Mechanical property modifier, preparation method and application

Abstract

The invention relates to the technical field of oil-gas field development, in particular to a mechanical property modifier, a preparation method and application. The invention relates to a mechanical property modifier. The mechanical property modifier is prepared from the following raw materials: serpentine, silica sol, allyl polyglycol ether polycarboxylic acid and sodium polyacrylate. The invention provides a mechanical modifier preparation method, which comprises: (1) crushing serpentine, and carrying out acid washing to obtain serpentine wet powder; (2) carrying out a reaction I on a mixture I containing serpentine wet powder and silica sol to obtain modified serpentine; and (3) carrying out a reaction II on a mixture II containing the modified serpentine, the allyl polyglycol ether polycarboxylic acid solution and the sodium polyacrylate solution to obtain the mechanical property modifier. The mechanical property modifier provided by the invention can obviously improve and enhance the mechanical property of high-temperature oil well set cement, so that the high-temperature oil well set cement has the characteristics of high strength and high toughness.

Description

Technical Field

[0001] In the field of oil and gas well cementing operations, this specifically relates to a mechanical property modifier, its preparation method, and its application. Background Technology

[0002] In deep, high-temperature, and high-pressure oil and gas extraction, cement sheaths are subjected to high temperatures and high stresses, making them highly susceptible to structural damage, loss of mechanical sealing properties, and problems such as annular pressure or annular seal failure. Wellbore sealing integrity is crucial for oil and gas field production and development; however, as oil and gas exploration and development continue to advance into deeper formations, the integrity of cement sheaths faces severe challenges. Oil well cement stone is a brittle material with inherent defects such as low compressive strength, poor high-temperature resistance, and low flexural and tensile strength. The integrity of the cement sheath is easily compromised, leading to wellbore sealing failure and seriously affecting the normal production, safety, and profitability of oil and gas resources.

[0003] To meet the requirements of cement stone mechanical properties and cement sheath sealing integrity under complex conditions such as deep formation, high temperature, and high stress, current cementing operations typically incorporate elastic particles, latex, or fibers into the cement stone to improve its brittleness, reduce its elastic modulus, and form a resilient cement stone, achieving some success. However, the addition of organic materials such as elastic particles and latex significantly reduces the compressive strength of the cement stone, and these materials also have poor high-temperature resistance and high cost. Fiber materials can improve the tensile and flexural strength of the cement stone, but their effect on enhancing the compressive strength is relatively weak, and excessively long fibers or excessive amounts can easily lead to serious accidents such as blockage.

[0004] With the continuous advancement of oil and gas exploration, development, and production enhancement in my country, higher requirements are being placed on the mechanical properties of cement sheaths in complex wellbore environments such as deep oil and gas formations. Cement stone is required to possess higher compressive strength and better tensile and flexural strength. Therefore, researching and developing oil well cement stone with high strength, high tensile strength, and high flexural strength has become a key focus and challenge in the modification and improvement of the mechanical properties of oil well cement stone.

[0005] Chinese patent CN112939527B discloses an ultra-high strength and toughness cement slurry system for cementing, its preparation, and its application. This invention incorporates materials such as whiskers, microsilica, quartz sand, and metakaolin into the cement slurry system, resulting in cement stone with ultra-high strength (compressive strength up to 80 MPa). This effectively meets the cementing requirements of deep shale gas formations and high-temperature deep wells, avoiding strength degradation of the cement stone caused by high temperatures. However, the understanding of the hydration process and microstructure of this cement slurry system is insufficient; it merely represents an optimized combination of various materials and cannot form a commonly used method for microstructure control and strength enhancement.

[0006] Chinese patent application CN114644480A discloses a resilient cement slurry containing thermoplastic elastic materials and its preparation method. The resilient cement slurry comprises the following raw materials in parts by weight: 100 parts cement; 5-15 parts modified thermoplastic elastic material; 0.1-2 parts retarder; 3-4 parts water-reducing agent; 0-30 parts quartz sand; and 40-56 parts water. This invention involves mixing the thermoplastic elastic material with a reactive solvent at a certain temperature and then polymerizing it with a water-soluble monomer solution. This results in the modified thermoplastic elastic material having hydrophilic groups on its surface, exhibiting better temperature resistance and hydrophilicity compared to toughening agents and elastic agents such as thermoplastic rubber modified by adsorption. However, this method does not substantially affect or improve the strength and flexural strength of cement paste, and remains a traditional method for improving the mechanical properties of cement paste.

[0007] Chinese patent CN110938171B discloses a method for modifying nanocellulose for cementing. This invention modifies the surface of nanocellulose particles by adding a specific amount of water-based monomers through a polymerization reaction, allowing the modified nanocellulose to be uniformly dispersed in the cement slurry system. By sealing the pores between cement particles, the reinforcing and toughening effect of the nanocellulose particles is effectively realized. However, the improvement in mechanical properties from simply adding nanomaterials is still limited, and excessive addition can cause the cement slurry to thicken, making it impossible to pump.

[0008] Chinese Patent CN112279543B discloses a composite ultra-high temperature cement stone mechanical modification material and its preparation method, mainly composed of the following components in parts by weight: 65-75 parts of a first high-temperature strength anti-fading material, 20-30 parts of a second high-temperature strength anti-fading material, and 5 parts of an ultra-high temperature toughening material. The first high-temperature strength anti-fading material is acid-washed quartz sand with a particle size of 400 mesh or larger. The second high-temperature strength anti-fading material is a mixture of two of wollastonite, kyanite, calcined alumina, and bauxite, with a fineness between 100-400 mesh. The ultra-high temperature toughening material is halloysite nanotubes. This invention can ensure that the strength of cement stone does not decline under ultra-high temperature conditions and has good toughness. However, this invention mainly addresses the problem of strength decline in cement stone at high temperatures, without substantially affecting or improving the strength and flexural strength of cement stone.

[0009] Chinese patent application CN115124979A discloses a composition of an elastic-toughness modifier for cementing oil and gas wells, its preparation method, and an elastic-toughness cement slurry system. The composition mainly consists of the following components in parts by weight: 1 part mixed fiber, 45-75 parts epoxy resin-coated rubber particles, and 0.5-5 parts nano-silica. The epoxy resin-coated rubber particles, acting as elastic particles, can buffer and absorb some energy, improving the impact resistance of the cement paste. The mixed fiber, evenly distributed within the cement paste, forms a dense network structure, improving the fracture toughness of the cement paste. However, this invention does not substantially affect or improve the strength of the cement paste; the compressive strength of the cement paste remains low, and it still belongs to the traditional method of improving the mechanical properties of cement paste.

[0010] Chinese patent CN112174568B discloses a modified toughening material for cementing, using 70-90% fiber material, 5-10% amylopectin-based organic dispersant, and 5-20% silicon-rich inorganic dispersant. The invention aims to provide a modified toughening material for cementing that can disperse fibers in cementitious materials and other gel materials, reducing agglomeration, increasing the proportion of fibers in cement-based materials, and improving the compressive strength, crack resistance, toughness, durability, and reducing shrinkage of cement slurry. This invention primarily addresses the fiber dispersion problem; the fibers mainly improve the flexural strength of cement paste, but have no substantial impact on or improvement on the strength, permeability, or microstructure of cement paste, thus remaining a traditional method for improving the mechanical properties of cement paste.

[0011] Chinese Patent CN112939527B discloses an ultra-high strength and toughness cement slurry system for cementing, its preparation, and its application. The specific components include: 100 parts by weight of cement, 20-40 parts by weight of high-temperature reinforcing material, 0.5-6 parts by weight of inorganic toughening material, 0.5-4 parts by weight of suspension stabilizer, 2-6 parts by weight of microsilica, 0.5-1.5 parts by weight of dispersant, 2-6 parts by weight of fluid loss reducing agent, 1-8 parts by weight of retarder, 0.2-1 parts by weight of defoamer, and 40-60 parts by weight of clean water. This cement stone possesses ultra-high strength and other properties, effectively meeting the cementing requirements of deep shale gas formations and high-temperature deep wells. However, this invention primarily addresses the strength degradation of cement stone at high temperatures, without substantially affecting or improving the strength and flexural strength of the cement stone itself.

[0012] Chinese patent CN115093173B discloses a biomimetic method for enhancing and toughening the microstructure of oil well cement stone, along with a cement slurry system and its application. Drawing inspiration from the microstructure characteristics of pearl oyster shells, it utilizes four key additives—hydration nucleation regulators, hydration morphology inducers, crystal reinforcing agents, and crystal binders—to effectively regulate the microstructure of cement stone at the nano, micro, meso, and macroscopic levels. This results in a biomimetic mechanical enhancement and toughening structure in the oil well cement stone, mimicking the function of pearl oyster shells. The invention establishes a biomimetic method for enhancing and toughening the microstructure of oil well cement stone and a cement slurry system, significantly improving the compressive strength, flexural strength, and toughness of the cement stone. However, this invention has a relatively low applicable temperature range and cannot address the problem of improving the compressive strength and flexural strength of cement stone at high temperatures.

[0013] In summary, the existing patents represent traditional methods for improving the mechanical properties of oil well cement stone by adding latex, polymer resin materials, fibers, siliceous chemically active materials, whisker fiber reinforcing and toughening materials, polymer-modified dispersants, and high-efficiency drag-reducing agents. These methods do not take into account the packing state and microstructure of cement hydration products, and therefore cannot form an efficient method for improving mechanical properties from the microstructure perspective. The mechanical properties of oil well cement stone, such as strength and flexural strength, urgently need further improvement.

[0014] As oil and gas development continues to advance into deeper and more complex reservoirs, higher demands are being placed on the mechanical properties of oil well cement stone and the quality of cementing. Existing technologies offer very limited improvement in the compressive, flexural, and tensile strength of oil well cement stone at high temperatures, making it difficult to meet the needs of current oil and gas extraction technologies. Therefore, there is an urgent need to develop methods and technologies for modifying and improving the compressive, flexural, and tensile strength of oil well cement stone at high temperatures. This will ensure the integrity of cement sheaths and extend the lifespan of oil and gas wells, providing technical support for efficient, economical, and safe oil and gas extraction. Summary of the Invention

[0015] To address the aforementioned problems in the prior art, this invention provides a mechanical property modifier, its preparation method, and its application.

[0016] In a first aspect, the present invention proposes a mechanical property modifier, the raw materials of which include: serpentine, silica sol, allyl polyethylene glycol ether polycarboxylic acid, and sodium polyacrylate.

[0017] As a specific embodiment of the present invention, the raw materials of the mechanical property modifier, by weight, include: 1 part serpentine, 0.4 to 2.5 parts silica sol, 0.02 to 0.08 parts allyl polyethylene glycol ether polycarboxylic acid solution, and 0.01 to 0.08 parts sodium polyacrylate solution.

[0018] Preferably, the raw materials for the mechanical property modifier, by weight, include: 1 part serpentine, 0.65 to 2.25 parts silica sol, 0.04 to 0.08 parts allyl polyethylene glycol ether polycarboxylic acid solution, and 0.02 to 0.05 parts sodium polyacrylate solution.

[0019] As a specific embodiment of the present invention, the silica sol has a mass percentage concentration of 30% to 35%, a particle size of 15 to 30 nm, and the solvent in the silica sol is water;

[0020] As a specific embodiment of the present invention, the molecular weight of allyl polyethylene glycol ether polycarboxylic acid is 3500-5000, the mass percentage concentration of allyl polyethylene glycol ether polycarboxylic acid solution is 30%-35%, and the solvent in the allyl polyethylene glycol ether polycarboxylic acid solution is water.

[0021] As a specific embodiment of the present invention, the molecular weight of sodium polyacrylate is 2000-3000, the mass percentage concentration of the sodium polyacrylate solution is 30%-50%, and the solvent in the sodium polyacrylate solution is water.

[0022] Preferably, the water in the solvent of silica sol, the water in the allyl polyethylene glycol ether polycarboxylic acid solvent, and the water in the sodium polyacrylate solvent are all deionized water.

[0023] In a second aspect, the present invention provides a method for preparing the mechanical modifier provided in the first aspect of the present invention, comprising the following steps:

[0024] (1) After pulverizing serpentine, acid washing is used to remove soluble impurities such as iron and calcium to obtain wet serpentine powder.

[0025] (2) A mixture I containing wet serpentine powder and silica sol is subjected to reaction I to obtain modified serpentine. During reaction I, the silica sol is first adsorbed on the surface of the serpentine, and then undergoes intermolecular dehydration condensation at high temperature to generate nano-silica, which is tightly deposited on the surface of the serpentine.

[0026] (3) A mixture II containing modified serpentine, allyl polyethylene glycol ether polycarboxylic acid solution, and sodium polyacrylate solution is reacted with reaction II to obtain a mechanical property modifier. During reaction II, the allyl polyethylene glycol ether polycarboxylic acid reacts strongly with the nano-silica deposited on the surface of the modified serpentine through chemical adsorption and hydrogen chain adsorption. The main function of sodium polyacrylate is to disperse the serpentine.

[0027] Specifically, in step (1), the serpentine crushing process includes: crushing at 3000-4000 rpm for 3-5 minutes on a crusher, and then grinding at 200-300 rpm for 5-8 minutes on a ball mill.

[0028] As a specific embodiment of the present invention, in step (1), hydrochloric acid is used to pickle the serpentine; preferably, the concentration of hydrochloric acid is 3wt% to 5wt%, and the mass ratio of serpentine to hydrochloric acid is 1:1.6 to 5.

[0029] Specifically, the pickling process is as follows: after pulverizing serpentine and mixing it with hydrochloric acid, stir the mixture at a low speed of 100-150 rpm for 6-10 minutes, and then filter and wash it 2-3 times to remove the hydrochloric acid residue on the surface of the raw material.

[0030] As a specific embodiment of the present invention, the conditions for reaction I include: a temperature of 300℃~350℃ and a time of 5h~10h.

[0031] Preferably, the conditions for reaction I include: a temperature of 310℃~330℃ and a time of 6h~8h.

[0032] Specifically, in step (2), the modified serpentine is cooled to 90°C to 95°C and then mixed with an allyl polyethylene glycol ether polycarboxylic acid solution and a sodium polyacrylate solution.

[0033] As a specific embodiment of the present invention, the conditions for reaction II include: a temperature of 100°C to 120°C and a time of 1.5h to 4h.

[0034] As a specific embodiment of the present invention, the conditions for reaction II include: a temperature of 105°C to 110°C and a time of 2 to 3 hours.

[0035] As a specific embodiment of the present invention, the product obtained after reaction II is pulverized in a pulverizer at 5000-6000 rpm for 1-3 minutes to obtain a mechanical property modifier.

[0036] Thirdly, the present invention provides a cement slurry comprising: a mechanical property modifier provided in the first aspect of the present invention or a mechanical property modifier prepared by the preparation method provided in the second aspect of the present invention, cement, silica sand, a drag-reducing agent, a water loss reducing agent, a retarder, an defoamer, and water. The cement stone formed from the cement slurry, cured at 150℃ / 20MPa for 7 days, exhibits a compressive strength of 58.0–60.1 MPa, a flexural strength of 7.75–8.5 MPa, and a tensile strength of 3.12–3.42 MPa.

[0037] As a specific embodiment of the present invention, the raw materials of the cement slurry, by weight, include: 1-4 parts of mechanical property modifier, 100 parts of cement, 35-50 parts of silica sand, 1-2.5 parts of drag reducer, 4-7.5 parts of water loss reducer, 1-3.5 parts of retarder, 0.4-0.6 parts of defoamer, and 44-55 parts of water.

[0038] Preferably, the raw materials of the cement slurry, by weight, include: 1.5 to 3.8 parts of mechanical property modifier, 100 parts of cement, 30 to 50 parts of silica sand, 1 to 2.5 parts of drag reducer, 4 to 7.5 parts of water loss reducer, 1 to 3.5 parts of retarder, 0.4 to 0.6 parts of defoamer, and 44 to 55 parts of water.

[0039] As a specific embodiment of the present invention, the cement is oil well cement, which is oil well grade G cement or oil well grade H cement.

[0040] As a specific embodiment of the present invention, the drag-reducing agent is a sulfonated aldehyde-ketone condensation polymer drag-reducing agent.

[0041] As a specific embodiment of the present invention, the water loss reducing agent is a copolymer of acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, or a copolymer of N,N-dimethylacrylamide and 2-acrylamide-2-methylpropanesulfonic acid.

[0042] As a specific embodiment of the present invention, the retarder is a copolymer of acrylic acid, acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, or a copolymer of itaconic acid, acrylamide and 2-acrylamide-2-methylpropanesulfonic acid.

[0043] As a specific embodiment of the present invention, the defoamer is one of the following: phosphate ester defoamer, organosiloxane defoamer, organic polyether defoamer, and organosilicone ether defoamer.

[0044] As a specific embodiment of the present invention, the water used in the cement slurry is fresh water or low-mineralized water.

[0045] Fourthly, the present invention provides a method for preparing cement slurry according to the third aspect of the present invention, wherein cement, silica sand and mechanical property modifier are mixed I to obtain a solid phase material; a water loss reducing agent, a retarder, a drag reducing agent, an antifoaming agent and water are mixed II to obtain a liquid phase material; and the solid phase material and the liquid phase material are mixed III to obtain cement slurry.

[0046] Preferably, the conditions for mixing II include: a stirring speed of 800-1200 rpm and a stirring time of 10-15 s.

[0047] Preferably, the conditions for mixing III include: maintaining a rotation speed of 3500-4500 rpm, mixing the liquid and solid phase materials within 15 seconds, controlling the rotation speed at 10000-15000 rpm, and stirring for 30-40 seconds.

[0048] Fifthly, the present invention provides an application of cement slurry prepared by the method for preparing cement slurry provided in the third aspect of the present invention or the method for preparing cement slurry provided in the fourth aspect of the present invention in cementing operations of oil and gas wells.

[0049] Compared with the prior art, the present invention has the following beneficial effects.

[0050] (1) The mechanical property modifier provided by the present invention can significantly improve the mechanical properties of oil well cement stone, giving it high strength and high toughness. Under high temperature of 150℃ and 20MPa, the compressive strength is increased by about 30% to 55% after 7 days of curing, the flexural strength is increased by about 20% to 56%, and the tensile strength is increased by about 22% to 58%, thus achieving the goal of high strength, high flexural strength and high tensile strength of high temperature oil well cement stone.

[0051] (2) The mechanical property modifier provided by this invention uses natural mineral materials as raw materials, which have the great advantages of wide availability and low cost. In addition, it innovatively uses the high-temperature dehydration polymerization of silica sol for coating, which can efficiently and easily deposit nano-silica on serpentine. The silica deposited on serpentine can act as a hydration nucleus, which can promote the directional growth and arrangement of oil well cement hydration products with nano-silica nuclei and serpentine as templates, thereby changing the morphology and accumulation form of oil well cement hydration products and forming a more ordered and dense microstructure. This makes the preparation process of the mechanical property modifier simple, low-cost, and has broad application prospects.

[0052] (3) The mechanical property modifier provided by the present invention has good compatibility with existing fluid loss reducing agents, retarders, drag reducing agents, etc. The cement slurry prepared fully meets the various performance requirements of the cementing standard, which facilitates on-site construction operations and has very important promotion and application value.

[0053] (4) The mechanical property modifier provided by this invention and the cement slurry prepared therefrom have excellent properties in various aspects of the slurry. The cement stone has high strength and high toughness. The cement slurry has a wide applicable temperature range, and can be used under conditions of 90 to 150℃. It has the characteristics of low water loss and zero free fluid (free fluid is 0). The properties such as flow index n≥0.7, water loss at 150℃≤50mL, and thickening time meet the requirements of field cementing construction and are adjustable. It can be well adapted to cementing operations in the process of deep high temperature and high pressure oil and gas extraction. It can also be applied to cementing operations in horizontal wells of deep shale oil and gas reservoirs, horizontal wells of low permeability or tight sandstone oil and gas reservoirs, and injection and production wells of high temperature gas storage. It can effectively ensure the integrity of cement sheath and wellbore under high temperature and high pressure alternating stress, effectively seal the formation, and has a very broad market application prospect. Attached Figure Description

[0054] Figure 1 The compressive strength of the cement stone formed by the cement slurry of Examples 13-16 and Comparative Example 6 after 1 day of curing.

[0055] Figure 2 The compressive strength of the cement stone formed by the cement slurry of Examples 13-16 and Comparative Example 6 after 5 days of curing.

[0056] Figure 3 The flexural strength of the cement stone formed by the cement slurry of Examples 13-16 and Comparative Example 6 after 1 day of curing.

[0057] Figure 4 The flexural strength of the cement stone formed by the cement slurry of Examples 13-16 and Comparative Example 6 after 5 days of curing. Detailed Implementation

[0058] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0059] The raw materials used in all embodiments of the present invention are commercially available, wherein,

[0060] Oil well cement: Grade G oil well cement from Weifang Shengwei Special Cement Co., Ltd. is used.

[0061] Serpentine fiber: Lingshou County Zhanxing Mineral Products Co., Ltd., 100-150 mesh.

[0062] Silica sol: Shandong Baite New Materials Co., Ltd., mass percentage concentration 30%, particle size 15-30nm, solvent is water.

[0063] Allyl polyethylene glycol ether polycarboxylate: Shandong Zhongwei New Materials Co., Ltd., model POLYFLEX TM 730.

[0064] The allyl polyethylene glycol ether polycarboxylic acid solution used in the embodiments and comparative examples of this invention has a mass percentage concentration of 30%, and the solvent is water.

[0065] Sodium polyacrylate: Zouping County Delin New Material Technology Co., Ltd., model: Derin 42N.

[0066] The sodium polyacrylate solution used in the embodiments and comparative examples of this invention has a mass percentage concentration of 30%, and the solvent is water.

[0067] Silica sand: Chengdu Omeke Petroleum Technology Co., Ltd.

[0068] Styrene-butadiene latex: Produced by Jinan Deqiao Chemical Technology Co., Ltd., with a styrene to butadiene ratio of (60-50):(40-50), a milky white emulsion, a solid content of about 45%-50%, negatively charged, and a pH value of 9.0-10.5.

[0069] Polypropylene fiber: sourced from Taian Haosong Fiber Co., Ltd., 5mm in length.

[0070] Drag reducer: Chengdu Omeke Petroleum Technology Co., Ltd., Model: Drag reducer for oil well cement QS-20L.

[0071] Fluid loss reducer: Chengdu Omeke Petroleum Technology Co., Ltd., Model: High-temperature oil well cement fluid loss reducer HX-12L.

[0072] Retarder: Chengdu Omeke Petroleum Technology Co., Ltd., Model: High-Temperature Oil Well Cement Retarder HX-36L.

[0073] Defoamer: Chengdu Omeke Petroleum Technology Co., Ltd., Model: Defoamer DF-A for Oil Well Cement.

[0074] Example 1

[0075] The mechanical property modifier in this embodiment is prepared using the following method:

[0076] (1) Serpentine fibers were pulverized in a high-speed pulverizer at 3000 rpm for 3 minutes, and then ground in a ball mill at 200 rpm for 5 minutes to obtain serpentine powder. Then, at room temperature, the serpentine powder was acid-washed with a 3wt% hydrochloric acid solution. The mass ratio of serpentine powder to hydrochloric acid was 1:1.6. The acid-washing process involved mixing the serpentine powder and hydrochloric acid and stirring at a low speed of 100 rpm for 6 minutes. Afterwards, the mixture was filtered and washed twice to remove residual hydrochloric acid from the surface of the raw material, thus obtaining wet serpentine powder.

[0077] (2) The wet serpentine powder and silica sol were mixed at a mass ratio of 1:0.65 to obtain a mixture. The mixture was then placed in a stainless steel plate tank and placed in an oven, heated to 310°C, and reacted at a constant temperature for 6 hours to prepare modified serpentine.

[0078] (3) The modified serpentine was naturally cooled to 90°C. Allyl polyethylene glycol ether polycarboxylic acid solution and sodium polyacrylate solution were added sequentially to the modified serpentine. The mass ratio of modified serpentine to allyl polyethylene glycol ether polycarboxylic acid solution and sodium polyacrylate solution was 1:0.04:0.02, resulting in a mixture. The mixture was heated to 105°C and held at that temperature for 2 hours before being naturally cooled to obtain a composition. The composition was then pulverized at 5000 rpm for 1 minute in a high-speed pulverizer to prepare a mechanical property modifier, designated S1.

[0079] Example 2

[0080] The mechanical property modifier in this embodiment is prepared using the following method:

[0081] (1) Serpentine fibers were pulverized in a high-speed pulverizer at 3000 rpm for 5 minutes, and then ground in a ball mill at 200 rpm for 8 minutes to obtain serpentine powder. Then, at room temperature, the serpentine powder was acid-washed with a 3wt% hydrochloric acid solution. The mass ratio of serpentine powder to hydrochloric acid was 1:2.0. The acid-washing process involved mixing the serpentine powder and hydrochloric acid and stirring at a low speed of 100 rpm for 10 minutes. Afterwards, the mixture was filtered and washed twice to remove residual hydrochloric acid from the surface of the raw material, thus preparing wet serpentine powder.

[0082] (2) The wet serpentine powder and silica sol were mixed at a mass ratio of 1:1.07 to obtain a mixture. The mixture was then placed in a stainless steel plate tank and placed in an oven, heated to 310°C, and reacted at a constant temperature for 8 hours to prepare modified serpentine.

[0083] (3) The modified serpentine was naturally cooled to 90°C. Allyl polyethylene glycol ether polycarboxylic acid solution and sodium polyacrylate solution were added sequentially to the modified serpentine. The mass ratio of modified serpentine to allyl polyethylene glycol ether polycarboxylic acid solution and sodium polyacrylate solution was 1:0.06:0.03, resulting in a mixture. The mixture was heated to 105°C and held at that temperature for 3 hours before being naturally cooled to obtain a composition. The composition was then pulverized at 5000 rpm for 3 minutes using a high-speed pulverizer to prepare a mechanical property modifier, designated S2.

[0084] Example 3

[0085] The mechanical property modifier in this embodiment is prepared using the following method:

[0086] (1) Serpentine fibers were pulverized in a high-speed pulverizer at 4000 rpm for 4 minutes, and then ground in a ball mill at 300 rpm for 6 minutes to obtain serpentine powder. Then, at room temperature, the serpentine powder was acid-washed with a 4 wt% hydrochloric acid solution. The mass ratio of serpentine powder to hydrochloric acid was 1:2.5. The acid-washing process involved mixing the serpentine powder and hydrochloric acid and stirring at a low speed of 130 rpm for 8 minutes. Afterwards, the mixture was filtered and washed twice to remove residual hydrochloric acid from the surface of the raw material, thus obtaining wet serpentine powder.

[0087] (2) The wet serpentine powder and silica sol were mixed at a mass ratio of 1:2.10 to obtain a mixture. The mixture was then placed in a stainless steel plate tank and placed in an oven, heated to 330℃ and reacted at a constant temperature for 7 hours to prepare modified serpentine.

[0088] (3) The modified serpentine was naturally cooled to 93°C. Allyl polyethylene glycol ether polycarboxylic acid solution and sodium polyacrylate solution were added sequentially to the modified serpentine. The mass ratio of modified serpentine to allyl polyethylene glycol ether polycarboxylic acid solution and sodium polyacrylate solution was 1:0.06:0.04, resulting in a mixture. The mixture was heated to 108°C and held at that temperature for 2.5 hours before naturally cooling to obtain a composition. The composition was then pulverized at 5500 rpm for 2 minutes using a high-speed pulverizer to prepare a mechanical property modifier, designated S3.

[0089] Example 4

[0090] The mechanical property modifier in this embodiment is prepared using the following method:

[0091] (1) Serpentine fibers were pulverized in a high-speed pulverizer at 3000 rpm for 4 minutes, and then ground in a ball mill at 250 rpm for 6 minutes to obtain serpentine powder. Then, at room temperature, the serpentine powder was acid-washed with a 5wt% hydrochloric acid solution. The mass ratio of serpentine powder to hydrochloric acid was 1:3.5. The acid-washing process involved mixing the serpentine powder and hydrochloric acid and stirring at a low speed of 150 rpm for 9 minutes. Afterwards, the mixture was filtered and washed twice to remove residual hydrochloric acid from the surface of the raw material, thus obtaining wet serpentine powder.

[0092] (2) The wet serpentine powder and silica sol were mixed at a mass ratio of 1:1.35 to obtain a mixture. The mixture was then placed in a stainless steel plate tank and placed in an oven, heated to 320°C, and reacted at a constant temperature for 6 hours to prepare modified serpentine.

[0093] (3) The modified serpentine was naturally cooled to 90°C. Allyl polyethylene glycol ether polycarboxylic acid solution and sodium polyacrylate solution were added sequentially to the modified serpentine. The mass ratio of modified serpentine to allyl polyethylene glycol ether polycarboxylic acid solution and sodium polyacrylate solution was 1:0.05:0.05, resulting in a mixture. The mixture was heated to 110°C and held at that temperature for 2 hours before being naturally cooled to obtain a composition. The composition was then pulverized at 5000 rpm for 2 minutes using a high-speed pulverizer to prepare a mechanical property modifier, designated S4.

[0094] Example 5

[0095] A cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 35 parts silica sand, 1.5 parts mechanical property modifier (label S1), 1.0 part drag reducer, 4.0 parts water loss reducer, 1.0 part retarder, 0.4 parts defoamer, and 44 parts water. The label is S5.

[0096] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and mechanical property modifier to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0097] Example 6

[0098] A cement slurry comprising the following raw materials in parts by weight: 100 parts oil well cement, 50 parts silica sand, 3.8 parts mechanical property modifier (labeled S1), 2.5 parts drag reducer, 7.5 parts water loss reducer, 3.5 parts retarder, 0.6 parts defoamer, and 55 parts water, labeled S6.

[0099] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and mechanical property modifier to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0100] Example 7

[0101] A cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 40 parts silica sand, 2.5 parts mechanical property modifier (labeled S2), 1.75 parts drag reducer, 6.5 parts water loss reducer, 2.25 parts retarder, 0.5 parts defoamer, and 50 parts water. The label is S7.

[0102] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and mechanical property modifier to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0103] Example 8

[0104] A cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 35 parts silica sand, 3.5 parts mechanical property modifier (labeled S3), 2.0 parts drag reducer, 5.0 parts water loss reducer, 1.35 parts retarder, 0.4 parts defoamer, and 48 parts water. The label is S8.

[0105] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and mechanical property modifier to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0106] Example 9

[0107] A cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 45 parts silica sand, 3.5 parts mechanical property modifier (label S4), 2.0 parts drag reducer, 4.5 parts water loss reducer, 2.0 parts retarder, 0.6 parts defoamer, and 52 parts water. The label is S9.

[0108] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and mechanical property modifier to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0109] Example 10

[0110] A cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 42 parts silica sand, 2.8 parts mechanical property modifier (labeled S4), 1.5 parts drag reducer, 5.3 parts water loss reducer, 1.7 parts retarder, 0.4 parts defoamer, and 48 parts water. The label is S10.

[0111] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and mechanical property modifier to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0112] Example 11

[0113] A cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 35 parts silica sand, 1.0 part mechanical property modifier (labeled S1), 1.0 part drag reducer, 4.0 parts water loss reducer, 1.0 part retarder, 0.4 parts defoamer, and 44 parts water. The label is S11.

[0114] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and mechanical property modifier to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0115] Example 12

[0116] A cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 35 parts silica sand, 4.0 parts mechanical property modifier (labeled S1), 1.0 part drag reducer, 4.0 parts water loss reducer, 1.0 part retarder, 0.4 parts defoamer, and 44 parts water. The label is S12.

[0117] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and mechanical property modifier to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0118] Comparative Example 1

[0119] A cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 40 parts silica sand, 1.5 parts drag reducer, 4.6 parts water loss reducer, 1.5 parts retarder, 0.6 parts defoamer, and 48 parts water. The label is BS1.

[0120] The steps for preparing cement slurry include: weighing and mixing oil well cement and silica sand to obtain a solid phase material; weighing and pouring the water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid phase material and liquid phase material in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0121] Comparative Example 2

[0122] A cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 40 parts silica sand, 10 parts styrene-butadiene latex, 2.0 parts drag reducer, 4.0 parts water loss reducer, 2.0 parts retarder, 0.6 parts defoamer, and 47 parts water. The label is BS2.

[0123] The steps for preparing cement slurry include: weighing and mixing oil well cement and silica sand to obtain a solid phase material; weighing and pouring styrene-butadiene latex, water loss reducer, retarder, drag reducer, defoamer and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid phase material and liquid phase material in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0124] Comparative Example 3

[0125] A cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 40 parts silica sand, 0.5 parts polypropylene fiber, 1.7 parts drag reducer, 5.5 parts water loss reducer, 2.0 parts retarder, 0.6 parts defoamer, and 52 parts water. The label is BS3.

[0126] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and polypropylene fiber to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0127] Comparative Example 4

[0128] A cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 40 parts silica sand, 10 parts styrene-butadiene latex, 0.35 parts polypropylene fiber, 2.0 parts drag reducer, 4.0 parts water loss reducer, 2.0 parts retarder, 0.6 parts defoamer, and 52 parts water. The label is BS4.

[0129] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and polypropylene fiber to obtain a solid phase material; weighing and pouring styrene-butadiene latex, water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0130] Comparative Example 5

[0131] A cement slurry comprises the following raw materials in parts by weight: 100 parts oil well cement, 35 parts silica sand, 1.5 parts serpentine powder, 1.0 part drag reducer, 4.0 parts water loss reducer, 1.0 part retarder, 0.4 parts defoamer, and 44 parts water. The grade is BS5.

[0132] The serpentine powder used in this comparative example is the same serpentine powder obtained from serpentine fibers through pulverization and ball milling in Example 1. The serpentine powder was not subjected to acid washing or subsequent modification treatment.

[0133] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and serpentine powder to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0134] Experimental Example 1: Cement Grout Performance Test

[0135] The slurry properties of the cement slurries prepared in Examples 5-12 and Comparative Examples 1-5 were tested. Test samples were prepared according to standard GB / T19139-2012 "Test Methods for Oil Well Cement" and the slurry properties of the cement slurries were tested according to standard SY / T 6544-2017 "Performance Requirements for Oil Well Cement Slurry". The test results are shown in Table 1.

[0136] Table 1 Comparison of the slurry properties of different cement pastes

[0137]

[0138]

[0139] According to the test results in Table 1, the mechanical property modifier of the present invention has good compatibility with drag reducers, fluid loss reducers and retarder, so that the rheological properties, fluid loss and thickening time properties of the prepared cement slurry fully meet the relevant industry cementing standards and are basically consistent with the performance of existing cement slurries. This fully demonstrates that the mechanical property modifier can be fully used in high-temperature cementing operation environments.

[0140] Experimental Example 2: Compressive Strength Test of Cement Stone

[0141] The compressive strength of the cement stone formed by the cement slurries prepared in Examples 5-12 and Comparative Examples 1-5 was tested. Test samples were prepared according to standard GB / T 19139-2012 "Test Methods for Oil Well Cement," and the compressive strength of the cement stone formed by the cement slurry was tested according to standard SY / T 6544-2017 "Performance Requirements for Oil Well Cement Slurry." The test results are shown in Table 2.

[0142] Table 2 Comparison of compressive strength properties of cement pastes with different cement grouts

[0143]

[0144]

[0145] According to the test results in Table 2, the mechanical property modifier of the present invention and the cement paste prepared therefrom have excellent overall compressive strength properties. The compressive strength of the cement paste at different temperatures is significantly improved compared with the compressive strength of the comparative example, with the compressive strength increased by more than 30%.

[0146] Experimental Example 3: Testing of Flexural and Tensile Strength Properties of Cement Stone

[0147] The flexural and tensile strengths of the cement pastes formed by the cement slurries prepared in Examples 5-12 and Comparative Examples 1-5 were tested. Test samples were prepared according to standard GB / T 19139-2012 "Test Methods for Oil Well Cement," and the flexural and tensile strengths of the cement pastes formed by the cement slurries were tested according to standard SY / T6544-2017 "Performance Requirements for Oil Well Cement Slurry." The test results are shown in Table 3.

[0148] Table 3 Comparison of flexural and tensile strength properties of cement stone in different mud systems

[0149]

[0150] According to the test results in Table 3, the mechanical property modifier of the present invention and the cement paste prepared therefrom have excellent overall flexural strength and tensile strength. The flexural strength and tensile strength of the cement paste at different temperatures are significantly higher than those of the comparative cement paste, with the flexural strength and tensile strength increasing by more than 20% respectively.

[0151] Experimental Example 4: Porosity and Permeability Test of Cement Stone

[0152] The porosity and permeability of the cement slurries prepared in Examples 5-12 and Comparative Examples 1-5 were compared. Test samples were prepared according to standard GB / T 19139-2012 "Test Methods for Cement in Oil Wells," and the porosity and permeability of the cement stone samples formed by the cement slurries were tested using mercury intrusion porosimetry and liquid permeability testing, referring to standard SY / T6544-2017 "Performance Requirements for Cement Slurries in Oil Wells." The test results are shown in Table 4.

[0153] Table 4. Test results of cement stone porosity and permeability of different cement pastes.

[0154]

[0155] According to the test results in Table 4, the mechanical property modifier of the present invention and the cement stone prepared by it have relatively small overall porosity and permeability. The porosity and permeability of the cement stone at different temperatures are significantly lower than those of the comparative cement stone. This fully demonstrates that the cement stone prepared by the mechanical property modifier of the present invention has a denser microstructure.

[0156] The mechanical property modifiers used in Examples 13 to 16 are prepared using the following methods:

[0157] (1) Serpentine fibers were pulverized in a high-speed pulverizer at 3000 rpm for 3 minutes, and then ground in a ball mill at 200 rpm for 5 minutes to obtain serpentine powder. Then, at room temperature, the serpentine powder was acid-washed with a 3wt% hydrochloric acid solution. The mass ratio of serpentine powder to hydrochloric acid was 1:1.6. The acid-washing process involved mixing the serpentine powder and hydrochloric acid and stirring at a low speed of 100 rpm for 6 minutes. Afterwards, the mixture was filtered and washed twice to remove residual hydrochloric acid from the surface of the raw material, thus obtaining wet serpentine powder.

[0158] (2) The wet serpentine powder and silica sol were mixed at a mass ratio of 1:1.5 to obtain a mixture. The mixture was then placed in a stainless steel plate tank and placed in an oven, heated to 310°C, and reacted at a constant temperature for 6 hours to prepare modified serpentine.

[0159] (3) The modified serpentine was naturally cooled to 90°C. Allyl polyethylene glycol ether polycarboxylic acid solution and sodium polyacrylate solution were added sequentially to the modified serpentine. The mass ratio of modified serpentine to allyl polyethylene glycol ether polycarboxylic acid solution and sodium polyacrylate solution was 1:0.06:0.03, resulting in a mixture. The mixture was heated to 105°C and held at that temperature for 2 hours before naturally cooling to obtain a composition. The composition was then pulverized at 5000 rpm for 1 minute in a high-speed pulverizer to prepare a mechanical property modifier.

[0160] Example 13

[0161] A cement slurry system comprising the following raw materials in parts by weight: 100 parts cement; 35 parts silica sand; 1.5 parts mechanical property modifier; 0.2 parts drag reducer; 4.5 parts water loss reducer; 1.2 parts retarder; 0.2 parts defoamer; and 51 parts water.

[0162] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and mechanical property modifier to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0163] Example 14

[0164] A cement slurry system comprising the following raw materials in parts by weight: 100 parts cement; 35 parts silica sand; 2 parts mechanical property modifier; 0.3 parts drag reducer; 4.5 parts water loss reducer; 1.2 parts retarder; 0.2 parts defoamer; and 51 parts water.

[0165] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and mechanical property modifier to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0166] Example 15

[0167] A cement slurry system comprising the following raw materials in parts by weight: 100 parts cement; 35 parts silica sand; 2.5 parts mechanical property modifier; 0.4 parts drag reducer; 4.5 parts water loss reducer; 1.2 parts retarder; 0.2 parts defoamer; and 51 parts water.

[0168] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and mechanical property modifier to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0169] Example 16

[0170] A cement slurry system comprising the following raw materials in parts by weight: 100 parts cement; 35 parts silica sand; 3 parts mechanical property modifier; 0.6 parts drag reducer; 4.5 parts water loss reducer; 1.2 parts retarder; 0.2 parts defoamer; and 51 parts water.

[0171] The steps for preparing cement slurry include: weighing and mixing oil well cement, silica sand, and mechanical property modifier to obtain a solid phase material; weighing and pouring a water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid and liquid phase materials in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0172] Comparative Example 6

[0173] A cement slurry system comprising the following raw materials in parts by weight: 100 parts cement; 35 parts silica sand; 0.2 parts drag reducer; 4.5 parts water loss reducer; 1.2 parts retarder; 0.2 parts defoamer; and 51 parts water.

[0174] The steps for preparing cement slurry include: weighing and mixing oil well cement and silica sand to obtain a solid phase material; weighing and pouring the water loss reducer, retarder, drag reducer, defoamer, and water into the mixing cup of a constant speed mixer, stirring at a low speed of 1000 rpm for 15 seconds to mix the liquid phase material; continuously pouring the solid phase material into the mixing cup within 15 seconds at a speed of 4000 rpm, mixing the solid phase material and liquid phase material in the mixing cup, then adjusting the speed to 12000 rpm and stirring for 35 seconds to prepare the oil well cement slurry.

[0175] Experimental Example 5

[0176] Test the slurry properties of cement slurry in Examples 13-16. Test samples were prepared according to standard GB / T 19139-2012 "Test Methods for Cement in Oil Wells", and the slurry properties of cement slurry were tested with reference to standard SY / T 6544-2017 "Performance Requirements for Cement Slurry in Oil Wells".

[0177] Table 5. Slurry performance parameters of cement slurry system

[0178]

[0179] As can be seen from the data in Table 5, the cement slurry system prepared by the present invention has stable performance and has the advantages of low water loss, zero free liquid, good rheological properties, and adjustable thickening time.

[0180] Experimental Example 6

[0181] The slurry properties of cement slurries in Examples 13-16 and Comparative Example 6 were tested. Test samples were prepared according to standard GB / T19139-2012 "Test Methods for Oil Well Cement," and the compressive strength of the cement stone formed by the cement slurry was tested according to standard SY / T 6544-2017 "Performance Requirements for Oil Well Cement Slurry" after 1 day and 5 days of curing at different curing temperatures. The test results are presented by […]. Figure 1 and Figure 2 As shown.

[0182] in, Figure 1 The compressive strength of the cement stone formed by the cement slurry of Examples 13-16 and Comparative Example 6 after 1 day of curing. Figure 2 The compressive strength of the cement paste formed by the cement slurry of Examples 13-16 and Comparative Example 6 after 5 days of curing is given. FS-C represents a mechanical property modifier, and 1.5%, 2.0%, 2.5%, and 3% represent the amount of mechanical property modifier added to the cement slurry as a percentage of the cement mass.

[0183] Depend on Figure 1 , Figure 2It can be seen that after 1 day of curing, the compressive strength of cement paste was significantly improved when the amount of mechanical property modifier FS-C was within the range of 1.5% to 3.0% of the cement mass. The best improvement in compressive strength was observed at 90℃, 120℃, and 150℃ with an FS-C addition of 3.0%, compared to no mechanical property modifier, with strength increases of 37.14%, 30%, and 22.01%, respectively, reaching 29 MPa, 31.2 MPa, and 32.7 MPa. MPa; After 5 days of curing, the compressive strength of cement stone was significantly improved when the amount of mechanical property modifier FS-C was in the range of 1.5% to 3.0% of the cement mass. Among them, the compressive strength improvement effect was best when the amount of FS-C was 3.0% at 90℃, 120℃ and 150℃. Compared with no mechanical property modifier, the strength increased by 38.2%, 56.9% and 37.4% respectively, and the strength reached 35MPa, 56MPa and 62MPa respectively.

[0184] Experimental Example 7

[0185] The slurry properties of cement slurries in Examples 13-16 and Comparative Example 6 were tested. Test samples were prepared according to standard GB / T19139-2012 "Test Methods for Oil Well Cement," and the cement stone formed by the cement slurry was tested according to standard SY / T 6544-2017 "Performance Requirements for Oil Well Cement Slurry." The flexural strength was measured after 1 day and 5 days of curing at different curing temperatures. The test results are presented by […]. Figure 3 and Figure 4 As shown.

[0186] in, Figure 3 The flexural strength of the cement stone formed by the cement slurry of Examples 13-16 and Comparative Example 6 after 1 day of curing. Figure 4 The flexural strength of the cement paste formed by the cement slurry of Examples 13-16 and Comparative Example 6 after 5 days of curing is given. FS-C represents a mechanical property modifier, and 1.5%, 2.0%, 2.5%, and 3% represent the amount of mechanical property modifier added to the cement slurry as a percentage of the cement mass.

[0187] Depend on Figure 3 , Figure 4It can be seen that, after 1 day of curing, compared with Comparative Example 6, the flexural strength of the cement stone formed by the cement slurry prepared in Examples 13-16 was significantly improved. At 90℃ and 120℃, when the amount of mechanical property modifier added was 2.5% of the cement mass, the flexural strength of the cement stone was most significantly improved, with the flexural strength of the formed cement stone increasing by 16.07% and 24.29% respectively compared with the cement slurry without mechanical property modifier. At 150℃, when the amount of mechanical property modifier added was 2.0% and 2.5% of the cement mass, the flexural strength of the cement stone was significantly improved, with the flexural strength of the formed cement stone increasing by 27.63% compared with the cement slurry without mechanical property modifier. After 5 days of curing, at 90℃ and 120℃, the flexural strength of the cement stone increased most significantly when the mechanical property modifier was added at 2.5wt% of the cement mass, increasing by 18.46% and 25% respectively; at 150℃, the flexural strength of the cement stone increased significantly when the mechanical property modifier was added at 2.0% of the cement mass, increasing by 20.93%.

[0188] In summary, the mechanical property modifier of this invention and the cement slurry prepared therefrom can significantly improve the compressive strength, flexural strength, and tensile strength of cement stone. The rheological parameters, water loss, and thickening time of the cement slurry of this invention fully meet the relevant standard requirements for high-temperature cementing construction. The mudstone of this invention has low porosity and permeability, indicating a dense structure of cement stone. These characteristics are highly beneficial for ensuring the mechanical properties of cement sheaths, sealing integrity, and well life in high-temperature oil and gas wells, providing technical support for the efficient, economical, and safe exploitation of high-temperature oil and gas reservoirs, and demonstrating excellent application prospects.

[0189] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A mechanical property modifier, characterized in that, The raw materials for the mechanical property modifier include: serpentine, silica sol, allyl polyethylene glycol ether polycarboxylic acid, and sodium polyacrylate.

2. The mechanical property modifier according to claim 1, characterized in that, The raw materials of the mechanical property modifier, by weight, include: 1 part serpentine, 0.4 to 2.5 parts silica sol, 0.02 to 0.08 parts allyl polyethylene glycol ether polycarboxylic acid solution, and 0.01 to 0.08 parts sodium polyacrylate solution.

3. The mechanical property modifier according to claim 1 or 2, characterized in that, The raw materials of the mechanical property modifier, by weight, include: 1 part serpentine, 0.65 to 2.25 parts silica sol, 0.04 to 0.08 parts allyl polyethylene glycol ether polycarboxylic acid solution, and 0.02 to 0.05 parts sodium polyacrylate solution.

4. The mechanical property modifier according to any one of claims 1 to 3, characterized in that, The silica sol has a mass percentage concentration of 30% to 35% and a particle size of 15 to 30 nm. The solvent in the silica sol is water.

5. The mechanical property modifier according to any one of claims 1 to 4, characterized in that, The allyl polyethylene glycol ether polycarboxylic acid solution has a mass percentage concentration of 30% to 35%, and the solvent in the allyl polyethylene glycol ether polycarboxylic acid solution is water; preferably, the molecular weight of the allyl polyethylene glycol ether polycarboxylic acid is 3500 to 5000.

6. The mechanical property modifier according to any one of claims 1 to 5, characterized in that, The sodium polyacrylate solution has a mass percentage concentration of 30% to 50%, and the solvent in the sodium polyacrylate solution is water; preferably, the molecular weight of the sodium polyacrylate is 2000 to 3000.

7. A method for preparing the mechanical property modifier according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) After crushing the serpentine, acid washing was performed to obtain wet serpentine powder; (2) A mixture I containing serpentine wet powder and silica sol is reacted with reaction I to obtain modified serpentine; (3) A mixture II containing modified serpentine, allyl polyethylene glycol ether polycarboxylic acid solution, and sodium polyacrylate solution is reacted with reaction II to obtain the mechanical property modifier.

8. The preparation method according to claim 7, characterized in that, The serpentine is acid-washed with hydrochloric acid; preferably, the concentration of hydrochloric acid is 3wt% to 5wt%, and the mass ratio of serpentine to hydrochloric acid is 1:1.6 to 5.

9. The preparation method according to claim 7 or 8, characterized in that, The reaction conditions for reaction I include: a temperature of 300℃~350℃ and a time of 5h~10h; And / or, the reaction conditions for reaction II include: a temperature of 100℃~120℃ and a time of 1.5h~4h.

10. The application of a mechanical property modifier according to any one of claims 1 to 6 or a mechanical property modifier prepared by any one of claims 7 to 9 in cement slurry; preferably, the cement slurry is a cement slurry used in oil and gas well cementing operations.

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