Anti-corrosion material for cement slurry, carbon dioxide corrosion resistant cement slurry, and preparation method and application thereof

Abstract

This invention relates to the field of cement slurry technology for oil and gas well cementing, and discloses anti-corrosion materials for cement slurries, carbon dioxide corrosion-resistant cement slurries, their preparation methods, and applications. The anti-corrosion material comprises mixture A and mixture B; wherein, mixture A comprises activated carbon, nano-silica, and nano-alumina; mixture B comprises component C and component D; component C is selected from diatomaceous earth and / or fly ash; component D is selected from one or more of metakaolin, pumice, and coal gangue. The carbon dioxide corrosion-resistant cement slurry prepared using this anti-corrosion material exhibits good corrosion resistance in CO2-resistant wells. 2 It exhibits excellent corrosion resistance in corrosive environments. Before corrosion, the cement stone has high compressive strength and a dense structure. After corrosion, the compressive strength of the cement stone does not significantly decrease, and it has low permeability, good mechanical properties, good settling stability, and good rheological properties. These comprehensive properties ensure the cementing quality of CCUS wells and achieve CO2 production. 2 Efficient sealing.

Description

Corrosion-resistant materials for cement slurry, carbon dioxide corrosion-resistant cement slurry, their preparation methods and applications Technical Field

[0001] This invention relates to the field of cement slurry technology for oil and gas well cementing, specifically to anti-corrosion materials for cement slurry, carbon dioxide corrosion resistant cement slurry, their preparation methods and applications. Background Technology

[0002] Carbon capture, utilization, and storage (CCUS) is currently the only feasible technology capable of significantly reducing CO2 emissions. The integrity of the cement sheath is a key technology determining the successful implementation and long-term storage of CO2 in geological storage projects. As is well known, CO2 exists downhole in a supercritical state, characterized by low viscosity and high permeability. Meanwhile, silicate cement systems are strongly alkaline, while CO2 is an acidic gas. Under long-term CO2 erosion, the cement sheath is prone to excessive carbonization and decalcification, leading to changes in composition, strength reduction, increased porosity and permeability, ultimately destroying the overall structure of the cement sheath and jeopardizing the long-term effective sealing of the wellbore.

[0003] Currently, to address the corrosion problem of well cement sheaths by acidic gases such as CO2, anti-corrosion cement slurry systems are widely used both domestically and internationally. Oil well cement CO2 anti-corrosion materials mainly employ ultrafine inert materials and active silica-based materials. For example, Sinopec Dezhou Research Institute adds inert ultrafine barite, and Li Guanying et al. from National Cheng Kung University add fly ash, silica powder, and other active materials. These methods improve the CO2 corrosion resistance of cement stone by reducing its permeability through a physical compaction effect and by reacting with cement minerals to reduce its alkalinity. However, this approach only weakens the exchange source of dissolving ions and slows down the penetration rate of the CO2 corrosive medium. Once the corrosive medium enters the cement stone, it will continue to damage the gel structure, rendering it unable to continue its anti-corrosion function. Therefore, the anti-corrosion effect is not ideal.

[0004] CN114133172A discloses a carbon dioxide corrosion resistant cement slurry for cementing and its preparation method. The slurry uses silicate cement, nano-silica, UF cellulose fiber, a fluid loss reducer, and a dispersant. The nano-silica fills and plugs the micropores inside the cement stone, participates in the hydration reaction to increase the Si / Ca ratio of the hydration products, and improves the corrosion resistance of the hydration products. The UF cellulose improves the mechanical properties of the cement stone. However, the applicable temperature range is not given; the example temperature is 60℃, indicating a narrow applicable temperature range and insufficient system adaptability.

[0005] Therefore, there is an urgent need to develop a cement slurry with good corrosion resistance in a CO2 corrosive environment to ensure the cementing quality of CCUS wells and achieve efficient CO2 storage. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem in existing technologies where cement stone cannot maintain corrosion resistance after being invaded by CO2 corrosive media. This invention provides anti-corrosion materials for cement slurry, carbon dioxide corrosion-resistant cement slurry, its preparation method, and applications. Under the corrosive conditions of CO2 geological storage wells, the carbon dioxide corrosion-resistant cement slurry prepared using the anti-corrosion materials of this invention exhibits high compressive strength, low permeability, good settling stability, good rheological properties, and a wide applicable temperature range after corrosion, ensuring long-term effective sealing of CO2 geological storage wells.

[0007] To achieve the above objectives, a first aspect of the present invention provides an anti-corrosion material for cement slurry, the anti-corrosion material comprising mixture A and mixture B; wherein, mixture A comprises activated carbon, nano-silica and nano-alumina; mixture B comprises component C and component D; component C is selected from diatomaceous earth and / or fly ash; component D is selected from one or more of metakaolin, pumice and coal gangue.

[0008] Preferably, in the mixture A, the mass ratio of activated carbon, nano-silica, and nano-alumina is 1:0.05-0.1:0.05-0.1.

[0009] Preferably, the mass ratio of component C to component D is 1-2:1.

[0010] Preferably, the mass ratio of mixture A to mixture B is 1:2-4.

[0011] Preferably, the average particle size of the activated carbon is 40-60 μm.

[0012] Preferably, the nano-silica has a SiO2 content greater than 99% and an average particle size of 30-40 nm.

[0013] Preferably, the nano-alumina has an Al2O3 content greater than 99% and an average particle size of 10-30 nm.

[0014] Preferably, the average particle size of component C is 10-20 μm.

[0015] Preferably, the average particle size of component D is 20-40 μm.

[0016] A second aspect of the present invention provides a method for preparing an anti-corrosion material for cement slurry, the method comprising:

[0017] Activated carbon, nano-silica, and nano-alumina are mixed to obtain mixture A;

[0018] Component C and component D are mixed to obtain mixture B; wherein, component C is selected from diatomaceous earth and / or fly ash; and component D is selected from one or more of metakaolin, pumice, and coal gangue.

[0019] Mixture A and mixture B are mixed under low stirring rate conditions, and then stirred at high speed to obtain the corrosion-resistant material.

[0020] Preferably, the low stirring rate is 3800-4200 r / min, and the high stirring rate is 11500-12500 r / min.

[0021] The third aspect of the present invention provides the application of the anti-corrosion material described in the first aspect or the anti-corrosion material prepared by the preparation method described in the second aspect in cement slurry, preferably in the application of carbon dioxide corrosion resistant cement slurry.

[0022] The fourth aspect of this invention provides a carbon dioxide corrosion resistant cement slurry, which is made from the following raw materials in parts by weight: 100 parts of G-grade oil well cement, 2-6 parts of anti-corrosion material, 2-5 parts of microsilica, 3-6 parts of reinforcing material, 3-5 parts of expansion and toughening material, 1-3 parts of latex powder, 0-2 parts of stabilizer, 0.3-2 parts of dispersant, 2-5 parts of water loss reducer, 0.1-2 parts of retarder, 0.2-0.5 parts of defoamer, and 48-56 parts of water, wherein the anti-corrosion material is the anti-corrosion material described in the first aspect above or the anti-corrosion material prepared by the preparation method described in the second aspect above.

[0023] The fifth aspect of this invention provides a method for preparing a carbon dioxide corrosion resistant cement slurry, the method comprising:

[0024] Grade G oil well cement is mixed with anti-corrosion materials, microsilica, reinforcing materials, expansion toughening materials, latex powder, stabilizers and dispersants to obtain a dry mix.

[0025] The water loss reducer is mixed with the retarder, defoamer and water to obtain a wet mixture;

[0026] The dry mix and the wet mix are mixed to obtain a carbon dioxide corrosion resistant cement slurry.

[0027] The sixth aspect of this invention provides the application of the carbon dioxide corrosion resistant cement slurry described in the fourth aspect above or the carbon dioxide corrosion resistant cement slurry prepared by the preparation method described in the fifth aspect above in cementing operations of oil and gas wells.

[0028] Preferably, the service temperature of the carbon dioxide corrosion resistant cement slurry is 30-150℃.

[0029] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0030] (1) The cement slurry made with the anti-corrosion material for cement slurry provided by the present invention has an applicable temperature range of 30-150℃. After corrosion, the compressive strength of the cement stone is greater than 20MPa and the permeability is less than 0.1mD, or even less than 0.05mD, which significantly improves the anti-CO2 corrosion ability of the cement stone. At the same time, it has no adverse effect on other engineering properties of the cement slurry and can ensure the long-term effective sealing of the cement ring under CCUS corrosion conditions.

[0031] (2) The present invention is used for anti-carbon dioxide corrosion cement slurry with good anti-corrosion ability in CO2 corrosion environment. Before corrosion, the cement stone has high compressive strength and dense structure. After corrosion, the cement stone has no significant decline in compressive strength, low permeability, good mechanical properties, good settling stability, good rheological properties and other comprehensive properties. It is applicable to anti-CO2 corrosion cement slurry system with temperature of 30-150℃ and below, ensuring the cementing quality of CCUS wells, and ensuring the long-term effective sealing performance of cement sheath under CCUS corrosion conditions, so as to achieve efficient CO2 sealing. Detailed Implementation

[0032] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0033] The first aspect of the present invention provides an anti-corrosion material for cement slurry, the anti-corrosion material comprising mixture A and mixture B; wherein, mixture A comprises activated carbon, nano-silica and nano-alumina; mixture B comprises component C and component D; component C is selected from diatomaceous earth and / or fly ash; component D is selected from one or more of metakaolin, pumice and coal gangue.

[0034] In this invention, mixture A comprises activated carbon, nano-silica, and nano-alumina. The nano-silica and nano-alumina are adsorbed within the pores of the activated carbon, allowing for slow, sustained, and restorative release. Mixture A primarily functions in the later stages.

[0035] In this invention, when cement stone comes into contact with carbon dioxide, mixture B, exhibiting strong pozzolanic activity, initiates the pozzolanic reaction, consuming Ca(OH)₂ in the cement stone and generating dense substances such as hydrated calcium silicate and hydrated calcium aluminate. These substances adhere to the outer surface of the cement stone, providing protection and preventing CO₂ from penetrating further, thus initially forming a protective film on the cement stone's exterior. As the hydration reaction continues, the hydration products such as hydrated calcium silicate and hydrated calcium aluminate are continuously consumed, damaging the protective film and causing further damage to the cement stone's microstructure. Mixture A slowly releases nano-silica and nano-alumina, acting as a filler and blocker, forming a dense protective film on the cement stone's exterior. Simultaneously, the nano-silica continues to react with Ca(OH)₂ in the cement stone, preventing acidic gases from further penetrating. Therefore, mixture A strengthens and densifies the outer protective film of the cement stone, achieving long-term effective corrosion protection. This invention achieves long-term corrosion protection with excellent long-term anti-corrosion effects through optimized anti-corrosion material formulation.

[0036] This invention involves mixing mixture A and mixture B, and is simple, convenient, and highly feasible.

[0037] In some embodiments of the present invention, the mass ratio of activated carbon, nano-silica, and nano-alumina in mixture A is 1:0.05-0.1:0.05-0.1.

[0038] In some embodiments of the present invention, the mass ratio of component C to component D is 1-2:1.

[0039] In some embodiments of the present invention, the mass ratio of mixture A to mixture B is 1:2-4.

[0040] The carbon dioxide corrosion resistant cement slurry made from the above raw materials has good corrosion resistance in CO2 corrosion environment. Before corrosion, the cement stone has high compressive strength and dense structure. After corrosion, the compressive strength of the cement stone does not decline significantly (strength decline rate is less than 20%), and the permeability is less than 0.1mD, or even less than 0.05mD.

[0041] Cement grout containing the above anti-corrosion materials is suitable for temperatures ranging from 30 to 150°C. It can significantly improve the CO2 corrosion resistance of cement stone, and after corrosion, the compressive strength of cement stone is greater than 20 MPa. It has low permeability and has no adverse effects on other properties of cement stone. It can ensure the long-term effective sealing performance of cement ring under CCUS corrosion conditions.

[0042] In some embodiments of the present invention, the average particle size of the activated carbon is 40-60 μm.

[0043] In some embodiments of the present invention, the SiO2 content of the nano-silica is greater than 99%, and the average particle size is 30-40 nm.

[0044] In some embodiments of the present invention, the Al2O3 content of the nano-alumina is greater than 99%, and the average particle size is 10-30 nm.

[0045] In some embodiments of the present invention, the average particle size of component C is 10-20 μm.

[0046] In some embodiments of the present invention, the average particle size of component D is 20-40 μm.

[0047] A second aspect of the present invention provides a method for preparing an anti-corrosion material for cement slurry, the method comprising:

[0048] Activated carbon, nano-silica, and nano-alumina are mixed to obtain mixture A;

[0049] Component C and component D are mixed to obtain mixture B; wherein, component C is selected from diatomaceous earth and / or fly ash; and component D is selected from one or more of metakaolin, pumice, and coal gangue.

[0050] Mixture A and mixture B are mixed under low stirring rate conditions, and then stirred at high speed to obtain the corrosion-resistant material.

[0051] In some embodiments of the present invention, the low stirring rate is 3800-4200 r / min, and the high stirring rate is 11500-12500 r / min.

[0052] In some embodiments of the present invention, the mass ratio of activated carbon, nano-silica, and nano-alumina in mixture A is 1:0.05-0.1:0.05-0.1.

[0053] In some embodiments of the present invention, the mass ratio of component C to component D is 1-2:1.

[0054] In some embodiments of the present invention, the mass ratio of mixture A to mixture B is 1:2-4.

[0055] In some embodiments of the present invention, the activated carbon has a particle size of 40-60 μm.

[0056] In some embodiments of the present invention, the SiO2 content of the nano-silica is greater than 99%, and the average particle size is 30-40 nm.

[0057] In some embodiments of the present invention, the Al2O3 content of the nano-alumina is greater than 99%, and the average particle size is 10-30 nm.

[0058] In some embodiments of the present invention, the average particle size of component C is 10-20 μm.

[0059] In some embodiments of the present invention, the average particle size of component D is 20-40 μm.

[0060] The third aspect of the present invention provides the application of the anti-corrosion material described in the first aspect or the anti-corrosion material prepared by the preparation method described in the second aspect in cement slurry, preferably in the application of carbon dioxide corrosion resistant cement slurry.

[0061] The corrosion-resistant material of this invention is used to prepare carbon dioxide corrosion-resistant cement slurry. The process is simple and convenient. When cement stone comes into contact with carbon dioxide, mixture B undergoes a pozzolanic reaction, consuming Ca(OH)₂ in the cement stone and producing hydrated calcium silicate, hydrated calcium aluminate, and other substances. This protects the cement stone from carbon dioxide corrosion, initially forming a protective film. As the hydration reaction continues, the hydration products are further consumed, leading to signs of damage to the cement stone's microstructure. At this point, mixture A slowly releases nano-silica and nano-alumina, which act as a filler and blocker, forming a dense protective film on the outside of the cement stone. Simultaneously, the nano-silica continues to react with Ca(OH)₂ in the cement stone, preventing acidic gases from further penetrating the cement stone. Therefore, the prepared cement slurry provides long-lasting resistance to carbon dioxide corrosion.

[0062] The fourth aspect of this invention provides a carbon dioxide corrosion resistant cement slurry, which is made from the following raw materials in parts by weight: 100 parts of G-grade oil well cement, 2-6 parts of anti-corrosion material, 2-5 parts of microsilica, 3-6 parts of reinforcing material, 3-5 parts of expansion and toughening material, 1-3 parts of latex powder, 0-2 parts of stabilizer, 0.3-2 parts of dispersant, 2-5 parts of water loss reducer, 0.1-2 parts of retarder, 0.2-0.5 parts of defoamer, and 48-56 parts of water, wherein the anti-corrosion material is the anti-corrosion material described in the first aspect above or the anti-corrosion material prepared by the preparation method described in the second aspect above.

[0063] In this invention, the carbon dioxide corrosion resistant cement slurry made from the above raw materials has good corrosion resistance in a CO2 corrosion environment. Before corrosion, the cement stone has high compressive strength and dense structure. After corrosion, the compressive strength of the cement stone does not decline significantly, the permeability is low, and the mechanical properties are good. At the same time, the comprehensive properties such as settling stability and rheology are good. It can be used in CO2 corrosion resistant cement slurry systems with temperatures of 30-150℃ and below, ensuring the cementing quality of CCUS wells and achieving efficient CO2 sequestration.

[0064] In some embodiments of the present invention, the SiO2 content of the microsilicon is not less than 90%, the average particle size is 5-10 μm, and the residue on a 45 μm sieve is ≤5%.

[0065] In this invention, the reinforcing material is selected from reinforcing materials used in cementing oil wells.

[0066] In some embodiments of the present invention, the reinforcing material is selected from inorganic mineral powder materials, preferably DRB-1S mineral powder produced by China Petroleum Engineering Technology Research Institute Co., Ltd.

[0067] In this invention, the expandable toughening material is selected from expandable toughening materials used in cementing oil wells.

[0068] In some embodiments of the present invention, the expanded toughening material is selected from rubber-based materials, preferably rubber DRE-3S.

[0069] In this invention, the latex powder is selected from latex powder used in cementing oil wells.

[0070] In some embodiments of the present invention, the latex powder is selected from polymers, preferably polymer DRT-1S.

[0071] In this invention, the stabilizer is selected from stabilizers used in cementing oil wells.

[0072] In some embodiments of the present invention, the stabilizer is selected from attapulgite materials, preferably DRK-2S ore powder.

[0073] In some embodiments of the present invention, the dispersant is selected from polystyrene sulfonate compounds and / or condensates of formaldehyde and acetone.

[0074] In some embodiments of the present invention, the water loss reducing agent is selected from polyacrylamide compounds.

[0075] In some embodiments of the present invention, the retarder is selected from acrylamide compounds.

[0076] In some embodiments of the present invention, the defoamer is selected from one or more of tributyl phosphate, polyoxypropylene glycerol, and polydimethylsiloxane.

[0077] The fifth aspect of this invention provides a method for preparing a carbon dioxide corrosion resistant cement slurry, the method comprising:

[0078] Grade G oil well cement is mixed with anti-corrosion materials, microsilica, reinforcing materials, expansion toughening materials, latex powder, stabilizers and dispersants to obtain a dry mix.

[0079] The water loss reducer is mixed with the retarder, defoamer and water to obtain a wet mixture;

[0080] The dry mix and the wet mix are mixed to obtain a carbon dioxide corrosion resistant cement slurry.

[0081] The G-grade oil well cement, anti-corrosion materials, microsilica, reinforcing materials, expansion and toughening materials, latex powder, stabilizers, dispersants, fluid loss reducers, retarders and defoamers mentioned above are the same as those in the fourth aspect. Please refer to the previous description for details, which will not be repeated here.

[0082] The sixth aspect of this invention provides the application of the carbon dioxide corrosion resistant cement slurry described in the fourth aspect above or the carbon dioxide corrosion resistant cement slurry prepared by the preparation method described in the fifth aspect above in cementing operations of oil and gas wells.

[0083] In some embodiments of the present invention, the application temperature of the carbon dioxide corrosion resistant cement slurry is 30-150°C.

[0084] According to a particularly preferred embodiment of the present invention, the method for preparing carbon dioxide corrosion resistant cement slurry specifically includes the following steps:

[0085] (1) Preparation of anti-corrosion material: Activated carbon, nano-silica, and nano-alumina are thoroughly mixed at a mass ratio of 1:0.05-0.1:0.05-0.1 to obtain mixture A; at least one of diatomaceous earth and fly ash is mixed with at least one of metakaolin, pumice, and coal gangue at a mass ratio of 1-2:1 to obtain mixture B; mixture A and mixture B are uniformly mixed at a mass ratio of 1:2-4 to obtain anti-corrosion material;

[0086] (2) Weigh out the oil well cement, anti-corrosion material, microsilica, reinforcing material, expansion toughening material, latex powder, stabilizer and dispersant according to the formula, and mix them evenly to obtain dry mixture; weigh out the water loss reducer, retarder and defoamer according to the formula, and stir evenly to obtain wet mixture; pour the dry mixture evenly into the wet mixture at a speed of 4000±200r / min. After the dry mixture is completely added into the wet mixture, cover the mixing cup, adjust the speed of the stirrer to 12000±500r / min, and continue stirring for 30-40s, preferably 35s, to obtain carbon dioxide corrosion resistant cement slurry.

[0087] The present invention will be described in detail below through embodiments.

[0088] Unless otherwise specified in the following examples and comparative examples, all conditions were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0089] Grade G oil well cement is a high sulfate-resistant (HSR) grade G oil well cement produced by Dalian Cement Group Co., Ltd.

[0090] Microsilicon: Its SiO2 content is 95%, the average particle size is 8μm, and the residue on a 45μm sieve is 4.2%.

[0091] The reinforcing material is DRB-1S ore powder, a reinforcing material for cementing oil wells, produced by China Petroleum Engineering Technology Research Institute Co., Ltd.

[0092] The expansion toughening material is DRE-3S, a toughening rubber material for cementing oil wells, produced by China Petroleum Engineering Technology Research Institute Co., Ltd.

[0093] The latex powder is DRT-1S, a polymer latex powder for cementing oil wells, produced by China Petroleum Engineering Technology Research Institute Co., Ltd.

[0094] The stabilizer is DRK-2S, a high-temperature stabilizer for cementing oil wells and cement ore powder, produced by China Petroleum Engineering Technology Research Institute Co., Ltd.

[0095] The dispersant is DRS-1S, an aldehyde-ketone condensate dispersant for cementing oil wells, produced by China Petroleum Engineering Technology Research Institute Co., Ltd.

[0096] The fluid loss reducing agent is DRF-1S, an acrylamide-based fluid loss reducing agent for cementing oil wells, produced by China Petroleum Engineering Technology Research Institute Co., Ltd.

[0097] The retarder is DRH-1L, an organic acid retarder for cementing oil wells, produced by China Petroleum Engineering Technology Research Institute Co., Ltd.

[0098] The defoamer is an organic ester-based defoamer DRX-1L for cementing oil wells, produced by China Petroleum Engineering Technology Research Institute Co., Ltd.

[0099] Experiments were conducted according to the national standard GB / T 19139-2012 "Test Methods for Cement in Oil Wells" to evaluate the conventional engineering properties (density, fluidity, API water loss) of the cement slurry system, as well as its compressive strength and permeability before and after corrosion. The main experimental instruments included: a 30-60 type corrugated agitator; a TG7370D type pressure curing kettle (Shenyang Taige Petroleum Instrument Equipment Manufacturing Co., Ltd.); an HH-420 type constant temperature digital display water tank (Changzhou Yineng Experimental Instrument Factory); a YAW-300B hydraulic pressure testing machine (Jinan Xinshijin Testing Machine Co., Ltd.); and a CO2 corrosion environment simulation system (product of China Petroleum Engineering Technology Research Institute Co., Ltd.).

[0100] Flowability: Tested in accordance with national standard GB / T 19139-2012 "Test Methods for Cement in Oil Wells".

[0101] API water loss: Tested in accordance with the national standard GB / T 19139-2012 "Test Methods for Cement in Oil Wells".

[0102] The corrosion of cement stone is treated using the "CO2 Corrosion Environment Simulation System" invented by China Petroleum Engineering & Technology Co., Ltd., or a device capable of pressurized curing in a CO2 gas / liquid environment.

[0103] Compressive strength before and after corrosion: Tested according to national standard GB / T 19139-2012 "Test Methods for Cement in Oil Wells".

[0104] Strength loss rate: Strength loss rate = (T2-T1) / T1, where T1 is the compressive strength of cement stone before corrosion and T2 is the compressive strength of cement stone after corrosion.

[0105] Permeability: Tested in accordance with the national standard GB / T 19139-2012 "Test Methods for Cement in Oil Wells".

[0106] Preparation Example 1

[0107] A method for preparing an anti-corrosion material specifically includes the following steps:

[0108] (1) Activated carbon, nano-silica, and nano-alumina are thoroughly mixed evenly in a mass ratio of 1:0.05:0.05. The activated carbon is commercially available and has a mesh size of 325. The nano-silica is commercially available and has a SiO2 content of 99.5% and an average particle size of 30 nm. The nano-alumina is commercially available and has an average particle size of 30 nm and an Al2O3 content of 99.3%. The above three substances are uniformly mixed to obtain mixture A.

[0109] (2) Mix diatomaceous earth and metakaolin evenly at a mass ratio of 1:1 to obtain mixture B;

[0110] (3) Mix the mixture A and the mixture B evenly at a mass ratio of 1:2 to obtain the anti-corrosion material.

[0111] Preparation Example 2

[0112] A method for preparing an anti-corrosion material specifically includes the following steps:

[0113] (1) Activated carbon, nano-silica, and nano-alumina are thoroughly mixed evenly in a mass ratio of 1:0.1:0.1. The nano-silica is commercially available with a SiO2 content of 99.9% and an average particle size of 40 nm. The nano-alumina is commercially available with an average particle size of 20 nm and an Al2O3 content of 99.9%. The above three substances are uniformly mixed to obtain mixture A.

[0114] (2) Mix fly ash and coal gangue evenly in a mass ratio of 2:1 to obtain mixture B;

[0115] (3) Mix the mixture A and the mixture B evenly at a mass ratio of 1:3 to obtain the anti-corrosion material.

[0116] Preparation Example 3

[0117] A method for preparing an anti-corrosion material specifically includes the following steps:

[0118] (1) Activated carbon, nano-silica, and nano-alumina are thoroughly mixed evenly in a mass ratio of 1:0.2:0.1. The activated carbon is commercially available and has a mesh size of 325. The nano-silica is commercially available and has a SiO2 content of 99.8% and an average particle size of 30 nm. The nano-alumina is commercially available and has an average particle size of 30 nm and an Al2O3 content of 99.5%. The above three substances are uniformly mixed to obtain mixture A.

[0119] (2) Mix fly ash and pumice evenly at a mass ratio of 3:1 to obtain mixture B;

[0120] (3) Mix the mixture A and the mixture B evenly at a mass ratio of 1:5 to obtain the anti-corrosion material.

[0121] Preparation of Comparative Example 1

[0122] Diatomaceous earth and coal gangue are mixed and stirred evenly at a mass ratio of 2:1 to obtain an anti-corrosion material.

[0123] Preparation of Comparative Example 2

[0124] (1) Nano silica and nano alumina are thoroughly mixed evenly in a mass ratio of 1:1. The nano silica is commercially available with a SiO2 content of 99.5% and an average particle size of 30 nm. The nano alumina is commercially available with an average particle size of 30 nm and an Al2O3 content of 99.3%. The two substances are mixed evenly to obtain mixture A.

[0125] (2) Mix diatomaceous earth and metakaolin evenly at a mass ratio of 1:1 to obtain mixture B;

[0126] (3) Mix the mixture A and the mixture B evenly at a mass ratio of 1:3 to obtain the anti-corrosion material.

[0127] Example 1

[0128] The cement slurry formulation by weight percentage is as follows: 100 parts Grade G oil well cement, 3 parts anti-corrosion material obtained in Preparation Example 1, 3 parts microsilica, 5 parts reinforcing material, 4 parts expansion toughening material, 2 parts latex powder, 1 part stabilizer, 1 part dispersant, 3 parts water loss reducer, 0.5 parts retarder, 0.2 parts defoamer, and 53 parts water. The cement slurry density is 1.88 g / cm³. 3 The experimental results are shown in Table 1.

[0129] Example 2

[0130] The cement slurry formulation by weight percentage is as follows: 100 parts Grade G oil well cement, 3 parts anti-corrosion material obtained in Preparation Example 2, 3 parts microsilica, 5 parts reinforcing material, 4 parts expansion toughening material, 2 parts latex powder, 1 part stabilizer, 1 part dispersant, 3 parts water loss reducer, 0.5 parts retarder, 0.2 parts defoamer, and 53 parts water. The cement slurry density is 1.88 g / cm³. 3 The experimental results are shown in Table 1.

[0131] Example 3

[0132] Compared to Example 2, different amounts of anti-corrosion materials were added. The cement slurry formulation by weight percentage is as follows: 100 parts G-grade oil well cement, 5 parts anti-corrosion material obtained in Example 2, 3 parts microsilica, 5 parts reinforcing material, 4 parts expansion toughening material, 2 parts latex powder, 1 part stabilizer, 1 part dispersant, 3 parts water loss reducer, 0.5 parts retarder, 0.2 parts defoamer, and 53 parts water. The cement slurry density is 1.88 g / cm³. 3 The experimental results are shown in Table 1.

[0133] Example 4

[0134] The cement slurry formulation by weight percentage is as follows: 100 parts Grade G oil well cement, 6 parts anti-corrosion material obtained in Preparation Example 2, 2 parts microsilica, 6 parts reinforcing material, 3 parts expansion toughening material, 1 part latex powder, 2 parts stabilizer, 2 parts dispersant, 2 parts water loss reducer, 2 parts retarder, 0.2 parts defoamer, and 56 parts water. The cement slurry density is 1.88 g / cm³. 3 The experimental results are shown in Table 1.

[0135] Example 5

[0136] The cement slurry formulation by weight percentage is as follows: 100 parts Grade G oil well cement, 2 parts anti-corrosion material obtained in Preparation Example 2, 5 parts microsilica, 3 parts reinforcing material, 6 parts expansion toughening material, 3 parts latex powder, 0.4 parts stabilizer, 1 part dispersant, 5 parts water loss reducer, 0.1 parts retarder, 0.2 parts defoamer, and 48 parts water. The cement slurry density is 1.88 g / cm³. 3 The experimental results are shown in Table 1.

[0137] Example 6

[0138] Compared to Example 2, different anti-corrosion materials were added. The cement slurry formulation by weight percentage is as follows: 100 parts G-grade oil well cement, 3 parts anti-corrosion material obtained in Preparation 3, 3 parts microsilica, 5 parts reinforcing material, 4 parts expansion toughening material, 2 parts latex powder, 1 part stabilizer, 1 part dispersant, 3 parts water loss reducer, 0.5 parts retarder, 0.2 parts defoamer, and 53 parts water. The cement slurry density is 1.88 g / cm³. 3 The experimental results are shown in Table 1.

[0139] Comparative Example 1

[0140] Compared to Example 2, different anti-corrosion materials were added. The cement slurry formulation by weight percentage is as follows: 100 parts G-grade oil well cement, 3 parts anti-corrosion material obtained in Comparative Example 1, 3 parts microsilica, 5 parts reinforcing material, 4 parts expanding toughening material, 2 parts latex powder, 1 part stabilizer, 1 part dispersant, 3 parts water loss reducer, 0.5 parts retarder, 0.2 parts defoamer, and 53 parts water. The cement slurry density is 1.88 g / cm³. 3 The experimental results are shown in Table 1.

[0141] Comparative Example 2

[0142] Compared to Example 2, different anti-corrosion materials were added. The cement slurry formulation by weight percentage is as follows: 100 parts G-grade oil well cement, 3 parts anti-corrosion material obtained in Comparative Example 2, 3 parts microsilica, 5 parts reinforcing material, 4 parts expanding toughening material, 2 parts latex powder, 1 part stabilizer, 1 part dispersant, 3 parts water loss reducing agent, 0.5 parts retarder, 0.2 parts defoamer, and 53 parts water. The cement slurry density is 1.88 g / cm³. 3 The experimental results are shown in Table 1.

[0143] Comparative Example 3

[0144] Compared to Example 2, no anti-corrosion materials were added. The cement slurry formulation by weight percentage is as follows: 100 parts G-grade oil well cement, 3 parts microsilica, 5 parts reinforcing material, 4 parts expansion toughening material, 2 parts latex powder, 1 part stabilizer, 1 part dispersant, 3 parts water loss reducer, 0.5 parts retarder, 0.2 parts defoamer, and 53 parts water. The cement slurry density is 1.88 g / cm³. 3 The experimental results are shown in Table 1.

[0145] Table 1. Experimental results of the examples and comparative examples.

[0146]

[0147]

[0148] Table 1. Results of Experiments in Examples and Comparative Examples (Continued)

[0149]

[0150] As shown in Table 1, the flowability of all embodiments was greater than 20 cm, and the API water loss was less than 50 mL, meeting the requirements for cementing construction. The compressive strength after corrosion of all embodiments was greater than 20 MPa, the strength loss rate was less than 20%, and the permeability was less than 0.1 mD, indicating good performance and meeting the requirements for cementing sealing.

[0151] As can be seen from the experimental data of Examples 1-3, using the cement slurry of Example 1, after 60 days of corrosion, the compressive strength decreased from 32.6 MPa to 27.9 MPa. The post-corrosion compressive strength is greater than 20 MPa, and the permeability is less than 0.05 mD. The cement stone exhibits good mechanical properties after corrosion, meeting the sealing requirements. Within the scope defined by this invention, adjusting the proportions of each component in the anti-corrosion material and the amount of anti-corrosion material added has no adverse effects on the density, fluidity, and API water loss of the cement slurry system. Furthermore, the post-corrosion compressive strength of the cement stone is always greater than 20 MPa, and the permeability is less than 0.05 mD, indicating good anti-corrosion performance of the cement stone.

[0152] As can be seen from the experimental data of Examples 2, 4, and 5, after temperature changes, by adjusting the amount of different admixtures as needed, the resulting cement slurry system exhibits good engineering performance. Furthermore, after curing under corrosive conditions, the compressive strength is greater than 20 MPa, the permeability is less than 0.05 mD, and the corrosion resistance is good. In other words, within the range of the amount of each material added, adjustments can be made according to different temperatures to meet the usage requirements at different temperatures.

[0153] As can be seen from the data of Example 2 and Comparative Examples 1-2, after corrosion, the compressive strength of Comparative Examples 1-2 decreased significantly, all less than 20 MPa, and the permeability increased significantly, even greater than 0.1 mD. Furthermore, the fluidity of Comparative Example 2 was 17 cm, indicating a deterioration in fluidity.

[0154] The data from Comparative Example 4 show that when no anti-corrosion material is added to the cement slurry, the strength of the cement stone before corrosion is 31.5 MPa. However, after 60 days of corrosion, the compressive strength deteriorates to 15.6 MPa, a decrease of 50.48%, and the permeability increases from 0.049 mD to 0.203 mD. The strength deteriorates significantly and the permeability increases significantly.

[0155] In summary, the cement slurry of the present invention has an applicable temperature range of 30-150℃. After corrosion, the compressive strength of the cement stone is greater than 20MPa and the permeability is less than 0.05mD, which significantly improves the CO2 corrosion resistance of the cement stone. At the same time, it has no adverse effects on other engineering properties of the cement slurry and can ensure the long-term effective sealing of the cement ring under CCUS corrosion conditions.

[0156] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A corrosion-resistant material for cement slurry in oil and gas wells, characterized in that, The corrosion-resistant material comprises mixture A and mixture B; wherein, mixture A comprises activated carbon, nano-silica, and nano-alumina; mixture B comprises component C and component D; component C is selected from diatomaceous earth and / or fly ash; component D is selected from one or more of metakaolin, pumice, and coal gangue; in mixture A, the mass ratio of activated carbon, nano-silica, and nano-alumina is 1:0.05-0.1:0.05-0.1; the mass ratio of component C to component D is 1-2:1; and the mass ratio of mixture A to mixture B is 1:2-4.

2. The anti-corrosion material according to claim 1, wherein, The activated carbon has an average particle size of 40-60 μm; and / or, the nano-silica has a SiO2 content greater than 99% and an average particle size of 30-40 nm; and / or, the nano-alumina has an Al2O3 content greater than 99% and an average particle size of 10-30 nm; and / or, the component C has an average particle size of 10-20 μm; and / or, the component D has an average particle size of 20-40 μm.

3. A method for preparing an anti-corrosion material for oil and gas well cement slurry, characterized in that, The preparation method includes: mixing activated carbon, nano-silica, and nano-alumina to obtain mixture A; mixing component C and component D to obtain mixture B; wherein component C is selected from diatomaceous earth and / or fly ash; component D is selected from one or more of metakaolin, pumice, and coal gangue; mixing mixture A and mixture B under low stirring rate conditions, and then stirring at high speed to obtain the anti-corrosion material; the low stirring rate is 3800-4200 r / min, and the high stirring rate is 11500-12500 r / min; in mixture A, the mass ratio of activated carbon, nano-silica, and nano-alumina is 1:0.05-0.1:0.05-0.1; the mass ratio of component C to component D is 1-2:1; and the mass ratio of mixture A to mixture B is 1:2-4.

4. The preparation method according to claim 3, wherein, The activated carbon has an average particle size of 40-60 μm; and / or, the nano-silica has a SiO2 content greater than 99% and an average particle size of 30-40 nm; and / or, the nano-alumina has an Al2O3 content greater than 99% and an average particle size of 10-30 nm; and / or, the component C has an average particle size of 10-20 μm; and / or, the component D has an average particle size of 20-40 μm.

5. The application of the anti-corrosion material as described in claim 1 or 2, or the anti-corrosion material prepared by the preparation method as described in claim 3 or 4, in oil and gas well cement slurry.

6. The application according to claim 5, wherein, The application of the corrosion-resistant material in cement slurry for oil and gas wells resistant to carbon dioxide corrosion.

7. A cement slurry for oil and gas wells resistant to carbon dioxide corrosion, characterized in that, The oil and gas well cement slurry is made from the following raw materials in parts by weight: 100 parts of G-grade oil well cement, 2-6 parts of anti-corrosion material, 2-5 parts of microsilica, 3-6 parts of reinforcing material, 3-5 parts of expansion and toughening material, 1-3 parts of latex powder, 0-2 parts of stabilizer, 0.3-2 parts of dispersant, 2-5 parts of water loss reducer, 0.1-2 parts of retarder, 0.2-0.5 parts of defoamer, and 48-56 parts of water; wherein the anti-corrosion material is the anti-corrosion material according to claim 1 or 2 or the anti-corrosion material prepared by the preparation method according to claim 3 or 4.

8. The oil and gas well cement slurry according to claim 7, wherein, The microsilicon has a SiO2 content of not less than 90%, an average particle size of 5-10 μm, and a 45 μm sieve residue of ≤5%.

9. The oil and gas well cement slurry according to claim 7 or 8, wherein, The reinforcing material is selected from inorganic mineral powder materials; and / or, the expanded toughening material is selected from rubber materials; and / or, the latex powder is selected from polymers.

10. The oil and gas well cement slurry according to claim 9, wherein, The reinforcing material is ore powder DRB-1S; and / or, the expanding toughening material is rubber DRE-3S; and / or, the latex powder is polymer DRT-1S; and / or, the stabilizer is ore powder DRK-2S.

11. The oil and gas well cement slurry according to claim 7 or 8, wherein, The dispersant is selected from polystyrene sulfonate compounds and / or formaldehyde and acetone condensates; and / or, the water loss reducing agent is selected from polyacrylamide compounds; and / or, the retarder is selected from acrylamide compounds; and / or, the defoamer is selected from one or more of tributyl phosphate, polyoxypropylene glycerol, and polydimethylsiloxane.

12. A method for preparing a carbon dioxide corrosion resistant oil and gas well cement slurry, characterized in that, The preparation method includes: mixing G-grade oil well cement with anti-corrosion material, microsilica, reinforcing material, expansion toughening material, latex powder, stabilizer and dispersant to obtain a dry mixture; wherein, the anti-corrosion material is the anti-corrosion material according to claim 1 or 2 or the anti-corrosion material prepared by the preparation method according to claim 3 or 4; mixing a water loss reducing agent with a retarder, defoamer and water to obtain a wet mixture; and mixing the dry mixture and the wet mixture to obtain a carbon dioxide corrosion resistant oil and gas well cement slurry.

13. The application of the carbon dioxide corrosion resistant oil and gas well cement slurry according to any one of claims 7-11 or the carbon dioxide corrosion resistant oil and gas well cement slurry prepared by the preparation method according to claim 12 in oil and gas well cementing operations.

14. The application according to claim 13, wherein, The operating temperature of the carbon dioxide corrosion resistant oil and gas well cement slurry is 30-150℃.

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