Water-based well drilling fluid consolidating solid wall agent, its preparation method and application

Abstract

The application provides a water-based well drilling fluid cementing wall stabilizer and a preparation method and application thereof, and comprises the following steps: (1) mixing a first material system comprising a vinylamide, a vinylpyrrolidone, a tannic acid, a carbon fiber and an initiator with a first solvent to obtain a core material; (2) mixing a second material system comprising an emulsifier, a flexible polymer and a curing agent with a second solvent to obtain a shell material; (3) mixing the core material with part of the shell material, and then performing shearing homogenization to obtain a water-in-oil emulsion; and (4) mixing the water-in-oil emulsion with the remaining shell material, and then performing a polycondensation reaction to obtain the cementing wall stabilizer. The cementing wall stabilizer provided by the application is suitable for a water-based well drilling fluid system and has good dispersion stability and high-temperature and high-pressure structural stability.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, specifically to a water-based drilling fluid cementing and wall-stabilizing agent, its preparation method, and its application. Background Technology

[0002] As oil and gas exploration and development extend into deeper, ultra-deep, and unconventional reservoirs, fractured formations are frequently encountered during drilling. These formations typically contain fractures, voids, and weak cementation, making them prone to complex situations such as wellbore instability, lost circulation, and wellbore enlargement during drilling, severely impacting drilling safety and efficiency.

[0003] To address wellbore instability in fractured formations, common water-based drilling fluid treatments include physical particle plugging, chemical inhibition, and polymeric filtration reduction. Physical particle plugging agents, which rely on solid particles to form a mechanical barrier in fractures or pores, are effective to some extent. However, due to the varying fracture sizes and strong pore connectivity, particle plugging often suffers from incomplete sealing and easy backflow. Chemical inhibitors can reduce shale hydration swelling, but their effect on large-scale fractures in fractured formations is limited. Polymeric filtration reduction agents can improve filtration performance, but they are difficult to use for deep formation cementation and structural reinforcement.

[0004] Currently, chemically cemented wall-stabilizing agents are gradually becoming a research hotspot for stabilizing formations and wellbore walls. Among existing technologies, Chinese patent CN 117986520A describes a method that involves demethylating lignin and then reacting it with isocyanate monomers and castor oil. This allows it to rapidly penetrate into the pores and fractures of fractured rock formations, forming a dense cemented network structure through synergistic effects of hydrogen bonds, van der Waals forces, and hydrophobicity. This significantly improves the bonding strength between the wall-stabilizing agent and rock particles, thereby enhancing wellbore stability during drilling through fractured rock formations and providing good viscosity enhancement and filtration reduction for drilling fluids. Chinese patent CN 114854379B describes a wall-stabilizing agent synthesized from polymers and tannic acid, which can cement fractured formations, improve rock strength, inhibit shale hydration dispersion, and reduce drilling fluid filtration. Chinese patent CN 114716984A describes a cementing and plugging wall-stabilizing agent. This agent is formed through free radical polymerization of modified silica, acrylamide, acrylic acid, sodium p-styrene sulfonate, dimethyl diallyl ammonium chloride, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, and dopamine hydrochloride. It effectively cements and seals fractures in broken formations, inhibits shale hydration dispersion, and reduces drilling fluid loss, thereby helping to maintain or even enhance rock strength and stabilizing the wellbore in broken formations. While this wall-stabilizing agent can stabilize the formation, in the complex environment of drilling fluids, it can negatively impact the performance of the drilling fluid. Furthermore, it is difficult for the wall-stabilizing agent to directly act on the target formation in such conditions, resulting in poor performance.

[0005] The development of a cementing and wall-stabilizing agent suitable for water-based drilling fluid systems, possessing both good dispersion stability and high-temperature and high-pressure structural stability, has become a research hotspot in this field. Summary of the Invention

[0006] This invention provides a water-based drilling fluid cementing and wall-stabilizing agent, its preparation method, and its application. The cementing and wall-stabilizing agent is suitable for water-based drilling fluid systems and has both good dispersion stability and high-temperature and high-pressure structural stability.

[0007] In a first aspect, the present invention provides a method for preparing a cementing and wall-stabilizing agent, comprising the following steps: (1) mixing a first material system comprising vinylamide, vinylpyrrolidone, tannic acid, carbon fiber, and an initiator with a first solvent to obtain a core material; (2) mixing a second material system comprising an emulsifier, a flexible polymer, and a curing agent with a second solvent to obtain a shell material; (3) mixing the core material with a portion of the shell material, and after shearing and homogenization, obtaining a water-in-oil emulsion; (4) mixing the water-in-oil emulsion with the remaining shell material, and performing a polycondensation reaction to obtain the cementing and wall-stabilizing agent.

[0008] Optionally, the vinylamide includes acrylamide.

[0009] Optionally, the vinylamide content in the core material is 10% to 20% by mass.

[0010] Optionally, the tannic acid in the core material has a mass percentage content of 10% to 15%.

[0011] Optionally, the carbon fiber in the core material has a mass percentage content of 2% to 5%.

[0012] Optionally, the initiator in the core material has a mass percentage content of 0.1% to 0.5%.

[0013] Optionally, the initiator includes one or more of benzoyl peroxide, lauroyl peroxide, 2,2'-azobisisobutyronitrile, and ammonium persulfate.

[0014] Optionally, the core material contains 5% to 10% by mass of vinylpyrrolidone.

[0015] Optionally, the first solvent includes water.

[0016] Optionally, the second solvent includes an organic solvent.

[0017] Optionally, the emulsifier includes one or more of sorbitan oleate, sorbitan palmitate, and sorbitan laurate.

[0018] Optionally, the emulsifier in the core material has a mass percentage content of 1% to 3%.

[0019] Optionally, the flexible polymer includes tetradecyl acrylate and methyl methacrylate.

[0020] Optionally, the mass percentage of tetradecyl acrylate in the core material is 10% to 20%.

[0021] Optionally, the mass percentage of methyl methacrylate in the core material is 5% to 10%.

[0022] Optionally, the curing agent includes one or more of ethylene glycol dimethacrylate, trimethylolpropane triacrylate, and divinylbenzene.

[0023] Optionally, the curing agent in the core material has a mass percentage content of 1% to 3%.

[0024] Optionally, in step (3), the mass of the portion of the shell material accounts for one-third to one-half of the total mass of the shell material.

[0025] Optionally, the shearing rate for the shearing homogenization is 5000 rpm / min to 7000 rpm / min.

[0026] Optionally, the temperature of the polycondensation reaction is 70°C to 80°C.

[0027] Secondly, the present invention provides a cementing and wall-stabilizing agent, which is prepared according to the above-described method for preparing the cementing and wall-stabilizing agent.

[0028] Thirdly, the present invention provides a water jet drilling fluid, comprising the cementing agent prepared according to the above-described method for preparing the cementing agent or the above-described cementing agent.

[0029] This invention provides a water-based drilling fluid cementing and wall-stabilizing agent, its preparation method, and its application, which has at least the following beneficial effects: The preparation method of the cementing and wall-stabilizing agent of this invention, through a core-shell structure design, combines the flexible dispersibility of the shell material with the chemical cementing ability of the core material to achieve stable dispersion, self-adaptive crack sealing, and synergistic cementing with formation rocks in the water-based drilling fluid system. Specifically, the flexible properties of the shell material endow the cementing and wall-stabilizing agent with the ability to adapt to complex drilling fluid environments, avoiding structural damage caused by mechanical shearing or temperature fluctuations; tannic acid and monomers such as vinylamide in the core material form a gel network through free radical polymerization, wherein the phenolic hydroxyl groups provided by tannic acid can chemically bond with the rock surface, significantly improving the cementing strength; in addition, the step-by-step dripping process optimizes the emulsification reaction kinetics, ensuring the crosslinking degree and coating efficiency of the shell material, so that the cementing and wall-stabilizing agent gradually releases the core material gel in the target formation, achieving self-adaptive crack filling and long-term stability. The overall process takes into account both material performance and preparation efficiency, providing an efficient and stable wellbore reinforcement solution for drilling in fractured formations. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In a first aspect, embodiments of the present invention provide a method for preparing a cementing and wall-fixing agent, comprising the following steps: (1) mixing a first material system comprising vinylamide, vinylpyrrolidone, tannic acid, carbon fiber, and an initiator with a first solvent to obtain a core material; (2) mixing a second material system comprising an emulsifier, a flexible polymer, and a curing agent with a second solvent to obtain a shell material; (3) mixing the core material with a portion of the shell material, and after shearing and homogenization, obtaining a water-in-oil emulsion; (4) mixing the water-in-oil emulsion with the remaining shell material, and carrying out a polycondensation reaction to obtain a cementing and wall-fixing agent.

[0032] According to research and analysis, the preparation method of the cementing wall-stabilizing agent of this invention, through core-shell structure design, combines the flexible dispersibility of the shell material with the chemical bonding ability of the core material to achieve stable dispersion, self-adaptive crack sealing, and synergistic bonding with formation rocks in water-based drilling fluid systems. Specifically, the flexible properties of the shell material endow the cementing wall-stabilizing agent with the ability to adapt to complex drilling fluid environments, avoiding structural damage caused by mechanical shearing or temperature fluctuations; tannic acid and vinyl amide monomers in the core material form a gel network through free radical polymerization, wherein the phenolic hydroxyl groups provided by tannic acid can chemically bond with the rock surface, significantly improving the bonding strength; in addition, the stepwise dripping process optimizes the emulsification reaction kinetics, ensuring the crosslinking degree and coating efficiency of the shell material, allowing the cementing wall-stabilizing agent to gradually release the core material gel in the target formation, achieving self-adaptive crack filling and long-term stability. The overall process takes into account both material performance and preparation efficiency, providing an efficient and stable wellbore reinforcement solution for drilling in fractured formations.

[0033] (1) A first material system comprising vinylamide, vinylpyrrolidone, tannic acid, carbon fiber and initiator is mixed with a first solvent to obtain a core material.

[0034] For example, step (1) may specifically include: mixing a first material system including vinylamide, vinylpyrrolidone, tannic acid, carbon fiber and initiator with a first solvent, and stirring at 20°C to 25°C for 2 min to 10 min to obtain a core material.

[0035] In some embodiments, vinylamide may include acrylamide.

[0036] Vinylamides meet the above criteria and possess the characteristics of high reactivity, strong hydrophilicity, and easy modification and crosslinking. On the one hand, they can better adapt to water-based drilling fluids, and on the other hand, they can better form a gel network with tannic acid, thereby improving the stability of cementing wall-stabilizing agents.

[0037] In the core material, the mass percentage of vinylamide can be 10% to 20%, for example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any combination thereof.

[0038] When the mass percentage of vinylamide meets the above range, it can better form a gel network with tannic acid that has moderate cross-linking density, certain strength, and water absorption and swelling properties. This network can not only firmly encapsulate other core material components but also release them when needed.

[0039] In the core material, the mass percentage of vinylpyrrolidone can be 5% to 10%, for example, 5%, 6%, 7%, 8%, 9%, 10%, or any combination thereof.

[0040] When the mass percentage of vinylpyrrolidone meets the above range, it can effectively improve the flexibility and adhesion of the gel network, reduce its brittleness, thereby promoting a more uniform gel network structure, further optimizing mechanical properties, and ultimately enhancing the mechanical stability of the cementing and wall-fixing agent.

[0041] In the core material, the mass percentage of tannic acid can be 10% to 15%, for example, 10%, 11%, 12%, 13%, 14%, 15%, or any combination thereof.

[0042] When the mass percentage of tannic acid meets the above-mentioned range, it provides adequate cross-linking points, enhancing the strength of the gel network. Simultaneously, the abundant phenolic hydroxyl groups in tannic acid can undergo condensation reactions with hydroxyl groups on the rock surface, forming stable chemical bonds. This mechanism not only strengthens the interfacial bonding between the wall-stabilizing agent and the formation rock but also helps improve the overall mechanical strength of fractured rock formations, thereby significantly improving wellbore stability.

[0043] In some specific embodiments, the mass percentage of carbon fiber in the core material can be 2% to 5%, for example, 2%, 3%, 4%, 5% or any combination thereof.

[0044] Carbon fiber can be used as a reinforcing filler to strengthen, toughen, and conduct fluid in the gel network. When the mass percentage of carbon fiber meets the above range, it can improve the mechanical strength, toughness, and crack resistance of the gel network, and may form a thermally conductive pathway, thereby further improving the structural stability of the cementing wall-fixing agent under high temperature and high pressure conditions.

[0045] In the core material, the mass percentage of the initiator can be 0.1% to 0.5%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any combination thereof.

[0046] Specifically, the initiator includes one or more of benzoyl peroxide, lauroyl peroxide, 2,2'-azobisisobutyronitrile, and ammonium persulfate, with ammonium persulfate being preferred.

[0047] The first solvent may include water.

[0048] The stirring speed can be from 100 rpm / min to 300 rpm / min, for example, 100, 200, 300 rpm / min or any combination thereof.

[0049] The stirring time can be 2 min to 10 min, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10 min or any combination thereof.

[0050] The stirring temperature can be 20°C to 25°C, for example, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, or any combination thereof, preferably 25°C.

[0051] (2) The second material system, including emulsifier, flexible polymer and curing agent, is mixed with the second solvent to obtain shell material.

[0052] For example, step (2) may specifically include: mixing a second material system including an emulsifier, a flexible polymer, and a curing agent with a second solvent, and stirring at 20°C to 25°C for 2 min to 10 min to obtain a shell material.

[0053] In some specific embodiments, the emulsifier may include one or more of sorbitan oleate (such as Span 80), sorbitan palmitate (such as Span 40), and sorbitan laurate (such as Span 20), preferably sorbitan oleate (Span 80) and sorbitan laurate (Span 20) in a mass ratio of 1:(1~1.5).

[0054] The mass ratio of sorbitan oleate (Span80) to sorbitan laurate (Span20) can be 1:(1 to 1.5), for example, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5 or any combination thereof.

[0055] Emulsifiers that meet the above criteria can reduce the interfacial tension between oil and water, which is beneficial for the subsequent formation of stable water-in-oil emulsions.

[0056] In the core material, the mass percentage of emulsifier can be 1% to 3%, for example, 1%, 2%, 3% or any combination thereof.

[0057] The emulsifier's mass percentage content meeting the above range is beneficial for the formation of a stable emulsion in the shell layer, resulting in fine and uniformly distributed emulsion droplets, which is conducive to the preparation of the shell structure of the core-shell structure cementing and wall-solidifying agent.

[0058] In some embodiments, the flexible polymer may include tetradecyl acrylate and methyl methacrylate.

[0059] Flexible polymers meet the above criteria and can better form a flexible skeleton for the cementitious wall-forming agent shell, thereby improving the elasticity and impact resistance of the cementitious wall-forming agent.

[0060] Furthermore, in the core material, the mass percentage of tetradecyl acrylate can be 10% to 20%, for example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any combination thereof.

[0061] When the mass percentage of tetradecyl acrylate meets the above range, it can improve the flexibility of the shell structure of the cementitious wall-forming agent, making it less brittle and further improving the mechanical properties of the cementitious wall-forming agent.

[0062] In the core material, the mass percentage of methyl methacrylate is 5% to 10%, for example, 5%, 6%, 7%, 8%, 9%, 10%, or any combination thereof.

[0063] When the mass percentage of methyl methacrylate meets the above range, it can improve the flexibility of the shell structure of the cementitious wall-forming agent, making it less brittle and further improving the mechanical properties of the cementitious wall-forming agent.

[0064] The curing agent may include one or more of ethylene glycol dimethacrylate, trimethylolpropane triacrylate, and divinylbenzene, preferably ethylene glycol dimethacrylate.

[0065] The curing agent meets the above requirements and can better react with the active groups (such as -OH, -NCO) on the flexible polymer to form a three-dimensional network, giving the shell final strength, heat resistance and solvent resistance, thereby further improving the compressive strength of the cementing wall agent under high temperature and high pressure.

[0066] In the core material, the mass percentage of the curing agent can be 1% to 3%, for example, 1%, 2%, 3% or any combination thereof.

[0067] When the mass percentage of the curing agent meets the above range, it can better react with the active groups (such as -OH, -NCO) on the flexible polymer to form a three-dimensional network, giving the shell final strength, heat resistance and solvent resistance, thereby further improving the compressive strength of the cementing wall agent under high temperature and high pressure.

[0068] The second solvent includes organic solvents; specifically, the second solvent may include diesel fuel, preferably No. 0 diesel fuel.

[0069] The stirring speed can be from 100 rpm / min to 300 rpm / min, for example, 100, 200, 300 rpm / min or any combination thereof.

[0070] The stirring time can be 2 min to 10 min, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10 min or any combination thereof.

[0071] The stirring temperature can be 20°C to 25°C, for example, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, or any combination thereof, preferably 25°C.

[0072] (3) Mix the core material with part of the shell material, and after shearing and homogenization, obtain an oil-in-water emulsion.

[0073] For example, step (3) may specifically include: mixing the core material with a portion of the shell material, and shearing and homogenizing it in a homogenizer at a speed of 5000 rpm / min to 7000 rpm / min for 20 min to 40 min to obtain an oil-in-water emulsion.

[0074] Specifically, the mass of a portion of the shell material accounts for one-third to one-half of the total mass of the shell material, for example, one-third, two-fifths, one-half, or any combination thereof.

[0075] If the proportion of the shell material's mass to the total mass of the shell material meets the above range, the viscosity of the oil phase (shell material) can be reduced, thereby obtaining smaller and more uniform water-in-oil emulsion (W / O emulsion) droplets during homogenization, creating conditions for the subsequent uniform and dense growth of the shell layer.

[0076] The shearing rate for shear homogenization can be 5000 rpm / min to 7000 rpm / min, for example, 5000, 6000, 7000 rpm / min or any combination thereof.

[0077] When the shear rate meets the above range, smaller and more uniform water-in-oil (W / O) emulsion droplets can be obtained, creating conditions for the subsequent uniform and dense growth of the shell layer.

[0078] The shearing and homogenization time can be 20 min to 40 min, for example, 20, 25, 30, 35, 40 min or any combination thereof.

[0079] (4) Mix the water-in-oil emulsion with the remaining shell material and carry out a polycondensation reaction to obtain a cementing and wall-fixing agent.

[0080] For example, step (4) may specifically include: transferring the water-in-oil emulsion to a three-necked flask, adding the remaining shell material to the water-in-oil emulsion at a rate of 40 drops / min to 80 drops / min, carrying out a polycondensation reaction at 70°C to 80°C for 3 to 5 hours, and obtaining a cementing and wall-fixing agent after washing and drying.

[0081] The remaining shell material can account for one-half to two-thirds of the total shell material mass, for example, one-half, three-fifths, or two-thirds.

[0082] If the quality of the remaining shell material meets the above range, it can achieve uniform and dense growth of the shell layer, which is beneficial to further improve the compressive strength of the cementing wall-consolidating agent under high temperature and high pressure.

[0083] The dripping rate of the remaining shell material can be 40 drops / min to 80 drops / min, for example, 40, 50, 60, 70, or 80 drops / min, preferably 60 drops / min.

[0084] Stirring can be carried out during the dripping process. The stirring speed can be 300 rpm / min to 500 rpm / min, for example, 300, 350, 400, 450, 500 rpm / min or any combination thereof, preferably 400 rpm / min.

[0085] When the stirring speed meets the above range, it is possible to shift from high-intensity mechanical dispersion to mild mechanical and thermodynamic control, protecting the formed water-in-oil emulsion droplets and preventing them from re-aggregating (demulsification) or being broken due to excessive shear force. This enables the further preparation of a cementing and wall-consolidating agent with uniform shell thickness and stable mechanical properties.

[0086] In some embodiments, the temperature of the polycondensation reaction can be 70°C to 80°C, for example, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80°C or any combination thereof.

[0087] When the temperature of the polycondensation reaction meets the above range, it is beneficial to control the growth thickness and cross-linking density of the shell layer, forming a dense and uniform shell structure, and further improving the mechanical stability of the cementing and wall-fixing agent.

[0088] The polycondensation reaction can take 3 to 5 hours, for example, 3, 4, 5 hours or any combination thereof.

[0089] Meeting the above-mentioned time range for the polycondensation reaction is beneficial for controlling the growth thickness and cross-linking density of the shell layer, forming a dense and uniform shell structure, and further improving the mechanical stability of the cementing and wall-fixing agent.

[0090] In some specific embodiments, the detergent used in the above washing process can be ethanol, and the number of washing cycles can be 3 to 8 times, for example, 3, 4, 5, 6, 7, 8 times or any combination thereof, preferably 5 times.

[0091] The drying temperature can be 60°C to 70°C, for example, 60, 65, 70°C or any combination thereof, preferably 65°C.

[0092] The drying time can be 46h to 50h, for example, 46, 47, 48, 49, 50h or any combination thereof, preferably 48h.

[0093] The prepared cementing wall-stabilizing agent exhibits a typical core-shell structure. The shell layer possesses good flexibility and dispersibility in water-based drilling fluids. During the process of sealing fractures, it can form a dense barrier through accumulation, effectively preventing liquid phase intrusion. As drilling time increases, under the influence of temperature and pressure, the temperature resistance of the shell layer becomes limited, and the shell layer gradually degrades and is consumed. The internal core material then transforms into a gel. This gel has strong self-adaptive sealing capabilities and can achieve close adhesion to the formation rock surface. At the same time, the phenolic hydroxyl groups rich in tannic acid in the core material can undergo a condensation reaction with the hydroxyl groups on the rock surface to form stable chemical bonds, thereby further enhancing wellbore stability.

[0094] Secondly, embodiments of the present invention provide a cementing and wall-stabilizing agent, which is prepared according to the above-described method for preparing the cementing and wall-stabilizing agent.

[0095] The shell layer of the aforementioned cementing wall-stabilizing agent endows it with excellent flexibility and dispersibility, enabling it to maintain a stable dispersion in water-based drilling fluid systems without significantly interfering with key properties such as rheology, lubricity, and rock-carrying capacity of the water-based drilling fluid, thus ensuring the overall stability of the drilling fluid system. During drilling, the cementing wall-stabilizing agent first accumulates in formation fractures and pores through its shell layer, forming a dense barrier to prevent rapid liquid phase intrusion. As time and temperature and pressure conditions change, the shell layer is gradually consumed, and the core material transforms into a gel, achieving adaptive filling and cementation of fractures, thereby significantly improving wellbore stability and reducing the risk of lost circulation.

[0096] Thirdly, embodiments of the present invention provide a water-based drilling fluid, comprising a cementing agent prepared by the above-described method for preparing a cementing agent or the above-described cementing agent.

[0097] The aforementioned water-based drilling fluid has excellent wall-stabilizing effect.

[0098] Cementing wall-stabilizing agents have good dispersibility and stability in water-based drilling fluids. They can penetrate into fractured formations and pores with the drilling fluid, first forming an effective seal on the wellbore surface. This allows the wall-stabilizing agent to remain in the fractures and then form a stable cemented structure with the wellbore surface, thereby effectively improving wellbore stability, reducing the risk of well leakage, and ensuring the safe and efficient conduct of drilling operations.

[0099] In some specific implementations, water-based drilling fluid may include bentonite, wall-binding agents, and water.

[0100] Furthermore, the water-based drilling fluid (water-based drilling fluid system) can be a bentonite drilling fluid, with the amount of bentonite added being 2% to 4% based on the mass of water (100%), for example, 2%, 3%, 4%, or any combination thereof.

[0101] The amount of cementitious wall-stabilizing agent added is 2% to 3% based on the mass of water (100%), for example, 2%, 2.5%, 3%, or any combination thereof.

[0102] In addition, water-based drilling fluids may include one or more of the following: filtration loss reducers, pH adjusters, and potassium chloride.

[0103] Filtration reducers can form a low-permeability, tough filter cake on the wellbore, minimizing the loss of liquid phase from the drilling fluid to the formation.

[0104] Specifically, pH adjusters may include caustic soda (such as sodium hydroxide or sodium carbonate) to adjust the pH of water-based drilling fluids, which is beneficial for the dispersion and hydration of clay particles such as bentonite.

[0105] Potassium chloride, as a shale inhibitor in water-based drilling fluids, can inhibit clay hydration and stabilize the wellbore.

[0106] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0107] Example 1

[0108] This embodiment provides a method for preparing a cementing and wall-strengthening agent, the specific steps of which are as follows:

[0109] (1) The first material system, comprising 21g acrylamide (vinylamide), 11g vinylpyrrolidone, 17g tannic acid, 4g carbon fiber and 0.5g ammonium persulfate (initiator), is mixed with 100g water (first solvent) and stirred at 300rpm / min for 10min at 25°C to obtain the core material (core material mixed phase).

[0110] (2) The second material system, comprising 3 g emulsifier, 26 g tetradecyl acrylate (flexible polymer), 10 g methyl methacrylate (flexible polymer), and 4 g ethylene glycol dimethacrylate (curing agent), is mixed with 100 g No. 0 diesel oil (second solvent) and stirred at 300 rpm / min for 10 min at 25°C to obtain the shell material (shell material mixed phase).

[0111] (3) Mix the core material with one-third of the shell material and homogenize it in a homogenizer at a speed of 7000 rpm / min for 30 min to obtain a water-in-oil emulsion;

[0112] (4) Transfer the water-in-oil emulsion to a three-necked flask, add the remaining shell material to the water-in-oil emulsion at a rate of 60 drops / min, carry out a polycondensation reaction at 70°C for 3 hours, wash with ethanol 5 times, and dry at 65°C for 48 hours to obtain the cementing and wall-solidifying agent.

[0113] Example 2

[0114] This embodiment is the same as that in embodiment 1, except that the mass of acrylamide in step (1) is 14.72g, and the rest of the steps are the same as those in embodiment 1.

[0115] Example 3

[0116] This embodiment is the same as that in embodiment 1, except that the mass of acrylamide in step (1) is 16.56g, and the rest of the steps are the same as those in embodiment 1.

[0117] Example 4

[0118] This embodiment is the same as that in embodiment 1, except that the mass of vinylpyrrolidone in step (1) is 7.5g, and the rest of the steps are the same as those in embodiment 1.

[0119] Example 5

[0120] This embodiment is the same as that in embodiment 1, except that the mass of vinylpyrrolidone in step (1) is 15.83g, and the rest of the steps are the same as those in embodiment 1.

[0121] Example 6

[0122] This embodiment is the same as that in embodiment 1, except that the mass of tannic acid in step (1) is 15.16g, and the rest of the steps are the same as those in embodiment 1.

[0123] Example 7

[0124] This embodiment is the same as that in embodiment 1, except that the mass of tannic acid in step (1) is 24.08g, and the rest of the steps are the same as those in embodiment 1.

[0125] Example 8

[0126] This embodiment is the same as Embodiment 1, except that the mass of carbon fiber in step (1) is 3.05g, and the rest of the steps are the same as in Embodiment 1.

[0127] Example 9

[0128] This embodiment is the same as Embodiment 1, except that the mass of carbon fiber in step (1) is 7.87g, and the rest of the steps are the same as in Embodiment 1.

[0129] Example 10

[0130] This embodiment is the same as that in embodiment 1, except that the mass of ammonium persulfate in step (1) is 0.15g, and the rest of the steps are the same as those in embodiment 1.

[0131] Example 11

[0132] This embodiment is the same as that in embodiment 1, except that the mass of ammonium persulfate in step (1) is 0.76g, and the rest of the steps are the same as those in embodiment 1.

[0133] Example 12

[0134] This embodiment is the same as that of embodiment 1, except that the mass of the emulsifier in step (2) is 1.39g, and the rest of the steps are the same as those of embodiment 1.

[0135] Example 13

[0136] This embodiment is the same as that of embodiment 1, except that the mass of the emulsifier in step (2) is 4.33g, and the rest of the steps are the same as those of embodiment 1.

[0137] Example 14

[0138] This embodiment is the same as that in embodiment 1, except that the mass of tetradecyl acrylate in step (2) is 13g, and the rest of the steps are the same as those in embodiment 1.

[0139] Example 15

[0140] This embodiment is the same as that in Embodiment 1, except that the mass of tetradecyl acrylate in step (2) is 29.25g, and the rest of the steps are the same as those in Embodiment 1.

[0141] Example 16

[0142] This embodiment is the same as that in embodiment 1, except that the mass of methyl methacrylate in step (2) is 7g, and the rest of the steps are the same as those in embodiment 1.

[0143] Example 17

[0144] This embodiment is the same as that in embodiment 1, except that the mass of methyl methacrylate in step (2) is 14.77g, and the rest of the steps are the same as those in embodiment 1.

[0145] Example 18

[0146] This embodiment is the same as that in embodiment 1, except that the mass of ethylene glycol dimethacrylate in step (2) is 1.4g, and the rest of the steps are the same as those in embodiment 1.

[0147] Example 19

[0148] This embodiment is the same as that in embodiment 1, except that the mass of ethylene glycol dimethacrylate in step (2) is 4.3g.

[0149] Example 20

[0150] This embodiment is the same as that of embodiment 1, except that the mass of acrylamide in step (1) is 10g, and the rest of the steps are the same as those of embodiment 1.

[0151] Example 21

[0152] This embodiment is the same as that of Embodiment 1, except that the mass of acrylamide in step (1) is 18g, and the rest of the steps are the same as those of Embodiment 1.

[0153] Example 22

[0154] This embodiment is the same as that in embodiment 1, except that the mass of vinylpyrrolidone in step (1) is 6g, and the rest of the steps are the same as those in embodiment 1.

[0155] Example 23

[0156] This embodiment is the same as that of Embodiment 1, except that the mass of vinylpyrrolidone in step (1) is 18g, and the rest of the steps are the same as those of Embodiment 1.

[0157] Example 24

[0158] This embodiment is the same as that of embodiment 1, except that the mass of tannic acid in step (1) is 12g, and the rest of the steps are the same as those of embodiment 1.

[0159] Example 25

[0160] This embodiment is the same as that of embodiment 1, except that the mass of tannic acid in step (1) is 30g, and the rest of the steps are the same as those of embodiment 1.

[0161] Example 26

[0162] This embodiment is the same as embodiment 1, except that the mass of carbon fiber in step (1) is 2g, and the rest of the steps are the same as in embodiment 1.

[0163] Example 27

[0164] This embodiment is the same as embodiment 1, except that the mass of carbon fiber in step (1) is 9g, and the rest of the steps are the same as in embodiment 1.

[0165] Example 28

[0166] This embodiment is the same as that in embodiment 1, except that the mass of ammonium persulfate in step (1) is 0.05g, and the rest of the steps are the same as those in embodiment 1.

[0167] Example 29

[0168] This embodiment is the same as that in embodiment 1, except that the mass of ammonium persulfate in step (1) is 1g, and the rest of the steps are the same as those in embodiment 1.

[0169] Example 30

[0170] This embodiment is the same as that of embodiment 1, except that the mass of the emulsifier in step (2) is 1g, and the rest of the steps are the same as those of embodiment 1.

[0171] Example 31

[0172] This embodiment is the same as that of embodiment 1, except that the mass of the emulsifier in step (2) is 6g, and the rest of the steps are the same as those of embodiment 1.

[0173] Example 32

[0174] This embodiment is the same as that in embodiment 1, except that the mass of tetradecyl acrylate in step (2) is 10g, and the rest of the steps are the same as those in embodiment 1.

[0175] Example 33

[0176] This embodiment is the same as that in embodiment 1, except that the mass of tetradecyl acrylate in step (2) is 35g, and the rest of the steps are the same as those in embodiment 1.

[0177] Example 34

[0178] This embodiment is the same as that in embodiment 1, except that the mass of methyl methacrylate in step (2) is 5g, and the rest of the steps are the same as those in embodiment 1.

[0179] Example 35

[0180] This embodiment is the same as that in embodiment 1, except that the mass of methyl methacrylate in step (2) is 17g, and the rest of the steps are the same as those in embodiment 1.

[0181] Example 36

[0182] This embodiment is the same as that in embodiment 1, except that the mass of ethylene glycol dimethacrylate in step (2) is 1g, and the rest of the steps are the same as those in embodiment 1.

[0183] Example 37

[0184] This embodiment is the same as that in embodiment 1, except that the mass of ethylene glycol dimethacrylate in step (2) is 5g, and the rest of the steps are the same as those in embodiment 1.

[0185] Example 38

[0186] This embodiment is basically the same as that of Embodiment 1, except that: the shearing homogenization speed in step (3) is 5000 rpm / min; the polycondensation reaction temperature in step (4) is 80℃, and the other steps are the same as those in Embodiment 1.

[0187] Example 39

[0188] This embodiment is basically the same as that of Embodiment 1, except that: the shearing homogenization speed in step (3) is 6000 rpm / min; the polycondensation reaction temperature in step (4) is 75°C, and the other steps are the same as those in Embodiment 1.

[0189] Comparative Example 1

[0190] The procedure is basically the same as in Example 1, except that no acrylamide is added, while the rest of the steps are the same as in Example 1.

[0191] Comparative Example 2

[0192] It is basically the same as Example 1, except that tannic acid is not added, and the rest of the steps are the same as in Example 1.

[0193] Comparative Example 3

[0194] The procedure is basically the same as in Example 1, except that no flexible polymer is added, while the remaining steps are the same as in Example 1.

[0195] Test case

[0196] 1. Test of breakage rate of cementitious wall-consolidating agent

[0197] The wall-binding agent and wetting agent (sodium dodecylbenzenesulfonate, Jinan Shengming Chemical Co., Ltd.) were added to deionized water and mixed. The mixture was then sealed in an aging tank and aged at 120°C for 16 hours. The integrity of the wall-binding agent was then tested. The test results showed that the breakage rate of the wall-binding agent was less than 20%.

[0198] 2. Joint plate bearing capacity test

[0199] Preparation of base slurry: Add 16g bentonite and 0.024g anhydrous sodium carbonate to 400ml water, stir at 2000rpm / min for 2h at room temperature, and let stand at 25℃ (room temperature) for 24h for hydration.

[0200] Preparation of water-based drilling fluid: 8% (by weight, water as 100%) of the cementing and wall-stabilizing agents prepared in the examples and comparative examples were added to the base slurry, and stirred at 6000 rpm / min for 20 min. The prepared samples were filled into 20–40 μm slotted plates and aged at 120℃ for 48 h. The lamination capacity of the slotted plates was tested, and the test results are shown in Table 1.

[0201] Table 1 Results of the pressure-bearing test of the joint plate

[0202]

[0203] As shown in Table 1, the experimental results indicate that the compressive strength of the base slurry itself is 0 MPa, meaning that the system has almost no compressive strength without the addition of the examples or comparative samples. After adding the cementing and wall-strengthening agent, the compressive strength of the system is significantly improved. The compressive strength of the base slurry + Examples 1-19 group increases to 5.3-9.4 MPa, significantly better than the "base slurry + comparative example" group. Specifically, when the samples of Examples 20-29 are added, their compressive strength is 2.7-3.3 MPa. This may be closely related to the monomer type and ratio in the gel formation process of the core material. Insufficient monomer design leads to a significantly lower gel strength than Examples 1-19, but still better than the comparative examples. For Examples 30-39, the compressive strength further decreases to 2.3-2.9 MPa. It is speculated that the shell material breaks before the gel is fully formed, thus changing the reagent ratio and reaction process, resulting in an incomplete gel network structure and reduced system strength, but the results are still better than the comparative examples. Comprehensive analysis shows that the cementing and wall-stabilizing agents synthesized in Examples 1-19 can effectively form a stable gel network in the base slurry and significantly slow down pressure transmission in the system, thereby preferentially enhancing the overall stability of the wellbore. In contrast, the comparative examples are significantly less effective in slowing down pressure transmission and improving wellbore stability. Slowing down pressure transmission can preferentially enhance wellbore stability.

[0204] 3. Quartz sand solidification experiment

[0205] Weigh 360g of 80-100 mesh quartz sand and mix it with 10g of comparative and example samples. Place the mixture in a cylindrical compaction container, cover it with 3MPa pressure, stabilize the pressure for 2 hours, and then place it in an aging furnace at 120℃ for 48 hours. Apply a certain pressure above the prepared sample and record the pressure when the sample breaks. The experimental results are shown in Table 2.

[0206] Table 2 Results of Quartz Sand Solidification Experiment

[0207]

[0208] As shown in Table 2, pure quartz sand molds exhibit almost no compressive strength, failing under 0.11 MPa pressure, indicating a loose structure and difficulty in forming a stable consolidation system. After modification, the sample of Example 1, compounded with quartz sand, showed the best compressive strength, reaching 6.42 MPa, significantly better than other examples and comparative examples, indicating that this formulation is most effective in enhancing the consolidation ability of quartz sand. In contrast, Examples 2-19 reduced the amount of some key synthetic monomers in their formulations, resulting in a slight decrease in the strength of the gel network and thus a slight decrease in compressive strength compared to Example 1, but the overall decrease was small, maintaining a good consolidation effect. Examples 20-27 mainly modified the temperature resistance of the shell material, but had limited improvement on the gel consolidation ability; therefore, although their compressive strength decreased, the decrease was not significant, and their stability was still better than some inefficient formulations. In contrast, Examples 20-29, due to the excessive proportion of key synthetic monomers, resulted in a loose and weak gel network structure, significantly reducing its binding ability on the quartz sand particles and thus substantially decreasing the compressive strength of the quartz sand columns. However, the results were still better than the comparative examples. Particularly in Examples 24-25, the altered amount of tannic acid further weakened the cementing effect on the quartz sand, lowering the binding rate between the hydroxyl groups of the gel and the hydroxyl groups on the quartz sand surface, leading to a more pronounced decrease in compressive strength. Nevertheless, the results were still better than the comparative examples. Comparative Examples 1-3, lacking key synthetic monomers, could not form the target product, resulting in ineffective cementation of the quartz sand and a sharp decrease in compressive strength.

[0209] 4. Construction of water-based drilling fluid system

[0210] Preparation of base slurry: Add 16g bentonite and 0.14g anhydrous sodium carbonate to 400mL of water, stir thoroughly at 2000r / min for 2h, and then seal and let stand at room temperature for 24h for hydration.

[0211] Preparation of water-based drilling fluid: Take 400 mL of base slurry and add 0.5% sodium hydroxide (caustic soda), 2.5% filtration loss reducer (PAC-LV), and 8% potassium chloride. Add 4% of the wall-binding agent from Example 1 to this system, and compare with the blank sample without the wall-binding agent. The drilling fluid sample is aged using a roller furnace at 120°C for 16 h. After aging, stir at 6000 r / min for 20 min, and test the rheological parameters (apparent viscosity, plastic viscosity, and dynamic shear force) of the prepared drilling fluid according to GB / T 16783.2-2014.

[0212] Table 3 Compatibility Experiment

[0213]

[0214] AV is apparent viscosity, in mPa•s; PV is plastic viscosity, in mPa•s; YP is dynamic shear force, in Pa; HTHP is high temperature and high pressure filtration loss, in mL.

[0215] As shown in Table 3, the wall-binding agent of this invention has minimal impact on the rheological properties of the drilling fluid, and the system as a whole maintains good rheological properties. This indicates that the wall-binding agent has good compatibility with water-based drilling fluid systems, and can significantly improve wellbore stability while minimizing negative impacts on the rheological properties of water-based drilling fluids. Furthermore, the wall-binding agent also exhibits a certain filtration loss reduction effect, which helps to further improve the overall performance of the drilling fluid.

[0216] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a wall-bonding and solidifying agent, characterized in that, Includes the following steps: (1) A first material system comprising vinylamide, vinylpyrrolidone, tannic acid, carbon fiber, and initiator is mixed with a first solvent to obtain a core material; (2) A second material system comprising an emulsifier, a flexible polymer, and a curing agent is mixed with a second solvent to obtain a shell material; (3) The core material is mixed with a portion of the shell material, and after shearing and homogenization, an oil-in-water emulsion is obtained; (4) The water-in-oil emulsion is mixed with the remaining shell material and subjected to a polycondensation reaction to obtain the cementing and wall-fixing agent.

2. The method for preparing the cementing and wall-strengthening agent according to claim 1, characterized in that, The vinylamide includes acrylamide.

3. The method for preparing the cementing and wall-strengthening agent according to claim 1 or 2, characterized in that, In the core material, the mass percentage of vinylamide is 10% to 20%.

4. The method for preparing the cementing and wall-strengthening agent according to claim 1 or 2, characterized in that, In the core material, the mass percentage of tannic acid is 10% to 15%.

5. The method for preparing the cementing and wall-stabilizing agent according to claim 1 or 2, characterized in that, In the core material, the carbon fiber has a mass percentage content of 2% to 5%.

6. The method for preparing the cementing and wall-stabilizing agent according to claim 1 or 2, characterized in that, In the core material, the initiator has a mass percentage content of 0.1% to 0.5%.

7. The method for preparing the cementing and wall-stabilizing agent according to claim 6, characterized in that, The initiator includes one or more of benzoyl peroxide, lauroyl peroxide, 2,2'-azobisisobutyronitrile, and ammonium persulfate.

8. The method for preparing the cementing and wall-strengthening agent according to claim 1 or 2, characterized in that, In the core material, the mass percentage of vinylpyrrolidone is 5% to 10%.

9. The method for preparing the cementing and wall-strengthening agent according to claim 1 or 2, characterized in that, The first solvent includes water.

10. The method for preparing the cementing and wall-stabilizing agent according to claim 1 or 2, characterized in that, The second solvent includes organic solvents.

11. The method for preparing the cementing and wall-strengthening agent according to claim 1 or 2, characterized in that, The emulsifier includes one or more of sorbitan oleate, sorbitan palmitate, and sorbitan laurate.

12. The method for preparing the cementing and wall-stabilizing agent according to claim 11, characterized in that, In the core material, the mass percentage of the emulsifier is 1% to 3%.

13. The method for preparing the cementing and wall-strengthening agent according to claim 1 or 2, characterized in that, The flexible polymer includes tetradecyl acrylate and methyl methacrylate.

14. The method for preparing the cementing and wall-strengthening agent according to claim 13, characterized in that, In the core material, the mass percentage of tetradecyl acrylate is 10% to 20%.

15. The method for preparing the cementing and wall-strengthening agent according to claim 13, characterized in that, In the core material, the mass percentage of methyl methacrylate is 5% to 10%.

16. The method for preparing the cementing and wall-stabilizing agent according to claim 1 or 2, characterized in that, The curing agent includes one or more of ethylene glycol dimethacrylate, trimethylolpropane triacrylate, and divinylbenzene.

17. The method for preparing the cementing and wall-strengthening agent according to claim 16, characterized in that, In the core material, the curing agent has a mass percentage content of 1% to 3%.

18. The method for preparing the cementing and wall-stabilizing agent according to claim 1 or 2, characterized in that, In step (3), the mass of the portion of the shell material accounts for one-third to one-half of the total mass of the shell material.

19. The method for preparing the cementing and wall-strengthening agent according to claim 1 or 2, characterized in that, The shearing rate for the homogenization process is 5000 rpm / min to 7000 rpm / min.

20. The method for preparing the cementing and wall-stabilizing agent according to claim 1 or 2, characterized in that, The polycondensation reaction is carried out at a temperature of 70℃~80℃.

21. A wall-bonding and solidifying agent, characterized in that, The cementing and wall-consolidating agent is prepared according to the method described in any one of claims 1-20.

22. A water-based drilling fluid, characterized in that, This includes the cementing and wall-stabilizing agent prepared according to the preparation method of the cementing and wall-stabilizing agent according to any one of claims 1-20, or the cementing and wall-stabilizing agent according to claim 21.

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