Parent type high-temperature-resistant micro-nano plugging agent and method for hard and brittle shale borehole wall stabilization using the same

Abstract

The application discloses a kind of parent type high-temperature-resistant micro-nano plugging agent and the method for hard and brittle mud shale well wall stability using it, steps are as follows: configuration potassium chloride amine-based water-based drilling fluid base paste;Continuously drill and judge the depth and position of entering mud shale formation;Drilling fluid sampling is carried out, and parent type high-temperature-resistant micro-nano plugging agent, parent type polymeric fiber while drilling plugging agent is added, and strong plugging water-based drilling fluid sample is prepared and evaluation test is carried out;According to the test results, the amount of parent type high-temperature-resistant micro-nano plugging agent and parent type polymeric fiber while drilling plugging agent required to be added in the total amount of drilling fluid circulation at construction site is calculated;Through slurry mixing funnel, parent type high-temperature-resistant micro-nano plugging agent and parent type polymeric fiber while drilling plugging agent are evenly added into drilling fluid in one cycle of drilling fluid, i.e., strong plugging potassium chloride amine-based drilling fluid is obtained.The application can effectively reduce the failure rate when drilling hard and brittle mud shale formation, and improve the well wall stability.

Description

Technical Field

[0001] This invention relates to an amphiphilic high-temperature resistant micro / nano plugging agent, and also to a method for stabilizing the wellbore of hard and brittle shale using the amphiphilic high-temperature resistant micro / nano plugging agent, belonging to the field of oil and gas drilling technology. Background Technology

[0002] With the expansion of oil and gas resource exploration and development, especially the development of unconventional oil and gas resources such as shale gas and tight oil, the instability of brittle shale wellbore has become an urgent problem to be solved. Based on relevant research data, the following conclusions can be drawn: Brittle shale often contains closed or open bedding planes and microfractures, with pore throat sizes generally between 5 and 50 nm and an average pore throat diameter of 10 to 30 nm. Under the combined effects of positive pressure differential and capillary pressure, drilling fluid filtrate easily intrudes along bedding planes and microfractures, causing hydration and expansion of clay minerals between shale layers. This leads to the continuous longitudinal and transverse opening or expansion of the shale along fracture surfaces or bedding planes. Furthermore, drilling fluid filtrate reduces the friction coefficient between fracture surfaces or bedding planes, decreasing the strength of the shale and thus increasing wellbore instability. Therefore, sealing nanoscale pore throats and fractures in shale has become crucial for solving shale wellbore instability.

[0003] The particle size and concentration of the material used as a plugging agent are crucial factors. It must prevent seepage while forming a thin, resilient mud cake. Hard, brittle shale has the smallest pore size of all rocks, and its nanoscale dimensions make plugging extremely difficult. Conventional plugging agents have particles that are too large to penetrate the pore throat; they remain on the surface, a phenomenon known as "sealing the gate." Most of these only address micron-sized pores and are difficult to penetrate the leaking layers within shale, accumulating on the surface without reaching the interior of the cracks, thus failing to achieve a proper seal. Over time, they are easily destroyed by external forces, making this type of seal temporary, and the underlying problems remain. Therefore, only nanoscale plugging agents can effectively seal micro-cracks in shale.

[0004] In recent years, foreign scholars have also conducted extensive research on nano-plugging agents in response to this problem. The particle size of conventional drilling fluid treatment agents is between 0.1 and 100 μm, and they are mainly suitable for plugging formation pore throats and fractures of 0.1 to 1 mm. This indicates that conventional treatment agents in drilling fluids are difficult to form mud cakes in shale formations.

[0005] Chinese invention patent application CN116496765A discloses a wellbore strengthening agent, its preparation method, and its application. The agent is mainly composed of amino-modified silica and a eutectic solvent. Micro-crosslinking of the amino-modified silica and the eutectic solvent improves the wellbore adhesion of the silica particles, reduces pressure sensitivity, and enhances its dispersibility and lubricity in drilling fluid systems, forming a deformable external plugging layer. However, this technical solution is only at the experimental simulation stage and has the following problems:

[0006] 1. Example 1: In the gelation temperature test of the well wall strengthening agent, the method used was roller furnace aging, but the aging time was not specified; the gelation fluidity evaluation was not characterized by professional instruments or data evaluation, but rather by "observing and recording the fluidity of the well wall strengthening agent at different temperatures". The fluidity of the suspension colloid was only observed by the naked eye, without data, which is not convincing.

[0007] 2. Example 3: Testing the compatibility of wellbore strengthening agents in Examples 1 to 28. (1) Testing the changes in the performance of oil-based drilling fluid before and after sample addition. There are too few data items for the performance index analysis of oil-based drilling fluid. In particular, for improving the plugging performance of oil-based drilling fluid, the high temperature and high pressure filtration loss index is very critical, but this application does not mention this index.

[0008] (2) The demulsification voltage of oil-based drilling fluid is a very important indicator. According to relevant requirements, the demulsification voltage of water-in-oil emulsion drilling fluid shall not be lower than 400V. In this application, only Example 2 has a demulsification voltage of 405V, and the rest are all less than 400V. It is questionable whether this meets the requirements for the electrical stability of oil-based drilling fluid.

[0009] (3) An important characteristic of water-in-oil emulsion drilling fluid is that its rheological properties are greatly affected by temperature and pressure. The test examples 1 to 28 in this application did not provide the test temperature, nor did they age the experimental formula, nor did they evaluate the changes in rheological properties before and after aging. The conclusion that "the range of rheological changes basically meets the requirements of on-site construction" is not convincing.

[0010] 3. Patent Experiment Example 4: Evaluation of the plugging performance of drilling fluids prepared with wellbore strengthening agents from Examples 1 to 35 and Comparative Examples 1 to 6. (1) The method used was to measure the plugging performance of the base slurry and various drilling fluids according to API specifications using a non-permeability meter (visual sand bed filter loss meter). This instrument cannot be heated, and the maximum evaluation pressure is 100 psi. Using this instrument to evaluate the plugging performance of oil-based drilling fluids is not very reliable. Currently, instruments used to evaluate drilling fluid plugging performance include: PPT pressure transmission test evaluation, high-temperature and high-pressure sand bed test, and sand disc plugging performance evaluation, which are more reasonable.

[0011] 4. The patented experimental portion consists entirely of indoor research and evaluation, without comprehensive performance evaluation against field-prepared well fluid. Whether the performance in all aspects truly achieves the expected results requires further verification. The methods for evaluating and testing the sealing pressure resistance of the drilling fluid, along with the relevant experimental data, are insufficient to prove its good sealing properties for hard and brittle shale.

[0012] In summary, to improve the wellbore stability of hard and brittle shale, it is necessary to research and develop a powdered material synthesized at high temperatures from nano- and micro-scale rigid materials, fine fibers, and fatty acid plant derivative surfactants. This material, combined with water-based drilling fluid and a salt-resistant, high-temperature-resistant filtration loss reducer, can effectively control filtration loss and sealing performance, thereby solving the problem of wellbore instability in hard and brittle shale. Summary of the Invention

[0013] The primary objective of this invention is to overcome the bottleneck problem existing in the prior art when drilling into hard and brittle shale formations using water-based drilling fluids. It provides a method for stabilizing the wellbore in hard and brittle shale formations using an amphiphilic, high-temperature resistant micro / nano plugging agent. This method can effectively reduce the rate of complex downhole failures caused by wellbore instability when drilling into hard and brittle shale formations using water-based or oil-based drilling fluids. It also has a positive effect on improving the wellbore stability of shale formations and enhancing the pressure-bearing capacity of the plugged formations.

[0014] To address the above technical problems, the present invention provides a method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent, comprising the following steps:

[0015] Step 1: Prepare potassium chloride amine-based water-based drilling fluid slurry as the drilling fluid for drilling into the upper formation;

[0016] Step 2: During continuous drilling, determine the depth and location of the well entering the shale formation based on geological strata and lithology.

[0017] Step 3: Take a sample of potassium chloride amine-based water-based drilling fluid, add amphiphilic high-temperature resistant micro-nano plugging agent and amphiphilic polymer fiber plugging agent to the drilling fluid sample and stir evenly to prepare a strong plugging water-based drilling fluid sample;

[0018] Step 4: Then, the strong-sealing water-based drilling fluid samples were subjected to sealing performance and high-temperature and high-pressure filtration loss evaluation tests.

[0019] Step 5: Based on the results of the sealing performance and high-temperature and high-pressure filtration loss evaluation test, calculate the required dosage range of amphiphilic high-temperature resistant micro-nano plugging agent and amphiphilic polymer fiber plugging agent for the total amount of drilling fluid circulating at the construction site.

[0020] Step 6: Using a mixing funnel, the amphiphilic high-temperature resistant micro-nano plugging agent and amphiphilic polymer fiber plugging agent are uniformly added to the drilling fluid during one circulation cycle to obtain a strong plugging potassium chloride amine-based drilling fluid.

[0021] Furthermore, step 7, during continued drilling, involves comprehensively judging the stability of the shale wellbore based on the shape and quantity of rock cuttings returned by the vibrating screen and the smoothness of tripping in and out of the drill string.

[0022] Furthermore, if the rock cuttings returned from the vibrating screen are of regular shape, without obvious peeling or breakage, and the amount of rock cuttings returned is basically consistent with the wellbore volume, and the tripping process is smooth without any sticking or obstruction, then the wellbore is stable; otherwise, return to step 5, increase the amount of the amphiphilic high-temperature resistant micro-nano plugging agent, and gradually increase the drilling fluid density to improve wellbore stability.

[0023] Furthermore, in step 2, 100 to 150 meters before the drill bit enters the mudstone and shale formation, a pretreatment is carried out by adding amphiphilic high-temperature resistant micro-nano plugging agent and amphiphilic polymer fiber plugging agent.

[0024] Furthermore, the preparation method of the potassium chloride amine-based water-based drilling fluid slurry in step 1 includes the following sub-steps in sequence:

[0025] Step 1.1: First, mix 1000 parts of water with 20-30 parts of sodium bentonite, stir at 1000-3000 rpm for 30-45 minutes, then stir at 6000-10000 rpm for 30-45 minutes, and let it cure at room temperature for 24 hours to form mixture 1.

[0026] Step 1.2: At a stirring speed of 6000-10000 rpm, add 1-2 parts of potassium polyacrylamide K-PAM and 5-8 parts of hydrolyzed potassium polyacrylonitrile K-PAN to mixture 1, stir evenly, then add 3-8 parts of potassium chloride, 2-4 parts of branched polyetheramine and 20-30 parts of cationic asphalt, stir evenly, then add 20-40 parts of ultrafine calcium carbonate, while stirring, add 20-40 parts of environmentally friendly bio-lubricant JS-LUB-Ⅱ, then add 15-20 parts of inorganic-organic hybrid anti-high temperature filtration loss agent, stir thoroughly to form mixture 2;

[0027] Step 1.3: Adjust the pH of mixture 2 to 8-10 with KOH to form mixture 3;

[0028] Step 1.4: Add 300-380 parts of barite to mixture 3, stir evenly, and then prepare potassium chloride amine-based water-based drilling fluid slurry.

[0029] Furthermore, in step 3: the amount of the amphiphilic high-temperature resistant micro-nano plugging agent added to 100 drilling fluid samples is 1 to 2 parts, and the amount of the amphiphilic polymer fiber plugging agent while drilling is 1 to 4 parts.

[0030] Furthermore, the preparation of the amphiphilic high-temperature resistant micro / nano plugging agent includes the following steps:

[0031] Step A1: 40-60 parts of styrene and butadiene, 5-20 parts of epoxy resin, 10-20 parts of vinylpyrrolidone, 1-5 parts of Tween-20 emulsifier, 0.15-0.6% lauroyl peroxide initiator and 0.1-0.5% polyvinyl alcohol aqueous solution are added to a protective colloid to carry out a seed polymerization reaction to obtain a seed copolymer emulsion, which is then uniformly sprayed onto 10-15 parts of silica microcrystalline particles using a spraying device;

[0032] Step A2: Dry the product obtained in step A1 at a low temperature of 40-50°C;

[0033] Step A3: Prepare the seed copolymer emulsion described in step A1 again, and spray it evenly onto the silica microcrystalline particles obtained in step A2.

[0034] Step A4: Dry the product obtained in step A3 at a low temperature of 40-50°C;

[0035] Step A5: Dissolve the product obtained in step A4 with the amphiphilic modifier and oxalic acid in distilled water, then add a small amount of sulfuric acid catalyst to react. After the reaction, filter to obtain the initial product; wash with distilled water and dry to obtain dried short fibers.

[0036] Step A6: The dried short fibers are cut, crushed and sieved multiple times to obtain fine fibers smaller than 1mm;

[0037] Step A7: The fine fiber is mixed evenly with 15-20 parts of filler and 10-15 parts of other ingredients to obtain an amphiphilic high-temperature resistant micro-nano sealing agent.

[0038] Furthermore, the molar ratio of styrene to butadiene is 1:1, and the hydrophilic modifier in the amphiphilic modifier is polyethylene glycol, while the hydrophobic modifier is polypyrrole.

[0039] Furthermore, the other ingredients are one or a mixture of two of the following: modified asphalt powder, cationic asphalt powder, modified micron-nano silica powder, ultrafine calcium carbonate, modified silicon-based fiber, tetraethyl orthosilicate, and amorphous soil.

[0040] Furthermore, the preparation method of the potassium chloride amine-based water-based drilling fluid slurry includes the following sub-steps in sequence:

[0041] Step 1.1: First, mix 1000 parts water with 20 parts sodium bentonite, stir at 1000 rpm for 30 minutes, then stir at 6000 rpm for 30 minutes, and let it cure at room temperature for 24 hours to form mixture 1.

[0042] Step 1.2: At a stirring speed of 6000 rpm, add 1 part of potassium polyacrylamide K-PAM and 5 parts of hydrolyzed potassium polyacrylonitrile K-PAN to mixture 1, stir evenly, then add 3 parts of potassium chloride, 2 parts of branched polyetheramine and 20 parts of cationic asphalt, stir evenly, then add 20 parts of ultrafine calcium carbonate, while stirring, add 20 parts of environmentally friendly bio-lubricant JS-LUB-Ⅱ, then add 15 parts of inorganic-organic hybrid anti-high temperature filtration loss agent, stir thoroughly to form mixture 2;

[0043] Step 1.3: Adjust the pH of mixture 2 to 8 with KOH to form mixture 3;

[0044] Step 1.4: Add 300 parts of barite to mixture 3, stir evenly, and then prepare potassium chloride amine-based water-based drilling fluid slurry.

[0045] Furthermore, the preparation method of the potassium chloride amine-based water-based drilling fluid slurry includes the following sub-steps in sequence:

[0046] Step 1.1: First, mix 1000 parts water with 25 parts sodium bentonite, stir at 2000 rpm for 40 minutes, then stir at 8000 rpm for 35 minutes, and let it cure at room temperature for 24 hours to form mixture 1.

[0047] Step 1.2: At a stirring speed of 8000 rpm, add 1.5 parts of potassium polyacrylamide K-PAM and 6 parts of hydrolyzed potassium polyacrylonitrile K-PAN to mixture 1, stir evenly, then add 5 parts of potassium chloride, 3 parts of branched polyetheramine and 25 parts of cationic asphalt, stir evenly, then add 30 parts of ultrafine calcium carbonate, while stirring, add 30 parts of environmentally friendly bio-lubricant JS-LUB-Ⅱ, then add 18 parts of inorganic-organic hybrid anti-high temperature filtration loss agent, stir thoroughly to form mixture 2;

[0048] Step 1.3: Adjust the pH of mixture 2 to 9 with KOH to form mixture 3;

[0049] Step 1.4: Add 350 parts of barite to mixture 3, stir evenly, and then prepare potassium chloride amine-based water-based drilling fluid slurry.

[0050] Furthermore, the preparation method of the potassium chloride amine-based water-based drilling fluid slurry includes the following sub-steps in sequence:

[0051] Step 1.1: First, mix 1000 parts water with 30 parts sodium bentonite, stir at 3000 rpm for 45 minutes, then stir at 10000 rpm for 45 minutes, and let it cure at room temperature for 24 hours to form mixture 1.

[0052] Step 1.2: At a stirring speed of 10,000 rpm, add 2 parts of potassium polyacrylamide K-PAM and 8 parts of hydrolyzed potassium polyacrylonitrile K-PAN to mixture 1. After stirring evenly, add 8 parts of potassium chloride, 4 parts of branched polyetheramine and 30 parts of cationic asphalt. After stirring evenly, add 40 parts of ultrafine calcium carbonate. While stirring, add 40 parts of environmentally friendly bio-lubricant JS-LUB-Ⅱ. Then add 20 parts of inorganic-organic hybrid anti-high temperature filtration loss agent. After stirring thoroughly, mixture 2 is formed.

[0053] Step 1.3: Adjust the pH of mixture 2 to 10 with KOH to form mixture 3;

[0054] Step 1.4: Add 380 parts of barite to mixture 3, stir evenly, and then prepare potassium chloride amine-based water-based drilling fluid slurry.

[0055] Furthermore, the raw material composition and weight content of the strong plugging potassium chloride amine-based drilling fluid are as follows: the amount of the amphiphilic high-temperature resistant micro-nano plugging agent added in 100 parts of drilling fluid sample is 1 part, and the amount of the amphiphilic polymer fiber plugging agent while drilling is 1 part.

[0056] Furthermore, the raw material composition and weight content of the strong plugging potassium chloride amine-based drilling fluid are as follows: the amount of the amphiphilic high-temperature resistant micro-nano plugging agent added in 100 parts of drilling fluid sample is 2 parts, and the amount of the amphiphilic polymer fiber plugging agent while drilling is 2 parts.

[0057] Furthermore, the raw material composition and weight content of the strongly plugging potassium chloride amine-based drilling fluid are as follows: the amount of the amphiphilic high-temperature resistant micro-nano plugging agent added in 100 parts of drilling fluid sample is 2 parts, and the amount of the amphiphilic polymer fiber plugging agent while drilling is 4 parts.

[0058] Another objective of this invention is to overcome the bottleneck problem existing in the prior art when drilling into hard and brittle shale formations using water-based and oil-based drilling fluids, and to provide an amphiphilic high-temperature resistant micro-nano plugging agent that can effectively reduce the rate of complex downhole failures caused by wellbore instability when drilling into hard and brittle shale formations using water-based or oil-based drilling fluids. It also has a good effect on improving the wellbore stability of shale formations and enhancing the pressure-bearing capacity of the plugged formations.

[0059] To solve the above technical problems, the present invention provides an amphiphilic high-temperature resistant micro / nano plugging agent, which is prepared by following the steps below:

[0060] Step A1: 40-60 parts of styrene and butadiene, 5-20 parts of epoxy resin, 10-20 parts of vinylpyrrolidone, 1-5 parts of Tween-20 emulsifier, 0.15-0.6% lauroyl peroxide initiator and 0.1-0.5% polyvinyl alcohol aqueous solution are added to a protective colloid to carry out a seed polymerization reaction to obtain a seed copolymer emulsion, which is then uniformly sprayed onto 10-15 parts of silica microcrystalline particles using a spraying device;

[0061] Step A2: Dry the product obtained in step A1 at a low temperature of 40-50°C;

[0062] Step A3: Prepare the seed copolymer emulsion described in step A1 again, and spray it evenly onto the silica microcrystalline particles obtained in step A2.

[0063] Step A4: Dry the product obtained in step A3 at a low temperature of 40-50°C;

[0064] Step A5: Dissolve the product obtained in step A4 with the amphiphilic modifier and oxalic acid in distilled water, then add a small amount of sulfuric acid catalyst to react. After the reaction, filter to obtain the initial product; wash with distilled water and dry to obtain dried short fibers.

[0065] Step A6: The dried short fibers are cut, crushed and sieved multiple times to obtain fine fibers smaller than 1mm;

[0066] Step A7: The fine fiber is mixed evenly with 15-20 parts of filler and 10-15 parts of other ingredients to obtain an amphiphilic high-temperature resistant micro-nano sealing agent.

[0067] Further, in step A1: 40 parts of styrene and butadiene, 5 parts of epoxy resin, 10 parts of vinylpyrrolidone, 1 part of Tween-20 emulsifier, 0.15% lauroyl peroxide initiator and 0.1% polyvinyl alcohol aqueous solution are added and uniformly sprayed onto 10 parts of silica microcrystalline particles using a spraying device.

[0068] In steps A2 and A4: the low-temperature drying temperature is 40℃;

[0069] In step A7: the filler is 15 parts and the other ingredients are 10 parts.

[0070] Further, in step A1: 50 parts of styrene and butadiene, 10 parts of epoxy resin, 15 parts of vinylpyrrolidone, 3 parts of Tween-20 emulsifier, 0.4% lauroyl peroxide initiator and 0.3% polyvinyl alcohol aqueous solution are added and uniformly sprayed onto 12 parts of silica microcrystalline particles using a spraying device.

[0071] In steps A2 and A4: the low-temperature drying temperature is 45℃;

[0072] In step A7: the filler is 18 parts and the other ingredients are 12 parts.

[0073] Further, in step A1: 60 parts of styrene and butadiene, 20 parts of epoxy resin, 20 parts of vinylpyrrolidone, 5 parts of Tween-20 emulsifier, 0.6% lauroyl peroxide initiator and 0.5% polyvinyl alcohol aqueous solution are added and uniformly sprayed onto 15 parts of silica microcrystalline particles using a spraying device.

[0074] In steps A2 and A4: the low-temperature drying temperature is 50℃;

[0075] In step A7: the filler is 20 parts and the other ingredients are 15 parts.

[0076] Compared with the prior art, the present invention achieves the following beneficial effects: 1. When drilling through hard and brittle shale formations prone to collapse, the strong-suppressing potassium chloride amine-based water-based drilling fluid of the present invention, with the dual action of potassium polyacrylamide (K-PAM) and branched polyetheramine, enhances the overall inhibitory effect of the water-based drilling fluid. The addition of potassium chloride, on the one hand, reduces the activity of the drilling fluid water due to its inorganic salt nature, and on the other hand, ionizes to release potassium chloride. +1 The dense structure formed by potassium ions in the shale crystal layers through lattice fixation and ion exchange weakens the shale lattice hydration, further enhancing the drilling fluid's ability to inhibit shale hydration.

[0077] 2. The inorganic-organic hybrid high-temperature filtration loss reducer is a salt-resistant and high-temperature filtration loss reducer with a "core-shell" structure formed by the hybridization of inorganic nanoparticles and organic polymers. It can effectively control the high-temperature and high-pressure filtration loss of drilling fluid, and is environmentally friendly and easily biodegradable. For hard and brittle shale, high-temperature and high-pressure filtration loss control is one of the important factors in preventing wellbore instability.

[0078] 3. The amphiphilic high-temperature resistant micro / nano plugging agent is made from a variety of composite materials through special processes and surface treatments. Its median particle size distribution is mainly between 90-100 nanometers. Its functions are: First, it bridges the formation wellbore surface, creating an internal filter cake and improving the quality of the external mud cake; second, its nano-size and deformable properties allow it to enter micro / nano-sized pores, sealing the throat and rapidly forming a filter cake. This fills micro-fractures and forms a low-permeability plugging membrane on the wellbore surface, achieving shielding and isolation between the wellbore and the formation. This stabilizes the wellbore, strengthens the wellbore, prevents lost circulation, protects the reservoir, and prevents differential pressure sticking. The addition of amphiphilic polymer fiber-based plugging agent and cationic asphalt further enhances its plugging performance.

[0079] 4. The addition of amphiphilic high-temperature resistant micro-nano plugging agent can gradually improve the pressure bearing capacity of the formation, thereby improving wellbore stability, extending the wellbore stability period, and improving the pressure bearing capacity and safety density window of the plugged formation. It has excellent plugging, anti-collapse, and anti-leakage characteristics.

[0080] 5. The addition of amphiphilic high-temperature resistant micro-nano plugging agent can greatly reduce the penetration depth of drilling fluid in the well wall and greatly reduce the damage of solid or liquid phases in drilling fluid to oil and gas reservoirs.

[0081] 6. Amphiphilic polymeric fiber plugging agent is a powdered material synthesized at high temperature from nano- and micro-scale rigid materials, fine fibers, and fatty acid plant derivative surfactants. This agent rapidly forms a high-strength seal near the wellbore, significantly reducing the transmission of wellbore fluid pressure to wellbore pores caused by the presence of formation micro-voids (micro-fractures). It prevents the reduction in the support force of the wellbore fluid column on the wellbore due to transmission, effectively increasing the support force of the wellbore fluid column on the wellbore without increasing density. This improves wellbore stability, extends the wellbore stability period, and enhances the pressure-bearing capacity and safe density window of the sealed formation. It has excellent sealing, anti-collapse, and anti-leakage characteristics.

[0082] 7. Cationic asphalt is a high-quality powdered asphalt treatment agent produced from natural asphalt and composite surfactants through a special process. Its asphalt content is much higher than that of sulfonated asphalt and cationic emulsified asphalt. It relies on the film-forming properties of asphalt treatment agents to help improve the overall sealing effect of drilling fluid.

[0083] 8. The combined synergistic effect of the above points can greatly improve the wellbore stability of water-based drilling fluids when encountering hard, brittle shale formations prone to collapse. By employing a combination of physical and chemical methods, safe and smooth drilling can be achieved. Compared with existing similar water-based drilling fluids, the strong-plugging potassium chloride-amine-based water-based drilling fluid of this invention features stable rheological properties, excellent lubricity, strong inhibition, good wall-building performance after water loss, and strong plugging ability.

[0084] 9. Another special feature of amphiphilic high-temperature resistant micro-nano plugging agents is their amphiphilic properties. They can be used not only in water-based systems but also in oil-based systems, and both have a good function of stabilizing the well wall. They greatly reduce the transmission of wellbore fluid column pressure to well wall pores caused by the presence of formation micro-voids (micro-fractures), and prevent the reduction of wellbore fluid column support force on the well wall caused by transmission.

[0085] 10. Oil-based drilling fluids can also be used in combination with amphiphilic plugging agents and amphiphilic high-temperature resistant polymer fibers to improve the plugging ability of oil-based drilling fluids, thereby solving the problem of wellbore instability in shale formations; this can reduce the daily consumption of oil-based drilling fluids and save costs. Attached Figure Description

[0086] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The drawings are provided for reference and illustration only and are not intended to limit the present invention.

[0087] Figure 1 The image shows the laser particle size distribution results of the amphiphilic high-temperature resistant micro / nano plugging agent.

[0088] Figure 2 Figure 1 shows the results of laser particle size analysis of amphiphilic polymeric fiber plugging agent during drilling.

[0089] Figure 3 Electron microscopy images of amphiphilic high-temperature resistant micro / nano plugging agents;

[0090] Figure 4 The fiber structure of the amphiphilic polymer fiber plugging agent under an 80x optical microscope;

[0091] Figure 5 The fiber structure of the amphiphilic polymer fiber plugging agent under a 200x optical microscope;

[0092] Figure 6 The fiber structure of the amphiphilic polymer fiber plugging agent under a 400x optical microscope; Detailed Implementation

[0093] In the following description of the present invention, the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not mean that the device must have a specific orientation.

[0094] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.

[0095] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention.

[0096] Example 1

[0097] The amphiphilic high-temperature resistant micro / nano plugging agent was prepared by following these steps:

[0098] Step A1: 40 parts styrene and butadiene, 5 parts epoxy resin, 10 parts vinylpyrrolidone, and 1 part Tween-20 emulsifier (styrene to butadiene molar ratio 1:1) are added to a protective colloid containing 0.15% lauroyl peroxide initiator and 0.1% polyvinyl alcohol aqueous solution to induce a seed polymerization reaction, yielding a seed copolymer emulsion. The reaction process is as follows:

[0099]

[0100] Use a spraying device to evenly spray onto 10 portions of silica microcrystalline particles;

[0101]

[0102] Step A2: Dry the product obtained in step A1 at a low temperature of 40°C;

[0103] Step A3: Prepare the seed copolymer emulsion described in step A1 again, and spray it evenly onto the silica microcrystalline particles obtained in step A2.

[0104] Step A4: Dry the product obtained in step A3 at a low temperature of 40°C;

[0105] Step A5: Dissolve the product obtained in step A4 with the amphiphilic modifier and oxalic acid in distilled water, then add a small amount of sulfuric acid catalyst to react. After the reaction, filter to obtain the initial product; wash with distilled water and dry to obtain dried short fibers; the hydrophilic modifier in the amphiphilic modifier is polyethylene glycol and the hydrophobic modifier is polypyrrole.

[0106] Step A6: The dried short fibers are cut, crushed and sieved multiple times to obtain fine fibers smaller than 1mm;

[0107] Step A7: The fine fiber is mixed evenly with 15 parts of filler and 10 parts of modified asphalt powder to obtain an amphiphilic high-temperature resistant micro-nano sealant.

[0108] Example 2

[0109] The amphiphilic high-temperature resistant micro / nano plugging agent was prepared by following these steps:

[0110] Step A1: 50 parts styrene and butadiene, 10 parts epoxy resin, 15 parts vinylpyrrolidone, 3 parts Tween-20 emulsifier, with a styrene to butadiene molar ratio of 1:1, are added to a protective colloid containing 0.4% lauroyl peroxide initiator and 0.3% polyvinyl alcohol aqueous solution to undergo a seed polymerization reaction to obtain a seed copolymer emulsion. The emulsion is then uniformly sprayed onto 12 parts silica microcrystalline particles using a spraying device.

[0111] Step A2: Dry the product obtained in step A1 at a low temperature of 45°C;

[0112] Step A3: Prepare the seed copolymer emulsion described in step A1 again, and spray it evenly onto the silica microcrystalline particles obtained in step A2.

[0113] Step A4: Dry the product obtained in step A3 at a low temperature of 45°C;

[0114] Step A5: Dissolve the product obtained in step A4 with the amphiphilic modifier and oxalic acid in distilled water, then add a small amount of sulfuric acid catalyst to react. After the reaction, filter to obtain the initial product; wash with distilled water and dry to obtain dried short fibers.

[0115] Step A6: The dried short fibers are cut, crushed and sieved multiple times to obtain fine fibers smaller than 1mm;

[0116] Step A7: The fine fiber is mixed evenly with 18 parts of filler and 12 parts of modified micron-nano silica powder to obtain an amphiphilic high-temperature resistant micro-nano sealing agent.

[0117] Example 3

[0118] The amphiphilic high-temperature resistant micro / nano plugging agent was prepared by following these steps:

[0119] Step A1: 60 parts styrene and butadiene, 20 parts epoxy resin, 20 parts vinylpyrrolidone, 5 parts Tween-20 emulsifier, with a styrene to butadiene molar ratio of 1:1, are added to a protective colloid containing 0.6% lauroyl peroxide initiator and 0.5% polyvinyl alcohol aqueous solution to undergo a seed polymerization reaction to obtain a seed copolymer emulsion. The emulsion is then uniformly sprayed onto 15 parts silica microcrystalline particles using a spraying device.

[0120] Step A2: Dry the product obtained in step A1 at a low temperature of 50°C;

[0121] Step A3: Prepare the seed copolymer emulsion described in step A1 again, and spray it evenly onto the silica microcrystalline particles obtained in step A2.

[0122] Step A4: Dry the product obtained in step A3 at a low temperature of 50°C;

[0123] Step A5: Dissolve the product obtained in step A4 with the amphiphilic modifier and oxalic acid in distilled water, then add a small amount of sulfuric acid catalyst to react. After the reaction, filter to obtain the initial product; wash with distilled water and dry to obtain dried short fibers.

[0124] Step A6: The dried short fibers are cut, crushed and sieved multiple times to obtain fine fibers smaller than 1mm;

[0125] Step A7: The fine fibers are mixed evenly with 20 parts of filler and 15 parts of ultrafine calcium carbonate of different mesh sizes to obtain an amphiphilic high-temperature resistant micro-nano sealing agent.

[0126] Example 4

[0127] Prepare potassium chloride amine-based water-based drilling fluid slurry by following these steps:

[0128] Step 1.1: First, mix 1000 parts water with 20 parts sodium bentonite, stir at 1000 rpm for 30 minutes, then stir at 6000 rpm for 30 minutes, and let it cure at room temperature for 24 hours to form mixture 1.

[0129] Step 1.2: At a stirring speed of 6000 rpm, add 1 part of potassium polyacrylamide K-PAM and 5 parts of hydrolyzed potassium polyacrylonitrile K-PAN to mixture 1, stir evenly, then add 3 parts of potassium chloride, 2 parts of branched polyetheramine and 20 parts of cationic asphalt, stir evenly, then add 20 parts of ultrafine calcium carbonate, while stirring, add 20 parts of environmentally friendly bio-lubricant JS-LUB-Ⅱ, then add 15 parts of inorganic-organic hybrid anti-high temperature filtration loss agent, stir thoroughly to form mixture 2;

[0130] Step 1.3: Adjust the pH of mixture 2 to 8 with KOH to form mixture 3;

[0131] Step 1.4: Add 300 parts of barite to mixture 3, stir evenly, and then prepare potassium chloride amine-based water-based drilling fluid slurry.

[0132] Example 5

[0133] Prepare potassium chloride amine-based water-based drilling fluid slurry by following these steps:

[0134] Step 1.1: First, mix 1000 parts water with 25 parts sodium bentonite, stir at 2000 rpm for 40 minutes, then stir at 8000 rpm for 35 minutes, and let it cure at room temperature for 24 hours to form mixture 1.

[0135] Step 1.2: At a stirring speed of 8000 rpm, add 1.5 parts of potassium polyacrylamide K-PAM and 6 parts of hydrolyzed potassium polyacrylonitrile K-PAN to mixture 1, stir evenly, then add 5 parts of potassium chloride, 3 parts of branched polyetheramine and 25 parts of cationic asphalt, stir evenly, then add 30 parts of ultrafine calcium carbonate, while stirring, add 30 parts of environmentally friendly bio-lubricant JS-LUB-Ⅱ, then add 18 parts of inorganic-organic hybrid anti-high temperature filtration loss agent, stir thoroughly to form mixture 2;

[0136] Step 1.3: Adjust the pH of mixture 2 to 9 with KOH to form mixture 3;

[0137] Step 1.4: Add 350 parts of barite to mixture 3, stir evenly, and then prepare potassium chloride amine-based water-based drilling fluid slurry.

[0138] Example 6

[0139] Prepare potassium chloride amine-based water-based drilling fluid slurry by following these steps:

[0140] Step 1.1: First, mix 1000 parts water with 30 parts sodium bentonite, stir at 3000 rpm for 45 minutes, then stir at 10000 rpm for 45 minutes, and let it cure at room temperature for 24 hours to form mixture 1.

[0141] Step 1.2: At a stirring speed of 10,000 rpm, add 2 parts of potassium polyacrylamide K-PAM and 8 parts of hydrolyzed potassium polyacrylonitrile K-PAN to mixture 1. After stirring evenly, add 8 parts of potassium chloride, 4 parts of branched polyetheramine and 30 parts of cationic asphalt. After stirring evenly, add 40 parts of ultrafine calcium carbonate. While stirring, add 40 parts of environmentally friendly bio-lubricant JS-LUB-Ⅱ. Then add 20 parts of inorganic-organic hybrid anti-high temperature filtration loss agent. After stirring thoroughly, mixture 2 is formed.

[0142] Step 1.3: Adjust the pH of mixture 2 to 10 with KOH to form mixture 3;

[0143] Step 1.4: Add 380 parts of barite to mixture 3, stir evenly, and then prepare potassium chloride amine-based water-based drilling fluid slurry.

[0144] Example 7

[0145] This invention employs an amphiphilic, high-temperature resistant micro / nano plugging agent for stabilizing the wellbore of hard and brittle shale, comprising the following steps:

[0146] Step 1: Prepare the potassium chloride amine-based water-based drilling fluid slurry of Example 4 as the drilling fluid for drilling into the upper formation;

[0147] Step 2: During continuous drilling, determine the depth and location of the well entering the shale formation based on geological strata and lithology.

[0148] Step 3: Take a sample of potassium chloride amine-based water-based drilling fluid, add amphiphilic high-temperature resistant micro-nano plugging agent and amphiphilic polymeric fiber plugging agent while drilling to the drilling fluid sample and stir evenly to prepare a strong plugging water-based drilling fluid sample; add 1 part of the amphiphilic high-temperature resistant micro-nano plugging agent from Example 1 and 1 part of the amphiphilic polymeric fiber plugging agent while drilling to 100 parts of drilling fluid sample;

[0149] Step 4: Then, the strong-sealing water-based drilling fluid samples were subjected to sealing performance and high-temperature and high-pressure filtration loss evaluation tests.

[0150] Step 5: Based on the results of the sealing performance and high-temperature and high-pressure filtration loss evaluation test, calculate the required dosage range of amphiphilic high-temperature resistant micro-nano plugging agent and amphiphilic polymer fiber plugging agent for the total amount of drilling fluid circulating at the construction site.

[0151] Step 6: Through the mixing funnel, the amphiphilic high-temperature resistant micro-nano plugging agent and the amphiphilic polymer fiber plugging agent are uniformly added to the drilling fluid during one circulation cycle to obtain a strong plugging potassium chloride amine-based drilling fluid.

[0152] Step 7: During the continued drilling operation, the stability of the shale wellbore is comprehensively judged based on the shape and quantity of rock cuttings returned by the vibrating screen and the smoothness of tripping in and out of the drill string.

[0153] If the rock cuttings returned from the vibrating screen are of regular shape, without obvious peeling or breakage, and the amount of rock cuttings returned is basically consistent with the wellbore volume, and the tripping process is smooth without any sticking or obstruction, then the wellbore is stable; otherwise, return to step 5, increase the amount of the amphiphilic high-temperature resistant micro-nano plugging agent, and gradually increase the drilling fluid density to improve wellbore stability.

[0154] Example 8

[0155] This invention presents a method for stabilizing the wellbore of hard and brittle shale using an amphiphilic, high-temperature resistant micro / nano plugging agent.

[0156] In step 1, the potassium chloride amine-based water-based drilling fluid slurry of Example 5 is prepared as the drilling fluid for drilling into the upper formation.

[0157] In step 3, 2 parts of the amphiphilic high-temperature resistant micro-nano plugging agent from Example 2 and 2 parts of the amphiphilic polymer fiber plugging agent for drilling were added to 100 drilling fluid samples; the rest was the same as in Example 7.

[0158] Example 9

[0159] This invention presents a method for stabilizing the wellbore of hard and brittle shale using an amphiphilic, high-temperature resistant micro / nano plugging agent.

[0160] In step 1, the potassium chloride amine-based water-based drilling fluid slurry of Example 6 is prepared as the drilling fluid for drilling into the upper formation.

[0161] In step 3, 2 parts of the amphiphilic high-temperature resistant micro-nano plugging agent from Example 3 and 4 parts of the amphiphilic polymer fiber plugging agent were added to 100 drilling fluid samples; the rest was the same as in Example 7.

[0162] All drilling fluid treatment agents used in this invention, unless otherwise specified, are calculated in parts by weight and comply with the following standards: Sodium bentonite conforms to the national standard GB / T5005.2010 Technical Requirements for Drilling Fluid Grade Bentonite;

[0163] Potassium polyacrylamide (K-PAM) conforms to the enterprise standard of China National Petroleum Corporation, "SY / T5946-2019 Technical Requirements for Coated Inhibitors Potassium Polyacrylamide for Drilling Fluids".

[0164] Hydrolyzed potassium polyacrylonitrile (K-PAN) conforms to the China National Petroleum Corporation (CNPC) enterprise standard "Q / SHCG 55-2013 Technical Requirements for Hydrolyzed Polyacrylonitrile Salts in Drilling Fluids";

[0165] Potassium chloride meets the technical requirements of the national standard GB / T 7118-2008 Industrial Potassium Chloride;

[0166] Branched polyetheramine conforms to the enterprise standard Q / SHCG 99001 of China National Petroleum Corporation;

[0167] Cationic asphalt conforms to the enterprise standard FBJS-013 of Henan Longxiang Petroleum Additives Co., Ltd.

[0168] Potassium hydroxide conforms to the People's Republic of China Chemical Industry Standard HG / T3688-2010;

[0169] Ultrafine calcium carbonate conforms to the enterprise standard Q / SHCG37-2012 of China Petroleum & Chemical Corporation;

[0170] The environmentally friendly bio-lubricant JS-LUB-Ⅱ complies with the enterprise standard of Sinopec East China Petroleum Engineering Co., Ltd., "Technical Requirements for Environmentally Friendly Bio-lubricants for Drilling Fluids FBJS-01";

[0171] The inorganic-organic hybrid high-temperature filtration loss reducing agent meets the relevant technical standards of Southwest Petroleum University.

[0172] The amphiphilic polymer fiber plugging agent meets the relevant enterprise standard requirements of Sinopec East China Petroleum Engineering Co., Ltd.

[0173] The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro-nano plugging agent is a strong-seal, high-temperature resistant water-based drilling fluid suitable for safe construction in hard and brittle shale. This fluid is formed by adding an amphiphilic high-temperature resistant micro-nano plugging agent, an amphiphilic polymeric fiber plugging agent, and an inorganic-organic hybrid anti-high-temperature filtration reduction agent to a potassium chloride amine-based drilling fluid base. The comprehensive testing of its performance follows the testing methods in "Modern Drilling Fluid Experimental Technology" published by China University of Petroleum Press in 1999 and "Drilling Fluid Technology" published in 2001.

[0174] I. Particle size distribution test of micro / nano plugging agents and amphiphilic plugging agents

[0175] 1.1 Particle Size Distribution Analysis

[0176] The amphiphilic high-temperature resistant micro / nano plugging agent sample from Example 1 was prepared into a solution with a mass percentage concentration of 0.5%. The solution was ultrasonically dispersed for 5 minutes using an ultrasonic disperser, and the median particle size distribution was measured using a laser particle size analyzer. The results are as follows: Figure 1 As shown.

[0177] A sample of amphiphilic polymeric fiber plugging agent was prepared into a 0.5% (w / w) solution, ultrasonically dispersed for 5 min on an ultrasonic disperser, and the median particle size distribution was measured using a laser particle size analyzer. The results are as follows: Figure 2 As shown.

[0178] The amphiphilic high-temperature resistant micro-nano plugging agent, processed with a special technology, has a median particle size of 89% distributed between 30-60 nm, which fills micro-fractures. The amphiphilic polymeric fiber plugging agent used for drilling has a median particle size of 86% distributed between 90-100 nm and has an ultra-fine fibrous structure, making it an ideal material for plugging micro-fractures. The combination of the two plugging agents can form an effective plugging layer to seal micro-fractures in the target block of mudstone and shale, thereby improving wellbore stability.

[0179] 1.2 Microscopic imaging of micro / nano and amphiphilic polymeric fibers used in drilling plugging agents

[0180] 1.2.1 Micro / Nano Microstate

[0181] The microstructure of the micro / nano plugging agent was observed using scanning electron microscopy. The image shows an amphiphilic, high-temperature resistant micro / nano plugging agent. Figure 3 As shown.

[0182] Amphiphilic high-temperature resistant micro / nano plugging agent is a nano plugging agent made by special processes and surface treatment of inorganic nanomaterial particles with a particle size of 50-100 nanometers polymerized with alkyl sulfonates, alkyl esters, crosslinking agents, etc.

[0183] 1.2.2 Microstructure of Amphiphilic Polymer Fiber Drilling-While-Pluging Agent

[0184] Disperse 2 grams of amphiphilic polymeric fiber plugging agent in 10-20 ml of water, stir thoroughly, and use a dropper to draw an appropriate amount of the dispersion onto a glass slide. Cover with a coverslip and observe under an optical microscope at magnifications of 80, 200, and 400. The fibrous structure has an aspect ratio of approximately 1:3 to 1:7.

[0185] Amphiphilic polymeric fiber plugging agent fiber structure under 80x optical microscope as shown in the image. Figure 4 As shown, the fiber structure of the amphiphilic polymeric fiber plugging agent under a 200x optical microscope is as follows. Figure 5 As shown, the fiber structure of the amphiphilic polymeric fiber plugging agent under a 400x optical microscope is as follows. Figure 6 As shown.

[0186] 1.3 The unique high-temperature resistance of amphiphilic polymer fiber plugging agent during drilling

[0187] For the 200℃ high temperature resistance test, weigh 5g of the sample and put it into a crucible, then put it into a muffle furnace, heat it to 200℃ and keep it at that temperature for 8 hours, then cool it to room temperature, observe the appearance, weigh it, and calculate the rate of change of mass.

[0188] For the 900℃ high-temperature resistance test, 5g of sample was weighed, placed in a crucible, and then put into a muffle furnace. The temperature was heated to 900℃ and held for 15 minutes. After cooling to room temperature, the appearance was observed, and then the sample was weighed and the rate of mass change was calculated. The calculation results are shown in Table 1.

[0189] Table 1. Evaluation of the high-temperature resistance of amphiphilic polymeric fiber plugging agent used in drilling.

[0190]

[0191] As shown in Table 1 above, after being calcined at 200℃ and 900℃, the mass change rate of the amphiphilic polymer fiber plugging agent was 3% and 6%, respectively, which is better than the standard requirements. This indicates that it has good high temperature resistance and can be compounded with other materials to improve the overall temperature resistance of the drilling fluid and meet the needs of high temperature well depths.

[0192] II. Compatibility Evaluation of Micro / Nano Plugging Agents and Amphiphilic Leakage Plugging Agents with Water-Based Drilling Fluids

[0193] 2.1 Evaluation of the compatibility performance of micro / nano plugging agents and amphiphilic agents with water-based drilling fluids

[0194] The potassium chloride amine-based water-based drilling fluid slurry in Example 5 was used as a comparative example. The strong-suppressing potassium chloride amine-based drilling fluids in Examples 7 to 9, after adding amphiphilic high-temperature resistant micro-nano plugging agent and amphiphilic polymer fiber plugging agent, were then tested. The performance changes of the water-based drilling fluid before and after aging were tested to evaluate the compatibility of the two materials with the water-based drilling fluid. The aging conditions were 120℃×16h. The test results are shown in Table 2.

[0195] Table 2 Compatibility Evaluation with Water-Based Drilling Fluids Analyzing the data in Table 2 above: When micro-nano plugging agents and amphiphilic polymeric fiber plugging agents are added to potassium chloride amine-based water-based drilling fluid, the rheological properties before and after aging are compared. The apparent viscosity, plastic viscosity, and shear stress all increase slightly, but the medium-pressure filtration loss decreases significantly with the addition of both plugging agents. In particular, with the addition of micro-nano plugging agents and amphiphilic polymeric fiber plugging agents, the medium-pressure filtration loss decreases by 76.6% and 86.1% respectively before and after aging compared to the base fluid, indicating that the plugging performance of the system is significantly improved.

[0196] III. Comprehensive Performance Evaluation of Potassium Chloride Amine-Based Drilling Fluid with Strong Sealing Effect

[0197] 3.1 Inhibitory properties

[0198] The lithology of brown mudstone in a certain block was selected, and the system's inhibitory effect was evaluated through a rock cuttings recovery rate experiment.

[0199] Table 3. Evaluation results of inhibition performance

[0200] Serial Number Recovered grams / g First-time recovery rate / % Recovered grams / g Secondary recovery rate / % Comparative Example 1 6.5 13 5 10 Example 5 46 92 44 88

[0201] Comparative Example 1: Water + 50g core powder;

[0202] Example 5: Clean water + potassium chloride amine-based water-based drilling fluid slurry from Example 5 + 50g core powder;

[0203] As can be seen from the data in Table 3 above, the primary rock cuttings recovery rate of Example 8 of the present invention reached 92%, and the secondary rock cuttings recovery rate reached 88%, indicating that the system has strong inhibition properties.

[0204] 3.2 Temperature resistance and lubrication performance

[0205] 3.2.1 Evaluation of Temperature Resistance

[0206] First, potassium chloride amine-based water-based drilling fluid slurry was prepared according to Example 5. Then, amphiphilic high-temperature resistant micro-nano plugging agent and amphiphilic polymer fiber plugging agent were added according to the proportion of Example 8. The rheological properties and filtration loss of the drilling fluid before and after aging were tested. The aging conditions were 160℃×16h.

[0207] Table 4 Evaluation of Temperature Resistance

[0208] Analyzing the data in Table 4 above, the performance comparison of the strong-plugging potassium chloride amine-based drilling fluid before and after aging at 160℃ for 16 hours shows that this drilling fluid system has good temperature resistance.

[0209] 3.2.2 Evaluation of Lubrication Performance

[0210] According to Example 6, a potassium chloride amine-based water-based drilling fluid slurry 1# without environmentally friendly biological lubricant was first prepared, and then the environmentally friendly biological lubricant JS-LUB-Ⅱ was added to obtain the potassium chloride amine-based water-based drilling fluid slurry 2# as in Example 6. The drilling fluid performance before and after addition was tested, especially the extreme pressure lubrication coefficient, to evaluate the lubricant performance of the system.

[0211] Table 5 Lubricant Performance Evaluation

[0212] Analyzing the data in Table 5 above, the comprehensive performance tests before and after the addition of the environmentally friendly biological lubricant, especially the lubrication coefficient, show that the lubrication coefficient decreased by 68% and 84.2% before and after aging, respectively. The addition of the environmentally friendly biological lubricant JS-LUB-Ⅱ significantly improved the lubricity of this drilling fluid system.

[0213] 3.3 Evaluation of the plugging properties of water-based drilling fluids

[0214] Table 6 Evaluation of the Impact of Amphiphilic High-Temperature Resistant Micro / Nano Plugging Agents on the Plugging Performance of Water-Based Drilling Fluids

[0215]

[0216] Note: Instantaneous filtration V1 = 2(2V) 7.5 -V 30 ), mL; PPT filtration loss V PPT =2V 30 ,mL; Static filtration rate Vsf=2(V 30 -V 7.5 ) / 2.739,mL / min.

[0217] The sealing performance of the potassium chloride amine-based water-based drilling fluid slurry of Example 4 was compared with that of the strong-sealing potassium chloride amine-based drilling fluid of Example 7.

[0218] Analysis of the data in Table 6 shows that when amphiphilic plugging agents and micro / nano plugging agents are added to water-based drilling fluid systems, their filtration loss is measured under different pressure conditions. At 3.5 MPa, the filtration loss after 1 minute is reduced by 86.6% compared to the blank fluid, and the filtration loss after 30 minutes is reduced by 89.7%. At 7.0 MPa, the filtration loss after 1 minute is reduced by 86.9% compared to the blank fluid, and the filtration loss after 60 minutes is reduced by 84.7%. This indicates that amphiphilic polymer fiber plugging agents and amphiphilic high-temperature resistant micro / nano plugging agents greatly improve the plugging performance of water-based drilling fluids.

[0219] IV. Compatibility Evaluation of Micro / Nano Plugging Agents and Amphiphilic Leakage Plugging Agents with Oil-Based Drilling Fluids

[0220] Performance evaluation of amphiphilic high-temperature resistant micro / nano plugging agent in compatibility with oil-based drilling fluid

[0221] Prepare oil-based drilling fluid slurry by adding amphiphilic high-temperature resistant micro-nano plugging agent and amphiphilic polymeric fiber plugging agent separately, and by adding micro-nano plugging agent and amphiphilic polymeric fiber plugging agent in a 1:1 ratio. Test the changes in the performance of oil-based drilling fluid before and after aging to evaluate the compatibility of the two materials with oil-based drilling fluid.

[0222] Table 7. Compatibility Evaluation with Oil-Based Drilling Fluids

[0223]

[0224] The recipe is as follows:

[0225] #1: 320ml diesel oil + 2.5% primary emulsifier + 1.5% secondary emulsifier + 2% organic clay + 80ml 35% calcium chloride solution + 2% filtration loss reducer + 2% quicklime + barite (1238g), base slurry density 2.30g / cm³ 3 ;

[0226] 2#: 1# + 1.5% amphiphilic polymeric fiber plugging agent during drilling (aging conditions: 160℃ × 16h)

[0227] 3#: 1# + 1.5% amphiphilic high-temperature resistant micro / nano sealing agent (aging conditions: 160℃ × 16h)

[0228] 4#: 1# + 1.0% amphiphilic high-temperature resistant micro-nano plugging agent + 1.0% amphiphilic polymeric fiber plugging agent during drilling; (aging conditions: 160℃ × 16h)

[0229] Analyzing the data in the table above: When micro-nano plugging agents and amphiphilic polymeric fiber plugging agents are added to oil-based drilling fluids, comparing the rheological properties before and after aging, the apparent viscosity and plastic viscosity increase, but remain within acceptable ranges. Demulsification voltage: Before aging, the demulsification voltage is higher than that of the base fluid; after aging, it decreases, but the decrease is not significant, generally remaining above 800V, and has no impact on the electrical stability of the oil-based drilling fluid system. High-temperature and high-pressure filtration loss: After combining the two treatment agents, with a total addition of 2%, the high-temperature and high-pressure filtration loss is reduced by 78.5% compared to the base fluid. This indicates that the addition of the micro-nano and amphiphilic combination plugging agent improves the plugging performance of oil-based drilling fluids better. Overall performance evaluation shows that these two treatment agents have good compatibility with oil-based drilling fluids.

[0230] V. Evaluation of the plugging properties of micro / nano plugging agents and amphiphilic plugging agents with oil-based drilling fluids

[0231] The impact of a combination of micro / nano plugging agents and amphiphilic plugging agents on the overall performance of oil-based drilling fluid was evaluated in a selected well.

[0232] Table 8. Evaluation of the plugging properties of oil-based drilling fluids

[0233]

[0234] The recipe is as follows:

[0235] #1: On-site well slurry oil-water ratio 85:15, viscosity 103s, density 1.55g / cm³ 3 ;

[0236] 2#: 1# + 1% amphiphilic polymeric fiber plugging agent while drilling + 0.5% amphiphilic high-temperature resistant micro / nano plugging agent;

[0237] 3#: 1# + 0.5% amphiphilic polymeric fiber plugging agent during drilling + 1% amphiphilic high-temperature resistant micro-nano plugging agent.

[0238] Analyzing the data in the table above, the combination of amphiphilic polymeric fiber plugging agent and amphiphilic high-temperature resistant micro-nano plugging agent in different ratios has little impact on the electrical stability and rheological properties of crude oil-based drilling fluids before and after addition. However, the high-temperature and high-pressure fluid loss is significantly reduced, indicating that the plugging performance is further enhanced. In particular, the high-temperature and high-pressure fluid loss of the No. 2 formulation is reduced by 40%. However, after the combined use, the total addition is only 1.5%, which is lower than the previously recommended addition of 2% for the overall cost reduction.

[0239] The manufacturers and performance requirements of various drilling fluid treatment agents are shown in Table 9:

[0240] Table 9: Manufacturers and Performance Requirements of Various Drilling Fluid Treatment Agents

[0241]

[0242]

[0243]

[0244] The above description is merely a preferred embodiment of the present invention, showing and describing the basic principles, main features, and advantages of the present invention. It is not intended to limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. In addition to the above embodiments, the present invention may have other implementations without departing from the spirit and scope of the invention. Various changes and modifications to the present invention are possible, and all technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents. Technical features not described in the present invention can be implemented by or using existing technology, and will not be elaborated here.

Claims

1. A method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent, characterized in that, The steps are as follows: Step 1: Prepare potassium chloride amine-based water-based drilling fluid slurry as the drilling fluid for drilling into the upper formation; Step 2: During continuous drilling, determine the depth and location of the well entering the shale formation based on geological strata and lithology. Step 3: Take a sample of potassium chloride amine-based water-based drilling fluid, add amphiphilic high-temperature resistant micro-nano plugging agent and amphiphilic polymer fiber plugging agent to the drilling fluid sample and stir evenly to prepare a strong plugging water-based drilling fluid sample; Step 4: Then, the strong-sealing water-based drilling fluid samples were subjected to sealing performance and high-temperature and high-pressure filtration loss evaluation tests. Step 5: Based on the results of the sealing performance and high-temperature and high-pressure filtration loss evaluation test, calculate the required dosage range of amphiphilic high-temperature resistant micro-nano plugging agent and amphiphilic polymer fiber plugging agent for the total amount of drilling fluid circulating at the construction site. Step 6: Through the mixing funnel, the amphiphilic high-temperature resistant micro-nano plugging agent and the amphiphilic polymer fiber plugging agent are uniformly added to the drilling fluid during one circulation cycle to obtain a strong plugging potassium chloride amine-based drilling fluid. The preparation of the amphiphilic high-temperature resistant micro / nano plugging agent includes the following steps: Step A1: 40-60 parts of styrene and butadiene, 5-20 parts of epoxy resin, 10-20 parts of vinylpyrrolidone, 1-5 parts of Tween-20 emulsifier, 0.15-0.6% lauroyl peroxide initiator and 0.1-0.5% polyvinyl alcohol aqueous solution are added to a protective colloid to carry out a seed polymerization reaction to obtain a seed copolymer emulsion, which is then uniformly sprayed onto 10-15 parts of silica microcrystalline particles using a spraying device; Step A2: Dry the product obtained in step A1 at a low temperature of 40-50°C; Step A3: Prepare the seed copolymer emulsion described in step A1 again, and spray it evenly onto the silica microcrystalline particles obtained in step A2. Step A4: Dry the product obtained in step A3 at a low temperature of 40-50°C; Step A5: Dissolve the product obtained in step A4 with the amphiphilic modifier and oxalic acid in distilled water, then add a small amount of sulfuric acid catalyst to react. After the reaction, filter to obtain the initial product; wash with distilled water and dry to obtain dried short fibers. Step A6: The dried short fibers are cut, crushed and sieved multiple times to obtain fine fibers smaller than 1mm; Step A7: The fine fiber is mixed evenly with 15-20 parts of filler and 10-15 parts of other ingredients to obtain an amphiphilic high-temperature resistant micro-nano sealing agent.

2. The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent according to claim 1, characterized in that, It also includes step 7, during continued drilling, to comprehensively judge the stability of the shale well wall based on the shape and quantity of rock cuttings returned by the vibrating screen and whether the tripping and pulling are smooth.

3. The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent according to claim 2, characterized in that, If the rock cuttings returned from the vibrating screen are of regular shape, without obvious peeling or breakage, and the amount of rock cuttings returned is basically consistent with the wellbore volume, and the tripping process is smooth without any sticking or obstruction, then the wellbore is stable; otherwise, return to step 5, increase the amount of the amphiphilic high-temperature resistant micro-nano plugging agent, and gradually increase the drilling fluid density to improve wellbore stability.

4. The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent according to claim 1, characterized in that, In step 2, 100 to 150 meters before the drill bit enters the mudstone and shale formation, a pretreatment is carried out by adding amphiphilic high-temperature resistant micro-nano plugging agent and amphiphilic polymer fiber plugging agent.

5. The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent according to claim 1, characterized in that, The preparation method of potassium chloride amine-based water-based drilling fluid slurry described in step 1 includes the following sub-steps in sequence: Step 1.1: First, mix 1000 parts of water with 20-30 parts of sodium bentonite, stir at 1000-3000 rpm for 30-45 minutes, then stir at 6000-10000 rpm for 30-45 minutes, and let it cure at room temperature for 24 hours to form mixture 1. Step 1.2: At a stirring speed of 6000-10000 rpm, add 1-2 parts of potassium polyacrylamide K-PAM and 5-8 parts of hydrolyzed potassium polyacrylonitrile K-PAN to mixture 1, stir evenly, then add 3-8 parts of potassium chloride, 2-4 parts of branched polyetheramine and 20-30 parts of cationic asphalt, stir evenly, then add 20-40 parts of ultrafine calcium carbonate, while stirring, add 20-40 parts of environmentally friendly bio-lubricant JS-LUB-Ⅱ, then add 15-20 parts of inorganic-organic hybrid anti-high temperature filtration loss agent, stir thoroughly to form mixture 2; Step 1.3: Adjust the pH of mixture 2 to 8-10 with KOH to form mixture 3; Step 1.4: Add 300-380 parts of barite to mixture 3, stir evenly, and then prepare potassium chloride amine-based water-based drilling fluid slurry.

6. The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent according to claim 1 or 5, characterized in that, In step 3: the amount of amphiphilic high-temperature resistant micro-nano plugging agent added to 100 drilling fluid samples is 1-2 parts, and the amount of amphiphilic polymer fiber plugging agent while drilling is 1-4 parts.

7. The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent according to claim 1, characterized in that, The molar ratio of styrene to butadiene is 1:1, and the hydrophilic modifier in the amphiphilic modifier is polyethylene glycol, while the hydrophobic modifier is polypyrrole.

8. The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent according to claim 1, characterized in that, The other ingredients are one or a mixture of two of the following: modified asphalt powder, cationic asphalt powder, modified micron-nano silica powder, ultrafine calcium carbonate, modified silicon-based fiber, tetraethyl orthosilicate, and amorphous soil.

9. The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent according to claim 5, characterized in that, The preparation method of the potassium chloride amine-based water-based drilling fluid slurry includes the following sub-steps in sequence: Step 1.1: First, mix 1000 parts water with 20 parts sodium bentonite, stir at 1000 rpm for 30 minutes, then stir at 6000 rpm for 30 minutes, and let it cure at room temperature for 24 hours to form mixture 1. Step 1.2: At a stirring speed of 6000 rpm, add 1 part of potassium polyacrylamide K-PAM and 5 parts of hydrolyzed potassium polyacrylonitrile K-PAN to mixture 1, stir evenly, then add 3 parts of potassium chloride, 2 parts of branched polyetheramine and 20 parts of cationic asphalt, stir evenly, then add 20 parts of ultrafine calcium carbonate, while stirring, add 20 parts of environmentally friendly bio-lubricant JS-LUB-Ⅱ, then add 15 parts of inorganic-organic hybrid anti-high temperature filtration loss agent, stir thoroughly to form mixture 2; Step 1.3: Adjust the pH of mixture 2 to 8 with KOH to form mixture 3; Step 1.4: Add 300 parts of barite to mixture 3, stir evenly, and then prepare potassium chloride amine-based water-based drilling fluid slurry.

10. The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent according to claim 5, characterized in that, The preparation method of the potassium chloride amine-based water-based drilling fluid slurry includes the following sub-steps in sequence: Step 1.1: First, mix 1000 parts water with 25 parts sodium bentonite, stir at 2000 rpm for 40 minutes, then stir at 8000 rpm for 35 minutes, and let it cure at room temperature for 24 hours to form mixture 1. Step 1.2: At a stirring speed of 8000 rpm, add 1.5 parts of potassium polyacrylamide K-PAM and 6 parts of hydrolyzed potassium polyacrylonitrile K-PAN to mixture 1, stir evenly, then add 5 parts of potassium chloride, 3 parts of branched polyetheramine and 25 parts of cationic asphalt, stir evenly, then add 30 parts of ultrafine calcium carbonate, while stirring, add 30 parts of environmentally friendly bio-lubricant JS-LUB-Ⅱ, then add 18 parts of inorganic-organic hybrid anti-high temperature filtration loss agent, stir thoroughly to form mixture 2; Step 1.3: Adjust the pH of mixture 2 to 9 with KOH to form mixture 3; Step 1.4: Add 350 parts of barite to mixture 3, stir evenly, and then prepare potassium chloride amine-based water-based drilling fluid slurry.

11. The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent according to claim 5, characterized in that, The preparation method of the potassium chloride amine-based water-based drilling fluid slurry includes the following sub-steps in sequence: Step 1.1: First, mix 1000 parts water with 30 parts sodium bentonite, stir at 3000 rpm for 45 minutes, then stir at 10000 rpm for 45 minutes, and let it cure at room temperature for 24 hours to form mixture 1. Step 1.2: At a stirring speed of 10,000 rpm, add 2 parts of potassium polyacrylamide K-PAM and 8 parts of hydrolyzed potassium polyacrylonitrile K-PAN to mixture 1. After stirring evenly, add 8 parts of potassium chloride, 4 parts of branched polyetheramine and 30 parts of cationic asphalt. After stirring evenly, add 40 parts of ultrafine calcium carbonate. While stirring, add 40 parts of environmentally friendly bio-lubricant JS-LUB-Ⅱ. Then add 20 parts of inorganic-organic hybrid anti-high temperature filtration loss agent. After stirring thoroughly, mixture 2 is formed. Step 1.3: Adjust the pH of mixture 2 to 10 with KOH to form mixture 3; Step 1.4: Add 380 parts of barite to mixture 3, stir evenly, and then prepare potassium chloride amine-based water-based drilling fluid slurry.

12. The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent according to claim 6, characterized in that, The raw material composition and weight content of the strong plugging potassium chloride amine-based drilling fluid are as follows: the amount of the amphiphilic high-temperature resistant micro-nano plugging agent added in 100 parts of drilling fluid sample is 1 part, and the amount of the amphiphilic polymer fiber plugging agent while drilling is 1 part.

13. The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent according to claim 6, characterized in that, The raw material composition and weight content of the strong plugging potassium chloride amine-based drilling fluid are as follows: the amount of the amphiphilic high-temperature resistant micro-nano plugging agent added in 100 parts of drilling fluid sample is 2 parts, and the amount of amphiphilic polymer fiber plugging agent while drilling is 2 parts.

14. The method for stabilizing the wellbore of hard and brittle shale using an amphiphilic high-temperature resistant micro / nano plugging agent according to claim 6, characterized in that, The raw material composition and weight content of the strong plugging potassium chloride amine-based drilling fluid are as follows: the amount of the amphiphilic high-temperature resistant micro-nano plugging agent added in 100 parts of drilling fluid sample is 2 parts, and the amount of amphiphilic polymer fiber plugging agent while drilling is 4 parts.

15. An amphiphilic high-temperature resistant micro / nano plugging agent, characterized in that, It is prepared in the following steps: Step A1: 40-60 parts of styrene and butadiene, 5-20 parts of epoxy resin, 10-20 parts of vinylpyrrolidone, 1-5 parts of Tween-20 emulsifier, 0.15-0.6% lauroyl peroxide initiator and 0.1-0.5% polyvinyl alcohol aqueous solution are added to a protective colloid to carry out a seed polymerization reaction to obtain a seed copolymer emulsion, which is then uniformly sprayed onto 10-15 parts of silica microcrystalline particles using a spraying device; Step A2: Dry the product obtained in step A1 at a low temperature of 40-50°C; Step A3: Prepare the seed copolymer emulsion described in step A1 again, and spray it evenly onto the silica microcrystalline particles obtained in step A2. Step A4: Dry the product obtained in step A3 at a low temperature of 40-50°C; Step A5: Dissolve the product obtained in step A4 with the amphiphilic modifier and oxalic acid in distilled water, then add a small amount of sulfuric acid catalyst to react. After the reaction, filter to obtain the initial product; wash with distilled water and dry to obtain dried short fibers. Step A6: The dried short fibers are cut, crushed and sieved multiple times to obtain fine fibers smaller than 1mm; Step A7: The fine fiber is mixed evenly with 15-20 parts of filler and 10-15 parts of other ingredients to obtain an amphiphilic high-temperature resistant micro-nano sealing agent.

16. A method for stabilizing the wellbore of hard and brittle shale using the amphiphilic high-temperature resistant micro / nano plugging agent according to claim 15, characterized in that, In step A1: 40 parts of styrene and butadiene, 5 parts of epoxy resin, 10 parts of vinylpyrrolidone, 1 part of Tween-20 emulsifier, 0.15% lauroyl peroxide initiator and 0.1% polyvinyl alcohol aqueous solution are added and sprayed evenly onto 10 parts of silica microcrystalline particles using a spraying device. In steps A2 and A4: the low-temperature drying temperature is 40℃; In step A7: the filler is 15 parts and the other ingredients are 10 parts.

17. A method for stabilizing the wellbore of hard and brittle shale using the amphiphilic high-temperature resistant micro / nano plugging agent according to claim 15, characterized in that, In step A1: 50 parts of styrene and butadiene, 10 parts of epoxy resin, 15 parts of vinylpyrrolidone, 3 parts of Tween-20 emulsifier, 0.4% lauroyl peroxide initiator and 0.3% polyvinyl alcohol aqueous solution are added and sprayed evenly onto 12 parts of silica microcrystalline particles using a spraying device. In steps A2 and A4: the low-temperature drying temperature is 45℃; In step A7: the filler is 18 parts and the other ingredients are 12 parts.

18. A method for stabilizing the wellbore of hard and brittle shale using the amphiphilic high-temperature resistant micro / nano plugging agent according to claim 15, characterized in that, In step A1: 60 parts of styrene and butadiene, 20 parts of epoxy resin, 20 parts of vinylpyrrolidone, 5 parts of Tween-20 emulsifier, 0.6% lauroyl peroxide initiator and 0.5% polyvinyl alcohol aqueous solution are added and sprayed evenly onto 15 parts of silica microcrystalline particles using a spraying device. In steps A2 and A4: the low-temperature drying temperature is 50℃; In step A7: the filler is 20 parts and the other ingredients are 15 parts.

Images