Fast-filtering consolidation pressure sealing agent for oil-based drilling fluid

Abstract

The application discloses a quick-filtering consolidation pressure-bearing leak-stopping agent for oil-based drilling fluid and relates to the technical field of leak-stopping agents.The quick-filtering consolidation pressure-bearing leak-stopping agent comprises a consolidation agent, a composite filter aid, a polymer, a toughening agent and a curing agent, wherein the polymer is prepared through free radical polymerization of short-chain acrylate, long-chain acrylate and modified monomers; and the modified monomers are prepared from castor oil and acryloyl chloride.The quick-filtering consolidation pressure-bearing leak-stopping agent for oil-based drilling fluid has a relatively low total filtration time, a relatively high compressive strength and a breakthrough pressure gradient, and a relatively low leakage amount during plugging, and can be well applied to the leak stopping of oil-based drilling fluid.

Description

Technical Field

[0001] This invention relates to the field of plugging agent technology, specifically to a fast-filtration, solidified, pressure-bearing plugging agent for oil-based drilling fluids. Background Technology

[0002] Compared to water-based drilling fluids, oil-based drilling fluids are more expensive, and they suffer greater losses when dealing with lost circulation formations. Therefore, high-filtration-loss plugging agents are typically needed for oil-based drilling fluids. However, in current technology, most high-filtration-loss plugging agents are used in water-based drilling fluids, with very few applicable to oil-based drilling fluids. Furthermore, some existing high-filtration-loss plugging agents exhibit relatively poor pressure resistance after solidification. Summary of the Invention

[0003] To address at least one of the aforementioned problems, the present invention provides a fast-filtration, solidification, pressure-bearing plugging agent for oil-based drilling fluids.

[0004] The technical solution of the present invention to solve the above problems is as follows: a fast-filtration solidification pressure-bearing plugging agent for oil-based drilling fluid, comprising, by weight: 100 parts of solidifying agent, 20-30 parts of composite filter aid, 5-20 parts of polymer, 2-8 parts of toughening agent, and 10-20 parts of curing agent. The monomers for preparing the polymer are: 10 parts short-chain acrylate, 2-5 parts long-chain acrylate, and 1-3 parts modified monomer. The polymer is prepared by free radical polymerization. The modified monomer is prepared as follows: castor oil and acryloyl chloride are reacted in a molar ratio of 1:1-1.5 under the action of an acid-binding agent. After the reaction is completed, the modified monomer is obtained by separation and purification.

[0005] This invention uses a consolidating agent and a curing agent as the basic components of the plugging agent, which can form a high-strength plugging layer to achieve sealing. The composite filter aid in this invention can accelerate the filtration loss of drilling fluid during the formation of the plugging layer, thereby rapidly forming the plugging layer. The polymer of this invention, on the one hand, increases the viscosity of the drilling fluid, allowing the consolidating agent, composite filter aid, toughening agent, and curing agent in the drilling fluid to be uniformly and stably distributed within the fluid; on the other hand, after the plugging layer is formed, it makes the plugging layer more tough and dense, thereby improving the strength of the plugging layer and the success rate of sealing. The toughening agent of this invention can further improve the strength of the plugging layer.

[0006] The polymer of this invention uses acrylate as the main monomer because polyacrylate has good solubility in oil-based drilling fluids. Furthermore, this invention uses a combination of long-chain and short-chain acrylates to prepare the polymer, resulting in a comb-like structure that further enhances the polymer's performance. In this invention, a modifying monomer, castor oil with a monoacryloyloxy group, is also added to the polymer. The inventors found through experiments that this monomer can significantly increase the viscosity of the drilling fluid and simultaneously increase the strength of the plugging layer.

[0007] In the preparation process of the polymer of this invention, all monomers used are oil-soluble monomers. Therefore, in actual operation, the solvent used is also an oil-soluble solvent, such as common ethyl acetate and butyl acetate. At the same time, free radical polymerization requires an initiator. In this invention, common oil-soluble initiators can be used, such as azobisisobutyronitrile (AIBN) and azobisisoheptanenitrile (AIH). The specific reaction temperature for free radical polymerization needs to be set based on the initiation temperature of the initiator. For example, for AIBN, the amount added is usually 0.2-1.0% of the total mass of all monomers, the reaction temperature is usually set to 60-80°C, and the reaction time is usually 4-6 hours. For AIH, the amount added is usually 0.2-0.8% of the total mass of all monomers, the reaction temperature is usually 50-70°C, and the reaction time is usually 2-4 hours.

[0008] One embodiment of the present invention comprises: 100 parts of a binder, 23-26 parts of a composite filter aid, 12-14 parts of a polymer, 4-5 parts of a toughening agent, and 5-10 parts of a curing agent. Under these proportions, the sealant exhibits better performance.

[0009] One embodiment of the present invention involves using blast furnace slag as the solidifying agent. Blast furnace slag is a cementing material that can solidify rapidly when it has a small particle size and a large specific surface area. Furthermore, blast furnace slag is a solid waste, and the present invention utilizes it for solid waste disposal, resulting in lower costs and greater environmental friendliness.

[0010] Furthermore, the blast furnace slag is graded by particle size, with the first grade having a particle size of 20-40 mesh and the second grade having a particle size of 80-120 mesh, and the mass ratio of the first grade blast furnace slag to the second grade blast furnace slag being 5:1-10. This graded blast furnace slag arrangement yields better results: smaller particle sizes result in a larger specific surface area, better surface activity, and faster solidification; larger particle sizes provide a framework and increase the strength of the sealing layer. Additionally, the second grade can use even smaller particle sizes, such as 150 mesh; a three-stage configuration can also be used: a first grade of 10-20 mesh, a second grade of 40-80 mesh, and a third grade of 120-150 mesh. Those skilled in the art can also set other gradations based on specific site conditions.

[0011] One embodiment of the present invention involves the composite filter aid being one or more of diatomaceous earth and mesoporous silica. Diatomaceous earth is a common filter aid in the art, and mesoporous silica is also a porous material; both can be used alone or in combination. Specifically, considering the performance of both, diatomaceous earth can be used alone, or it can be compounded with mesoporous silica in a ratio of 1:0.5 to 3.

[0012] Furthermore, the mesoporous silica or diatomaceous earth is modified using a lipophilic silane coupling agent via vacuum impregnation. The vacuum impregnation method in this step is specifically operated as follows: First, the mesoporous silica or diatomaceous earth is dried at 100-120°C for 3-8 hours; the silane coupling agent is added to an ethanol-water solution (ethanol to water volume ratio of 100:5-10) and stirred for 30 minutes. After stirring, the dried diatomaceous earth or mesoporous silica is added to the silane coupling agent solution, maintaining a vacuum of not less than 0.1 MPa, and reacting at room temperature for 30-60 minutes. After the reaction, the solvent is removed, the solid phase is washed several times with ethanol, and then dried to obtain the final product. In this step, the selected lipophilic silane coupling agent can be one of hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltriethoxysilane, octadecyltrimethoxysilane, or phenyltrimethoxysilane. During operation, the amount of lipophilic silane coupling agent added is 10-20% of the inorganic phase (mesoporous silica, diatomaceous earth). The lipophilic modified filter aid can accelerate the filtration loss of oil-based drilling fluids and help the rapid formation of filter cake. On the other hand, for water-in-oil type oil-based drilling fluids, some water will remain in the filter cake, which helps the solidification of the solidifying agent in the filter cake.

[0013] One embodiment of the present invention is that the short-chain acrylate is one of butyl acrylate, butyl methacrylate, propyl acrylate, and propyl methacrylate, and the long-chain acrylate is one of lauryl acrylate, tetradecyl acrylate, hexadecyl acrylate, and octadecyl acrylate.

[0014] One embodiment of the present invention involves preparing the modified monomer under the following conditions: castor oil and acryloyl chloride are dissolved separately in chloroform as a solvent, and an acid-binding agent is added to the castor oil solution. Under ice bath conditions, the acryloyl chloride solution is added dropwise to the castor oil solution. After the addition is complete, the reaction is carried out at 20-40°C for 2-5 hours. After the reaction is completed, the mixture is extracted successively with saturated brine and distilled water. The organic phase is then dried under reduced pressure to obtain the final product. The acid-binding agent is triethylamine, and the amount of triethylamine added is 1-1.5 times the molar amount of acryloyl chloride.

[0015] In one embodiment of the present invention, the toughening agent is one or more of polypropylene fiber, polyester fiber, and basalt fiber, with a diameter of 10-100 micrometers and a length of 0.2-2.0 mm.

[0016] One embodiment of the present invention involves a curing agent comprising diethanolamine, calcium sulfate, and sodium silicate in a mass ratio of 1:1 to 3:2 to 5. Although blast furnace slag is a common inorganic cementing material, it is difficult to hydrate in oil-based drilling fluids due to their inherent characteristics. Even with common water-in-oil drilling fluids, hydration is challenging. Therefore, in this invention, a specialized curing agent is added to address the characteristics of water-in-oil drilling fluids and the fast-filtration plugging agent of this invention. This agent assists in the curing process. Under these operating conditions, the strength of the cured blast furnace slag is lower than that in water-based drilling fluids, but higher than that of most oil-based drilling fluid plugging agents. In practical applications, the addition of diethanolamine can be appropriately reduced or even omitted, but calcium sulfate and sodium silicate must be added.

[0017] The beneficial effects of this invention are as follows: the rapid-filtration, solidification, and pressure-bearing plugging agent for oil-based drilling fluids of this invention has a low total filtration loss time, high compressive strength, and breakthrough pressure gradient, while exhibiting low leakage during the plugging process. It can be effectively applied to plugging leaks in oil-based drilling fluids. Detailed Implementation

[0018] The specific embodiments of the present invention will be clearly and completely described below with reference to examples. Obviously, the described examples are only some embodiments of the present invention, and not all embodiments.

[0019] Unless otherwise specified, all pharmaceutical agents used in the following examples are conventional commercial products.

[0020] Unless otherwise specified, all operations used in the following embodiments are conventional operations in the art.

[0021] In the following embodiments, unless otherwise specified, all parts are parts by weight.

[0022] The modification method of modified mesoporous silica / modified diatomaceous earth in the following embodiments is as follows: Mesoporous silica / diatomaceous earth is dried at 120°C for 4 hours; an ethanol-water solution is prepared by mixing ethanol and water in a volume ratio of 10:1; a lipophilic silane coupling agent is added to the aforementioned ethanol-water solution and stirred continuously for 30 minutes to hydrolyze the lipophilic silane coupling agent; mesoporous silica / diatomaceous earth is added to the hydrolysate; a vacuum is drawn using a vacuum pump to make the system vacuum degree 0.1 MPa; the system is sealed and the vacuum degree is maintained; the reaction is carried out at room temperature for 50 minutes; after the reaction is completed, the liquid phase is removed; the solid phase is washed several times with ethanol and then dried to obtain the product; wherein, the mass ratio of mesoporous silica / diatomaceous earth to silane coupling agent is 10:1.5.

[0023] Example 1: A fast-filtration, solidified, pressure-bearing plugging agent for oil-based drilling fluid, comprising the following components: 40 parts blast furnace slag with a particle size of 20-40 mesh, 60 parts blast furnace slag with a particle size of 80-120 mesh, 10 parts modified diatomaceous earth (with hexadecyltrimethoxysilane as the lipophilic silane coupling agent), 15 parts modified mesoporous silica (with hexadecyltrimethoxysilane as the lipophilic silane coupling agent), 13 parts polymer, 4.5 parts polypropylene fiber (approximately 1 mm in length and approximately 21 μm in diameter), 2 parts diethanolamine, 5 parts calcium sulfate, and 8 parts sodium silicate. The preparation method of the polymer is as follows: Preparation of modified monomer: Using chloroform as solvent, 93.3 parts of castor oil and 12.0 parts of acryloyl chloride were added and dissolved. The solution was then dissolved in castor oil. 16.3 parts of triethylamine were added and dissolved completely. Under ice bath conditions, the acryloyl chloride solution was added dropwise to the castor oil solution. After the addition was complete, the reaction was carried out at 30°C for 3 hours. After the reaction was completed, the product was extracted with an equal volume of saturated brine and distilled water. The organic phase was collected and dried under reduced pressure to obtain the product.

[0024] Preparation of polymer: Take 10 parts of butyl acrylate, 3.5 parts of hexadecyl acrylate, and 2 parts of modified monomer and add them to butyl acetate. After mixing evenly, purge with nitrogen to remove oxygen for 30 min, heat to 60℃, add 0.093 parts of azobisisoheptanenitrile and react for 3 h. After the reaction is completed, dry under reduced pressure to remove low-boiling substances to obtain the polymer.

[0025] Example 2 differs from Example 1 in that it uses unmodified diatomaceous earth and unmodified mesoporous silica, while all other aspects remain the same.

[0026] Example 3 differs from Example 1 in that it does not use 80-120 mesh blast furnace slag, and the amount of 20-40 mesh blast furnace slag used is 100 parts, while the rest are the same.

[0027] Example 4 differs from Example 1 in that modified mesoporous silica was not added, the amount of modified diatomaceous earth added was 28 parts, the amount of polymer added was 8 parts, the amount of polypropylene fiber added was 7 parts, the amount of ethylene glycolamine added was 2 parts, the amount of calcium sulfate added was 3 parts, and the amount of sodium silicate added was 10 parts, while the rest were the same.

[0028] Example 5 differs from Example 1 in that the lipophilic silane coupling agent for the modified diatomaceous earth and modified mesoporous silica is phenyltrimethoxysilane, diethanolamine is not added, the amount of calcium sulfate added is 8 parts, the amount of sodium silicate added is 9 parts, and the rest are the same.

[0029] Example 6 differs from Example 1 in that, during the preparation of the polymer, 10 parts of butyl acrylate are replaced with 10 parts of propyl acrylate, and 3.5 parts of hexadecyl acrylate are replaced with 2.5 parts of lauryl acrylate; all other steps remain the same.

[0030] Comparative Example 1 differs from Example 1 in that it does not contain diethanolamine, calcium sulfate, and sodium silicate, while all other ingredients are the same.

[0031] Comparative Example 2 differs from Example 1 in that castor oil was used to replace the modified monomer in the polymer preparation process, while the rest were the same.

[0032] To further illustrate the performance of the sealing agents prepared in the embodiments and comparative examples of the present invention, tests were conducted below.

[0033] Before testing, the sealing slurry was prepared as follows: 20 parts of 30wt% calcium chloride aqueous solution was used as the dispersed phase, 80 parts of 0# diesel oil was used as the continuous phase, 0.15 parts of calcium stearate was used as the main emulsifier, and 0.03 parts of Span-80 was used as the co-emulsifier. The mixture was stirred at high speed to emulsify it into a base slurry. The sealing agents prepared in Examples 1-6 and Comparative Examples 1-2 were added to the aforementioned base slurry at a concentration of 30wt%, and stirred at 800r / min for 5min to obtain the final product.

[0034] Total filtration time: 300 mL of plugging slurry was added to an API medium-pressure filtration meter (with API filter paper), and its filtration time was measured under the condition of 0.7 MPa. The final results are shown in Table 1.

[0035] Compressive strength test: The filter cake after the total filtration time test was taken and placed in the base slurry. It was cured at 80℃ for 0h, 6h and 24h. After curing, its compressive strength was measured by pressure test. The final results are shown in Table 1.

[0036] Leakage sealing test: A synthetic steel core was placed in a core holder with a crack inlet width of 3 mm, a crack outlet width of 1 mm, and a core length of 20 cm. Using a constant-speed pump, the sealing grout was injected at a rate of 2 mL / min until no liquid phase was discharged for 10 seconds, and the filtration loss was recorded. The core was then kept at 150℃ for 6 hours. After the heat preservation was completed, the base grout was injected at a rate of 2 mL / min until liquid phase was discharged from the core holder outlet, and the maximum pressure during this process was recorded. The breakthrough pressure gradient η was calculated: η = P / L, where P represents the maximum pressure and L represents the core length. The final results are shown in Table 1.

[0037] Table 1 Test Results As can be seen from Table 1, the plugging agent prepared in the embodiments of the present invention has a low total filtration time, high compressive strength, and high breakthrough pressure gradient, while its leakage is low during the plugging process. Comparative Example 1 shows that without a curing agent, its overall strength is low; Comparative Example 2 shows that without castor oil, its leakage is relatively high, resulting in a higher overall cost.

[0038] The present invention has been disclosed above through preferred embodiments; however, those skilled in the art should understand that these embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Further modifications can be made without departing from the principles of the invention, and these modifications should also be considered within the scope of protection of the present invention.

Claims

1. A rapid-filtration, solidification, pressure-bearing plugging agent for oil-based drilling fluids, characterized in that, By weight, it includes: 100 parts of binder, 20-30 parts of composite filter aid, 5-20 parts of polymer, 2-8 parts of toughening agent, and 10-200 parts of curing agent; The polymer is prepared by the following monomers: 10 parts short-chain acrylate, 2-5 parts long-chain acrylate, and 1-3 parts modified monomer. The polymer is prepared by free radical polymerization. The modified monomer is prepared by the following method: castor oil and acryloyl chloride are reacted in a molar ratio of 1:1 to 1.5 under the action of an acid-binding agent. After the reaction is completed, the modified monomer is obtained by separation and purification. The consolidating agent is blast furnace iron slag; the particle size of the blast furnace iron slag is graded, with the first grade having a particle size of 20-40 mesh and the second grade having a particle size of 80-120 mesh, and the mass ratio of the first grade blast furnace iron slag to the second grade blast furnace iron slag is 5:1-10. The composite filter aid is one or more of diatomaceous earth and mesoporous silica; the mesoporous silica or diatomaceous earth is modified with a lipophilic silane coupling agent based on vacuum impregnation method. The toughening agent is one or more of polypropylene fiber, polyester fiber, and basalt fiber, with a diameter of 10-100 micrometers and a length of 0.2-2.0 mm; The curing agent is diethanolamine, calcium sulfate, and sodium silicate in a mass ratio of 1:1~3:2~5; The short-chain acrylate is one of butyl acrylate, butyl methacrylate, propyl acrylate, and propyl methacrylate, and the long-chain acrylate is one of lauryl acrylate, tetradecyl acrylate, hexadecyl acrylate, and octadecyl acrylate.

2. The rapid-filtration, solidification, pressure-bearing plugging agent for oil-based drilling fluids according to claim 1, characterized in that, The sealing agent comprises: 100 parts of a binder, 23-26 parts of a composite filter aid, 12-14 parts of a polymer, 4-5 parts of a toughening agent, and 10-20 parts of a curing agent.

3. The rapid-filtration, solidification, pressure-bearing plugging agent for oil-based drilling fluids according to claim 1, characterized in that, The preparation conditions of the modified monomer are as follows: castor oil and acryloyl chloride are dissolved separately in chloroform, and an acid-binding agent is added to the castor oil solution. Under ice bath conditions, the acryloyl chloride solution is added dropwise to the castor oil solution. After the addition is complete, the reaction is carried out at 20~40℃ for 2~5 hours. After the reaction is completed, the mixture is extracted successively with saturated brine and distilled water. The organic phase is collected and dried under reduced pressure to obtain the modified monomer. The acid-binding agent is triethylamine, and the amount of triethylamine added is 1~1.5 times the molar amount of acryloyl chloride.

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