtain polyvinyl alcohol-coated water and strong water-absorbing sponge particle capsules, i.e., capsule activator.

[0071] Example 2

[0072] This embodiment provides a capsule activator and a preparation method thereof, the specific details of which are as follows:

[0073] S1: Dissolve polyvinyl alcohol with a molecular weight of 174,000 (high degree of polymerization) and a degree of alcoholysis of 89% in hot water at 75°C to obtain a polyvinyl alcohol aqueous solution with a mass fraction of 3%.

[0074] S2: Add 0.5% palm fiber by mass to the polyvinyl alcohol solution, stir to fully disperse it, and disperse 60% by volume of highly absorbent sponge particles with a particle size of 2 mm in a 20wt% calcium chloride solution.

[0075] S3: In a reactor, the calcium chloride solution containing the highly absorbent sponge particles and the polyvinyl alcohol solution are mixed in a volume ratio of 3:4 under air atmosphere, and the reactor is heated to 50°C.

[0076] S4: Add 5wt% paraffin emulsion, wherein the paraffin emulsion contains 0.5wt% emulsifier SP80, place it in a high-speed stirrer at a stirring rate of 10000rpm and stir it evenly, heat it to 85°C, react for 1.5 hours, and finally cool it to room temperature, filter, wash with anhydrous ethanol, and freeze-dry to obtain polyvinyl alcohol-coated water and strong water-absorbing sponge particle capsules, i.e., capsule activator.

[0077] Example 3

[0078] This embodiment provides a capsule activator and a preparation method thereof, the specific details of which are as follows:

[0079] S1: Dissolve polyvinyl alcohol with a molecular weight of 190,000 (high degree of polymerization) and a degree of alcoholysis of 87.6% in hot water at 80°C to obtain a polyvinyl alcohol aqueous solution with a mass fraction of 4.5%.

[0080] S2: Add 1.5% by mass of sisal fiber to the polyvinyl alcohol solution, stir to fully disperse it, and disperse 50% by volume of highly absorbent sponge particles with a particle size of 4 mm in a 10wt% by mass calcium chloride solution.

[0081] S3: In a reactor, the calcium chloride solution containing the highly absorbent sponge particles and the polyvinyl alcohol solution are mixed in a volume ratio of 3:4 under air atmosphere, and the reactor is heated to 50°C.

[0082] S4: Add 8wt% paraffin emulsion, wherein the paraffin emulsion contains 0.5wt% emulsifier SP80, place it in a high-speed stirrer at a stirring rate of 10000rpm and stir it evenly, heat it to 85°C, react for 1.5 hours, and finally cool it to room temperature, filter, wash with anhydrous ethanol, and freeze-dry to obtain polyvinyl alcohol-coated water and strong water-absorbing sponge particle capsules, i.e., capsule activator.

[0083] Example 4

[0084] This embodiment provides a capsule activator and a preparation method thereof, the specific details of which are as follows:

[0085] S1: Dissolve polyvinyl alcohol with a molecular weight of 205,000 (high degree of polymerization) and a degree of alcoholysis of 85% in hot water at 60°C to obtain a polyvinyl alcohol aqueous solution with a mass fraction of 2.5%.

[0086] S2: Add 3% jute fiber by mass to the polyvinyl alcohol solution and stir to fully disperse it. Disperse 8mm strong water-absorbing sponge particles by volume at 65% in 12wt% calcium chloride solution.

[0087] S3: In a reactor, the calcium chloride solution containing the highly absorbent sponge particles and the polyvinyl alcohol solution are mixed in a volume ratio of 3:4 under air atmosphere, and the reactor is heated to 50°C.

[0088] S4: Add 9wt% paraffin emulsion, wherein the paraffin emulsion contains 0.5wt% emulsifier SP80, place it in a high-speed stirrer at a stirring rate of 10000rpm and stir it evenly, heat it to 85°C, react for 1.5 hours, and finally cool it to room temperature, filter, wash with anhydrous ethanol, and freeze-dry to obtain polyvinyl alcohol-coated water and strong water-absorbing sponge particle capsules, i.e., capsule activator.

[0089] Example 5

[0090] This embodiment provides a capsule activator and a preparation method thereof, the specific details of which are as follows:

[0091] S1: Dissolve polyvinyl alcohol with a molecular weight of 180,000 (high degree of polymerization) and a degree of alcoholysis of 86.5% in hot water at 80°C to obtain a polyvinyl alcohol aqueous solution with a mass fraction of 3.5%.

[0092] S2: Add 2% by mass of sisal fiber to the polyvinyl alcohol solution, stir to fully disperse it, and disperse 55% by volume of highly absorbent sponge particles with a particle size of 5 mm in a 16wt% calcium chloride solution.

[0093] S3: In a reactor, the calcium chloride solution containing the highly absorbent sponge particles and the polyvinyl alcohol solution are mixed in a volume ratio of 3:4 under air atmosphere, and the reactor is heated to 50°C.

[0094] S4: Add 6wt% paraffin emulsion, wherein the paraffin emulsion contains 0.5wt% emulsifier SP80, place it in a high-speed stirrer at a stirring rate of 10000rpm and stir it evenly, heat it to 85°C, react for 1.5 hours, and finally cool it to room temperature, filter, wash with anhydrous ethanol, and freeze-dry to obtain polyvinyl alcohol-coated water and strong water-absorbing sponge particle capsules, i.e., capsule activator.

[0095] Test Example 1

[0096] A high-speed stirring experiment under heating conditions was used to verify whether the water capsule coated with the capsule activator was broken or not. The experimental method was to add 30% of the capsule activator by mass volume ratio to 100mL of white oil, and at the same time disperse the powdered color-changing silica gel in the white oil, adjust the temperature and stirring speed, and judge whether the capsule activator was broken by the color change of the color-changing silica gel. If the color-changing silica gel changes from blue to red, it indicates that the capsule activator is broken and free water is released, and the color-changing silica gel absorbs water and changes color. The experimental results are shown in Table 1.

[0097] Table 1 Results of the rupture test of capsule activator-coated water capsules under different conditions

[0098]

[0099]

[0100] Example 6

[0101] This embodiment provides a strong plugging plugging agent, a strong plugging plugging slurry and a preparation method thereof, and the specific details are as follows:

[0102] A strong plugging agent for oil-based drilling fluid comprises 80wt% of sodium-based bentonite, 14wt% of red mud, 3wt% of calcium oxide and 3wt% of lithium magnesium silicate reinforcing agent.

[0103] A method for preparing a strong plugging slurry for oil-based drilling fluid is as follows:

[0104] A: Based on the mass of white oil, first add 150wt% of oil-based drilling fluid plugging agent into the white oil, stir at a high speed of 10000rpm for 30min to fully disperse;

[0105] B: Then continue to add 20wt% of the white oil mass of the capsule activator prepared in Example 1, and stir at a low speed of 400rpm for 20min to disperse it evenly to obtain a strong plugging slurry for oil-based drilling fluid.

[0106] Example 7

[0107] This embodiment provides a strong plugging plugging agent, a strong plugging plugging slurry and a preparation method thereof, and the specific details are as follows:

[0108] A strong plugging agent for oil-based drilling fluid comprises 60wt% of sodium-based bentonite, 30wt% of red mud, 5wt% of calcium oxide and 5wt% of magnesium aluminum silicate reinforcing agent in a mass ratio.

[0109] A method for preparing a strong plugging slurry for oil-based drilling fluid is as follows:

[0110] A: Based on the mass of white oil, first add 100wt% of oil-based drilling fluid plugging agent into the white oil, stir at a high speed of 10000rpm for 30min to fully disperse;

[0111] B: Then continue to add 25wt% of the white oil mass of the capsule activator prepared in Example 3, and stir at a low speed of 500rpm for 20min to disperse it evenly to obtain a strong plugging slurry for oil-based drilling fluid.

[0112] Example 8

[0113] This embodiment provides a strong plugging plugging agent, a strong plugging plugging slurry and a preparation method thereof, and the specific details are as follows:

[0114] A strong plugging agent for oil-based drilling fluid comprises 72wt% of sodium-based bentonite, 20wt% of red mud, 4wt% of calcium oxide and 4wt% of lithium magnesium silicate enhancer in terms of mass ratio.

[0115] A method for preparing a strong plugging slurry for oil-based drilling fluid is as follows:

[0116] A: Based on the diesel mass, first add 80wt% of the oil-based drilling fluid plugging agent into the diesel, stir at a high speed of 10000rpm for 30min to fully disperse;

[0117] B: Then continue to add the capsule activator prepared in Example 5 in an amount of 50 wt% of the diesel mass, and stir at a low speed of 500 rpm for 20 minutes to disperse it evenly to obtain a strong plugging slurry for oil-based drilling fluid.

[0118] Example 9

[0119] This embodiment provides a strong plugging plugging agent, a strong plugging plugging slurry and a preparation method thereof, and the specific details are as follows:

[0120] A strong plugging agent for oil-based drilling fluid comprises: 80wt% sodium-based bentonite, 14wt% red mud, 3wt% calcium oxide, and 3wt% lithium magnesium silicate reinforcing agent.

[0121] A method for preparing a strong plugging slurry for oil-based drilling fluid is as follows:

[0122] A: Based on the diesel mass, add 100wt% of oil-based drilling fluid plugging agent into the diesel, stir at a high speed of 10000rpm for 30min to fully disperse;

[0123] B: Then, 40 wt % of the capsule activator prepared in Example 5 was added, and the mixture was stirred at a high speed of 10000 rpm for 20 min to obtain a plugging slurry for oil-based drilling fluid.

[0124] Comparative Example 1

[0125] This comparative example provides a strong plugging plugging agent, a strong plugging plugging slurry and a preparation method thereof, and the specific details are as follows:

[0126] A strong plugging agent for oil-based drilling fluid comprises 80wt% of sodium-based bentonite, 14wt% of red mud, 3wt% of calcium oxide and 3wt% of lithium magnesium silicate reinforcing agent.

[0127] A method for preparing a strong plugging slurry for oil-based drilling fluid is as follows: based on the mass of white oil, 100% of the strong plugging agent for oil-based drilling fluid is added to the white oil, and the mixture is stirred at a high speed of 10000 rpm for 30 minutes to fully disperse the mixture.

[0128] Comparative Example 2

[0129] This comparative example provides a strong plugging plugging agent, a strong plugging plugging slurry and a preparation method thereof, and the specific details are as follows:

[0130] A strong plugging agent for oil-based drilling fluid comprises 95wt% of sodium-based bentonite and 5wt% of calcium oxide.

[0131] A method for preparing a strong plugging slurry for oil-based drilling fluid is as follows:

[0132] A: Based on the mass of white oil, add 100wt% of oil-based drilling fluid plugging agent into the white oil, stir at high speed for 30 minutes, and fully disperse;

[0133] B: Then, 20% of the capsule activator prepared in Example 1 was added, and the mixture was stirred at a low speed of 500 rpm for 20 minutes to disperse the capsule activator evenly, thereby obtaining a strong plugging slurry for oil-based drilling fluid.

[0134] Comparative Example 3

[0135] This comparative example provides a strong plugging plugging agent, a strong plugging plugging slurry and a preparation method thereof, and the specific details are as follows:

[0136] A strong plugging agent for oil-based drilling fluid comprises 80wt% of sodium-based bentonite, 19wt% of red mud and 1wt% of polyurethane fiber with a pore size of 10ppi.

[0137] A method for preparing a strong plugging slurry for oil-based drilling fluid is as follows:

[0138] A: Based on the diesel mass, add 100wt% of oil-based drilling fluid plugging agent into the diesel, stir at a high speed of 10000rpm for 30min to fully disperse;

[0139] B: Then, 30% of the capsule activator prepared in Example 5 was added, and the mixture was stirred at a low speed of 500 rpm for 20 minutes to disperse the capsule activator evenly, thereby obtaining a strong plugging slurry for oil-based drilling fluid.

[0140] Comparative Example 4

[0141] This comparative example provides a strong plugging plugging agent, a strong plugging plugging slurry and a preparation method thereof, and the specific details are as follows:

[0142] A strong plugging agent for oil-based drilling fluid comprises: 97wt% sodium-based bentonite and 3wt% sisal fiber toughening agent with a length of 2mm.

[0143] A method for preparing a strong plugging slurry for oil-based drilling fluid is as follows:

[0144] A: Based on the mass of white oil, add 100wt% of oil-based drilling fluid plugging agent into the white oil, stir at a high speed of 10000rpm for 30min to fully disperse;

[0145] B: Then, 35 wt % of the capsule activator prepared in Example 3 was added, and the mixture was stirred at a low speed of 500 rpm for 20 min to disperse the capsule activator evenly, thereby obtaining a strong plugging slurry for oil-based drilling fluid.

[0146] Test Example 2

[0147] This experiment uses a high-temperature and high-pressure visual sand bed test device for evaluation. First, fill the high-temperature and high-pressure visual sand bed evaluation device with quartz sand with a particle size of 2-3mm, and the quartz sand filling height is 50cm. Then pour the prepared oil-based drilling fluid into the upper container of the high-temperature and high-pressure sand bed test device with a strong plug plugging slurry, connect the pipeline, heat it to 120℃, open the valve and quickly increase the pressure to 5MPa (simulating high-speed shear), and the plugging slurry enters the sand bed. Record the invasion depth and leakage of the plugging slurry in the sand bed for 30 minutes.

[0148] Table 2 Test results of the embodiments and comparative examples

[0149]

[0150] It can be seen from the experimental results that without adding capsule activator, the plugging layer cannot be formed. The reaction of oil-based drilling fluid plugging agent with capsule activator can form a dense pressure-bearing plugging layer, the drilling fluid loss invasion depth is shallow, and the plugging effect is good. The addition of red mud, accelerator, enhancer, toughening agent, etc. greatly improves the pressure-bearing plugging effect.

[0151] Application Examples

[0152] The FY1-X well in Shengli Oilfield experienced leakage at 4765.3m, with a leakage rate of 22.5m 3 / h, the bridge plugging was used twice to plug the leak but it was ineffective, so it was decided to use the strong plugging plugging slurry provided by the present invention to plug the leak, and the strong plugging plugging slurry prepared in Example 6 was used for plugging the leak, and the specific details are as follows:

[0153] Add 20m3 of white oil to the drilling fluid tank on site 3 , based on the mass of white oil, add 150wt% of the strong plugging agent for oil-based drilling fluid prepared in Example 6, stir at a high speed of 10000rpm for 30min to fully disperse; continue to add 20wt% of the capsule activator prepared in Example 1, stir at a low speed of 500rpm for 20min to make it evenly dispersed. Drill down to 4762m, use a drilling fluid pump to pump the strong plugging slurry prepared in Example 6 into the wellbore, and replace 35m 3Then, the drill was pulled up to 4200m and the drilling fluid was squeezed in for 3m 3 The casing pressure was 5.0MPa. After stopping the pump for 10 minutes, the casing pressure dropped to 4.6MPa. The pressure was stable. There was no leakage in the large-volume circulation, and the leak was plugged successfully.

[0154] In summary, compared with simple bridging plugging, the capsule activator and strong plugging slurry of the present invention have strong adaptability to cracks and a wide range of plugging capabilities. The formed gel precipitate is dense, highly tough, has a strong plugging ability, and is not prone to re-leakage. The problem of the lack of existing plugging materials for oil-based drilling fluids and the difficulty of oil-based plugging is solved. The method described in the present invention causes the capsule to rupture at the bottom of the well after passing through the nozzle, and the two components react rapidly to form a dense plugging layer, avoiding the problem of the inability to achieve precise point-to-point reaction of the two substances and the inability to effectively retain them in the double-liquid method, and the plugging effect is good.

[0155] Any numerical value mentioned in the present invention, if there is only an interval of two units between any minimum value and any maximum value, includes all values ​​from the minimum value to the maximum value each time increasing by one unit. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is declared to be 50-90, in this specification it means that 51-89, 52-88... and 69-71 and 70-71 are specifically listed. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 can be appropriately considered as a unit. These are just some specially specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0156] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to 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 words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A capsule activator, characterized in that: The capsule activator is a coated capsule, which includes an inner coating and an outer capsule shell; the capsule shell includes a toughening agent and polyvinyl alcohol, the coating includes water and highly absorbent sponge particles, and the volume water absorption rate of the highly absorbent sponge particles is 40-70%; the toughening agent is a fiber with a length of 0.2-2 mm.

2. A method for preparing a capsule activator, characterized in that: The following steps are involved: S1: dispersing a toughening agent in a polyvinyl alcohol aqueous solution to obtain a first mixture; S2: dispersing the highly absorbent sponge particles in a calcium chloride solution to obtain a second mixture; the highly absorbent sponge particles have a volume water absorption rate of 40-70%; S3: mixing the first mixture obtained in step S1 and the second mixture obtained in step S2 to perform a first reaction to obtain a first reaction product; S4: adding paraffin emulsion to the first reaction product obtained in step S3 to carry out a second reaction, cooling, filtering, washing, and freeze-drying to obtain polyvinyl alcohol-coated water and strong water-absorbing sponge particle capsules, i.e., capsule activators; the toughening agent is a fiber with a length of 0.2-2 mm.

3. The preparation method according to claim 2, characterized in that: In step S1, the number average molecular weight of the polyvinyl alcohol is 170,000-220,000, the alcoholysis degree is 85-89%; and / or the concentration of the polyvinyl alcohol aqueous solution is 3-15wt%; And / or, the toughening agent comprises at least one of sisal fiber, palm fiber, coconut shell fiber and jute fiber; and / or the toughening agent is added in an amount of 0.5-3wt% of the polyvinyl alcohol aqueous solution in terms of mass ratio.

4. The preparation method according to claim 2 or 3, characterized in that: In step S2, the particle size of the highly absorbent sponge particles is 2-8 mm; and / or the amount of the highly absorbent sponge particles added is 50-75% by volume of the calcium chloride solution; And / or, the mass fraction of the calcium chloride solution is 10-20wt%.

5. The preparation method according to claim 2 or 3, characterized in that: In step S3, the first mixture and the second mixture are mixed in a volume ratio of 4:3; The first reaction conditions include: air atmosphere, the reaction temperature is 40-60° C., and the reaction time is 0.3-0.6 h.

6. The preparation method according to claim 2 or 3, characterized in that: In the step S4, the mass fraction of the paraffin emulsion is 5-10wt%; The second reaction conditions include: an inert atmosphere; a reaction temperature of 80-90° C.; a reaction time of 1-2 h; And / or, the washing comprises washing with anhydrous ethanol.

7. The preparation method according to claim 6, characterized in that: In step S4, the paraffin emulsion contains 0.5% of emulsifier SP80; And / or, the second reaction condition includes: a nitrogen atmosphere.

8. A strong plugging slurry, characterized in that: Its components include: mineral oil, the capsule activator according to claim 1 or the capsule activator obtained by the preparation method according to any one of claims 2 to 7, and a strong plugging agent; the strong plugging agent components include, by mass ratio: 60-80wt% sodium bentonite, 10-30wt% red mud, 3-5wt% accelerator, and 2-5wt% reinforcing agent; the accelerator is at least one of CaO, MgO, and ZnO; The reinforcing agent is at least one of lithium magnesium silicate or aluminum magnesium silicate.

9. The strong plugging slurry according to claim 8 is characterized in that: The sodium-based bentonite is at least one of Xiazijie sodium soil or Wyoming sodium soil; and / or the sodium-based bentonite has a montmorillonite content of 75-90wt%, an attapulgite content of 3-8wt%, a feldspar content of 2-5wt%, and a slurry rate of 16-25m 3 / t; And / or, the red mud is polluting waste slag discharged when alumina is extracted in the aluminum industry.

10. The strong plugging slurry according to claim 9 is characterized in that: The red mud particle size is 0.09-0.13 mm; and / or the Al2O3 content in the red mud is 18-30wt%, and / or the SiO2 content is 15-25wt%, and / or the CaO content is 12-17wt%, and / or the Na2O content is 8-15wt%.

11. The strong plugging slurry according to claim 8 is characterized in that: The mineral oil includes white oil or diesel; And / or, the mass ratio of the mineral oil, the strong plugging agent and the capsule activator is 1: (0.8-1.5): (0.2-0.5).

12. A method for preparing the strong plugging slurry according to any one of claims 8 to 11, characterized in that: The following steps are involved: A: Adding a strong plugging agent into mineral oil, mixing and dispersing, to obtain a first mixture; B: Add capsule activator to the first mixture obtained in step A, mix and disperse to obtain strong plugging slurry.

13. The preparation method according to claim 12, characterized in that: In step A, the amount of the strong plugging agent added is 80-150wt% of the mineral oil; And / or, the stirring and dispersing is high-speed stirring.

14. The preparation method according to claim 13, characterized in that: In the step A, the stirring rate is 8000-11000 rpm; and / or the stirring time is 20-40 min.

15. The preparation method according to any one of claims 12 to 14, characterized in that: In step B, the amount of the capsule activator added is 20-50wt% of the mineral oil; And / or, the stirring and dispersing is low-speed stirring.

16. The preparation method according to claim 15, characterized in that: In the step B, the stirring rate is 300-500 rpm; and / or the stirring time is 10-30 min.

17. Use of the strong plugging and plugging slurry described in any one of claims 8 to 11 or the strong plugging and plugging slurry prepared by the preparation method described in any one of claims 12 to 16 in the field of oil-based drilling fluids.

18. The use according to claim 17, characterized in that The strong plugging slurry is used as a plugging section and injected into the leaking layer to plug the leak.

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