Preparation method of heat control coagulant for natural gas hydrate layer cementing

Abstract

The application discloses a preparation method of a heat control coagulant for a natural gas hydrate layer cementing, and comprises the following steps: dispersing or dissolving a skeleton support material in deionized water to form a uniform and stable solution; adding a silicon source precursor and continuously stirring at a certain rotating speed; adjusting the pH value of the solution to 4-6, and reacting at 40-60 DEG C for 8-12 hours to form a uniform sol; placing an inorganic hydrated salt in a beaker, increasing the temperature to completely melt the hydrated salt into a hydrated salt solution; adding a heat conduction enhancer, a melting point modifier, a thickening agent and a nucleating agent into the hydrated salt solution to form a uniform mixed solution; pouring the sol into the mixed solution, stirring, pouring into a culture dish, and forming a gel after 48 hours at normal temperature; and freezing and drying the gel to obtain the heat control coagulant. The application has the advantages of simple process, easily obtained raw materials, controllable preparation process, and the synthesized product can effectively improve early strength of cement, control hydration heat release, and has a wide market application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of cementing in deep water and ultra-deep water oil and gas field development, and particularly relates to a preparation method of a heat control coagulation accelerator for controlling hydration heat release and improving early strength of a cement slurry for cementing in deep water and ultra-deep water natural gas hydrate layers. BACKGROUND

[0002] The South China Sea region is rich in oil and gas resources. The proven oil and gas reserves in the South China Sea are about 20 billion tons, and the natural gas reserves are about 4 trillion cubic meters, accounting for 1 / 3 of the total resources in China. Among them, 70% is stored in the deep water area of 153.7 x 10 4 km 2 The development of oil and gas resources in deep water and ultra-deep water areas is an important strategy for the development of China's oil industry. However, the exploration and development of oil and gas resources in deep water and ultra-deep water areas are different from those on land, and will face complex geological conditions, low temperature, and the presence of natural gas hydrates, etc., which pose great challenges to cementing operations. In cementing construction in unconventional areas, it is necessary to shorten the cementing period as much as possible, so the cement stone is required to have excellent early strength. The most severe challenge in cementing in the above-mentioned areas is low temperature, and the mudline temperature at the seabed is only about 4 ℃. In addition, the presence of natural gas hydrates requires low hydration heat release of the cement slurry to prevent the dissociation of natural gas hydrates, which may cause submarine landslides, formation collapse, etc., posing a great threat to the safe production of oil and gas wells. The early strength of conventional cement slurry develops slowly or even stops hydrating in a low-temperature environment, which not only increases the cost of oil and gas production, but also seriously affects the cementing quality and brings great safety hazards. Therefore, the development of a low-temperature cementing early-strength low-heat cement slurry system suitable for deep water and ultra-deep water areas to improve the early strength of the cement stone to meet the requirements of cementing in unconventional areas is of great significance to the further safe and efficient development of oil and gas resources.

[0003] To improve the early strength of cement at low temperature, the most common means is to introduce early-strength coagulation accelerator into the cement slurry system to accelerate the cement hydration reaction. However, there are many types of early-strength coagulation accelerators, and they have problems such as dosage sensitivity, easy to cause poor performance of the cement slurry, limited coagulation effect, etc. In addition, although the early-strength coagulation accelerator can improve the early strength of the cement stone to some extent, it also brings high cement hydration heat release, which causes poor stability of natural gas hydrates, and thus causes dissociation, releases a large amount of methane gas, and causes safety accidents. Therefore, it is limited in actual application. To reduce the cement hydration heat release, auxiliary cementitious materials such as fly ash and slag are usually introduced into the cement slurry system, but this will cause a serious shortage of early strength development of the cement stone.

[0004] In order to reduce the negative impact on the strength of the cement stone and control the cement hydration heat, the researchers at home and abroad introduce the phase change material into the cement paste system, and good effect of controlling the cement hydration heat is obtained. But its application temperature range is high, generally about 15 ℃, and the effect is not clear at lower temperature, and the phase change materials used are all paraffin, alcohol and fatty acid organic phase change materials, which have the problems of poor compatibility with cement paste, easy to cause mechanical property decline and the like. If the microcapsule coating method is used to solve the above problems, the type of microcapsule shell material, the possible core material leakage and the relatively high cost still limit its development to some extent. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a heat control accelerator for natural gas hydrate layer cementing, which uses modified inorganic hydrated salt phase change material as a heat control agent and modified silica aerogel material as a carrier. The process is simple, raw materials are easy to obtain, the synthesis process is controllable, the prepared heat control accelerator has good compatibility with cement paste, and the structure is stable and the phase change temperature is low. It is used in deep water and ultra-deep water natural gas hydrate layer cementing cement system, which can improve the early strength of cement and control the hydration heat. The current organic phase change material has the problems of poor environmental friendliness, high price and affecting the mechanical properties of cement matrix after leakage, and has a wide market application prospect.

[0006] In order to achieve the above technical purposes, the following technical solutions are adopted.

[0007] A preparation method of a heat control accelerator for natural gas hydrate layer cementing, comprising the following steps in sequence:

[0008] (1) dispersing or dissolving 0.1-0.8 parts by mass of a skeleton support material in 30-50 parts by mass of deionized water to form a uniform and stable solution;

[0009] (2) adding 5-10 parts by mass of a silicon source precursor to the solution of step (1) and continuously stirring under a certain speed;

[0010] (3) adding 0.1-1 mol / L of an acid solution drop by drop to the solution of step (2) to adjust the pH value of the solution to 4-6, and reacting the reaction system at 40-60 ℃ for 8-12 h to form a uniform sol;

[0011] (4) placing 6-10 parts by mass of an inorganic hydrated salt in a beaker, heating to above the phase change temperature of the inorganic hydrated salt and keeping the temperature constant, and continuously stirring under a certain speed to completely melt the hydrated salt into a hydrated salt solution;

[0012] (5) adding 0.2-0.4 parts by mass of a thermal conductivity enhancer, 2.5-5.2 parts by mass of a melting point modifier, 0.2-0.6 parts by mass of a thickening agent, and 0.1-0.3 parts by mass of a nucleating agent to the hydrated salt solution of step (4) and allowing them to be sufficiently dispersed to form a uniform mixed solution;

[0013] (6) pouring the sol of step (3) into the mixed solution of step (5), stirring for a certain time, and pouring the mixed solution into a petri dish to form a gel after 48 h at room temperature;

[0014] (7) freeze-drying the gel of step (6) to obtain a heat control accelerator for well cementing.

[0015] The backbone support material in step (1) is one or a combination of cellulose, chitosan, pectin, sodium alginate, and galactomannan.

[0016] The silicon source precursor in step (2) is one or a combination of tetraethyl orthosilicate, tetramethoxysilane, methyltrimethoxysilane, and trialkoxysilane.

[0017] The acid in step (3) is one or a combination of oxalic acid, hydrochloric acid, sulfuric acid, hydrobromic acid, nitric acid, and acetic acid.

[0018] The inorganic hydrated salt in step (4) is one or a combination of zinc chloride trihydrate, potassium phosphate dibasic hexahydrate, potassium fluoride tetrahydrate, manganese nitrate hexahydrate, calcium chloride hexahydrate, lithium nitrate trihydrate, sodium sulfate decahydrate, sodium carbonate decahydrate, calcium bromide hexahydrate, zinc nitrate hexahydrate, sodium phosphate dibasic dodecahydrate, calcium nitrate tetrahydrate, sodium thiosulfate pentahydrate, sodium acetate trihydrate, iron nitrate hexahydrate, barium hydroxide octahydrate.

[0019] The thermal conductivity enhancer in step (5) is one or a combination of graphite powder, graphene, graphene oxide, carbon fiber, silicon carbide, copper powder, and aluminum powder.

[0020] The melting point modifier in step (5) is one or a combination of sodium chloride, potassium chloride, ammonium chloride, magnesium chloride, lithium nitrate, ammonium nitrate, aluminum nitrate, and sodium acetate.

[0021] The thickening agent in step (5) is one or a combination of sodium carboxymethylcellulose, superabsorbent resin, sodium dodecylbenzenesulfonate, gelatin, bentonite, polyacrylamide, hydrophilic fumed nanosilica, and polyvinyl alcohol.

[0022] The nucleating agent in step (5) is one or a combination of sodium hexametaphosphate and borax.

[0023] The heat control accelerator uses modified inorganic hydrated salt phase change material as heat control agent and modified silica aerogel as carrier to reversibly absorb and release cement hydration heat. By adding heat conduction enhancer to the hydrated salt, the thermal conductivity of the hydrated salt phase change material can be increased, so that it can more efficiently absorb the heat released by cement hydration. The addition of melting point modifier can adjust the phase change temperature of the phase change material, so that the phase change material is more suitable for cementing operations under different working conditions to control the release of cement hydration heat to the outside. Considering the inherent defects of hydrated salt phase change material, such as supercooling and phase separation, which can cause failure during storage and transportation, nucleating agent is added to the phase change material. The nucleating agent can provide nucleation sites for the crystallization of hydrated salt, so that the hydrated salt can crystallize smoothly during solidification to avoid supercooling. The addition of thickening agent to the hydrated salt phase change material can increase the liquid viscosity of the solution, so that the anhydrous salt and nucleating agent are uniformly distributed in the solution system, preventing the nucleating agent and crystallized hydrated salt in the hydrated salt system from sinking to the bottom due to density difference, resulting in water and hydrated salt layering.

[0024] Pure silica aerogel is a silica gel with a three-dimensional network structure formed by sol-gel method. It is a porous solid material with complete gel pore structure by special drying process, but it is brittle due to weak connection between silica secondary particles, making it difficult to maintain its porous structure during use. By using natural polymers to modify and enhance pure silica aerogel, it can maintain its complete micro-nano pore structure, thereby confining hydrated salt particles. The modification and enhancement mechanism is that the silicon source precursor hydrolyzes to silicic acid under acidic conditions, and forms silica secondary particles through dehydration condensation of hydroxyl groups. However, there are a large number of hydroxyl groups on the surface, some of which can interact with the hydroxyl groups in the natural polymer, while the remaining part continues to dehydrate and condense, forming a gel with a stable three-dimensional spatial network structure. After freeze-drying, it can retain its internal micro-nano pores.

[0025] Since the loaded material is a phase change material, it can store and release heat by changing its physical state when the external temperature changes. When the cement hydration releases heat, the modified inorganic hydrated salt phase change material in the heat control accelerator will undergo phase transition to absorb the excess hydration heat and store the heat. When the cement hydration reaches a certain degree, the heat stored in the modified inorganic hydrated salt material is released to the outside environment, improving the local environmental temperature, promoting the cement hydration, and increasing the early strength. In addition, the modified silica aerogel as the carrier of the heat control accelerator has high reactivity, which can provide nucleation sites for cement hydration products and participate in the hydration reaction of cement. When the modified silica aerogel is consumed by participating in the hydration reaction, the modified inorganic hydrated salt material is released into the cement slurry, which can promote the hydration of cement again. The heat control accelerator can not only improve the early strength of the cement stone, but also effectively control the cement hydration heat release, which is especially suitable for meeting the requirements of deep water, ultra-deep water natural gas hydrate layer cementing.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] (1) The heat control accelerator has good compatibility with the cement slurry and has wide applicability;

[0028] (2) The heat control accelerator has high chemical stability, is resistant to acid and alkali corrosion, is easy to store and transport;

[0029] (3) The heat control accelerator has wide raw material sources, is environment-friendly, has low cost, and has the advantages of cost reduction and efficiency increase;

[0030] (4) The synthesis method of the heat control accelerator is simple, and the requirements for synthesis equipment and environment are low, so that large-scale production can be realized.

[0031] The modified silica aerogel is used as the carrier in the present application, which has good compatibility with the cement system, and its porous structure provides a large number of nucleation sites for the cement hydration products. The heat control agent uses modified inorganic hydrated salt phase change material, which has the advantages of effectively controlling the cement hydration heat release, being environment-friendly, and being low in price. In addition, the modified silica aerogel can realize the slow release of inorganic salts due to its porous structure, which can promote the hydration of cement and the self-repairing of micro-cracks in the later stage.

[0032] The application of the heat control accelerator in the deep water, ultra-deep water natural gas hydrate layer cementing cement slurry makes the cement obtain higher early strength at low temperature, reduces the hydration heat emission to the outside environment, and has certain self-repairing effect. The present application overcomes the problems of the traditional accelerator or heat control agent that can only play a single effect, and the core material leakage in other heat control materials that can cause the mechanical property degradation of the cement stone and environmental pollution. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1Fourier transform infrared spectrum of the heat-controlled coagulant prepared in Example 1.

[0034] Figure 2 Differential scanning calorimetry curve of the heat-controlled coagulant prepared in Example 1.

[0035] Figure 3 The image shows the heat control effect of the heat-controlling accelerator prepared in Example 1.

[0036] Figure 4 The image shows the coagulation effect of the heat-controlled coagulating agent prepared in Example 1.

[0037] Figure 5 The compressive strength curve of the heat-controlled accelerator prepared in Example 1. Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments to enable those skilled in the art to understand the invention. However, it should be understood that the present invention is not limited to the specific embodiments described herein. For those skilled in the art, any variations that fall within the spirit and scope of the invention as defined and determined by the appended claims are all within the scope of protection.

[0039] I. Preparation of heat-controlled coagulating agents Example 1

[0040] A method for preparing a heat-controlled accelerator for cementing natural gas hydrate formations, specifically including the following steps:

[0041] Dissolve 0.2 parts by mass of sodium alginate in 30 parts by mass of deionized water to form a homogeneous and stable solution. Add 5 parts by mass of tetraethyl orthosilicate and continuously stir magnetically at 100 r / min. Then, add 0.1 mol / L oxalic acid solution dropwise to adjust the pH of the solution to 4. React the system at 40 °C for 10 h to form a homogeneous sol. To prepare the inorganic hydrated salt solution, place 6 parts by mass of sodium sulfate decahydrate in a beaker, heat to above the inorganic hydrated salt phase transition temperature and maintain a constant temperature. Stir magnetically at 100 r / min until the hydrated salt is completely melted. Add 0.2 parts by mass of 10000 mesh graphite powder, 2.5 parts by mass of sodium chloride, 0.2 parts by mass of sodium carboxymethyl cellulose, and 0.2 parts by mass of sodium hexametaphosphate to the molten hydrated salt solution and disperse thoroughly to form a homogeneous mixed solution. The prepared sol was poured into a mixed solution of inorganic hydrated salts and stirred for 30 min. The mixed solution was then poured into a petri dish and placed at room temperature for 48 h to form a gel. Finally, the gel was placed in the cold trap of a freeze dryer and freeze-dried for 12 h to obtain a heat-controlled coagulant for cementing natural gas hydrate layers. Example 2

[0042] A method for preparing a heat-controlled accelerator for cementing natural gas hydrate formations, specifically including the following steps:

[0043] 0.3 parts by mass of galactomannan were dissolved in 30 parts by mass of deionized water to form a homogeneous and stable solution. 8 parts by mass of tetramethoxysilane were added, and the solution was continuously stirred magnetically at 200 r / min. Subsequently, 0.1 mol / L hydrochloric acid solution was added dropwise to adjust the pH to 4. The reaction system was then reacted at 50 °C for 8 h to form a homogeneous sol. To prepare the inorganic hydrated salt solution, 8 parts by mass of calcium chloride hexahydrate were placed in a beaker, heated to above the inorganic hydrated salt phase transition temperature, and maintained at a constant temperature. The hydrated salt was completely melted under magnetic stirring at 200 r / min. 0.4 parts by mass of 10000 mesh graphite powder, 2.5 parts by mass of ammonium chloride, 0.2 parts by mass of sodium carboxymethyl cellulose, and 0.3 parts by mass of borax were added to the molten hydrated salt solution and dispersed thoroughly to form a homogeneous mixed solution. The prepared sol was poured into a mixed solution of inorganic hydrated salts and stirred for 30 min. The mixed solution was then poured into a petri dish and placed at room temperature for 48 h to form a gel. Finally, the gel was placed in the cold trap of a freeze dryer and freeze-dried for 15 h to obtain a heat-controlled coagulant for cementing natural gas hydrate layers. Example 3

[0044] A method for preparing a heat-controlled accelerator for cementing natural gas hydrate formations, specifically including the following steps:

[0045] 0.4 parts by mass of cellulose were dispersed in 50 parts by mass of deionized water to form a homogeneous and stable solution. 8 parts by mass of methyltrimethoxysilane were added, and the solution was continuously stirred magnetically at 100 r / min. Subsequently, a 1 mol / L acetic acid solution was added dropwise to adjust the pH to 5. The reaction system was then reacted at 60 °C for 12 h to form a homogeneous sol. To prepare an inorganic hydrated salt solution, 8 parts by mass of sodium carbonate decahydrate were placed in a beaker, heated to above the inorganic hydrated salt phase transition temperature, and maintained at a constant temperature. The hydrated salt was completely melted under magnetic stirring at 100 r / min. 0.2 parts by mass of graphene, 4 parts by mass of aluminum nitrate, 0.2 parts by mass of bentonite, 0.1 parts by mass of sodium hexametaphosphate, and 0.2 parts by mass of borax were added to the molten hydrated salt solution and dispersed thoroughly to form a homogeneous mixed solution. The prepared sol was poured into a mixed solution of inorganic hydrated salts and stirred for 30 min. The mixed solution was then poured into a petri dish and placed at room temperature for 48 h to form a gel. Finally, the gel was placed in the cold trap of a freeze dryer and freeze-dried for 12 h to obtain a heat-controlled coagulant for cementing natural gas hydrate layers. Example 4

[0046] A method for preparing a heat-controlled accelerator for cementing natural gas hydrate formations, specifically including the following steps:

[0047] Dissolve 0.6 parts by mass of sodium alginate in 50 parts by mass of deionized water to form a homogeneous and stable solution. Add 6 parts by mass of trialkoxysilane and continuously stir magnetically at 120 r / min. Then, add 0.1 mol / L nitric acid solution dropwise to adjust the pH of the solution to 5. React the system at 50 °C for 10 h to form a homogeneous sol. To prepare the inorganic hydrated salt solution, place 8 parts by mass of sodium sulfate decahydrate in a beaker, heat to above the inorganic hydrated salt phase transition temperature and maintain a constant temperature. Stir magnetically at 120 r / min until the hydrated salt is completely melted. Add 0.4 parts by mass of copper powder, 3 parts by mass of potassium chloride, 0.4 parts by mass of sodium carboxymethyl cellulose, and 0.2 parts by mass of sodium hexametaphosphate to the molten hydrated salt solution and disperse thoroughly to form a homogeneous mixed solution. The prepared sol was poured into a mixed solution of inorganic hydrated salts and stirred for 30 min. The mixed solution was then poured into a petri dish and placed at room temperature for 48 h to form a gel. Finally, the gel was placed in the cold trap of a freeze dryer and freeze-dried for 12 h to obtain a heat-controlled coagulant for cementing natural gas hydrate layers. Example 5

[0048] A method for preparing a heat-controlled accelerator for cementing natural gas hydrate formations, specifically including the following steps:

[0049] 0.2 parts by mass of pectin were dispersed in 40 parts by mass of deionized water to form a homogeneous and stable solution. 5 parts by mass of tetraethyl orthosilicate and 5 parts by mass of trialkoxysilane were added, and the mixture was continuously stirred magnetically at 150 r / min. Subsequently, 0.6 mol / L hydrobromic acid solution was added dropwise to adjust the pH of the solution to 6. The reaction system was then reacted at 60 °C for 12 h to form a homogeneous sol. To prepare the inorganic hydrated salt solution, 10 parts by mass of calcium nitrate tetrahydrate were placed in a beaker, heated to above the inorganic hydrated salt phase transition temperature, and maintained at a constant temperature. The hydrated salt was completely melted under magnetic stirring at 150 r / min. 0.3 parts by mass of carbon fiber, 3 parts by mass of ammonium chloride, 0.2 parts by mass of gelatin, and 0.1 parts by mass of borax were added to the molten hydrated salt solution and thoroughly dispersed to form a homogeneous mixed solution. The prepared sol was poured into a mixed solution of inorganic hydrated salts and stirred for 50 min. The mixed solution was then poured into a petri dish and placed at room temperature for 48 h to form a gel. Finally, the gel was placed in the cold trap of a freeze dryer and freeze-dried for 18 h to obtain a heat-controlled coagulant for cementing natural gas hydrate layers.

[0050] Figure 1 The infrared spectra of sodium sulfate decahydrate, silica, and a heat-regulating accelerator are shown. Observing the characteristic peak of sodium sulfate decahydrate, it can be seen that it is at 1110 cm⁻¹. -1 1351 cm -1 SO4 2- The characteristic peak is at 618 cm⁻¹. -1 The location is Na + The characteristic peak, while at 3450 cm⁻¹ -1 The relatively broad characteristic peak at 1110 cm⁻¹ corresponds to -OH. The infrared spectrum of silicon dioxide shows a peak at 1110 cm⁻¹. -1 and 797 cm -1 The location corresponding to Si-O-Si is at 471 cm. -1 The peak at this location is a typical characteristic peak of Si-O. Comparative analysis of the characteristic peaks of the heat-controlled coagulant shows that it contains characteristic peaks of silica and sodium sulfate decahydrate, and no new characteristic peaks appear.

[0051] Figure 2 Differential scanning calorimetry (DSC) curves of the heat-controlled accelerator prepared in Example 1 are shown below. Figure 2 It is known that the phase change temperature range of the heat-controlled setting accelerator is 1.0~31.2 ℃, with a median phase change temperature of 16.5 ℃ and a latent heat of phase change of 454.59 J / g. Therefore, it can be concluded that the heat-controlled setting accelerator is sensitive to changes in external temperature, has a wide phase change temperature range, can absorb a large amount of heat, and is suitable for cementing systems in deep-water and ultra-deep-water natural gas hydrate formations.

[0052] Figure 3 The hydration temperature rise curves of Grade G oil well cement and Grade G oil well cement with added heat-controlled accelerator were tested at 4 ℃. Figure 3 It can be seen that the hydration temperature rise of G-grade oil well cement is as high as 26.8 ℃. After adding heat-controlling and setting-accelerating agent, the peak hydration temperature rise of cement is reduced to 23.5 ℃, but the maximum hydration temperature rise peak appears earlier.

[0053] Figure 4 The cumulative exothermic curves of Grade G oil well cement and Grade G oil well cement with added heat-controlling accelerator were obtained after testing at 4 ℃ for 72 hours. Figure 4 It can be seen that the heat-controlled accelerator accelerated the cumulative heat release of cement hydration within 36 hours, but reduced the total cumulative heat release. The cumulative heat release rate of hydration at 72 hours was 79.03 J / g, which was 23.36% lower than that of G-grade oil well cement.

[0054] Figure 5 The compressive strength of Grade G oil well cement and Grade G oil well cement stone mixed with heat-controlling and setting accelerator, cured at 4 ℃ for 24 h, 48 h and 72 h, was determined by... Figure 5It can be seen that when cured for 24 hours, the compressive strength of both groups of cement stone is 0 MPa. However, during the experiment, it was found that the cement stone mixed with heat-controlled accelerator had already formed and was relatively hard. When cured for 48 hours and 72 hours, the cement stone had strength, and the compressive strength of the cement stone mixed with heat-controlled accelerator was higher than that of the G-grade oil well cement stone.

Claims

1. A method for preparing a heat-controlled accelerator for cementing natural gas hydrate formations, comprising the following steps: (1) Disperse or dissolve 0.1-0.8 parts by weight of the skeleton support material in 30-50 parts by weight of deionized water to make it a homogeneous and stable solution. The skeleton support material is one or more of cellulose, pectin, sodium alginate and galactomannan. (2) Add 5-10 parts by mass of silicon source precursor to the solution in step (1) and stir continuously at a certain speed; (3) Add 0.1~1 mol / L acid solution dropwise to the solution in step (2), adjust the pH value of the solution to 4~6, and react the reaction system at 40~60 ℃ for 8~12 h to form a uniform sol; (4) Place 6-10 parts by mass of inorganic hydrated salt in a beaker, heat it to above the phase transition temperature of inorganic hydrated salt and keep the temperature constant so that the hydrated salt is completely melted and becomes a hydrated salt solution. (5) Add 0.2-0.4 parts by weight of thermal conductivity enhancer, 2.5-5.2 parts by weight of melting point modifier, 0.2-0.6 parts by weight of thickener and 0.1-0.3 parts by weight of nucleating agent to the hydrated salt solution in step (4), and disperse them fully to form a uniform mixed solution; the thermal conductivity enhancer is one or more of graphite powder, graphene, graphene oxide, carbon fiber, silicon carbide, copper powder and aluminum powder; the melting point modifier is one or more of sodium chloride, potassium chloride, ammonium chloride, magnesium chloride, lithium nitrate, ammonium nitrate, aluminum nitrate and sodium acetate; the nucleating agent is one or more of sodium hexametaphosphate and borax. (6) Pour the sol from step (3) into the mixed solution from step (5), stir, pour into a petri dish, and form a gel after 48 h at room temperature; (7) Freeze-dry the gel in step (6) to obtain a heat-controlled coagulating agent for cementing.

2. The preparation method of a heat-controlled accelerator for cementing natural gas hydrate formations as described in claim 1, characterized in that, The silicon source precursor in step (2) is one or more of tetraethyl orthosilicate, tetramethoxysilane, methyltrimethoxysilane, and trialkoxysilane.

3. The preparation method of a heat-controlled accelerator for cementing natural gas hydrate formations as described in claim 1, characterized in that, The acid in step (3) is one or a combination of oxalic acid, hydrochloric acid, sulfuric acid, hydrobromic acid, nitric acid, and acetic acid.

4. The preparation method of a heat-controlled accelerator for cementing natural gas hydrate formations as described in claim 1, characterized in that, The inorganic hydrated salt in step (4) is one or a combination of zinc chloride trihydrate, potassium hydrogen phosphate hexahydrate, potassium fluoride tetrahydrate, manganese nitrate hexahydrate, calcium chloride hexahydrate, lithium nitrate trihydrate, sodium sulfate decahydrate, sodium carbonate decahydrate, calcium bromide hexahydrate, zinc nitrate hexahydrate, sodium hydrogen phosphate dodecahydrate, calcium nitrate tetrahydrate, sodium thiosulfate pentahydrate, sodium acetate trihydrate, ferric nitrate hexahydrate, and barium hydroxide octahydrate.

5. The preparation method of a heat-controlled accelerator for cementing natural gas hydrate formations as described in claim 1, characterized in that, The thickener in step (5) is one or a combination of sodium carboxymethyl cellulose, superabsorbent resin, sodium dodecylbenzene sulfonate, gelatin, bentonite, polyacrylamide, hydrophilic fumed silica, and polyvinyl alcohol.

6. Using the heat-controlling and setting accelerator prepared by the method according to claim 1, 2, 3, 4 or 5, and applying it to the cementing system of deep-water and ultra-deep-water natural gas hydrate formations to improve the early strength of cement and control the heat release of hydration.

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