High-temperature well cementation cement expanding agent and preparation method thereof

Abstract

The invention discloses a high-temperature well cementation cement expanding agent and a preparation method thereof, and belongs to the technical field of oil-gas well engineering well cementation materials. The high-temperature well cementation cement expanding agent is prepared from the following raw materials in parts by weight: 30-40 parts of dolomite; 10 to 20 parts of serpentine; 5 to 10 parts of hedenbergite; 5 to 10 parts of scolecite; 25-35 parts of slaked lime powder; 5-10 parts of quartz powder; the high-temperature well cementation cement expanding agent comprises the following chemical components in percentage by weight: more than 13wt.% and less than 23wt.% of MgO, more than 38wt.% and less than 55wt.% of CaO, more than 18wt.% and less than 32wt.% of SiO2, less than 3.5 wt.% of Al2O3 and less than 1wt.% of Fe2O3. The particle sizes of the high-temperature well cementation cement expanding agent are as follows: Dx (10) is less than or equal to 4 microns, Dx (50) is less than or equal to 10 microns, and Dx (90) is less than or equal to 20 microns. The invention also discloses a preparation method of the high-temperature well cementation cement expanding agent. Starting from cement main body minerals, through lattice solid solution, core-shell structure wrapping and other means, an expansion component and the hydration process of cement can achieve a synergistic reaction, and therefore the effective expansion effect is achieved in the cement gelling structure forming process.

Description

Technical Field

[0001] This invention belongs to the field of cementing materials technology for oil and gas well engineering, and more specifically relates to a high-temperature cementing expansion agent and its preparation method. Background Technology

[0002] The development of deep and ultra-deep oil and gas resources has become an important strategic direction for ensuring national energy security. During oil and gas extraction, the primary function of cement sheaths is to ensure the integrity of the wellbore and provide a guarantee for subsequent safe operations. However, the inherent volume shrinkage characteristics of cement-based materials under high-temperature conditions can easily lead to micro-annular gaps between the cement sheath and the formation (second interface) or the casing (first interface). Simultaneously, the residual loose mud cake and weak cemented layer at the interface further weaken the interlayer sealing capacity, triggering sustained Annular Pressure (SAP) and interzonal communication, seriously threatening the production safety of oil and gas wells.

[0003] To suppress cement shrinkage, existing technologies commonly employ chemical expanding agents to compensate for volume changes. Studies show that expanding agents need to play a crucial role in the plastic state of the cement paste (i.e., the solidification transition period): premature action (in the liquid stage) leads to gas escape or loss of expansion energy; delayed action (in the hardening stage) may damage the microstructure of the cement paste and even induce cracking. Current mainstream expanding agents include gas-generating agents (such as aluminum powder and nitrogen-based agents) and crystalline agents (such as calcium oxide and sulfoaluminates), but they generally suffer from expansion aging control failure in high-temperature environments (typically ≥120℃). Specifically:

[0004] (1) High-temperature adaptability defects of gas-generating expansion agents: A typical example is a slow-release gas expansion agent proposed in patent CN 119285269A, which uses a microencapsulation method to encapsulate nitrogen gas-generating agents in alkali-soluble resin, achieving slow gas release through gradual dissolution in the alkaline environment of the cement slurry. This technology can slow down the gas generation rate at low temperatures, but in high-temperature environments, the thermal stability of the resin wall material decreases sharply, causing the core material to release prematurely and react rapidly. A large amount of gas escapes before the plasticity period of the cement slurry, which cannot effectively compensate for shrinkage.

[0005] (2) Insufficient hydration synergy of crystalline expansion agents: For example, patent CN 115504700A uses dolomite to prepare an expansion agent by incorporating diatomite. Although it delays expansion at low temperatures, it accelerates reaction kinetics at high temperatures, resulting in a misalignment between the expansion peak and the plasticity period of cement. More importantly, this material is significantly affected by admixtures such as retarders and dehydration reducers, resulting in poor adaptability to working conditions. Although the composite expansion agent (containing calcium oxide whiskers, calcined magnesium oxide, etc.) developed by patent CN119569368A claims to have very low dosage sensitivity and temperature sensitivity, stable expansion performance, high temperature resistance, and good compatibility with cement slurry, the solubility of its components increases dramatically in high-temperature cement slurry. The active components such as calcium oxide and magnesium oxide hydrate rapidly in the early stage of slurry mixing, and the expansion energy is released prematurely and becomes ineffective.

[0006] (3) Kinetic mismatch problem of mineral-encapsulated expansive agents: For example, patent CN 119683894A encapsulates free lime and periclase with tetracalcium aluminoferrite, which theoretically can achieve stepwise expansion. However, at high temperatures, the hydration acceleration rate of the dominant minerals of silicate cement, tricalcium silicate and dicalcium silicate, is different from that of tetracalcium aluminoferrite. The timing of the released expansive components deviates from the formation of the main hydration products, making it difficult to achieve optimal expansive performance. Moreover, at high temperatures, this expansive performance will decline sharply.

[0007] Therefore, how to accurately control the expansion timing of the expansion agent under high temperature conditions and dynamically match it with the cement hydration and plasticization period has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] One of the objectives of this invention is to provide a high-temperature cementing expansion agent that solves the problem in the prior art that the expansion timing of the expansion agent and the cement hydration rate are difficult to synchronize under high-temperature conditions.

[0009] The second objective of this invention is to provide a method for preparing the high-temperature cementing expansion agent.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] The first aspect of this invention provides a high-temperature cementing expansion agent, the raw materials of which include the following components by weight: 30-40 parts dolomite; 10-20 parts serpentine; 5-10 parts calcium iron pyroxene; 5-10 parts calcium zeolite; 25-35 parts quicklime powder; and 5-10 parts quartz powder.

[0012] The chemical composition of the high-temperature cementitious expansion agent is as follows: 13 wt.% < MgO < 23 wt.%, 38 wt.% < CaO < 55 wt.%, 18 wt.% < SiO2 < 32 wt.%, Al2O3 < 3.5 wt.%, Fe2O3 < 1 wt.%.

[0013] The particle size of the high-temperature cementing expansion agent is Dx(10)≤4μm, Dx(50)≤10μm, and Dx(90)≤20μm.

[0014] In some embodiments of the present invention, the dolomite has a purity ≥95 wt.%, an MgO content >20 wt.%, and a CaO content >28 wt.%.

[0015] In some embodiments of the present invention, the serpentine has a purity ≥95 wt.%, an MgO content >40 wt.%, and a SiO2 content >40 wt.%.

[0016] In some embodiments of the present invention, the calcium iron pyroxene has a purity ≥90 wt.%, a CaO content >20 wt.%, a SiO2 content >43 wt.%, and an FeO content >26 wt.%.

[0017] In some embodiments of the present invention, the calcium zeolite has a purity ≥90 wt.%, a CaO content >12 wt.%, an Al2O3 content >23 wt.%, and a SiO2 content >41 wt.%.

[0018] In some embodiments of the present invention, the fineness of the slaked lime powder is ≥325 mesh, and the CaO content is >74 wt.%.

[0019] In some embodiments of the present invention, the quartz powder has a fineness ≥325 mesh and a SiO2 content >98 wt.%.

[0020] A second aspect of this invention provides a method for preparing the above-mentioned high-temperature cementing expansion agent, comprising the following steps:

[0021] S1. Prepare each raw material according to the proportion, then mix dolomite, serpentine, calcium iron pyroxene and calcium zeolite, crush, grind, calcine, cool, and form Class A mixture;

[0022] S2. Grind the type A mixture with the remaining raw materials until uniform to obtain type B mixture;

[0023] S3. Calcine the type B mixture and then cool it to obtain the type C mixture;

[0024] S4. Place the C-type mixture into a ball mill for grinding, and control the particle fineness to be Dx(10)≤4μm, Dx(50)≤10μm, and Dx(90)≤20μm. After grinding evenly, the high-temperature cementing expansion agent is obtained.

[0025] In some embodiments of the present invention, in step S1, dolomite, serpentine, calcium iron pyroxene and calcium zeolite are mixed evenly and then crushed, with the crushing ratio controlled at 60-75.

[0026] Preferably, the crushed mixture is ground into fine powder, and the grinding ratio is controlled at 700-850.

[0027] Preferably, the mixed fine materials are fed into a high-temperature calcining furnace for calcination. The calcination temperature is controlled at 950℃~1000℃, the heating time is controlled at 20~40min, preferably 30min, and the holding time is controlled at 100~140min, preferably 120min.

[0028] In some embodiments of the present invention, in step S3, the B-type mixture is calcined. The calcination process is carried out in two stages, wherein the calcination temperature of the first stage is controlled at 850-950°C, preferably 900°C; the heating time is controlled at 20-40 min, preferably 30 min; and the holding time is controlled at 5-15 min, preferably 10 min.

[0029] The second stage calcination temperature is controlled at 1300–1350℃; the heating time is controlled at 30–50 min, preferably 40 min; and the holding time is controlled at 100–140 min, preferably 120 min.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This invention is scientifically designed and ingeniously conceived. The high-temperature cementing expansion agent of this invention starts from the main cement minerals and, through methods such as lattice solid solution and core-shell structure encapsulation, enables the expansion component to achieve a synergistic reaction with the cement hydration process, thereby playing an effective expansion role in the formation of the cementitious structure. This high-temperature cementing expansion agent is an inorganic material that not only maintains stable performance and does not fail under high-temperature conditions, but also has good compatibility, being highly compatible with high-temperature admixtures and various additives. It has a wide range of applications and excellent prospects for engineering applications.

[0032] (1) The expanding agent prepared in this invention contains a large amount of Ca2SiO4 mineral, utilizing Mg 2+ With Ca 2+ The similarity and compatibility between them, under high-temperature calcination conditions, cause Mg to undergo lattice distortion. 2+ Partially replaces Ca 2+ Sites, thus forming Ca 2-x Mg x SiO4 solid solution. This solid solution causes only a slight shrinkage of the lattice parameters during formation, and the overall structure remains stable. When the retarding effect of high-temperature cementitious slurry gradually fails and enters the rapid hydration stage, due to the Ca... 2-x Mg xSiO4 solid solution is highly similar in structure and composition to cement matrix minerals (such as Ca3SiO5 and Ca2SiO4), and its hydration process can proceed synchronously with that of the cement matrix minerals, producing a synergistic reaction effect. During this process, Ca... 2-x Mg x Mg is released during the hydration and decomposition of SiO4 solid solution. 2+ The rapid formation of Mg(OH)2 triggers volume expansion. This expansion effect occurs precisely when the cement is in a plastic state (i.e., the stage of gelation structure formation), thus effectively avoiding the problem of premature failure of expansion in the liquid stage of the paste, or excessive expansion in the solid stage that damages the internal structure of the cement paste.

[0033] (2) In the preparation method of the expansion agent described in this invention, before high-temperature sintering (i.e., below 1000℃), MgO particles are uniformly dispersed in the Ca2SiO4 mineral precursor (a mixture of CaO and SiO2) by ball milling. During the high-temperature sintering and heat preservation stage, as the Ca2SiO4 crystals grow, unreacted MgO particles are encapsulated, forming composite particles with an MgO core-Ca2SiO4 shell structure. When the high-temperature cement slurry enters the rapid hydration reaction stage, because the outer shell of this encapsulated structure is consistent with the main cement mineral, its hydration process can proceed synchronously with the cement mineral, achieving a synergistic reaction. After the outer shell gradually hydrolyzes and breaks down, the MgO particles in the core are rapidly released and react with water to generate Mg(OH)2, thereby triggering volume expansion. This expansion process effectively acts on the cement cementitious structure formation stage, achieving matching and synergy between the expansion component and the cement hydration reaction, thereby improving the utilization rate of the expansion effect and the ability to control the volume stability of the cement stone.

[0034] (3) In this invention, the chemical composition of the high-temperature cementitious expansion agent is clearly defined. This chemical composition ratio is specifically designed to address the failure of cement slurry expansion performance under high-temperature hydrothermal conditions and the potential for expansion cracking of cement stone in the later stages. Only within the specified range of the content of each component can the material's optimal performance be fully utilized, effectively addressing the aforementioned technical problems.

[0035] (4) This invention further limits the particle size of the high-temperature cementitious expansion agent. If the material is too fine, it will affect its compatibility with other admixtures, for example, it may cause abnormal gelation reactions or performance conflicts, which is detrimental to construction safety; if the material is too coarse, the reactivity of its expansion particles will be significantly reduced, and it will be unable to exert the due expansion effect in time, thereby interfering with the synergistic hydration reaction between the expansion component and the cement main mineral. Therefore, only by controlling the particle size within a specific range can the optimal performance of the material be fully utilized. Particle sizes exceeding this range are difficult to achieve the expected results, so it is necessary to reasonably limit the fineness of the material used in this invention application.

[0036] (5) The high-temperature cementing expansion agent of the present invention is an inorganic material, and its design and application will not have any negative impact on the engineering performance of cement slurry or the mechanical properties of cement stone. This expansion agent can not only maintain stable performance and avoid failure in high-temperature hydrothermal environment, but also shows good compatibility with cement base material, high-temperature admixtures and various additives, thereby ensuring the synergistic effect and construction reliability of the overall system.

[0037] (6) This invention further specifies the requirements for the purity, fineness, and chemical composition of each component. By further defining and optimizing these parameters, it can be ensured that the compounded high-temperature cementitious expansion agent meets the target chemical composition requirements and achieves the best material performance. At the same time, the strict definition of the purity, fineness, and chemical composition of each component also helps to improve the success rate of compounding, so that the final material can stably achieve the expected technical effect. Detailed Implementation

[0038] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] The following examples all demonstrate the preparation of cement slurry according to GB / T 19139-2012 standard. In the cement slurry systems listed in the examples, the cement used is Jiahua G-grade high-resistance cement, and the quartz sand and metakaolin can be purchased from the market. The high-temperature stabilizer is AM-SSS-DEAA terpolymer, the high-temperature water loss reducing agent is AMPS-VP-AM-AA quaternary copolymer, the high-temperature retarder is AMPS-itaconic acid copolymer, and the liquid-to-solid ratio is 0.44.

[0040] Unless otherwise specified, all parts mentioned in this embodiment refer to parts by weight.

[0041] Example 1

[0042] As a preferred embodiment of the present invention, this embodiment discloses a high-temperature cementing expansion agent. The raw materials of the expansion agent include the following components by weight: 30 parts dolomite, 15 parts serpentine, 5 parts calcium iron pyroxene, 5 parts calcium zeolite, 35 parts quicklime powder, and 10 parts quartz powder.

[0043] The preparation method of the high-temperature cementing expansion agent in this embodiment is as follows:

[0044] S1. Prepare the raw materials according to the proportions. Mix 30 parts dolomite, 15 parts serpentine, 5 parts calcium iron pyroxene, and 5 parts calcium zeolite evenly, crush them, and control the crushing ratio at 60; grind the crushed mixture into fine powder, and control the grinding ratio at 700; send the fine powder to a high-temperature calcining furnace for calcination, control the calcination temperature at 950℃, control the heating time at 30 min, and control the holding time at 120 min; after calcination, the mixture is rapidly cooled to room temperature by an air-cooled refrigerator, and the cooling time is controlled at 10 min; after cooling, the type A mixture is obtained.

[0045] S2. The mixture A prepared in step S1 is mixed with 35 parts of quicklime powder and 10 parts of quartz powder in a ball mill and ground evenly to obtain mixture B.

[0046] S3. Compress the type B mixture into tablets. When the pressure reaches the peak pressure, immediately release the pressure to obtain type B mixture test tablets. The tableting conditions are: peak pressure controlled at 120kN, loading speed at 5kN / s. Place the type B mixture test tablets into a box-type blower for drying. The oven temperature is controlled at 100℃, and the drying time is 24h.

[0047] S4. Place the baked Class B mixture test pieces into a high-temperature calcining furnace for calcination. The calcination process is divided into two stages. The first stage calcination temperature is controlled at 900℃, the heating time is controlled at 30 min, and the holding time is controlled at 10 min; the second stage calcination temperature is controlled at 1300℃, the heating time is controlled at 40 min, and the holding time is controlled at 120 min; after calcination, the test pieces are rapidly cooled to room temperature using an air-cooled refrigerator, and the cooling time is controlled at 10 min; after cooling and pulverization, Class C mixture is obtained.

[0048] S5. Place the C-type mixture into a ball mill for grinding, and control the particle fineness to be Dx(10)≤4μm, Dx(50)≤10μm, and Dx(90)≤20μm. After grinding evenly, the high-temperature cementing expansion agent, referred to as "S1# material", is obtained.

[0049] The chemical composition of the "S1# material" prepared in this embodiment is as follows: 13 wt.% < MgO < 23 wt.%, 38 wt.% < CaO < 55 wt.%, 18 wt.% < SiO2 < 32 wt.%, Al2O3 < 3.5 wt.%, Fe2O3 < 1 wt.%.

[0050] In this embodiment, to ensure the content of each chemical component in the aforementioned "S1# material," the purity, chemical composition content, and fineness of the raw materials dolomite, serpentine, hedonicite, calcium zeolite, quicklime powder, and quartz powder are limited. Specifically:

[0051] Dolomite purity ≥ 95 wt.%, and its chemical composition requirements are: MgO > 20 wt.%, CaO > 28 wt.%;

[0052] Serpentine purity ≥ 95 wt.%, and its chemical composition requirements are: MgO > 40 wt.%, SiO2 > 40 wt.%;

[0053] The purity of calcium iron pyroxene is ≥90 wt.%, and its chemical composition requirements are: CaO > 20 wt.%, SiO2 > 43 wt.%, FeO > 26 wt.%.

[0054] The purity of calcium zeolite is ≥90 wt.%, and its chemical composition requirements are: CaO >12 wt.%, Al2O3 >23 wt.%, SiO2 >41 wt.%.

[0055] The fineness of quicklime powder is ≥325 mesh, and its chemical composition requirement is: CaO > 74 wt.%.

[0056] The fineness of the quartz powder is ≥325 mesh, and its chemical composition requirement is: SiO2 > 98 wt.%.

[0057] The formulation of the "S1# cement slurry system" prepared using the "S1# material" in this embodiment is as follows:

[0058] 100 parts of Grade G high-strength cement, 6 parts of S1# material, 40 parts of quartz sand, 9 parts of meta-high tertiary acid, 3 parts of high-temperature stabilizer (AM-SSS-DEAA terpolymer), 7 parts of high-temperature water loss reducer (AMPS-VP-AM-AA quaternary copolymer), 1.5 parts of high-temperature retarder (AMPS-itaconic acid copolymer), and 61 parts of water.

[0059] Example 2

[0060] As a preferred embodiment of the present invention, this embodiment discloses a high-temperature cementing expansion agent. The raw materials of the expansion agent include the following components by weight: 30 parts dolomite, 20 parts serpentine, 5 parts calcium iron pyroxene, 8 parts calcium zeolite, 30 parts slaked lime powder, and 7 parts quartz powder.

[0061] The preparation method of the high-temperature cementing expansion agent in this embodiment is as follows:

[0062] S1. Prepare the raw materials according to the proportions. Mix 30 parts dolomite, 20 parts serpentine, 5 parts calcium iron pyroxene, and 8 parts calcium zeolite evenly, crush them, and control the crushing ratio at 65; grind the crushed mixture into fine powder, and control the grinding ratio at 750; send the fine powder to a high-temperature calcining furnace for calcination, control the calcination temperature at 965℃, control the heating time at 30min, and control the holding time at 120min; after calcination, the mixture is rapidly cooled to room temperature by an air-cooled refrigerator, and the cooling time is controlled at 12min; after cooling, the type A mixture is obtained.

[0063] S2. The mixture A prepared in step S1 is mixed with 30 parts of quicklime powder and 7 parts of quartz powder in a ball mill and ground evenly to obtain mixture B.

[0064] S3. Compress the type B mixture into tablets. When the pressure reaches the peak pressure, immediately release the pressure to obtain type B mixture test tablets. The tableting conditions are: peak pressure controlled at 130kN, loading speed at 5kN / s. Place the type B mixture test tablets into a box-type blower for drying. The oven temperature is controlled at 100℃, and the drying time is 24h.

[0065] S4. Place the baked Class B mixture test pieces into a high-temperature calcining furnace for calcination. The calcination process is divided into two stages. The first stage calcination temperature is controlled at 900℃, the heating time is controlled at 30 min, and the holding time is controlled at 10 min; the second stage calcination temperature is controlled at 1320℃, the heating time is controlled at 40 min, and the holding time is controlled at 120 min; after calcination, the test pieces are rapidly cooled to room temperature using an air-cooled refrigerator, and the cooling time is controlled at 12 min; after cooling and pulverization, Class C mixture is obtained.

[0066] S5. Place the C-type mixture into a ball mill for grinding, and control the particle fineness to be Dx(10)≤4μm, Dx(50)≤10μm, and Dx(90)≤20μm. After grinding evenly, the high-temperature cementing expansion agent, referred to as "S2# material", is obtained.

[0067] The chemical composition of the "S2# material" prepared in this embodiment is as follows: 13 wt.% < MgO < 23 wt.%, 38 wt.% < CaO < 55 wt.%, 18 wt.% < SiO2 < 32 wt.%, Al2O3 < 3.5 wt.%, Fe2O3 < 1 wt.%.

[0068] In order to ensure the content of each chemical component in the above-mentioned "S2# material", this embodiment limits the purity, chemical composition content, and fineness of the raw materials dolomite, serpentine, hedonicite, calcium zeolite, quicklime powder, and quartz powder. Specifically:

[0069] Dolomite purity ≥ 95 wt.%, and its chemical composition requirements are: MgO > 20 wt.%, CaO > 28 wt.%;

[0070] Serpentine purity ≥ 95 wt.%, and its chemical composition requirements are: MgO > 40 wt.%, SiO2 > 40 wt.%;

[0071] The purity of calcium iron pyroxene is ≥90 wt.%, and its chemical composition requirements are: CaO > 20 wt.%, SiO2 > 43 wt.%, FeO > 26 wt.%.

[0072] The purity of calcium zeolite is ≥90 wt.%, and its chemical composition requirements are: CaO >12 wt.%, Al2O3 >23 wt.%, SiO2 >41 wt.%.

[0073] The fineness of quicklime powder is ≥325 mesh, and its chemical composition requirement is: CaO > 74 wt.%.

[0074] The fineness of the quartz powder is ≥325 mesh, and its chemical composition requirement is: SiO2 > 98 wt.%.

[0075] The formulation of the "S2# cement slurry system" prepared using the "S2# material" in this embodiment is as follows:

[0076] 100 parts of Grade G high-strength cement, 6 parts of S2# material, 40 parts of quartz sand, 9 parts of meta-high tertiary acid, 3 parts of high-temperature stabilizer (AM-SSS-DEAA terpolymer), 7 parts of high-temperature water loss reducer (AMPS-VP-AM-AA quaternary copolymer), 1.5 parts of high-temperature retarder (AMPS-itaconic acid copolymer), and 61 parts of water.

[0077] Example 3

[0078] As a preferred embodiment of the present invention, this embodiment discloses a high-temperature cementing expansion agent. The raw materials of the expansion agent include the following components by weight: 35 parts dolomite, 20 parts serpentine, 7 parts calcium iron pyroxene, 8 parts calcium zeolite, 25 parts slaked lime powder, and 5 parts quartz powder.

[0079] The preparation method of the high-temperature cementing expansion agent in this embodiment is as follows:

[0080] S1. Prepare the raw materials according to the proportions. Mix 35 parts dolomite, 20 parts serpentine, 7 parts calcium iron pyroxene, and 8 parts calcium zeolite evenly, crush them, and control the crushing ratio at 70; grind the crushed mixture into fine powder, and control the grinding ratio at 800; send the fine powder to a high-temperature calcining furnace for calcination, control the calcination temperature at 980℃, control the heating time at 30 min, and control the holding time at 120 min; after calcination, the mixture is rapidly cooled to room temperature by an air-cooled refrigerator, and the cooling time is controlled at 13 min; after cooling, the A-type mixture is obtained.

[0081] S2. The mixture A prepared in step S1 is mixed with 25 parts of quicklime powder and 5 parts of quartz powder in a ball mill and ground evenly to obtain mixture B.

[0082] S3. Compress the type B mixture into tablets. When the pressure reaches the peak pressure, immediately release the pressure to obtain type B mixture test tablets. The tableting conditions are: peak pressure controlled at 140kN, loading speed at 5kN / s. Place the type B mixture test tablets into a box-type blower for drying. The oven temperature is controlled at 100℃, and the drying time is 24h.

[0083] S4. Place the dried Class B mixture test pieces into a high-temperature calcining furnace for calcination. The calcination process is divided into two stages: the first stage calcination temperature is controlled at 900℃, the heating time is controlled at 30 min, and the holding time is controlled at 10 min; the second stage calcination temperature is controlled at 1330℃, the heating time is controlled at 40 min, and the holding time is controlled at 120 min. After calcination, the test pieces are rapidly cooled to room temperature using an air-cooled refrigerator for 13 min; after cooling and pulverization, Class C mixture is obtained.

[0084] S5. Place the C-type mixture into a ball mill for grinding, and control the particle fineness to be Dx(10)≤4μm, Dx(50)≤10μm, and Dx(90)≤20μm. After grinding evenly, the high-temperature cementing expansion agent, referred to as "S3# material", is obtained.

[0085] The chemical composition of the "S3# material" prepared in this embodiment is as follows: 13 wt.% < MgO < 23 wt.%, 38 wt.% < CaO < 55 wt.%, 18 wt.% < SiO2 < 32 wt.%, Al2O3 < 3.5 wt.%, Fe2O3 < 1 wt.%.

[0086] In this embodiment, to ensure the content of each chemical component in the aforementioned "S3# material," the purity, chemical composition content, and fineness of the raw materials dolomite, serpentine, hedonicite, calcium zeolite, quicklime powder, and quartz powder are limited. Specifically:

[0087] Dolomite purity ≥ 95 wt.%, and its chemical composition requirements are: MgO > 20 wt.%, CaO > 28 wt.%;

[0088] Serpentine purity ≥ 95 wt.%, and its chemical composition requirements are: MgO > 40 wt.%, SiO2 > 40 wt.%;

[0089] The purity of calcium iron pyroxene is ≥90 wt.%, and its chemical composition requirements are: CaO > 20 wt.%, SiO2 > 43 wt.%, FeO > 26 wt.%.

[0090] The purity of calcium zeolite is ≥90 wt.%, and its chemical composition requirements are: CaO >12 wt.%, Al2O3 >23 wt.%, SiO2 >41 wt.%.

[0091] The fineness of quicklime powder is ≥325 mesh, and its chemical composition requirement is: CaO > 74 wt.%.

[0092] The fineness of the quartz powder is ≥325 mesh, and its chemical composition requirement is: SiO2 > 98 wt.%.

[0093] The formulation of the "S3# cement slurry system" prepared using the "S3# material" in this embodiment is as follows:

[0094] 100 parts of Grade G high-strength cement, 6 parts of S3# material, 40 parts of quartz sand, 9 parts of meta-high tertiary acid, 3 parts of high-temperature stabilizer (AM-SSS-DEAA terpolymer), 7 parts of high-temperature water loss reducer (AMPS-VP-AM-AA quaternary copolymer), 1.5 parts of high-temperature retarder (AMPS-itaconic acid copolymer), and 61 parts of water.

[0095] Example 4

[0096] As a preferred embodiment of the present invention, this embodiment discloses a high-temperature cementing expansion agent. The raw materials of the expansion agent include the following components by weight: 40 parts dolomite, 10 parts serpentine, 10 parts calcium iron pyroxene, 10 parts calcium zeolite, 25 parts quicklime powder, and 5 parts quartz powder.

[0097] The preparation method of the high-temperature cementing expansion agent in this embodiment is as follows:

[0098] S1. Prepare the raw materials according to the proportions. Mix 40 parts dolomite, 10 parts serpentine, 10 parts calcium iron pyroxene, and 10 parts calcium zeolite evenly, then crush them, controlling the crushing ratio at 75. Grind the crushed mixture into fine powder, controlling the grinding ratio at 850. Send the fine powder to a high-temperature calcining furnace for calcination, controlling the calcination temperature at 1000℃, the heating time at 30 minutes, and the holding time at 120 minutes. After calcination, the mixture is rapidly cooled to room temperature using an air-cooled refrigerator, controlling the cooling time at 15 minutes. After cooling, type A mixture is obtained.

[0099] S2. The mixture A prepared in step S1 is mixed with 25 parts of quicklime powder and 5 parts of quartz powder in a ball mill and ground evenly to obtain mixture B.

[0100] S3. Compress the type B mixture into tablets. When the pressure reaches the peak pressure, immediately release the pressure to obtain type B mixture test tablets. The tableting conditions are: peak pressure controlled at 150 kN, loading speed at 5 kN / s. Place the type B mixture test tablets into a box-type blower for drying. The oven temperature is controlled at 100℃, and the drying time is 24 hours.

[0101] S4. Place the dried B-type mixture test pieces into a high-temperature calcining furnace for calcination. The calcination process is divided into two stages: the first stage calcination temperature is controlled at 900℃, the heating time is controlled at 30 min, and the holding time is controlled at 10 min; the second stage calcination temperature is controlled at 1350℃, the heating time is controlled at 40 min, and the holding time is controlled at 120 min. After calcination, the test pieces are rapidly cooled to room temperature using an air-cooled refrigerator for 15 min; after cooling and pulverization, the C-type mixture is obtained.

[0102] S5. Place the C-type mixture into a ball mill for grinding, and control the particle fineness to be Dx(10)≤4μm, Dx(50)≤10μm, and Dx(90)≤20μm. After grinding evenly, the high-temperature cementing expansion agent, referred to as "S4# material", is obtained.

[0103] The chemical composition of the "S4# material" prepared in this embodiment is as follows: 13 wt.% < MgO < 23 wt.%, 38 wt.% < CaO < 55 wt.%, 18 wt.% < SiO2 < 32 wt.%, Al2O3 < 3.5 wt.%, Fe2O3 < 1 wt.%.

[0104] In order to ensure the content of each chemical component in the above-mentioned "S4# material", this embodiment limits the purity, chemical composition content, and fineness of the raw materials dolomite, serpentine, calcium iron pyroxene, calcium zeolite, quicklime powder, and quartz powder. Specifically:

[0105] Dolomite purity ≥ 95 wt.%, and its chemical composition requirements are: MgO > 20 wt.%, CaO > 28 wt.%;

[0106] Serpentine purity ≥ 95 wt.%, and its chemical composition requirements are: MgO > 40 wt.%, SiO2 > 40 wt.%;

[0107] The purity of calcium iron pyroxene is ≥90 wt.%, and its chemical composition requirements are: CaO > 20 wt.%, SiO2 > 43 wt.%, FeO > 26 wt.%.

[0108] The purity of calcium zeolite is ≥90 wt.%, and its chemical composition requirements are: CaO >12 wt.%, Al2O3 >23 wt.%, SiO2 >41 wt.%.

[0109] The fineness of quicklime powder is ≥325 mesh, and its chemical composition requirement is: CaO > 74 wt.%.

[0110] The fineness of the quartz powder is ≥325 mesh, and its chemical composition requirement is: SiO2 > 98 wt.%.

[0111] The formulation of the "S4# cement slurry system" prepared using the "S4# material" in this embodiment is as follows:

[0112] 100 parts of Grade G high-strength cement, 6 parts of S4# material, 40 parts of quartz sand, 9 parts of meta-high tertiary acid, 3 parts of high-temperature stabilizer (AM-SSS-DEAA terpolymer), 7 parts of high-temperature water loss reducer (AMPS-VP-AM-AA quaternary copolymer), 1.5 parts of high-temperature retarder (AMPS-itaconic acid copolymer), and 61 parts of water.

[0113] Step S3 in Embodiments 1-4 of this invention, which involves compressing the B-type mixture into tablets, primarily facilitates the full reaction of solid particles through bonding under high-temperature calcination conditions. In actual large-scale production, the B-type mixture obtained in step S2 is directly placed into a high-temperature rotary kiln for rolling calcination; that is, step S3 is omitted, and the process proceeds directly to step S4.

[0114] Comparative Example 1

[0115] Compared with Example 1, the cement slurry system in this comparative example does not contain "S1# material", and the corresponding "D1# cement slurry system" formula is as follows:

[0116] 100 parts of Grade G high-strength cement, 40 parts of quartz sand, 9 parts of meta-high terrestrial material, 3 parts of high-temperature stabilizer (inorganic ultrafine materials and clay-like substances), 7 parts of high-temperature water loss reducing agent (AMPS-VP-AM-AA quaternary copolymer), 1.5 parts of high-temperature retarder (AMPS-itaconic acid copolymer), and 58.4 parts of water.

[0117] Comparative Example 2

[0118] Compared with Example 2, this comparative example does not undergo the calcination and cooling process, i.e., step S4 is omitted, while all other conditions are the same. The high-temperature cementing expansion agent prepared in this comparative example is referred to as "D2# material".

[0119] The "D2# Cement Grout System" that comes with "D2# Material" is the same as the "S2# Cement Grout System" except that "S2# Material" is replaced with "D2# Material".

[0120] Comparative Example 3

[0121] The difference between this comparative example and Example 3 lies in the amount of raw materials used. The raw materials for this comparative example are, by weight, the following components: 20 parts dolomite, 5 parts serpentine, 20 parts calcium iron pyroxene, 20 parts calcium zeolite, 15 parts slaked lime powder, and 20 parts quartz powder. The preparation method of the expanding agent in this comparative example is the same as in Example 3.

[0122] The high-temperature cementing expansion agent prepared in this comparative example is referred to as "D3# material".

[0123] The "D3# Cement Grout System" that comes with "D3# Material" is the same as the "S3# Cement Grout System" except that "S3# Material" is replaced with "D3# Material".

[0124] Comparative Example 4

[0125] Compared with Example 4, the particle size of the high-temperature cementing expansion agent in this comparative example has changed, namely, the particle size is Dx(10)≤15μm, Dx(50)≤25μm, and Dx(90)≤40μm. The particle size of this expansion agent exceeds the range specified in Example 4, while all other conditions are the same. The high-temperature cementing expansion agent prepared in this comparative example is referred to as "D4# material".

[0126] The "D4# Cement Grout System" that comes with "D4# Material" is the same as the "S4# Cement Grout System" except that "S4# Material" is replaced with "D4# Material".

[0127] Experimental Example 1

[0128] According to GB / T 19139-2012 standard, the engineering and mechanical properties of each cement slurry system obtained in Examples 1-4 and Comparative Examples 1-4 were tested, and the test results are shown in Table 1.

[0129] The expansion rates of the cement slurry systems obtained from Test Examples 1-4 and Comparative Examples 1-4 were determined by adding high-temperature pressure curing based on the GB / T33293-2016 standard. The test results are shown in Table 2.

[0130] Table 1. Test results of engineering performance and mechanical properties of high-temperature cementing cement.

[0131]

[0132] Note: The curing conditions for the density difference test are: 200℃×20.7MPa×48h; the free liquid content test conditions are: 90℃×0.1MPa×2h; the API water loss test conditions are: 170℃×6.9MPa×30min; the cement stone compressive strength curing conditions are: 200℃×20.7MPa; and the thickening test conditions are: 170℃×90MPa×90min.

[0133] Table 2 Results of High-Temperature Cement Expansion Rate Test

[0134]

[0135] Note: The curing conditions for the cement expansion rate test are: 200℃ × 20.7MPa.

[0136] As shown in Table 1, the engineering performance and mechanical performance test results demonstrate that the high-temperature cementing slurry systems prepared in Examples 1-4 of this invention possess excellent fluidity, zero free fluid content, low API water loss, superior settling stability, and high-strength cement stone compressive strength without degradation. All indicators meet the requirements of the high-temperature cementing industry standard. Furthermore, the high-temperature cementing expansion agent in this invention exhibits excellent compatibility with other additives such as high-temperature stabilizers, high-temperature water loss reducers, and high-temperature retarders. Compared to the blank control sample (Comparative Example 1), the high-temperature cementing expansion agent of this invention has minimal impact on key performance parameters of the cement slurry system, such as fluidity, free fluid content, API water loss, settling stability, thickening time, and cement stone compressive strength, indicating its good applicability and stability in high-temperature cementing slurry systems.

[0137] As can be seen from the high-temperature cement expansion rate test results in Table 2, the high-temperature cement slurry systems prepared in Examples 1-4 of this invention exhibit excellent expansion performance. This system shows significant expansion in the early to mid-stages of cement hydration (before 3 days), while exhibiting only slight expansion in the later stages of cement stone hardening (after 7 days). Crucially, its expansion effect is concentrated in the plastic state of the cement (i.e., the period of cementitious structure formation). This precise timing design effectively avoids the risk of expansion failure in the liquid stage of the slurry or damage to the internal structure of the cement stone in the solid stage. Therefore, the expansion component can synergistically work with the cement hydration process, achieving effective expansion during the formation of the cementitious structure, ultimately improving the bonding quality of the second interface of the cement sheath.

[0138] Referring to the expansion rate test data in Table 2, compared with Example 1, the cement slurry system prepared in Comparative Example 1 showed almost no expansion characteristics during the setting and hardening process; even with the extension of the curing period, the cement stone did not show obvious expansion. This lack of expansion performance has a significant impact on the integrity of the cement sheath seal and can easily lead to problems such as annular pressure and interlayer flow.

[0139] Referring to the expansion rate test data in Table 2, compared with Example 2, the cementing slurry system prepared in Comparative Example 2 exhibited extremely weak expansion performance during the setting and hardening process; with the extension of the curing age, the expansion characteristics of the cement stone were still not significantly manifested. This indicates that the high-temperature cementing expansion agent prepared without calcination and cooling processes cannot effectively alleviate the volume shrinkage problem of high-temperature cement stone, further illustrating that each step in the preparation process of the high-temperature cementing expansion agent is crucial to ensuring the stability of the expansion performance of high-temperature cement stone.

[0140] Referring to the expansion rate test data in Table 2, compared with Example 3, the cementing slurry system prepared in Comparative Example 3 exhibited weaker expansion performance during the setting and hardening process; its expansion characteristics remained insignificant even with prolonged curing age. This indicates that when the chemical composition of the high-temperature cementing expansion agent exceeds the range defined in this application, the problem of high-temperature cement stone volume shrinkage cannot be effectively solved. This further illustrates that only by strictly meeting the requirements for the chemical composition of the high-temperature cementing expansion agent in this application can the expected performance goals be achieved, thereby solving the technical problems proposed in this application. This is because the high-temperature cementing expansion agent in this invention has a chemical composition ratio specifically designed based on the phenomenon of high-temperature cement stone volume shrinkage, where each component must be within a defined range to work synergistically and exert the best material performance.

[0141] As shown in Table 2, the expansion rate test data indicates that although the cementing slurry system prepared in Comparative Example 4 exhibits some expansion during the setting and hardening process, its expansion effect is significantly weaker than that of Example 4. With the extension of the curing period, the expansion performance of its cement stone still shows a significant difference compared to Example 4. This indicates that when the particle size of the high-temperature cementing expansion agent exceeds the range defined in this application, the expansion effect will be significantly reduced, making it difficult to effectively alleviate the volume shrinkage problem of high-temperature cement stone. This further illustrates that only by strictly meeting the particle size requirements of the high-temperature cementing expansion agent in this application can the expected performance goals be achieved and the technical problems proposed in this application be solved. This is because when the expansion agent particles are too coarse, the reactivity of the expansion component decreases, preventing it from exerting its proper expansion effect in a timely manner, thereby interfering with the synergistic reaction between the expansion component and the main mineral hydration process, and thus hindering the optimal performance of the material. Therefore, limiting the particle size of the high-temperature cementing expansion agent is a necessary technical requirement.

[0142] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A high-temperature cementing expansion agent, characterized in that, Its raw materials include the following components by weight: 30-40 parts dolomite; 10-20 parts serpentine; 5-10 parts calcium iron pyroxene; 5-10 parts calcium zeolite; 25-35 parts slaked lime powder; 5-10 parts quartz powder. The chemical composition of the high-temperature cementitious expansion agent is as follows: 13 wt.% < MgO < 23 wt.%, 38 wt.% < CaO < 55 wt.%, 18 wt.% < SiO2 < 32 wt.%, Al2O3 < 3.5 wt.%, Fe2O3 < 1 wt.%. The particle size of the high-temperature cementing expansion agent is Dx(10)≤4μm, Dx(50)≤10μm, and Dx(90)≤20μm.

2. The high-temperature cementing expansion agent according to claim 1, characterized in that, The dolomite has a purity of ≥95 wt.%, an MgO content >20 wt.%, and a CaO content >28 wt.%.

3. The high-temperature cementing expansion agent according to claim 1, characterized in that, The serpentine has a purity of ≥95 wt.%, MgO content >40 wt.%, and SiO2 content >40 wt.%.

4. The high-temperature cementing expansion agent according to claim 1, characterized in that, The calcium iron pyroxene has a purity ≥90 wt.%, CaO content >20 wt.%, SiO2 content >43 wt.%, and FeO content >26 wt.%.

5. The high-temperature cementing expansion agent according to claim 1, characterized in that, The calcium zeolite has a purity ≥90 wt.%, CaO content >12 wt.%, Al2O3 content >23 wt.%, and SiO2 content >41 wt.%.

6. The high-temperature cementing expansion agent according to claim 1, characterized in that, The fineness of the hydrated lime powder is ≥325 mesh, and the CaO content is >74 wt.%.

7. The high-temperature cementing expansion agent according to claim 1, characterized in that, In some embodiments of the present invention, the quartz powder has a fineness ≥325 mesh and a SiO2 content >98 wt.%.

8. The method for preparing the high-temperature cementing expansion agent according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Prepare each raw material according to the proportion, then mix dolomite, serpentine, calcium iron pyroxene and calcium zeolite, crush, grind, calcine, cool, and form a Class A mixture; S2. Grind the type A mixture with the remaining raw materials until uniform to obtain type B mixture; S3. Calcine the type B mixture and then cool it to obtain the type C mixture; S4. Place the C-type mixture into a ball mill for grinding, and control the particle fineness to be Dx(10)≤4μm, Dx(50)≤10μm, and Dx(90)≤20μm. After grinding evenly, the high-temperature cementing expansion agent is obtained.

9. The method for preparing the high-temperature cementing expansion agent according to claim 8, characterized in that, In step S1, dolomite, serpentine, calcium iron pyroxene and calcium zeolite are mixed evenly and then crushed, with the crushing ratio controlled at 60-75. Preferably, the crushed mixture is ground into fine powder, and the grinding ratio is controlled at 700-850. Preferably, the mixed fine materials are fed into a high-temperature calcining furnace for calcination. The calcination temperature is controlled at 950℃~1000℃, the heating time is controlled at 20~40min, preferably 30min, and the holding time is controlled at 100~140min, preferably 120min.

10. The method for preparing the high-temperature cementing expansion agent according to claim 8 or 9, characterized in that, In step S3, the B-type mixture is calcined, and the calcination process is carried out in two stages; The first stage calcination temperature is controlled at 850–950℃, preferably 900℃; the heating time is controlled at 20–40 min, preferably 30 min; and the holding time is controlled at 5–15 min, preferably 10 min. The second stage calcination temperature is controlled at 1300–1350℃; the heating time is controlled at 30–50 min, preferably 40 min; and the holding time is controlled at 100–140 min, preferably 120 min.

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