Long-term anti-degradation low-density cementing material hydrothermally synthesized under ultra-high temperature environment and preparation method thereof

Abstract

This invention provides a hydrothermal-synthesized, long-term, anti-degradation, low-density cementing material for ultra-high temperature environments and its preparation method. This cementing material incorporates calcium oxide, silicon oxide, and various calcium aluminates into its formulation. The hydration reaction of these raw materials at high temperatures generates a substance with a certain strength. Simultaneously, under high-temperature conditions, the three types of calcium aluminates in a specific ratio can react with calcium oxide and silicon oxide to form hydrated calcium aluminosilicate (C-A-S-H), which exhibits long-term high-temperature resistance, thus ensuring the long-term high-temperature performance of the cementing material. Through this method, a cementing material that does not experience strength degradation under long-term high-temperature conditions (90 days of curing at 240℃) is obtained, effectively solving the problem of strength degradation at high temperatures in existing cement slurries used in deep wells.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction technology, and in particular to a hydrothermal synthetic long-term anti-decay low-density cementing material under ultra-high temperature environment and its preparation method. Background Technology

[0002] In recent years, deep oil and gas resources have become a key focus of resource development. With the continuous development of deep oil and gas resources, the number of oil and gas wells with bottomhole static temperatures exceeding 200℃ is also increasing. When the downhole temperature exceeds 110℃, the semi-crystalline calcium silicate hydrate (CSH) in the hydration products of silicate cement-based systems gradually transforms into a crystalline phase, leading to a decrease in compressive strength and an increase in permeability. With further increases in bottomhole temperature, the mechanical properties of the cement stone will further deteriorate. This behavior of Portland cement at high temperatures is called cement strength degradation. In the past, materials rich in SiO2 (mainly silica fume) were often added to the cement slurry to prevent strength degradation of cement solidified at high temperatures. Recent research results indicate that this method can only alleviate strength degradation within a short curing period, but cannot completely prevent long-term (over 30 days) strength degradation above 200℃. Therefore, in order to improve the cementing quality and wellbore integrity of deep wells, it is urgent to find or develop a new material that does not experience strength degradation at high temperatures.

[0003] Deep wells often have low-pressure, easily leaking areas. Using conventional density cement slurry can easily cause slurry to leak into the reservoir. In addition, using low-density cement slurry can reduce the pressure damage to the wellbore and tubing. Therefore, in deep wells with high leakage risk areas, long-term high-temperature resistant low-density cementing fluid is required. However, conventional low-density cement slurry systems are almost unusable because their strength deteriorates more severely at high temperatures.

[0004] In view of this, it is necessary to design an improved hydrothermal synthesis type of long-term aging-resistant low-density cementing material and its preparation method under ultra-high temperature environment in order to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a hydrothermal synthetic long-term resistant low-density cementing material and its preparation method under ultra-high temperature conditions.

[0006] To achieve the above-mentioned objectives, on the one hand, this invention provides a hydrothermal synthetic long-term anti-decay low-density cementing material under ultra-high temperature environment, comprising the following raw materials in parts by weight: 13-38 parts of retarder, 185-280 parts of solid reactant, 6-11 parts of stabilizer, 6-11 parts of fluid loss reducing agent, 1-4 parts of dispersant, 0.7-1.1 parts of defoamer, and 89-129 parts of water;

[0007] The solid reactants comprise the following raw materials in parts by weight: 26-110 parts calcium hydroxide, 100 parts silica sand, and 39.1-87 parts a mixture of calcium aluminate; the retarder accounts for 7-14% of the total mass of the solid reactants.

[0008] The calcium aluminate mixture includes monocalcium aluminate, dicalcium aluminate, and dicalcium aluminosilicate, with mass percentages of 22-27%, 34-48%, and 28-37%, respectively.

[0009] In one embodiment of the present invention, the retarder is a high-temperature resistant retarder HX-36L.

[0010] In one embodiment of the present invention, the stabilizer is a high-temperature resistant suspension stabilizer O-SP.

[0011] In one embodiment of the present invention, the water loss reducing agent is a high-temperature resistant water loss reducing agent HX-12L.

[0012] In one embodiment of the present invention, the dispersant is dispersant USD-1.

[0013] On the other hand, the present invention also provides a method for preparing the hydrothermal synthetic long-term anti-decay low-density cementing material under ultra-high temperature environment, comprising the following steps: mixing raw materials with the following composition: 13-38 parts of retarder, 185-280 parts of solid reactant, 6-11 parts of stabilizer, 6-11 parts of fluid loss reducer, 1-4 parts of dispersant, 0.7-1.1 parts of defoamer, and 89-129 parts of water evenly, and then curing them at 240℃ and 50MPa for 90 days to obtain the cementing material;

[0014] The solid reactants comprise the following raw materials in parts by weight: 26-110 parts calcium hydroxide, 100 parts silica sand, and 39.1-87 parts a mixture of calcium aluminate; the retarder accounts for 7-14% of the total mass of the solid reactants.

[0015] The calcium aluminate mixture includes monocalcium aluminate, dicalcium aluminate, and dicalcium aluminosilicate, with mass percentages of 22-27%, 34-48%, and 28-37%, respectively.

[0016] In one embodiment of the present invention, after all raw materials are mixed evenly, the resulting slurry has a density of 1.65 g / cm³. 3 .

[0017] The beneficial effects of this invention are:

[0018] This invention provides a hydrothermal-synthesized, long-term, anti-fading, low-density cementing material for ultra-high temperature environments. By introducing calcium oxides, silicon oxides, and various calcium aluminates (including a mixture of monocalcium aluminate, dicalcium aluminate, and dicalcium aluminosilicate) into the material's formulation, a substance with a certain strength can be generated through the hydration reaction of these raw materials at high temperatures. Simultaneously, under high-temperature conditions, the three types of calcium aluminates in a specific ratio can react with calcium oxides and silicon oxides to form hydrated calcium aluminosilicate (CASH), which possesses long-term high-temperature resistance, thus ensuring the cementing material's long-term high-temperature performance. Furthermore, the slurry obtained using the formulation proposed in this invention has a low density (1.65 g / cm³). 3 Due to its properties, the low-density slurry can effectively reduce structural pressure during application. Furthermore, its good fluidity, strong adhesion, and good sealing properties make it suitable for deep wells. Through this method, a cementing material that does not experience strength degradation under long-term high-temperature conditions (90 days of curing at 240℃) is obtained, effectively solving the problem of strength degradation at high temperatures in existing cement slurries used in deep wells. Attached Figure Description

[0019] Figure 1 The reaction time test chart is for a calcium-silicon-aluminum molar ratio of 4:4:1 in the preliminary experiment.

[0020] Figure 2 The reaction time test chart is for a calcium-silicon-aluminum molar ratio of 2:2:1 in the preliminary experiment.

[0021] Figure 3 The reaction time test chart is for the formulation with a calcium-silicon-aluminum molar ratio of 2:4:1 in the preliminary experiment;

[0022] Figure 4 The reaction time test chart is for a calcium-silicon-aluminum molar ratio of 1:2:1 in the preliminary experiment.

[0023] Figure 5 The compressive strength of the cementing materials obtained in Examples 1 to 9;

[0024] Figure 6 The water permeability of the cementing materials prepared in Examples 1 to 9;

[0025] Figure 7 This is a diagram showing the changes in mineral composition before and after the reaction in Example 1. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0028] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0029] The present invention provides a hydrothermal synthetic long-term anti-decay low-density cementing material for ultra-high temperature environments, comprising the following raw materials in parts by weight: 13-38 parts of retarder, 185-280 parts of solid reactants, 6-11 parts of stabilizer, 6-11 parts of fluid loss reducer, 1-4 parts of dispersant, 0.7-1.1 parts of defoamer, and 89-129 parts of water; wherein the solid reactants comprise the following raw materials in parts by weight: 26-110 parts of calcium hydroxide, 100 parts of silica sand, and 39.1-87 parts of a calcium aluminate mixture, wherein the calcium aluminate mixture comprises monocalcium aluminate, dicalcium aluminate, and dicalcium aluminosilicate, with mass percentages of 22-27%, 34-48%, and 28-37%, respectively, and the retarder accounts for 7-14% of the total mass of the solid reactants. It should be noted that the calcium aluminate mixture can also be replaced with substances containing monocalcium aluminate, diacalcium aluminate, and dicalcium aluminosilicate, or compounds of silicon and aluminum, such as high-alumina cement and aluminum silicate. This is because: the calcium aluminate mixture can be made from high-alumina cement, which also contains monocalcium aluminate, diacalcium aluminate, and dicalcium aluminosilicate. Both high-alumina cement and aluminum silicate have similar effects to the calcium aluminate mixture. The aluminum compounds in the mixture can increase the chemical reaction participation rate of aluminum, and the hydration reaction between aluminum and calcium oxides and silicon oxides can also generate hydrated calcium aluminosilicate with long-term high-temperature resistance, thus giving the cementing material long-term high-temperature resistance.

[0030] In one embodiment of the present invention, the retarder is a high-temperature resistant retarder HX-36L.

[0031] In one embodiment of the present invention, the stabilizer is a high-temperature resistant suspension stabilizer O-SP.

[0032] In one embodiment of the present invention, the water loss reducing agent is a high-temperature resistant water loss reducing agent HX-12L.

[0033] In one embodiment of the present invention, the dispersant is dispersant USD-1.

[0034] Furthermore, this invention also provides a method for preparing the above-mentioned hydrothermal synthetic long-term anti-decay low-density cementing material under ultra-high temperature conditions, comprising the following steps: mixing raw materials comprising 13-38 parts of retarder, 185-280 parts of solid reactants, 6-11 parts of stabilizer, 6-11 parts of fluid loss reducing agent, 1-4 parts of dispersant, 0.7-1.1 parts of defoamer, and 89-129 parts of water evenly, and then curing them at 240℃ and 50MPa for 90 days to obtain the cementing material for ultra-high temperature formations; wherein the solid reactants include the following... Raw materials by weight: 26-110 parts calcium hydroxide, 100 parts silica sand, and 39.1-87 parts calcium aluminate mixture, which includes monocalcium aluminate, dicalcium aluminate, and dicalcium aluminosilicate, with mass percentages of 22-27%, 34-48%, and 28-37%, respectively. The retarder accounts for 7-14% of the total mass of the solid reactants. The retarder is a high-temperature resistant retarder HX-36L, the stabilizer is a high-temperature resistant suspension stabilizer O-SP, the water loss reducer is a high-temperature resistant water loss reducer HX-12L, and the dispersant is dispersant USD-1.

[0035] The following specific embodiments further illustrate the hydrothermal synthesis of the long-term aging-resistant low-density cementing material and its preparation method under ultra-high temperature conditions according to the present invention:

[0036] Examples 1 to 9

[0037] This section of the embodiments provides a formulation and preparation method for a hydrothermal synthetic long-term anti-decay low-density cementing material under ultra-high temperature conditions. The raw materials used in the preparation process are as follows: calcium hydroxide was purchased from Sinopharm Chemical Reagent Co., Ltd.; silica sand was purchased from Henan Tongbai Processing Plant; YF calcium aluminate (specifically composed of 22% monocalcium aluminate, 48% dicalcium aluminate and 28% dicalcium aluminosilicate, with the remainder being impurities) was purchased from Gongyi Yangfan Water Treatment Materials Co., Ltd.; YX calcium aluminate (specifically composed of 27% monocalcium aluminate, 34% dicalcium aluminate and 37% dicalcium aluminosilicate, with the remainder being impurities) was purchased from Shaoguan Yunxing Chemical Reagent Co., Ltd.; high-temperature resistant retarder HX-36L, high-temperature resistant suspension stabilizer O-SP, and high-temperature resistant fluid loss reducing agent HX-12L were all purchased from Omec Petroleum Technology Co., Ltd.; defoamer G603 was purchased from Tianjin Zhongyou Boxing Engineering Technology Co., Ltd.; and dispersant USD-1 was purchased from Weihui Chemical Co., Ltd. Before preparation, the density and particle size of the dry powder material were tested using an UltraPYC 1200e fully automated true density analyzer from CANTA Corporation (USA) and a Malvern Mastersizer 2000 laser particle size analyzer from the UK. The test results are shown in Table 1.

[0038] Table 1 Performance of Dry Powder Materials

[0039] Material Name calcium hydroxide silica sand YF calcium aluminate YX calcium aluminate purity(%) 98.25 97.35 87.88 86.08 <![CDATA[Density (g / cm 3 )]]> 2.26 2.63 2.93 2.93 D50(μm) 4.2 14.2 34.0 19.4

[0040] To ensure the formulation reacts at a high temperature of 240℃ and to determine the optimal reaction time during the preparation process, preliminary experiments were conducted. The reaction time of each formulation was controlled by adjusting the amount of retarder added. During the experiments, a C80 high-temperature, high-pressure microcalorimeter manufactured by SETARAM (France) was used to test the reaction time of the slurry (the instrument required 107 minutes to reach the specified temperature and pressure), ultimately yielding a hydrothermal synthesis material formulation with a suitable reaction time. The hydration reaction time test was divided into two parts. The first part was the heating stage (the equipment took 107 minutes to heat from room temperature to 240℃). The heat flux during the heating stage was negligible. After the heating stage, the formulation reacted exothermically, producing an exothermic peak. We generally consider the time immediately following the appearance of the exothermic peak as the reaction time of that formulation.

[0041] During the preliminary experiments, a basic experimental formulation was designed based on the XRF test data of YF calcium aluminate and YX calcium aluminate, as well as the density of all materials. The design principle was to fix the density of all slurries at 1.65 g / cm³. 3 Four different calcium-silicon-aluminum (Ca / Si / Al) molar ratios were developed, each using two different types of calcium aluminate, resulting in a total of eight design formulations. The raw material usage in each formulation is shown in Table 2 (all raw material usage is by weight). The design process used the amount of silica sand as a baseline, and the amounts of other materials were calculated based on the amount of silica sand. Specifically, the Ca / Si / Al molar ratio for formulations 1 and 2 was 4:4:1; for formulations 3 and 4, it was 2:2:1; for formulations 5 and 6, it was 2:4:1; and for formulations 7 and 8, it was 1:2:1. Based on these, the reaction time of formulations with different amounts of retarder were tested.

[0042] Table 2 shows the usage of each raw material in the formula for the preliminary experiment.

[0043]

[0044] When the above formula is used for the reaction, the reaction time test graph corresponding to the elemental molar ratio of Ca / Si / Al of 4:4:1 is shown in the figure. Figure 1As shown in the figure, the reaction times for the YF calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 4:4:1, with retarder dosages of 24g, 36g, and 48g, are 120min, 170min, and 305min, respectively. For the YX calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 4:4:1, the reaction time with a retarder dosage of 48g is 640min, which can be appropriately reduced to 36g. We need a reaction time exceeding 3.5h (the equipment needs 3.5h to heat from room temperature to 240℃ during the curing experiment; to ensure the reaction occurs at 240℃, the reaction time needs to exceed 3.5h). Therefore, we choose a retarder dosage of 48g for the YF calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 4:4:1 and a retarder dosage of 36g for the YF calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 4:4:1. Based on the amount of silica sand, the dosage of retarder is 22.9 and 18.5.

[0045] The reaction time test graph for a Ca / Si / Al molar ratio of 2:2:1 is shown below. Figure 2 As shown in the figure, the reaction times for the YF calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 2:2:1, with 54g and 72g of retarder, are 205min and 380min, respectively. For the YX calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 2:2:1, the reaction time with 54g of retarder is 395min. Therefore, the recommended retarder dosage is 54g for the YX calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 2:2:1 and 72g for the YF calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 2:2:1. After conversion based on the amount of silica sand, the corresponding retarder dosages are 30.7g and 37.7g.

[0046] The reaction time test graph for a Ca / Si / Al molar ratio of 2:4:1 is shown below. Figure 3 As shown in the figure, the reaction times for the YF calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 2:4:1, with 42g and 48g of retarder, are 430min and 490min, respectively. For the YX calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 2:4:1, the reaction time with 24g of retarder is 320min; the dosage can be appropriately increased to 36g. Therefore, the recommended retarder dosages are 42g and 48g for the YF calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 2:4:1, and 36g for the YX calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 2:4:1. After conversion based on the amount of silica sand, the retarder dosages are 14.9, 17.1, and 13.7g, respectively.

[0047] The reaction time test graph for a Ca / Si / Al molar ratio of 1:2:1 is shown below. Figure 4As shown in the figure, the reaction time for the YF calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 1:2:1, with an add of 48g of retarder, is 315min. For the YX calcium aluminate formulation with a calcium-silicon-aluminum molar ratio of 1:2:1, the reaction time for an add of 36g of retarder is 310min. After conversion based on the amount of silica sand, the retarder dosages are 19.1 and 15.6, respectively.

[0048] Through the above experiments, the amount of retarder added in each formulation was determined. The formulations of Examples 1 to 9 are shown in Table 3. Among them, the elemental molar ratio of Ca / Si / Al in Examples 1 to 2 is 4:4:1; the elemental molar ratio of Ca / Si / Al in Examples 3 to 4 is 2:2:1; the elemental molar ratio of Ca / Si / Al in Examples 5 to 7 is 2:4:1. YF calcium aluminate was used in Examples 5 to 6, but more retarder was added in Example 6, which served as a control group for Example 5; the elemental molar ratio of Ca / Si / Al in Examples 8 to 9 is 1:2:1, and the density of all slurries is 1.65 g / cm³. 3 .

[0049] Table 3 Formulations of Examples 1 to 9

[0050]

[0051]

[0052] According to API RP 10B-2 standard, the formulations of Examples 1 to 9 were mixed to obtain cement slurry. The mixing process was carried out as follows: at a speed of 4000 r / min, a dry powder material composed of calcium hydroxide, silica sand, calcium aluminate powder (YF calcium aluminate or YX calcium aluminate) and solid additives was quickly added (added over 15 s) to the mixture of water and liquid additives. After stirring continuously for 15 s, the speed was adjusted to 12000 r / min and kept constant for 35 s to obtain the hydrated slurry. The slurry was then poured into a cylindrical steel mold with an inner diameter of 25 mm and a height of 70 mm and placed in a high-temperature and high-pressure curing autoclave. It was cured at 240℃ and 50 MPa for 2 days, 30 days and 90 days, respectively. The hydrothermal synthesis samples were taken out, and both ends were cut with a core cutting and grinding machine and the end faces were ground flat. The final sample height was about 50 mm.

[0053] To evaluate the high-temperature stability of the materials prepared using the formulations of Examples 1 to 9, specific evaluation indicators included compressive strength and water permeability. The compressive strength was measured using a UTM5105X microcomputer-controlled electronic universal testing machine from Shenzhen Sansi Zongheng Co., Ltd., and the results are as follows: Figure 5 As shown, by Figure 5 It can be seen from this:

[0054] (1) It can be seen from the compressive strength of each formula after curing for 2 days and 30 days that the strength decline of the formula when the element molar ratio of Ca / Si / Al is 4:4:1 and 2:2:1 is less than that of the formula when the element molar ratio of Ca / Si / Al is 2:4:1 and 1:2:1.

[0055] (2) The cementing material prepared in Example 1 has significantly better properties than that in Examples 2 to 9. Within the same curing time, Example 1 exhibits the highest compressive strength. Meanwhile, Figure 5 The degree of overlap of the error bars indicates that the compressive strength of Example 1 after 90 days of curing is comparable to that after 30 days of curing, demonstrating that the material did not exhibit strength degradation under long-term high-temperature conditions. Furthermore, the water permeability of Example 1 after 90 days of curing is slightly higher than that after 30 days of curing, although the increase is small, further indicating its excellent long-term high-temperature resistance.

[0056] (3) When the molar ratio of Ca / Si / Al is 4:4:1, the formulation with added YF calcium aluminate exhibits excellent long-term high-temperature resistance. When the molar ratio of Ca / Si / Al is 2:2:1, the formulation with added YX calcium aluminate has better high-temperature resistance than YF calcium aluminate. When the molar ratio of Ca / Si / Al is 2:4:1, the formulation with added two types of calcium aluminate has poor high-temperature resistance. When the molar ratio of Ca / Si / Al is 1:2:1, the compressive strength of the formulation is much lower than other formulations, and the water permeability is much higher than other formulations, especially after long-term curing, the permeability is extremely high and cannot be measured.

[0057] (4) Although the cementing materials prepared in Examples 2 to 4 showed strength degradation, the degradation was less than that in Examples 5 to 9. The degradation of all formulations was significantly lower than that of the ordinary low-density cement slurry system (the ordinary low-density cement slurry system here refers to the cement slurry prepared in "Pang X, Qin J, Sun L, et al. Long-term strength retrogression of silica-enriched oil well cement: A comprehensive multi-approach analysis[J]. Cement and Concrete Research, 2021, 144: 106424"), which shows the excellent performance of this type of system.

[0058] (5) The final preferred formulation of the long-term high-temperature and low-density hydrothermal synthesis material is Example 1, which consists of: 109.5 parts calcium hydroxide + 100 parts silica sand + 39.1 parts YF calcium aluminate + 8.6 parts stabilizer + 8.6 parts water loss reducer + 2.9 parts dispersant + 1 part defoamer + 22.9 parts retarder + 108.3 parts water.

[0059] (6) The cementing materials prepared by the formulations in Examples 2 to 9 also have excellent long-term high temperature resistance. The specific composition by weight is: 13-38 parts of retarder, 185-280 parts of solid reactant, 6-11 parts of stabilizer, 6-11 parts of fluid loss reducer, 1-4 parts of dispersant, 0.7-1.1 parts of defoamer, and 89-129 parts of water. The raw material composition of the solid reactant by weight is: 26-110 parts of calcium hydroxide, 100 parts of silica sand, and 39.1-87 parts of calcium aluminate (of which monocalcium aluminate accounts for 22-27%, dicalcium aluminate accounts for 34-48%, and dicalcium aluminosilicate accounts for 28-37%).

[0060] The water permeability of the materials prepared according to the formulations in Examples 1 to 9 was measured as follows: A hydrothermal synthesis sample was placed in a core holder, with a constant pressure and constant speed pump connected to the inlet and a small glass bottle connected to the outlet. The bottle was then placed on a high-precision balance. Under certain confining and driving pressures, the volumetric flow rate of the water was calculated based on the change in balance readings over time, selecting the stable linear segment. Finally, the flow rate was determined using the formula... The water permeability of the material was calculated, where L represents the sample length in cm and A represents the sample cross-sectional area in cm². 2 ;K W This indicates water permeability, measured in μm. 2 Q represents the water permeability flow rate, in cm³. 3 / s, ΔP represents the water permeability pressure difference, in MPa; μ W The viscosity is expressed in mPa·s. The water permeability test results of the cementing materials prepared in Examples 1 to 9 are as follows: Figure 6 As shown in the figure, it can be seen that when the molar ratio of calcium, silicon and aluminum is 4:4:1 and 2:2:1, the water permeability is lower than that of other formulations. In particular, the permeability change of Example 1 after 90 days of curing is extremely low (the permeability increased by about 100% compared to two days, while the permeability of conventional cement slurry cured at 200 degrees Celsius for 30 days increased by about two orders of magnitude), which shows the excellent long-term high temperature resistance of this example.

[0061] To investigate the form of calcium aluminate in cementing materials under high-temperature conditions during the curing process, a combination of XRD and thermogravimetric analysis was used to refine the XRD process and analyze the compositional changes and reaction extent of the hydrothermal synthesis formulation. The results are as follows: Figure 7As shown in the figure, calcium hydroxide, monocalcium aluminate, and dicalcium aluminate react completely, with only a small amount of silica sand remaining, and some dicalcium aluminosilicate also remaining. The reaction products mainly include calcareous silicate, calcareous silicate, hydrogrossular, amorphous phases (mainly CASH gel), and other minerals. Figure 7 The distribution of components before reaction (day 0) shows that the total amount of hydration products remained basically stable after two days of curing. With prolonged curing time, the content of amorphous phase decreased, the content of hard calcium silicate decreased, and the content of siliceous calcium silicate increased. Current research indicates that the high-temperature degradation mechanism of cement stone is complex, but generally manifests as the crystallization of hydrated calcium silicate gel and the transformation of siliceous calcium silicate into hard calcium silicate. However, in Example 1, with prolonged curing time, siliceous calcium silicate increased, hard calcium silicate decreased, and the total amount of siliceous calcium silicate and amorphous phase remained basically unchanged. This should be the key to the long-term high-temperature resistance of this example.

[0062] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A hydrothermally synthesized, long-term aging-resistant, low-density cementing material for ultra-high temperature environments, characterized in that... The raw materials include the following parts by weight: 13-38 parts of retarder, 185-280 parts of solid reactant, 6-11 parts of stabilizer, 6-11 parts of water loss reducer, 1-4 parts of dispersant, 0.7-1.1 parts of defoamer, and 89-129 parts of water; The solid reactants comprise the following raw materials in parts by weight: 26-110 parts calcium hydroxide, 100 parts silica sand, and 39.1-87 parts a mixture of calcium aluminate. The solid reactants satisfy the elemental molar ratio of Ca / Si / Al as 4:4:1 or 2:2:

1. The mass of the retarder is 7-14% of the total mass of the solid reactants. The calcium aluminate mixture includes monocalcium aluminate, dicalcium aluminate, and dicalcium aluminosilicate, with mass percentages of 22-27%, 34-48%, and 28-37%, respectively. The retarder is a high-temperature resistant retarder HX-36L, the stabilizer is a high-temperature resistant suspension stabilizer O-SP, the water loss reducing agent is a high-temperature resistant water loss reducing agent HX-12L, and the dispersant is a dispersant USD-1.

2. A method for preparing a long-term, aging-resistant, low-density cementing material synthesized under ultra-high temperature conditions as described in claim 1, characterized in that, The process includes the following steps: After the raw materials, which consist of 13-38 parts of retarder, 185-280 parts of solid reactant, 6-11 parts of stabilizer, 6-11 parts of fluid loss reducer, 1-4 parts of dispersant, 0.7-1.1 parts of defoamer, and 89-129 parts of water, are mixed evenly, the mixture is cured at 240℃ and 50MPa for 90 days to obtain the cementing material. The solid reactants comprise the following raw materials in parts by weight: 26-110 parts calcium hydroxide, 100 parts silica sand, and 39.1-87 parts a mixture of calcium aluminate; the retarder accounts for 7-14% of the total mass of the solid reactants. The calcium aluminate mixture includes monocalcium aluminate, dicalcalcium aluminate, and dicalcium aluminosilicate, with mass percentages of 22-27%, 34-48%, and 28-37%, respectively.

3. The preparation method according to claim 2, characterized in that, After all the raw materials are mixed evenly, the resulting slurry has a density of 1.65 g / cm³. 3 .

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