A method for quickly and stably controlling wellbore pressure in hydrate formation drilling in sea area

Abstract

This invention relates to a method for rapid and stable wellbore pressure control in marine hydrate formation drilling, belonging to the field of marine natural gas hydrate formation drilling. The method includes: calculating the volume of activated carbon glass microspheres to be added to the drilling fluid; injecting the drilling fluid with added activated carbon glass microspheres into the riser; when hydrate-bearing rock cuttings decompose and produce methane gas, the activated carbon glass microspheres adsorb the generated methane gas in real time, thereby maintaining stable bottom hole pressure; separating the gas-adsorbed activated carbon glass microspheres after the drilling fluid reaches the drilling platform; desorbing the separated activated carbon glass microspheres through a desorption device, filtering them through a filter device B, and then heating them; and adding the purified activated carbon glass microspheres back to the drilling fluid in the mud pit for reuse. This invention can quickly and effectively solve the problem of sudden overflows or well kicks caused by the decomposition of hydrate-bearing rock cuttings, which is beneficial for safe and efficient drilling in marine natural gas hydrate formations.

Description

Technical Field

[0001] This invention relates to a method for rapid and stable control of wellbore pressure in marine hydrate formations, belonging to the field of marine natural gas hydrate formation drilling technology. Background Technology

[0002] Natural gas hydrates are a new type of clean energy source, attracting widespread attention and continuous research from scholars in many countries due to their vast reserves and clean, efficient operation. Because of their phase equilibrium characteristics, natural gas hydrates are widely distributed in seafloor slope sediments and terrestrial permafrost, with the richest reserves found in marine areas. Multiple trial productions in China and Japan have demonstrated the feasibility of marine natural gas hydrate extraction. Currently, the main extraction methods for natural gas hydrates include depressurization, heat injection, carbon dioxide replacement, inhibitor injection, and combinations of these methods. All existing methods require drilling to establish flow channels. Therefore, safe and efficient drilling in natural gas hydrate formations is the foundation and prerequisite for achieving efficient extraction.

[0003] During drilling in hydrated formations in the ocean, hydrate-bearing rock cuttings generated by the drill bit breaking up the hydrated reservoir are carried upwards by the drilling fluid. During this upward movement, the annular pressure gradually decreases. At a certain point in the annulus, the temperature and pressure conditions cannot maintain the hydrate phase equilibrium, and the hydrates contained in the rock cuttings begin to decompose. The annular flow changes from a liquid-solid two-phase flow to a gas-liquid-solid three-phase flow. With the continued decomposition of the hydrate-bearing rock cuttings and the gas expansion caused by the decreasing annular pressure, the annular gas content gradually increases, and the bottomhole pressure gradually decreases. When the gas migrates to the upper part of the riser section, due to the lower annular pressure, the annular gas expands rapidly, causing a significant decrease in bottomhole pressure. This can lead to complex downhole situations such as overflows or even well kicks. Because adjusting drilling fluid density to control bottom hole pressure is not real-time, it takes at least tens of minutes to complete bottom hole pressure control after a significant drop in bottom hole pressure is detected. Furthermore, overflows or well kicks caused by the decomposition of hydrate cuttings in the annulus are sudden. Before reaching the top of the riser, the annulus pressure is relatively high, and the gas is compressed, resulting in a small annular gas phase content and a small drop in bottom hole pressure that is difficult to detect. Once the gas reaches the top of the riser, the annular gas expands rapidly, causing a significant drop in bottom hole pressure. This poses a great challenge to the safe control of wellbore pressure in marine hydrate formations. Currently, there is a lack of a rapid and stable wellbore pressure control method for marine hydrate formations, which is also a key technical difficulty restricting the safe and efficient drilling of marine natural gas hydrate formations. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for rapid and stable control of wellbore pressure in marine hydrate formations. This method can quickly and effectively solve the problem of sudden overflows or well kicks caused by the decomposition of hydrate-bearing rock cuttings, and is beneficial for safe and efficient drilling in marine natural gas hydrate formations.

[0005] Terminology Explanation:

[0006] Hydrate-bearing rock fragments: Rock fragments containing solid hydrates.

[0007] The present invention adopts the following technical solution:

[0008] A method for rapid and stable control of wellbore pressure in marine hydrate formations includes the following steps:

[0009] (1) Calculate the amount of gas generated by the decomposition of hydrate cuttings in the riser section based on the target reservoir hydrate saturation, mechanical drilling rate and cuttings return rate, and then calculate the volume of activated carbon glass microspheres to be added to the drilling fluid based on the amount of gas.

[0010] (2) The drilling fluid with added activated carbon glass microspheres is injected into the riser from the bottom of the riser using a booster line. When the hydrated rock cuttings decompose to produce methane and other gases, the activated carbon glass microspheres will adsorb the methane gas produced in real time, thereby maintaining the bottom pressure stability.

[0011] The booster pipeline is attached to the riser and distributed on both sides as a drilling auxiliary pipeline. Its upper end connects to the mud pit of the drilling platform, and its lower end connects to the injection port at the bottom of the riser. The drilling fluid flows from the mud pit through the surface pipeline and water hose to the swivel. The upper end of the drill pipe is connected to the swivel, and the lower end is connected to the drill bit. The upper end of the riser is connected to the wellhead of the drilling platform, and the lower end is connected to the mudline. The annulus between the riser and the drill pipe is called the riser annulus. The outer side of the surface casing below the mudline is the cement sheath, and the inner side is the drill pipe. The annulus between the drill pipe and the surface casing is called the casing annulus. The filter device A, sedimentation device, desorption device, filter device B, heating device, and mud pit are connected in sequence to represent the process of activated carbon glass microsphere purification and reuse.

[0012] (3) When the drilling fluid reaches the drilling platform, the activated carbon glass microspheres that adsorb the gas are separated by the filter device A and the sedimentation device.

[0013] (4) The separated activated carbon glass microspheres are desorbed by a desorption device containing carbon tetrachloride solution (desorption can be completed by directly entering the carbon tetrachloride solution desorption device. Since carbon tetrachloride has a high solubility for methane, the methane adsorbed on the activated carbon glass microspheres can be desorbed by taking advantage of the difference in solubility). After desorption, the activated carbon glass microspheres are filtered out by filter device B and then heated in a heating device to remove residual carbon tetrachloride.

[0014] (5) The purified activated carbon glass microspheres are added to the drilling fluid in the mud pit for reuse. During the repeated process, the number of activated carbon glass microspheres will be reduced. If the number is reduced, new activated carbon glass microspheres are added to the mud pit to make the total volume reach the volume calculated in step (1). Repeat steps (1) to (4).

[0015] Preferably, in step (1), the amount of gas (standard volume) generated by the decomposition of hydrate rock fragments in the water-proof pipe section is:

[0016]

[0017] Among them, V g The standard volume of gas produced by the decomposition of hydrate rock fragments in the riser section, in m. 3 ROP stands for mechanical drilling rate, in m / h; r w φ is the wellbore radius, in meters; φ is the porosity, dimensionless; s h v represents the target reservoir hydrate saturation, dimensionless; s H represents the velocity of rock cuttings transported in the annulus, in m / s. d The total length of the annular hydrate rock fragment decomposition section is in meters.

[0018] The volume of the activated carbon glass microspheres is:

[0019]

[0020] Among them, V t The volume of activated carbon glass microspheres added to the drilling fluid is m 3 ;ρ g The density of the gas under standard conditions is kg / m³. 3 S represents the equilibrium retention amount of activated carbon, taken as 30%, dimensionless; ρ c Density of activated carbon, kg / m³ 3 V c The volume of activated carbon attached to a single glass microsphere is m. 3 V b For the volume of a single glass microsphere, m 3 ;

[0021]

[0022] r t The radius of the glass microspheres after activated carbon is attached is m; r i denoted as the radius of the glass microspheres without activated carbon, in meters.

[0023] Preferably, the preparation method of activated carbon glass microspheres in step (1) is as follows:

[0024] ① Immersion Treatment: Hollow glass microspheres (radius 2 mm, wall thickness 0.25 mm) are immersed in an aqueous solution of polyacrylamide containing activated carbon powder (particle size 10–50 μm). The mass percentage of activated carbon in the polyacrylamide aqueous solution is 3.0–12.0 wt%, which is usually 3–5 times the amount of activated carbon powder adsorbed on the surface of the glass microspheres, depending on the number of porous glass microspheres prepared. The concentration of polyacrylamide is usually between 0.5–1.5 wt%. To improve the adhesion sites of activated carbon, 0.5–0.8 mol / L nitric acid is usually added to the polyacrylamide aqueous solution, and the immersion time is 10–12 h. Activated carbon particles possess a certain porous structure and surface functional groups (hydroxyl, carboxyl, etc.). During the soaking process, polyacrylamide can chemically react with the functional groups on the activated carbon surface, thereby forming a chemically cross-linked structure and improving the bonding force between the coating and the glass microspheres. Nitric acid can react with the surface functional groups (hydroxyl, carboxyl, etc.) in the activated carbon powder to form nitrates. After soaking, the nitrates are transformed into substances rich in oxygen atoms and carbon skeleton structures, thus forming a stable coating. Simultaneously, due to their high oxygen atom content, they can serve as active sites, enhancing the coating's adsorption capacity for gases such as methane. (The initial density of the hollow glass microspheres is 0.82 g / cm³.) 3 After soaking treatment, the concentration was 1.03–1.08 g / cm³. 3 );

[0025] ②Sintering treatment: After soaking, an activated carbon coating is initially formed on the surface of the glass microspheres, and polyacrylamide is also attached to the surface. The soaked glass microspheres are sintered in air. The polyacrylamide is sintered at a high temperature of 180-220℃ for 1-2 hours. During sintering, its molecules will break and rearrange to form a porous structure. This porous structure can effectively increase the adsorption force between the activated carbon coating and the glass microspheres.

[0026] ③ Activated carbonization treatment: The sintered glass microspheres are placed again at a high temperature of 180-220℃ for 1-2 hours for activated carbonization treatment, which can further expand the pores, form a firm activated carbon coating on the surface of the glass microspheres and form more active sites.

[0027] ④ Washing and drying: Finally, the glass microspheres with activated carbon coating are washed and dried.

[0028] Preferably, in step (2), the booster pipeline is an auxiliary pipeline of the riser. When drilling in hydrate formations, drilling fluid is injected from the bottom of the riser into the annulus through the booster pipeline to increase the rock-carrying efficiency of the drilling fluid in the annulus of the riser section.

[0029] Preferably, in step (3), after the drilling fluid containing activated carbon glass microspheres enters the filtration device A on the platform, the liquid phase of the drilling fluid is first separated from the solid phase of the activated carbon glass microspheres and rock cuttings through filtration. The separated solid phase, namely the activated carbon glass microspheres and rock cuttings, enters the settling device, where the density is 1.30 g / cm³. 3 A salt solution was used to separate the rock fragments by utilizing the density difference between activated carbon glass microspheres and rock debris. The density of the activated carbon glass microspheres was approximately 1.05 g / cm³. 3 The density of the rock fragments is approximately 2.50 g / cm³. 3 Due to the density difference, the activated carbon glass microspheres are suspended in the brine solution after entering the sedimentation device, while the rock debris settles at the bottom. After sedimentation and separation, the activated carbon glass microspheres are washed and dried.

[0030] Preferably, in step (4), the heating temperature of the heating device is 80-90°C. Since the boiling point of carbon tetrachloride is 76-77°C, the carbon tetrachloride remaining on the surface of the activated carbon glass microspheres can be removed by the heating device.

[0031] For any details not covered in this invention, please refer to the prior art.

[0032] The beneficial effects of this invention are as follows:

[0033] (1) The method of the present invention can quickly achieve stable control of wellbore pressure within minutes, and the absorption of gas in the annulus of the diaphragm by activated carbon glass microspheres is a smooth and continuous process, and the bottom pressure changes smoothly with a small amplitude.

[0034] (2) The preparation process of activated carbon glass microspheres is relatively simple and has low cost, and can be recycled;

[0035] (3) The density of activated carbon glass microspheres is consistent with that of drilling fluid and does not react with the components of drilling fluid. Therefore, its addition does not affect the density and performance of the drilling fluid system. Attached Figure Description

[0036] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.

[0037] Figure 1 A schematic diagram of a method for rapid and stable control of wellbore pressure in marine hydrate formations;

[0038] In the diagram, 1-pressurization pipeline, 2-injection location of glass microspheres containing activated carbon, 3-filtration device A, 4-sedimentation device, 5-desorption device, 6-filtration device B, 7-heating device, 8-mud tank, 9-water riser, 10-drill rod, 11-drill bit, 12-water riser annulus, 13-cement ring, 14-casing. Detailed Implementation

[0039] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. However, this is not the only description; all aspects not described in detail herein are based on conventional techniques in the art.

[0040] Example 1

[0041] A method for rapid and stable control of wellbore pressure in marine hydrate formations includes the following steps:

[0042] (1) Calculate the amount of gas generated by the decomposition of hydrate cuttings in the riser section based on the target reservoir hydrate saturation, mechanical drilling rate and cuttings return rate, and then calculate the volume of activated carbon glass microspheres to be added to the drilling fluid based on the amount of gas.

[0043] (2) The drilling fluid with added activated carbon glass microspheres is injected into the riser from the bottom of the riser using the booster line 1. When the hydrated rock cuttings decompose to produce methane and other gases, the activated carbon glass microspheres will adsorb the methane gas produced in real time, thereby maintaining the bottom pressure of the well.

[0044] like Figure 1 As shown, the booster line 1 is attached to the riser 9 and distributed on both sides as a drilling auxiliary line. Its upper end is connected to the mud pit 8 of the drilling platform, and its lower end is connected to the bottom injection port of the riser (i.e., position 2 in the figure, which contains the injection position of activated carbon glass microspheres). The drilling fluid comes from the mud pit 8 through the surface pipeline and water hose to the faucet. The upper end of the drill pipe 10 is connected to the faucet, and the lower end is connected to the drill bit 11. The upper end of the riser 9 is connected to the wellhead of the drilling platform, and the lower end is connected to the mud line. The annulus between the riser and the drill pipe is the riser annulus 12. The outer side of the surface casing below the mud line is the cement sheath 13, and the inner side is the drill pipe 10. The annulus between the drill pipe and the surface casing 14 is the casing annulus. The filter device A3, sedimentation device 4, desorption device 5, filter device B6, heating device 7, and mud pit 8 are connected in sequence to represent the process of activated carbon glass microsphere purification and reuse.

[0045] (3) When the drilling fluid reaches the drilling platform, the activated carbon glass microspheres that adsorb the gas are separated by the filter device A3 and the sedimentation device 4.

[0046] (4) The separated activated carbon glass microspheres are desorbed by the adsorbed methane through the desorption device 5 containing carbon tetrachloride solution (desorption can be completed by directly entering the carbon tetrachloride solution desorption device. Since carbon tetrachloride has a high solubility for methane, the methane adsorbed on the activated carbon glass microspheres can be desorbed by taking advantage of the difference in solubility). After desorption, the activated carbon glass microspheres are filtered out by the filter device B 6 and heated in the heating device 7 to remove the residual carbon tetrachloride.

[0047] (5) The purified activated carbon glass microspheres are added to the drilling fluid in the mud pit for reuse. During the repeated process, the number of activated carbon glass microspheres will be reduced. If the number is reduced, new activated carbon glass microspheres are added to the mud pit to make the total volume reach the volume calculated in step (1). Repeat steps (1) to (4).

[0048] Example 2

[0049] A method for rapid and stable control of wellbore pressure in marine hydrate formations, as described in Example 1, except that in step (1), the amount of gas (standard volume) generated by the decomposition of hydrate cuttings in the riser section is:

[0050]

[0051] Among them, V g The standard volume of gas produced by the decomposition of hydrate rock fragments in the riser section, in m. 3 ROP stands for mechanical drilling rate, in m / h; r w φ is the wellbore radius, in meters; φ is the porosity, dimensionless; s h v represents the target reservoir hydrate saturation, dimensionless; s H represents the velocity of rock cuttings transported in the annulus, in m / s. d The total length of the annular hydrate rock fragment decomposition section is in meters.

[0052] The volume of the activated carbon glass microspheres is:

[0053]

[0054] Among them, V t The volume of activated carbon glass microspheres added to the drilling fluid is m 3 ;ρ g The density of the gas under standard conditions is kg / m³. 3 S represents the equilibrium retention amount of activated carbon, taken as 30%, dimensionless; ρ c Density of activated carbon, kg / m³ 3 V c The volume of activated carbon attached to a single glass microsphere is m. 3 V b For the volume of a single glass microsphere, m3 ;

[0055]

[0056] r t The radius of the glass microspheres after activated carbon is attached is m; r i denoted as the radius of the glass microspheres without activated carbon, in meters.

[0057] Example 3

[0058] A method for rapid and stable control of wellbore pressure in marine hydrate formations, as described in Example 2, except that the preparation method of activated carbon glass microspheres in step (1) is as follows:

[0059] ① Immersion Treatment: Hollow glass microspheres (radius 2 mm, wall thickness 0.25 mm) are immersed in an aqueous solution of polyacrylamide containing activated carbon powder (particle size 10–50 μm). The mass percentage of activated carbon in the polyacrylamide aqueous solution is 3.0–12.0 wt%, which is usually 3–5 times the amount of activated carbon powder adsorbed on the surface of the glass microspheres, depending on the number of porous glass microspheres prepared. The concentration of polyacrylamide is usually between 0.5–1.5 wt%. To improve the adhesion sites of activated carbon, 0.5–0.8 mol / L nitric acid is usually added to the polyacrylamide aqueous solution, and the immersion time is 10–12 h. Activated carbon particles possess a certain porous structure and surface functional groups (hydroxyl, carboxyl, etc.). During the soaking process, polyacrylamide can chemically react with the functional groups on the activated carbon surface, thereby forming a chemically cross-linked structure and improving the bonding force between the coating and the glass microspheres. Nitric acid can react with the surface functional groups (hydroxyl, carboxyl, etc.) in the activated carbon powder to form nitrates. After soaking, the nitrates are transformed into substances rich in oxygen atoms and carbon skeleton structures, thus forming a stable coating. Simultaneously, due to their high oxygen atom content, they can serve as active sites, enhancing the coating's adsorption capacity for gases such as methane. (The initial density of the hollow glass microspheres is 0.82 g / cm³.) 3 After soaking treatment, the concentration was 1.03–1.08 g / cm³. 3 );

[0060] ②Sintering treatment: After soaking, an activated carbon coating is initially formed on the surface of the glass microspheres, and polyacrylamide is also attached to the surface. The soaked glass microspheres are sintered in air. The polyacrylamide is sintered at a high temperature of 180-220℃ for 1-2 hours. During sintering, its molecules will break and rearrange to form a porous structure. This porous structure can effectively increase the adsorption force between the activated carbon coating and the glass microspheres.

[0061] ③ Activated carbonization treatment: The sintered glass microspheres are placed again at a high temperature of 180-220℃ for 1-2 hours for activated carbonization treatment, which can further expand the pores, form a firm activated carbon coating on the surface of the glass microspheres and form more active sites.

[0062] ④ Washing and drying: Finally, the glass microspheres with activated carbon coating are washed and dried.

[0063] Example 4

[0064] A method for rapid and stable control of wellbore pressure in marine hydrate formation drilling, as described in Example 3, except that in step (2), the booster pipeline is an auxiliary pipeline of the riser (as shown in Figure 1). When drilling in hydrate formation, drilling fluid is injected from the bottom of the riser into the annulus through the booster pipeline to increase the rock-carrying efficiency of the drilling fluid in the annulus of the riser section.

[0065] In step (3), after the drilling fluid containing activated carbon glass microspheres enters the filtration device A on the platform, the liquid phase of the drilling fluid is first separated from the solid phase of the activated carbon glass microspheres and rock cuttings through filtration. The separated solid phase, namely the activated carbon glass microspheres and rock cuttings, enters the settling device, where the density is 1.30 g / cm³. 3 A salt solution was used to separate the rock fragments by utilizing the density difference between activated carbon glass microspheres and rock debris. The density of the activated carbon glass microspheres was approximately 1.05 g / cm³. 3 The density of the rock fragments is approximately 2.50 g / cm³. 3 Due to the density difference, the activated carbon glass microspheres are suspended in the brine solution after entering the sedimentation device, while the rock debris settles at the bottom. After sedimentation and separation, the activated carbon glass microspheres are washed and dried.

[0066] In step (4), the heating temperature of the heating device is 80-90°C. Since the boiling point of carbon tetrachloride is 76-77°C, the carbon tetrachloride remaining on the surface of the activated carbon glass microspheres can be removed by the heating device.

[0067] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for rapid and stable control of wellbore pressure in marine hydrate formations, characterized in that, Includes the following steps: (1) Calculate the amount of gas generated by the decomposition of hydrate cuttings in the riser section based on the target reservoir hydrate saturation, mechanical drilling rate and cuttings return rate, and then calculate the volume of activated carbon glass microspheres to be added to the drilling fluid based on the amount of gas. (2) The drilling fluid with added activated carbon glass microspheres is injected into the riser from the bottom of the riser using a booster line. When the hydrated rock cuttings decompose and produce methane gas, the activated carbon glass microspheres will adsorb the methane gas in real time, thereby maintaining the bottom pressure. (3) When the drilling fluid reaches the drilling platform, the activated carbon glass microspheres that adsorb the gas are separated by the filter device A and the sedimentation device. (4) The separated activated carbon glass microspheres are desorbed by a desorption device containing carbon tetrachloride solution. After desorption, the activated carbon glass microspheres are filtered out by filter device B and then heated in a heating device to remove residual carbon tetrachloride. (5) The purified activated carbon glass microspheres are added to the drilling fluid in the mud pit for reuse. During the repeated process, the number of activated carbon glass microspheres will be reduced. If the number is reduced, new activated carbon glass microspheres are added to the mud pit to make the total volume reach the volume calculated in step (1). Repeat steps (1) to (4). In step (1), the amount of gas generated by the decomposition of hydrate rock fragments in the water-proof pipe section is: （1） in, The standard volume of gas produced by the decomposition of hydrate rock fragments in the riser section, in m. 3 ; ROP The drilling speed is mechanical, in m / h; Let be the wellbore radius, in meters (m). Porosity is a dimensionless quantity. The target reservoir hydrate saturation is dimensionless. ρ represents the velocity of rock cuttings in the annulus, in m / s; The total length of the annular hydrate rock fragment decomposition section is in meters. The volume of the activated carbon glass microspheres is: （2） in, m is the volume of activated carbon glass microspheres added to the drilling fluid. 3 ; The density of the gas under standard conditions is kg / m³. 3 ; The activated carbon balance maintenance amount is taken as 30%, dimensionless; Density of activated carbon, kg / m³ 3 ; The volume of activated carbon attached to a single glass microsphere is m. 3 ; For the volume of a single glass microsphere, m 3 ; （3） The radius of the glass microspheres after activated carbon is attached, in meters; denoted as the radius of the glass microspheres without activated carbon, in meters.

2. The method for rapid and stable control of wellbore pressure in marine hydrate formations according to claim 1, characterized in that, The preparation method of activated carbon glass microspheres in step (1) is as follows: ① Immersion treatment: Hollow glass microspheres are immersed in an aqueous solution of polyacrylamide containing activated carbon powder. The mass percentage of activated carbon in the polyacrylamide aqueous solution is 3.0~12.0 wt%, and the concentration of polyacrylamide is between 0.5~1.5 wt%. In order to improve the adhesion sites of activated carbon, 0.5~0.8 mol / L nitric acid is added to the polyacrylamide aqueous solution. The immersion time is 10~12 h. Activated carbon particles have a porous structure and surface functional groups. During the immersion process, polyacrylamide reacts chemically with the functional groups on the surface of activated carbon to form a chemical cross-linked structure, thereby improving the bonding force between the coating and the glass microspheres. Nitric acid reacts with the surface functional groups in activated carbon powder to form nitrates. After soaking, the nitrates are transformed into substances rich in oxygen atoms and carbon skeleton structures, thus forming a stable coating. At the same time, due to their rich oxygen atoms, they can serve as active sites, improving the coating's adsorption capacity for methane gas. ②Sintering treatment: After soaking, an activated carbon coating is initially formed on the surface of the glass microspheres, and polyacrylamide is also attached to the surface. The soaked glass microspheres are sintered in air. The polyacrylamide is sintered at a high temperature of 180~220℃ for 1~2 hours. During sintering, its molecules will break and rearrange to form a porous structure. ③ Activated carbonization treatment: The sintered glass microspheres are placed again at a high temperature of 180~220℃ for 1~2 hours to carry out activated carbonization treatment, which further expands the pores, forms a firm activated carbon coating on the surface of the glass microspheres and forms more active sites. ④ Washing and drying: Finally, the glass microspheres with activated carbon coating are washed and dried.

3. The method for rapid and stable control of wellbore pressure in marine hydrate formations according to claim 2, characterized in that, In step ①, the hollow glass microspheres have a radius of 2 mm and a wall thickness of 0.25 mm; the activated carbon powder has a particle size of 10~50 μm. The initial density of the hollow glass microspheres is 0.82 g / cm³. 3 After soaking treatment, the concentration was 1.03~1.08 g / cm³. 3 .

4. The method for rapid and stable control of wellbore pressure in marine hydrate formations according to claim 3, characterized in that, In step (3), after the drilling fluid containing activated carbon glass microspheres enters the filtration device A on the platform, the liquid phase of the drilling fluid is first separated from the solid phase of the activated carbon glass microspheres and rock cuttings through filtration. The separated solid phase, namely the activated carbon glass microspheres and rock cuttings, enters the settling device, where the density is 1.30 g / cm³. 3 The salt solution is used to separate activated carbon glass microspheres and rock fragments by utilizing the density difference. Due to the density difference, the activated carbon glass microspheres are suspended in the salt solution after entering the sedimentation device, while the rock fragments settle at the bottom. After sedimentation and separation, the activated carbon glass microspheres are washed and dried.

5. The method for rapid and stable control of wellbore pressure in marine hydrate formations according to claim 4, characterized in that, In step (4), the heating temperature of the heating device is 80~90℃.

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