Anti-carbon dioxide corrosion foam cement slurry and preparation method thereof

Abstract

The present application relates to the technical field of foam cementing of oil and gas wells, and discloses a carbon dioxide corrosion-resistant foam cement slurry and a preparation method thereof. The raw material composition comprises cement, siliceous material, corrosion-resistant material, toughening and expanding material, fluid loss additive, retarder, drag reducing agent, foaming agent, foam stabilizer and water in terms of mass parts. The required amount of cement, siliceous material and corrosion-resistant material is mixed to obtain a solid phase material. The required amount of water is added with the fluid loss additive, retarder and drag reducing agent in sequence, and stirred respectively. Then, the foaming agent and foam stabilizer are added in sequence, and stirred uniformly to obtain a slurry preparation liquid. Finally, the solid phase material is added into the slurry preparation liquid and stirred to obtain the carbon dioxide corrosion-resistant foam cement slurry. The present application can reduce the permeability of cement stone, reduce the corrosion channeling passage, improve the compressive strength, toughness, cementing strength and corrosion resistance of low-density cement stone, and realize efficient CO2 storage and cyclic reinjection, which is green and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of foam cementing technology for oil and gas wells, and specifically to a carbon dioxide corrosion resistant foam cement slurry and its preparation method. Background Technology

[0002] Increasing the density of cement stone and improving the sealing integrity of the cement ring at the interface helps to further enhance the cement ring's resistance to CO2 corrosion and its sealing integrity.

[0003] CCUS-EOR, or Carbon Dioxide Capture and Storage Enhanced Oil Recovery Technology, captures, purifies, and liquefies industrial carbon dioxide before injecting it underground for oil displacement, while simultaneously achieving efficient carbon dioxide storage. It is a green development technology that reduces carbon emissions, turns waste into treasure, improves the recovery rate of low-permeability oilfields, and achieves both oil displacement and storage, emphasizing both economic benefits and environmental protection.

[0004] Currently, CCUS wells often utilize a network of modified old wells combined with new wells. Long-term exploitation of these old well production blocks leads to disrupted formation pressure systems, and low-pressure, easily leaking formations are common during drilling. Foamed cement slurry, with its unique properties of low density, low thermal conductivity, and strong compressibility, is widely used in low-density cementing. Its anti-gas channeling and anti-water intrusion characteristics make it an effective cementing method for low-pressure, easily leaking wells and low-density wells with long cemented sections. Because CO2 easily corrodes cement stone, it can easily cause annular gas channeling, wellhead pressurization, cement sheath seal failure, and secondary accidents. Furthermore, to improve the comprehensive utilization of CO2, circulating reinjection is crucial for ensuring efficient storage. Therefore, the integrity of the cement sheath corrosion is one of the key factors determining whether CO2 geological storage projects can be successfully implemented and ultimately achieve 100-year safe storage. Compared to conventional oil and gas wells, CCUS wells have higher requirements and greater challenges in maintaining wellbore integrity over the long term. There is a lack of highly efficient carbon dioxide corrosion-resistant foamed cement slurry systems in China.

[0005] Therefore, developing a carbon dioxide corrosion resistant foamed cement slurry system, coupled with wellbore cement sheath sealing technology, to increase the density of cement stone and improve the bonding ability of cement sheath at the interface, thereby enhancing the long-term sealing integrity of the wellbore under CO2 injection and geological storage conditions, is a guarantee for promoting the implementation and development of CCUS technology. Summary of the Invention

[0006] This invention provides a carbon dioxide corrosion resistant foamed cement slurry and its preparation method, which overcomes the shortcomings of the prior art. It can effectively solve the problem that carbon dioxide easily corrodes the cement stone in the existing carbon dioxide corrosion resistant foamed cement slurry system, causing annular air leakage and wellhead pressurization during mining, which leads to cement sheath seal failure and secondary accidents.

[0007] One of the technical solutions of this invention is achieved through the following measures: a carbon dioxide corrosion-resistant foamed cement slurry, the raw material composition by weight including 100 parts cement, 10 to 30 parts siliceous material, 6 to 15 parts anti-corrosion material, 4 to 8 parts toughening and expanding material, 2 to 6 parts water loss reducing agent, 0.2 to 5 parts retarder, 0.6 to 3 parts drag reducing agent, 5 to 10 parts foaming agent, 1 to 5 parts foam stabilizing agent, and 48 to 75 parts water, obtained by the following method: The first step is to mix the required amounts of cement, siliceous materials, anti-corrosion materials, and toughening and expansion materials to obtain a solid material. The second step is to add the water loss reducer, retarder, and drag reducer to the required amount of water in sequence and stir them separately. Then, add the foaming agent and foam stabilizer in sequence, mix and stir evenly to obtain the slurry. The third step is to add solid materials to the grout and stir to obtain carbon dioxide corrosion resistant foamed cement grout.

[0008] The following are further optimizations and / or improvements to one of the above-mentioned inventive technical solutions: In the first step above, the stirring conditions include a stirring speed of 1000 r / min to 1500 r / min; In the second step above, the stirring conditions include: the initial stirring speed is 1000 r / min to 1500 r / min, stirring for 20 seconds after adding the water loss reducer, stirring for 15 seconds after adding the retarder, stirring for 15 seconds after adding the drag reducer, and stirring for 35 seconds after adding the foaming agent and foam stabilizer, and then adjusting the stirring speed to 2000 r / min and stirring for 35 seconds. In the third step above, the stirring conditions include: a stirring speed of 3800 r / min to 4200 r / min, stirring for 60 s after adding solid material, wherein solid material is added within 15 s to 25 s after obtaining the slurry.

[0009] The above-mentioned cement is oil well grade G cement, which is one of the sulfur-resistant cements in MSR and high sulfur-resistant cements in HSR. The aforementioned siliceous materials are one or more of the following: microsilica, silicon powder, fly ash, and slag powder.

[0010] The aforementioned anti-corrosion materials are one or more of latex powder and rubber powder.

[0011] The aforementioned toughening and expanding materials are one or more of latex particles, nanomaterials, modified calcium whiskers, polypropylene fibers, glass fibers, and carbon fibers.

[0012] The aforementioned water loss reducing agent is a high-temperature resistant water loss reducing agent, which is one of a first copolymer, a second copolymer, a third copolymer, and a fourth copolymer. The first copolymer includes 2-acrylamido-2-methylpropanesulfonic acid and pyrrolidone; the second copolymer includes 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and N,N-dimethylacrylamide; the third copolymer includes 2-acrylamido-2-methylpropanesulfonic acid, maleic acid, and dimethyldiallylammonium chloride; and the fourth copolymer includes 2-acrylamido-2-methylpropanesulfonic acid, maleic acid, itaconic acid, and N,N-dimethylacrylamide.

[0013] The aforementioned retarder is one of the fifth copolymer and the sixth copolymer, wherein the fifth copolymer includes 2-acrylamido-2-methylpropanesulfonic acid, itaconic acid, and acrylamide, and the sixth copolymer includes 2-acrylamido-2-methylpropanesulfonic acid, maleic acid, acrylic acid, and dimethyldiallylammonium chloride.

[0014] The drag-reducing agent mentioned above is one of the following: a first condensation polymer, a naphthalene sulfonated resin, a seventh copolymer, and a second condensation polymer. The first condensation polymer includes polynaphthalene sulfonate and naphthalene sulfonate. The seventh copolymer includes sodium methacrylate sulfonate, acrylic acid, and isopentenyl alcohol polyoxyethylene ether. The second condensation polymer includes formaldehyde, acetone, and sodium sulfite.

[0015] The foaming agent mentioned above is one of sodium alkenyl sulfonate, alkylphenol polyoxyethylene ether, and sodium dodecylbenzene sulfonate; or / and the foam stabilizer is one of polyanionic cellulose, cocamidopropyl hydroxysulfonate, and sodium dodecyl sulfate.

[0016] The second technical solution of the present invention is achieved through the following measures: a method for preparing carbon dioxide corrosion resistant foamed cement slurry, which is carried out according to the following method: The first step is to mix the required amounts of cement, siliceous materials, anti-corrosion materials, and toughening and expansion materials to obtain a solid material. The second step is to add the water loss reducer, retarder, and drag reducer to the required amount of water in sequence and stir them separately. Then, add the foaming agent and foam stabilizer in sequence, mix and stir evenly to obtain the slurry. The third step is to add solid materials to the grout and stir to obtain carbon dioxide corrosion resistant foamed cement grout.

[0017] This invention can reduce the permeability of cement stone, reduce corrosion channeling, and improve the compressive strength, toughness, bonding strength and corrosion resistance of low-density cement stone. It also achieves efficient CO2 storage and recycling, making it green and environmentally friendly. Detailed Implementation

[0018] This invention is not limited to the following embodiments; specific implementation methods can be determined based on the technical solution of this invention and actual circumstances. Unless otherwise specified, all chemical reagents and chemical products mentioned in this invention are well-known and commonly used chemical reagents and chemical products in the prior art.

[0019] The present invention will be further described below with reference to embodiments: Example 1: This carbon dioxide corrosion-resistant foamed cement slurry comprises, by weight, 100 parts cement, 10 to 30 parts siliceous material, 6 to 15 parts anti-corrosion material, 4 to 8 parts toughening and expanding material, 2 to 6 parts water loss reducing agent, 0.2 to 5 parts retarder, 0.6 to 3 parts drag reducing agent, 5 to 10 parts foaming agent, 1 to 5 parts foam stabilizer, and 48 to 75 parts water, obtained according to the following method: The first step is to mix the required amounts of cement, siliceous materials, anti-corrosion materials, and toughening and expansion materials to obtain a solid material. The second step is to add the water loss reducer, retarder, and drag reducer to the required amount of water in sequence and stir them separately. Then, add the foaming agent and foam stabilizer in sequence, mix and stir evenly to obtain the slurry. The third step is to add solid materials to the grout and stir to obtain carbon dioxide corrosion resistant foamed cement grout.

[0020] This invention incorporates a certain amount of siliceous materials, anti-corrosion materials (anti-corrosion latex powder), and toughening and expanding materials. Through the effective particle size distribution between the solid materials of different particle sizes and cement, it reduces the permeability of cement stone, decreases corrosion channels, and improves the compressive strength of low-density cement stone. Simultaneously, latex microparticles and hydration products form a continuous network film that adheres to the internal pores and surface of the cement stone, reducing CO2 intrusion into the cement stone and enhancing its corrosion resistance. The toughening and expanding material, composed of modified calcium whiskers and low-elasticity modulus fibers, reacts to generate a fibrous lattice expansion effect. The low-elasticity modulus fibers disperse the directional stress of the cement stone, improving its toughness and bonding strength, ensuring efficient CO2 storage and reinjection. The addition of foaming agents and foam stabilizers fills the cement slurry with uniform and dense air bubbles. These stable bubbles significantly reduce the density of the cement slurry, resulting in a foamed cement slurry suitable for on-site application. By using anti-carbon dioxide corrosion foamed cement slurry to solve the technical problem of maintaining the long-term sealing integrity of the cement sheath, the technology integrates "carbon emission reduction - carbon capture - carbon flooding - carbon sequestration" into one, making carbon dioxide flooding (CCUS) technology achieve the goal of being green and environmentally friendly.

[0021] The density of this carbon dioxide corrosion-resistant foamed cement slurry is adjustable within the range of 1.00 g / cm³ to 1.75 g / cm³, exhibiting good slurry stability. The density difference between the upper and lower parts of the slurry is controlled within ±0.02 g / cm³. The thickening time is adjustable, and the compressive strength at 48 hours is ≥14 MPa. Under a CO2 partial pressure of 5.0 MPa, the 60-day compressive strength loss of the cement stone is ≤15%, and the 7-day Young's modulus is ≤7 GPa. This slurry can meet the requirements for long-term integrity and corrosion resistance of low-density foamed cement sheaths in wells for efficient carbon dioxide storage and oil displacement.

[0022] Example 2: As an optimization of the above example, in the first step, the stirring state includes: the stirring speed is 1000 r / min to 1500 r / min.

[0023] Example 3: As an optimization of the above example, in the second step, the stirring state includes: the initial stirring speed is 1000 r / min to 1500 r / min, stirring for 20 seconds after adding the water loss reducing agent, stirring for 15 seconds after adding the retarder, stirring for 15 seconds after adding the drag reducing agent, and stirring for 35 seconds after adding the foaming agent and foam stabilizing agent, and then adjusting the stirring speed to 2000 r / min and stirring for 35 seconds.

[0024] Example 4: As an optimization of the above example, in the third step, the stirring state includes: the stirring speed is 3800 r / min to 4200 r / min, and the solid material is added and stirred for 60 s, wherein the solid material is added within 15 s to 25 s after the slurry is obtained.

[0025] Example 5: As an optimization of the above example, the cement is oil well grade G cement, which is one of MSR sulfur-resistant cement and HSR high sulfur-resistant cement.

[0026] Example 6: As an optimization of the above examples, the siliceous material is one or more of microsilica, silicon powder, fly ash, and slag powder.

[0027] Example 7: As an optimization of the above examples, the toughening expansion material is one or more of latex particles, nanomaterials, modified calcium whiskers, polypropylene fibers, glass fibers, and carbon fibers.

[0028] Example 8: As an optimization of the above embodiment, the water loss reducing agent is a high-temperature water loss reducing agent, which is one of the first copolymer, the second copolymer, the third copolymer, and the fourth copolymer. The first copolymer includes 2-acrylamido-2-methylpropanesulfonic acid and pyrrolidone; the second copolymer includes 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and N,N-dimethylacrylamide; the third copolymer includes 2-acrylamido-2-methylpropanesulfonic acid, maleic acid, and dimethyldiallylammonium chloride; and the fourth copolymer includes 2-acrylamido-2-methylpropanesulfonic acid, maleic acid, itaconic acid, and N,N-dimethylacrylamide.

[0029] In this invention, the water loss reducing agent is a liquid water loss reducing agent or a solid water loss reducing agent.

[0030] Example 9: As an optimization of the above examples, the retarder is one of the fifth copolymer and the sixth copolymer, wherein the fifth copolymer includes 2-acrylamido-2-methylpropanesulfonic acid, itaconic acid, and acrylamide, and the sixth copolymer includes 2-acrylamido-2-methylpropanesulfonic acid, maleic acid, acrylic acid, and dimethyldiallylammonium chloride.

[0031] In this invention, the retarder is a liquid retarder.

[0032] Example 10: As an optimization of the above examples, the drag-reducing agent is one of the following: a first condensation polymer, a naphthalene sulfonated resin, a seventh copolymer, and a second condensation polymer. The first condensation polymer includes polynaphthalene sulfonate and naphthalene sulfonate. The seventh copolymer includes sodium methacrylate sulfonate, acrylic acid, and isopentenyl alcohol polyoxyethylene ether. The second condensation polymer includes formaldehyde, acetone, and sodium sulfite.

[0033] In this invention, the drag-reducing agent is a liquid drag-reducing agent or a solid drag-reducing agent.

[0034] Example 11: As an optimization of the above example, the foaming agent is one of sodium alkenyl sulfonate, alkylphenol polyoxyethylene ether, and sodium dodecylbenzene sulfonate; the foam stabilizer is one of polyanionic cellulose, cocamidopropyl hydroxysulfonate, and sodium dodecyl sulfate.

[0035] In this invention, the foaming agent is a liquid foaming agent, the foam stabilizer is a liquid foam stabilizer, and the water is one of fresh water, groundwater, and salt water.

[0036] Example 12: The preparation method of this carbon dioxide corrosion resistant foamed cement slurry is carried out according to the following method: The first step is to mix the required amounts of cement, siliceous materials, anti-corrosion materials, and toughening and expansion materials to obtain a solid material. The second step is to add the water loss reducer, retarder, and drag reducer to the required amount of water in sequence and stir them separately. Then, add the foaming agent and foam stabilizer in sequence, mix and stir evenly to obtain the slurry. The third step is to add solid materials to the grout and stir to obtain carbon dioxide corrosion resistant foamed cement grout.

[0037] All raw materials used in the following embodiments of the present invention are commercially available products. Specifically, the cement used is oil well grade G HSR high sulfur-resistant cement, provided by Hoboksar County Qingsong Nangangtun Nanjian Building Materials Co., Ltd.; the siliceous material used is a compound of microsilica, silica fume, and fly ash, with microsilica provided by Ningxia Yiyun Special Engineering Materials Co., Ltd., silica fume provided by Xinjiang Karamay Dima Co., Ltd., and fly ash provided by Henan Jinchuan Building Materials Co., Ltd.; the anti-corrosion material used, DRT-100S, is a latex powder with a density of 1.70 g / cm³, provided by CNPC Engineering Technology Research Institute Co., Ltd.; the toughening and expansion material used is a compound of glass fiber powder and modified calcium whiskers, with glass fiber powder provided by Taian Zhongshuo Glass Fiber Products Co., Ltd., and modified calcium whiskers provided by Chengdu Jubo Technology Co., Ltd.; and the water loss reducing agent used is 2-acrylamido-2-methyl The propanesulfonic acid (AMPS) pyrrolidone polymer-based water loss reducer HX-12L was provided by Chengdu Omeike Petroleum Technology Co., Ltd.; the drag reducer HX-21L, a naphthalene aldehyde sulfonated resin, was also provided by Chengdu Omeike Petroleum Technology Co., Ltd.; the retarder HX-31L, a copolymer of 2-acrylamide-2-methylpropanesulfonic acid (AMPS), itaconic acid (IA), and acrylamide (AM), was provided by Chengdu Omeike Petroleum Technology Co., Ltd.; the foaming agent AOS, sodium alkenyl sulfonate, was provided by Guangzhou Changlong Chemical Co., Ltd.; the foam stabilizer PAC-LV, a polyanionic cellulose, was provided by Hebei Yufei Chemical Co., Ltd.; and the weight-reducing agent HL60 (hollow glass microspheres) was provided by Zhengzhou Shenglait Hollow Microsphere New Material Co., Ltd.

[0038] Example 13: The carbon dioxide corrosion resistant foam cement slurry with a density of 1.00 g / cm3, suitable for foam cementing construction, was obtained according to the following method: The first step is to mix 300g of G-grade HSR high sulfur-resistant cement for oil wells, 60g of siliceous material (microsilica, silica powder, and fly ash in a weight ratio of 3:2:1), 45g of anti-corrosion material, and 24g of toughening and expansion material (glass fiber powder and modified calcium whiskers in a weight ratio of 3:1) evenly to obtain a solid phase material. The second step involves stirring with a constant speed stirrer at 1500 r / min. First, add 18 g of a water loss reducer (HX-12L, a polymer formed from 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and pyrrolidone) to 225 g of water and stir for 20 seconds. Then, add 9 g of a retarder (HX-31L, a copolymer composed of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), itaconic acid (IA), and acrylamide (AM)) and stir for 15 seconds. Next, add 3 g of a drag reducer (naphthalene aldehyde sulfonated resin HX-21L) and stir for 15 seconds. Then, add 30 g of a foaming agent (sodium alkenyl sulfonate AOS) and 15 g of a foam stabilizer (PAC-LV, polyanionic cellulose). Adjust the stirring speed to 2000 r / min and stir for 35 seconds until the mixture is homogeneous, thus obtaining the prepared slurry. The third step involves using a constant speed mixer at a speed of 4000 r / min to add solid material to the slurry within 20 seconds and stirring for 35 seconds to obtain a carbon dioxide corrosion resistant foamed cement slurry with a density of 1.00 g / cm3.

[0039] Example 14: The carbon dioxide corrosion resistant foam cement slurry with a density of 1.35 g / cm3, suitable for foam cementing construction, was obtained according to the following method: The first step is to mix 400g of G-grade HSR high sulfur-resistant cement for oil wells, 72g of siliceous material (microsilica, silica powder, and fly ash in a weight ratio of 3:2:1), 48g of anti-corrosion material, and 24g of toughening and expansion material (glass fiber powder and modified calcium whiskers in a weight ratio of 3:1) evenly to obtain a solid phase material. The second step involves stirring with a constant speed stirrer at 1500 rpm. In 272 g of water, first add 20 g of a water-loss reducing agent (HX-12L, a polymer formed from 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and pyrrolidone) and stir for 20 seconds. Then add 8.8 g of a retarder (HX-31L, a copolymer composed of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), itaconic acid (IA), and acrylamide (AM)) and stir for 15 seconds. Next, add 4.8 g of a drag-reducing agent (naphthalene aldehyde sulfonated resin HX-21L) and stir for 15 seconds. Then, add 32 g of a foaming agent (sodium alkenyl sulfonate AOS) and 16 g of a foam stabilizer (PAC-LV, polyanionic cellulose). Adjust the stirring speed to 2000 rpm and stir for 35 seconds. Mix thoroughly to obtain the prepared slurry. The third step involves using a constant speed mixer at a speed of 4000 r / min to add solid material to the slurry within 20 seconds and stirring for 35 seconds to obtain a carbon dioxide corrosion resistant foamed cement slurry with a density of 1.35 g / cm3.

[0040] Example 15: The carbon dioxide corrosion resistant foam cement slurry with a density of 1.50 g / cm3, suitable for foam cementing construction, was obtained according to the following method: The first step is to mix 500g of G-grade HSR high sulfur-resistant cement for oil wells, 70g of siliceous material (microsilica, silica powder, and fly ash in a weight ratio of 3:2:1), 50g of anti-corrosion material, and 25g of toughening and expansion material (glass fiber powder and modified calcium whiskers in a weight ratio of 3:1) evenly to obtain a solid phase material. The second step involves stirring with a constant speed stirrer at 1500 rpm. In 310 g of water, first add 15 g of a water-loss reducing agent (HX-12L, a polymer formed from 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and pyrrolidone) and stir for 20 seconds. Then add 9 g of a retarder (HX-31L, a copolymer composed of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), itaconic acid (IA), and acrylamide (AM)) and stir for 15 seconds. Next, add 7 g of a drag-reducing agent (naphthalene aldehyde sulfonated resin HX-21L) and stir for 15 seconds. Then, add 30 g of a foaming agent (sodium alkenyl sulfonate AOS) and 10 g of a foam stabilizer (PAC-LV, polyanionic cellulose). Adjust the stirring speed to 2000 rpm and stir for 35 seconds until the mixture is homogeneous, thus obtaining the prepared slurry. The third step involves using a constant speed mixer at a speed of 4000 r / min to add solid material to the slurry within 20 seconds and stirring for 35 seconds to obtain a carbon dioxide corrosion resistant foamed cement slurry with a density of 1.50 g / cm3.

[0041] Example 16: The carbon dioxide corrosion resistant foam cement slurry with a density of 1.75 g / cm3, suitable for foam cementing construction, was obtained according to the following method: The first step is to mix 600g of G-grade HSR high sulfur-resistant cement for oil wells, 60g of siliceous material (microsilica, silica powder, and fly ash in a weight ratio of 2:3:1), 36g of anti-corrosion material, and 24g of toughening and expansion material (glass fiber powder and modified calcium whiskers in a weight ratio of 3:1) evenly to obtain a solid phase material. The second step involves stirring with a constant speed stirrer at 1500 r / min. In 288 g of water, first add 12 g of a water-loss reducing agent (HX-12L, a polymer formed from 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and pyrrolidone) and stir for 20 seconds. Then add 9 g of a retarder (HX-31L, a copolymer composed of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), itaconic acid (IA), and acrylamide (AM)) and stir for 15 seconds. Next, add 9.6 g of a drag-reducing agent (naphthalene aldehyde sulfonated resin HX-21L) and stir for 15 seconds. Then, add 30 g of a foaming agent (sodium alkenyl sulfonate AOS) and 6 g of a foam stabilizer (PAC-LV, polyanionic cellulose). Adjust the stirring speed to 2000 r / min and stir for 35 seconds until the mixture is homogeneous, thus obtaining the prepared slurry. The third step involves using a constant speed mixer at a speed of 4000 r / min to add solid material to the slurry within 20 seconds and stirring for 35 seconds to obtain a carbon dioxide corrosion resistant foamed cement slurry with a density of 1.75 g / cm3.

[0042] Comparative Example 1: (1) The conventional foam cement slurry with a density of 1.35 g / cm3 suitable for foam cementing construction is composed of the following materials: 400 g of oil well G-grade HSR high sulfur-resistant cement, 80 g of weight-reducing agent (hollow glass microspheres), 48 g of microsilica, 32 g of fluid loss reducing agent, 16 g of drag reducing agent, 8 g of retarder, 32 g of foaming agent, 12 g of foam stabilizing agent, and 260 g of water. Among them, the fluid loss reducing agent, drag reducing agent, retarder, foaming agent, and foam stabilizing agent used are the same as those in Example 14.

[0043] (2) Preparation method: 400g of oil well grade G HSR high sulfur-resistant cement, 80g of light-reducing agent, and 48g of microsilica were mixed evenly to obtain the solid material for preparing cement slurry.

[0044] Using a mixer at a speed of 1200 r / min, first add 32 g of water loss reducer to 260 g of water and stir for 15 s, then add 8 g of retarder and stir for 15 s, then add 16 g of drag reducer and stir for 20 s, and finally add 32 g of foaming agent and 12 g of foam stabilizer. Adjust the stirring speed to 2500 r / min and stir for 35 s to obtain the slurry preparation solution for preparing cement slurry.

[0045] Adjust the stirring speed of the mixer to 4000 r / min, add the above solid material within 35s and continue stirring for 35s to obtain a conventional foamed cement slurry with a density of 1.35 g / cm3.

[0046] Comparative Example 2: (1) A conventional foam cement slurry with a density of 1.50 g / cm3 suitable for foam cementing construction is composed of the following materials: 500 g of oil well G-grade HSR high sulfur-resistant cement, 80 g of weight-reducing agent (hollow glass microspheres), 45 g of microsilica, 30 g of fluid loss reducing agent, 10 g of drag reducing agent, 10 g of retarder, 35 g of foaming agent, 10 g of foam stabilizing agent, and 310 g of water. The fluid loss reducing agent, drag reducing agent, retarder, foaming agent, and foam stabilizing agent used are the same as those in Example 15.

[0047] (2) Preparation method: 500g of oil well grade G HSR high sulfur-resistant cement, 80g of light-reducing agent, and 45g of microsilica were mixed evenly to obtain the solid material for preparing cement slurry.

[0048] Using a mixer at a speed of 1200 r / min, first add 30 g of water loss reducer to 310 g of water and stir for 15 s, then add 10 g of retarder and stir for 15 s, then add 10 g of drag reducer and stir for 20 s, and finally add 35 g of foaming agent and 10 g of foam stabilizer. Adjust the stirring speed to 2500 r / min and stir for 35 s to obtain the slurry preparation solution for preparing cement slurry.

[0049] Adjust the stirring speed of the mixer to 4000 r / min, add the above solid material within 35s and continue stirring for 35s to obtain a conventional foamed cement slurry with a density of 1.50 g / cm3.

[0050] Comparative Example 3 (1) The conventional foam cement slurry with a density of 1.60 g / cm3 suitable for foam cementing construction is composed of the following materials: 600 parts of oil well G-grade HSR high sulfur-resistant cement, 78 g of weight-reducing agent (hollow glass microspheres), 36 g of microsilica, 24 g of fluid loss reducing agent, 6 g of drag reducing agent, 12 g of retarder, 36 g of foaming agent, 6 g of foam stabilizing agent, and 330 g of water. Among them, the fluid loss reducing agent, drag reducing agent, retarder, foaming agent and foam stabilizing agent used are the same as those in Example 16.

[0051] (2) Preparation method: 600g of oil well grade G HSR high sulfur-resistant cement, 78g of weight-reducing agent, and 36g of microsilica were mixed evenly to obtain the solid material for preparing cement slurry.

[0052] Using a mixer at a speed of 1200 r / min, first add 24 g of water loss reducer to 330 g of water and stir for 15 s, then add 12 g of retarder and stir for 15 s, then add 6 g of drag reducer and stir for 20 s, and finally add 36 g of foaming agent and 6 g of foam stabilizer. Adjust the stirring speed to 2500 r / min and stir for 35 s to obtain the slurry preparation solution for preparing cement slurry.

[0053] Adjust the stirring speed of the mixer to 4000 r / min, add the above solid material within 35s and continue stirring for 35s to obtain a conventional foamed cement slurry with a density of 1.60 g / cm3.

[0054] Experimental Example 1: Settling Stability Test of Foamed Cement Slurry Resistant to Carbon Dioxide Corrosion Comparative experiments were conducted between Examples 13 to 16 and Comparative Examples 1 to 3, and the settling stability of the cement slurry was measured according to GB / T 19139-2012 Oil Well Cement Test Methods. The experimental results are shown in Table 1.

[0055] As can be seen from the experimental results in Table 1, in Examples 13 to 16, the density difference between the upper, middle and lower parts of the carbon dioxide corrosion resistant foamed cement slurry with different formulations and densities can be controlled within the range of ±0.02 g / cm³, which meets the on-site technical requirements.

[0056] Experiment Example 2: Test of compressive strength and corrosion resistance of carbon dioxide corrosion resistant foamed cement slurry Comparative experiments were conducted between Examples 13 to 16 and Comparative Examples 1 to 3. The compressive strength was determined according to GB / T 19139-2012, "Test Methods for Oil Well Cement," after conventional curing for 48 hours and 30 days, and after CO2 partial pressure corrosion curing for 30 days and 60 days. The experimental results are shown in Table 2.

[0057] As can be seen from the experimental results in Table 2, the compressive strength of the carbon dioxide corrosion resistant foamed cement slurry with different formulations and densities in Examples 13 to 16 all meet the on-site technical requirements. After CO2 corrosion curing, the strength attenuation rate is less than 15%, while the strength attenuation rate of conventional foamed cement slurry is greater than 23%. This indicates that the carbon dioxide corrosion resistant foamed cement slurry cement stone can resist CO2 corrosion and meet the long-term sealing integrity requirements of CCUS wellbore.

[0058] Experiment Example 3: Cement stone permeability test of carbon dioxide corrosion resistant foamed cement slurry Comparative experiments were conducted between Examples 13 to 16 and Comparative Examples 1 to 3. Permeability was measured after 30 and 60 days of corrosion curing under a CO2 partial pressure of 5.0 MPa, according to GB / T 19139-2012 "Test Methods for Cement in Oil Wells". The experimental results are shown in Table 3.

[0059] As can be seen from the experimental results in Table 3, Examples 13 to 16 of the present invention have a significant advantage in permeability compared with Comparative Examples 1 to 3. This indicates that the particle size distribution of various solid materials in the carbon dioxide corrosion resistant foamed cement slurry provided by the present invention is reasonable, which reduces porosity, lowers permeability, and keeps the cement stone in a dense structure.

[0060] Experiment Example 4: Young's Modulus Test of Carbon Dioxide Corrosion Resistance Foamed Cement Slurry Comparative experiments were conducted between Examples 13 to 16 and Comparative Examples 1 to 3. Young's modulus was determined after 7 days of curing according to "SY / T6466-2016 Test Method for Performance of Cement Stone in Oil Wells". The experimental results are shown in Table 4.

[0061] As can be seen from the experimental results in Table 4, in Examples 13 to 16, the Young's modulus of the carbon dioxide corrosion resistant foamed cement slurry with different formulations and densities is <7 GPa, and the cement stone has high toughness, which can ensure efficient CO2 storage and recycling.

[0062] The preparation method provided by this invention does not have special requirements for the preparation environment in the laboratory or on site. In on-site construction, cement trucks can be used for self-mixing and self-injection, or fixed tank and quantitative preparation can be carried out by pump truck for suction and injection, which is flexible and convenient to operate.

[0063] The carbon dioxide corrosion resistant foamed cement slurry provided by this invention has an adjustable density within the range of 1.00 g / cm³ to 1.75 g / cm³, and has the following beneficial technical effects: (1) Low permeability of cement stone: After adding siliceous materials and toughening expansion materials to the cement slurry system, several different particle sizes of siliceous materials form a reasonable particle size distribution with cement, latex particles and nanomaterials, filling the gaps between reaction products and increasing density, thereby reducing the permeability of cement stone.

[0064] (2) Improved corrosion resistance: The composite of silica materials with different particle sizes reduces the alkalinity of cement stone and the calcium / silicon ratio of hydration products, thereby reducing corrosion products. The latex particles cover the cement hydration products and, by adhering to the internal channels and the surface of cement stone, reduce the intrusion of CO2 fluid into the cement stone, thus enhancing the corrosion resistance of the cement stone.

[0065] (3) The strength and bonding strength of cement stone are improved. Modified calcium whiskers and low elastic modulus fibers are used to enhance the toughness of cement stone and avoid the loss of cement stone strength caused by the loss of cementitious substances. The composite material reacts with cement to generate fibrous material, which, in conjunction with the lattice expansion effect, directly improves the hardness of cement stone and increases mechanical strength and bonding strength.

[0066] (4) The Young's modulus is reduced. After adding toughening and expansion materials, the fibers are evenly distributed to form a random support, which disperses the directional stress of the cement stone, eliminates or reduces the number and size of microcracks, and enhances the toughness of the cement stone. The Young's modulus of foamed cement slurry is significantly reduced, which reduces the harm of stress damage, meets the requirements of efficient CO2 storage and cyclic injection and production, and improves the long-term sealing integrity of the wellbore.

[0067] In summary, this invention can reduce the permeability of cement stone, reduce corrosion flow channels, improve the compressive strength, toughness, bonding strength and corrosion resistance of low-density cement stone, and also achieve efficient CO2 storage and recycling, making it green and environmentally friendly.

[0068] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A carbon dioxide corrosion resistant foamed cement slurry, characterized in that... The raw material composition, by weight, includes 100 parts cement, 10 to 30 parts siliceous material, 6 to 15 parts anti-corrosion material, 4 to 8 parts toughening and expansion material, 2 to 6 parts water loss reducing agent, 0.2 to 5 parts retarder, 0.6 to 3 parts drag reducing agent, 5 to 10 parts foaming agent, 1 to 5 parts foam stabilizer, and 48 to 75 parts water, obtained according to the following method: The first step is to mix the required amounts of cement, siliceous materials, anti-corrosion materials, and toughening and expansion materials to obtain a solid material. The second step is to add the water loss reducer, retarder, and drag reducer to the required amount of water in sequence and stir them separately. Then, add the foaming agent and foam stabilizer in sequence, mix and stir evenly to obtain the slurry. The third step is to add solid materials to the grout and stir to obtain carbon dioxide corrosion resistant foamed cement grout.

2. The carbon dioxide corrosion resistant foamed cement slurry according to claim 1, characterized in that... In the first step, the stirring conditions include: a stirring speed of 1000 r / min to 1500 r / min; or / and in the second step, the stirring conditions include: an initial stirring speed of 1000 r / min to 1500 r / min, stirring for 20 seconds after adding the water loss reducer, stirring for 15 seconds after adding the retarder, stirring for 15 seconds after adding the drag reducer, and then adjusting the stirring speed to 2000 r / min and stirring for 35 seconds after adding the foaming agent and foam stabilizer; or / and in the third step, the stirring conditions include: a stirring speed of 3800 r / min to 4200 r / min, stirring for 60 seconds after adding the solid material, wherein the solid material is added within 15 to 25 seconds after obtaining the slurry.

3. The carbon dioxide corrosion resistant foamed cement slurry according to claim 1 or 2, characterized in that... The cement is oil well grade G cement, which is one of MSR medium sulfur-resistant cement or HSR high sulfur-resistant cement; or / and the siliceous material is one or more of microsilica, silica fume, fly ash, and slag powder.

4. The carbon dioxide corrosion resistant foamed cement slurry according to any one of claims 1 to 3, characterized in that... The anti-corrosion material is one or more of latex powder and rubber powder.

5. The carbon dioxide corrosion resistant foamed cement slurry according to any one of claims 1 to 4, characterized in that... The toughening and expanding material is one or more of the following: latex particles, nanomaterials, modified calcium whiskers, polypropylene fibers, glass fibers, and carbon fibers.

6. The carbon dioxide corrosion resistant foamed cement slurry according to any one of claims 1 to 5, characterized in that... The water loss reducing agent is a high-temperature resistant water loss reducing agent, which is one of a first copolymer, a second copolymer, a third copolymer, and a fourth copolymer. The first copolymer includes 2-acrylamido-2-methylpropanesulfonic acid and pyrrolidone; the second copolymer includes 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and N,N-dimethylacrylamide; the third copolymer includes 2-acrylamido-2-methylpropanesulfonic acid, maleic acid, and dimethyldiallylammonium chloride; and the fourth copolymer includes 2-acrylamido-2-methylpropanesulfonic acid, maleic acid, itaconic acid, and N,N-dimethylacrylamide.

7. The carbon dioxide corrosion resistant foamed cement slurry according to any one of claims 1 to 6, characterized in that... The retarder is one of the fifth copolymer and the sixth copolymer, wherein the fifth copolymer includes 2-acrylamide-2-methylpropanesulfonic acid, itaconic acid, and acrylamide, and the sixth copolymer includes 2-acrylamide-2-methylpropanesulfonic acid, maleic acid, acrylic acid, and dimethyldiallyl ammonium chloride.

8. The carbon dioxide corrosion resistant foamed cement slurry according to any one of claims 1 to 7, characterized in that... The drag-reducing agent is one of the following: a first condensation polymer, a naphthalene sulfonated resin, a seventh copolymer, and a second condensation polymer. The first condensation polymer includes polynaphthalene sulfonate and naphthalene sulfonate. The seventh copolymer includes sodium methacrylate sulfonate, acrylic acid, and isopentenyl alcohol polyoxyethylene ether. The second condensation polymer includes formaldehyde, acetone, and sodium sulfite.

9. The carbon dioxide corrosion resistant foamed cement slurry according to any one of claims 1 to 8, characterized in that... The foaming agent is one of sodium alkenyl sulfonate, alkylphenol polyoxyethylene ether, and sodium dodecylbenzene sulfonate; or / and the foam stabilizer is one of polyanionic cellulose, cocamidopropyl hydroxysulfonate, and sodium dodecyl sulfate.

10. A method for preparing carbon dioxide corrosion resistant foamed cement slurry according to any one of claims 1 to 9, characterized in that... Perform the following steps: The first step is to mix the required amounts of cement, siliceous materials, anti-corrosion materials, and toughening and expansion materials to obtain a solid material. The second step is to add the water loss reducer, retarder, and drag reducer to the required amount of water in sequence and stir them separately. Then, add the foaming agent and foam stabilizer in sequence, mix and stir evenly to obtain the slurry. The third step is to add solid materials to the grout and stir to obtain carbon dioxide corrosion resistant foamed cement grout.

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