Sealing device and sealing method for casing head of gas storage well

Abstract

The embodiment of the invention discloses a gas storage well casing head sealing device, a gas storage well casing head sealing method and related equipment. Relates to the field of drilling engineering, in particular to a gas storage well casing head sealing device which comprises a hanger sealing part, a sealing part and a sealing part, one end of the hanger sealing part is connected to the end, close to a well mouth, of a casing string, and at least two sealing grooves are formed in the peripheral side of the outer portion of a hanger; the hanger assembly is arranged in the casing head assembly in a sleeved mode, at least two sealing protruding parts are arranged on the inner circumferential side of the casing head assembly, and the sealing protruding parts and the sealing grooves are used for being meshed with each other under the action of external axial force to form a sealing area.

Description

Technical Field

[0001] The present specification relates to the field of drilling engineering, and more specifically, the present application relates to a gas storage well casing head sealing device, a gas storage well casing head sealing method and related equipment. Background Art

[0002] In order to improve the peak-shaving capacity of natural gas and increase strategic energy reserves, the construction of gas storage groups in my country has developed rapidly in recent years. Compared with general gas wells, gas storage injection and production wells have the characteristics of high gas pressure, fast gas flow rate, and long service life, and annular pressure phenomenon often occurs during operation. This requires that the casing head sealing device should be able to effectively block the pressure of the annular space of each layer of casing for a long time and reduce the risk of wellhead leakage.

[0003] At present, the casing head seal design of injection and production wells mostly adopts the method of metal seal combined with rubber seal. Although the rubber material has a good short-term sealing effect, it is easy to cause sealing failure due to material aging after 3-5 years of use; the metal seal is deformed by squeezing the metal seal by external force, and the gap between the hanger and the casing head body is sealed, and the service life is long. However, the conventional casing head hanger seal in the past includes multiple components such as the hanger body, upper pressure ring, lower pressure ring, and metal sealing ring. A slight deviation in the installation process will seriously damage the sealing effect. Therefore, the number of components should be reduced as much as possible on the basis of ensuring the sealing quality. In addition, the size of the load on the metal seal during the sealing operation is a key factor affecting its deformation. If the load is too small, the metal seal cannot completely seal the gap. At present, gravity sealing is mostly used in engineering. Since it is impossible to directly observe the sealing process in the hanger, when the metal seal and rubber seal act at the same time, it is difficult to judge whether the metal sealing ring effectively seals the annulus. Summary of the invention

[0004] A series of simplified concepts are introduced in the Summary of the Invention section, which will be further described in detail in the Detailed Description of the Invention section. The Summary of the Invention section of this application does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the scope of protection of the claimed technical solution.

[0005] In a first aspect, the present application proposes a gas storage well casing head sealing device, comprising:

[0006] A hanger seal, one end of which is connected to an end of the casing string close to the wellhead, and at least two sealing grooves are arranged on the outer peripheral side of the hanger;

[0007] The casing head assembly, the hanger assembly is sleeved in the casing head assembly, at least two sealing protrusions are arranged on the inner circumference of the casing head assembly, and the sealing protrusions and the sealing grooves are used to mesh with each other under the action of external axial force to form a sealing area.

[0008] In one embodiment, the hanger sealer comprises an upper sealing part and a lower sealing part, the upper sealing part and the lower sealing part are designed as an integrated whole, at least two first sealing grooves are arranged on the inner circumference of the upper sealing part, at least two second sealing grooves are arranged on the inner circumference of the lower sealing part, and the lower sealing part is connected to one end of the casing string close to the wellhead.

[0009] The casing head assembly comprises a primary casing head body, a secondary casing head body and a bolt assembly, at least two first sealing protrusions are arranged on the inner circumference of the secondary casing head body, at least two second sealing protrusions are arranged on the inner circumference of the primary casing head body, the first sealing groove and the first sealing protrusions form a secondary sealing area, and the second sealing groove and the second sealing protrusions form a primary sealing area;

[0010] The first-level casing head body and the second-level casing head body are connected by the target pre-tightening force applied by the bolt assembly.

[0011] In one embodiment, when the secondary casing head body is not installed, the gas storage sealer further comprises a protective cover and a binding strap, wherein the protective cover is sleeved on the upper sealing portion, and the binding strap wraps around the protective cover and the upper sealing portion to form a fixed connection.

[0012] In a second aspect, the present application further proposes a gas storage well casing head sealing method, which is used in the gas storage well casing head sealing device mentioned in the first aspect, comprising:

[0013] Based on the numerical simulation method, the target load of the main sealing area of ​​the casing head of the well to be sealed and the target preload force of the bolts of the casing head assembly are obtained;

[0014] Obtaining the total hanging weight and casing string buoyancy before sealing, wherein the total hanging weight is the sum of the hanging weights of the top drive, the landing joint, the hanger assembly and the casing string;

[0015] Determine the closing traction force according to the total suspended weight, the target load of the main closing area and the buoyancy of the casing string;

[0016] Applying the above-mentioned closing traction force at the end of the above-mentioned hanger seal away from the bottom hole to make the main sealing area approach the above-mentioned main sealing area target load;

[0017] The casing head assembly is connected according to the target preload force.

[0018] In one embodiment, the above-mentioned method based on numerical simulation to obtain the target load of the main sealing area of ​​the casing head of the well to be sealed and the target bolt preload of the casing head assembly includes:

[0019] Obtain the annular pressure of the well to be sealed based on current working condition information and historical annular pressure data;

[0020] Constructing a first mechanical simulation model and a first fluid simulation model corresponding to the primary sealing area;

[0021] Determine the target load of the primary sealing area according to the annular space pressure, the first mechanical simulation model and the first fluid simulation model;

[0022] Constructing a second mechanical simulation model corresponding to the secondary sealing area;

[0023] The target preload force of the bolt is determined according to the second mechanical simulation model.

[0024] In one embodiment, determining the target load of the primary sealing area according to the annular space pressure, the first mechanical simulation model and the first fluid simulation model includes:

[0025] Applying an initial load to the first mechanical simulation model to obtain deformation information;

[0026] Applying the deformation information and the annular pressure to the fluid simulation model to obtain a fluid simulation result;

[0027] According to the above fluid simulation results, an adjustment load is applied to perform a first mechanical and fluid mechanics cycle iterative simulation to obtain the above target load corresponding to the sealing area under the pressure judgment condition and the gas flow judgment condition, wherein the above initial load, the above adjustment load and the above target load are axial loads applied to the above hanger seal, and the above target load is the sum of the load values ​​of the above initial load and the above adjustment load.

[0028] In one embodiment, determining the target preload force of the bolt according to the second mechanical simulation model includes:

[0029] Applying the target load and the initial preload to the second mechanical simulation model to obtain deformation information;

[0030] According to the deformation information, an adjusted preload is applied to perform a second mechanical simulation in a loop iteration, so that the sealing area satisfies the corresponding bolt preload under the contact judgment condition, wherein the initial load, the adjusted load and the target load are axial loads applied to the hanger seal, and the target load is the sum of the initial load and the adjusted load.

[0031] In one embodiment, the sealing traction force is determined according to the total suspended weight, the target load of the main sealing area and the buoyancy of the casing string, including:

[0032] The difference between the total hanging weight, the casing string buoyancy and the target load of the main sealing area is used as a reference sealing traction force;

[0033] When the reference closed traction force is greater than or equal to zero, the reference traction force is used as the closed traction force;

[0034] In the case that the reference traction force is less than zero, the weight of the top coupling section and / or the top drive is increased to make the reference closing traction force greater than or equal to zero, and the reference traction force is used as the closing traction force.

[0035] In one embodiment, applying the closing traction force at the end of the hanger seal away from the bottom hole to make the main sealing area approach the main sealing area target load includes:

[0036] Connecting the load output unit to the end of the hanger seal away from the bottom of the well, wherein the load output unit includes a computer, a controller, a motor, a pull rope, a fixed pulley, a large hook, a tension sensor, a top drive and a top joint;

[0037] The working stroke of the motor is controlled so that the actual load of the tension sensor approaches the closing traction force, so that the main sealing area approaches the main sealing area target load.

[0038] In one embodiment, connecting the casing head assembly according to the target preload force comprises:

[0039] disconnecting the load output unit from the hanger seal;

[0040] Remove the protective covers and straps from the gas reservoir seal;

[0041] Sleeve the secondary casing head body on the upper sealing part of the hanger seal;

[0042] The target pre-tightening force applied by the bolt assembly is used to connect the primary casing head body and the secondary casing head body.

[0043] In summary, the casing head sealing device for a gas storage well proposed in the embodiment of the present application includes: a hanger seal, one end of which is connected to one end of the casing string close to the wellhead, and at least two sealing grooves are arranged on the outer circumference of the hanger; a casing head assembly, the hanger assembly is sleeved in the casing head assembly, and at least two sealing protrusions are arranged on the inner circumference of the casing head assembly, and the sealing protrusions and the sealing grooves are used to engage with each other under the action of external axial force to form a sealing area. The casing head sealing device for a gas storage well proposed in the embodiment of the present application integrates the hanger and the seal by designing a sealing structure on the casing head hanger, which can not only simplify the sealing path and reduce the difficulty of sealing, but also solve the problem of metal sealing failure caused by installation position deviation during construction. The hanger sealing structure designed by the present invention can realize the formation of multiple layers of metal seals through sealing grooves and sealing protrusions in one hanger, greatly improving the sealing effect.

[0044] The gas storage well casing head sealing device, gas storage well casing head sealing method and related equipment proposed in the embodiments of the present application, and other advantages, objectives and features of the present application will be partially reflected through the following description, and will also be partially understood by technical personnel in the field through research and practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present specification. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0046] Figure 1 A structural schematic diagram of a casing head sealing device for a gas storage well provided in an embodiment of the present application;

[0047] Figure 2 A schematic diagram of the principle of a gas storage well casing head sealing device provided in an embodiment of the present application;

[0048] Figure 3 A schematic diagram of a sealing method for a casing head sealing device for a gas storage well provided in an embodiment of the present application;

[0049] Figure 4 A schematic diagram of a load output unit provided in an embodiment of the present application;

[0050] Figure 5 A schematic diagram of the principle of a gas storage well casing head sealing device before sealing, as proposed in an embodiment of the present application;

[0051] Figure 6A schematic diagram of the principle of a gas storage well casing head sealing device after closure, as proposed in an embodiment of the present application;

[0052] Figure 1 The corresponding relationship between the component names and the reference numerals is as follows:

[0053] 10 Gas storage well casing head sealing device, 101 hanger seal, 1011 upper sealing portion, 10111 first sealing groove, 1012 lower sealing portion, 10121 second sealing groove, 102 casing head assembly, 1021 secondary casing head body, 1022 primary casing head body, 1023 bolt assembly, 10211 first sealing protrusion, 10221 second sealing protrusion. DETAILED DESCRIPTION

[0054] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices. The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0055] For this purpose, the present application proposes a gas storage well casing head sealing device 10, see Figure 1 , is a structural schematic diagram of a gas storage well casing head sealing device 10 provided in an embodiment of the present application, which may specifically include:

[0056] A hanger seal 101, one end of which is connected to one end of the casing string close to the wellhead, and at least two sealing grooves are arranged on the outer peripheral side of the hanger;

[0057] The casing head assembly 102, the hanger assembly is sleeved in the casing head assembly 102, at least two sealing protrusions are arranged on the inner circumference of the casing head assembly 102, and the sealing protrusions and the sealing grooves are used to mesh with each other under the action of external axial force to form a sealing area.

[0058] Exemplarily, the hanger seal 101 is connected to one end of the casing string close to the wellhead and is located near the wellhead. The hanger seal 101 is a rotating body design, and at least two sealing grooves are arranged on the outer peripheral side of the hanger.

[0059] The casing head assembly 102 accommodates and cooperates with the hanger seal 101. At least two sealing protrusions are provided on the inner circumference of the casing head assembly 102. These sealing protrusions are designed to engage with the sealing grooves of the hanger seal 101. This interlocking effect is to form an effective sealing area under the action of external axial force. When the external axial force is applied to the system, the mutual engagement between the sealing protrusions and the sealing grooves will create a sealing area. This sealing area can effectively prevent the gas and other fluids in the gas storage from leaking out from the connection point of the system. This hanger sealing device can be used in gas storage, and can also be used in oil wells, natural gas wells or other underground wellbore applications that need to maintain sealing. It is designed to cope with the pressure changes and external forces that may occur in different environments to ensure the safety and efficiency of wellbore operations. At the same time, the structure of this system should be carefully designed to be operable and reliable during assembly and maintenance.

[0060] It can be understood that the gas storage well casing head sealing device proposed in the embodiment of the present application can not only be used for sealing scenarios in gas storage, but can also be applied to gas injection wells, gas production wells and other wells that have higher requirements for casing head gas sealing.

[0061] In summary, the casing head sealing device 10 for a gas storage well proposed in the embodiment of the present application integrates the hanger and the seal by designing a sealing structure on the casing head hanger, which can not only simplify the sealing path and reduce the sealing difficulty, but also solve the problem of metal seal failure caused by installation position deviation during construction. The hanger sealing structure designed by the present invention can realize the formation of multi-layer metal seals through sealing grooves and sealing protrusions in one hanger, greatly improving the sealing effect.

[0062] In one embodiment, the hanger sealer includes an upper sealing portion 1011 and a lower sealing portion 1012, the upper sealing portion 1011 and the lower sealing portion 1012 are designed as an integrated whole, at least two first sealing grooves 10111 are arranged on the inner circumference of the upper sealing portion 1011, at least two second sealing grooves 10121 are arranged on the inner circumference of the lower sealing portion 1012, and the lower sealing portion 1012 is connected to one end of the casing string close to the wellhead.

[0063] The casing head assembly 102 includes a primary casing head body 1022, a secondary casing head body 1021 and a bolt assembly 1023. At least two first sealing protrusions 10211 are arranged on the inner circumference of the secondary casing head body 1021. At least two second sealing protrusions 10221 are arranged on the inner circumference of the primary casing head body 1022. The first sealing groove 10111 and the first sealing protrusions 10211 form a secondary sealing area, and the second sealing groove 10121 and the second sealing protrusions 10221 form a primary sealing area.

[0064] The primary casing head body 1022 and the secondary casing head body 1021 are connected by the target pre-tightening force applied by the bolt assembly 1023 .

[0065] In one embodiment, the hanger sealer is designed to be an integrated structure of an upper sealing part 1011 and a lower sealing part 1012. This design can increase the stability and durability of the sealing system because there are no separated parts to reduce potential leakage points. At least two second sealing grooves 10121 are arranged on the inner circumference of the lower sealing part 1012, and at least two second sealing protrusions 10221 are arranged on the inner circumference of the first-level casing head body 1022. The combination of these sealing grooves and sealing protrusions forms a main sealing area. The main sealing area is the main sealing point of the sealing system, which is used to resist leakage under high pressure and environment. The casing head sealing device 10 for the gas storage well also includes a first sealing groove 10111 and a first sealing protrusion 10211, which are respectively located on the inner circumference of the second-level casing head body 1021. These components form a secondary sealing area to provide an additional sealing layer. The secondary sealing area can be used as a backup seal to increase the reliability of the system, especially under extreme conditions, to increase the sealing reliability of the system. The casing head assembly 102 includes a secondary casing head body 1021, a primary casing head body 1022, and a bolt assembly 1023. This multi-component design allows for easier installation and maintenance of the system while ensuring the effectiveness of the seal.

[0066] It should be noted that a pin hole for a locating pin to pass through may be provided in the radial direction of the primary casing head body 1022 or the secondary casing head body 1021, and a shoulder for positioning with the locating pin may be provided on the upper sealing portion 1011 and the lower sealing portion 1012.

[0067] In one embodiment, when the secondary casing head body 1021 is not installed, the gas storage sealer further includes a protective cover and a binding strap, wherein the protective cover is sleeved on the upper sealing portion 1011, and the binding strap wraps around the protective cover and the upper sealing portion 1011 to form a fixed connection.

[0068] Exemplarily, in order to ensure that the upper sealing portion 1011 is not affected by the external environment when the secondary casing head body 1021 is not installed, a protective cover is placed on the upper sealing portion 1011. The function of this protective cover is to prevent dust, debris or other external substances from entering the sealing area, thereby maintaining the operational reliability of the system. In order to maintain the position of the protective cover and ensure that it is tightly connected to the upper sealing portion 1011, one or more straps are used to fix the protective cover in place. These straps wrap the protective cover around the upper sealing portion 1011 to form a secure connection. This safe fixing method helps prevent the protective cover from accidentally falling off or moving, thereby protecting the integrity of the sealing system.

[0069] In summary, the combined design of the protective cover and the binding strap ensures that the sealing device is still well protected even when the secondary casing head body 1021 is not installed. This is very important for maintaining the integrity of the sealing device during long-term storage, transportation or maintenance. It helps to reduce maintenance work because the sealing device can be quickly put into use when needed without additional cleaning or repair.

[0070] In one embodiment, Figure 2 As shown, another schematic diagram of the hanger sealing principle is given, the hanger seal 101 includes a suspension structure, a primary sealing area and a secondary sealing area; the primary sealing area includes ten metal sealing layers, the secondary sealing structure includes nine metal sealing layers, and sealing grooves are provided between adjacent sealing layers, the fourth metal sealing layer and the fifth metal sealing layer of the primary sealing area are meshed with the second protrusion 2 of the secondary casing head body 1021, the eighth metal sealing layer and the ninth metal sealing layer of the primary sealing area are meshed with the second protrusion 2 of the secondary casing head body 1021; the third metal sealing layer and the fourth metal sealing layer of the secondary sealing area are meshed with the first protrusion 2 of the primary casing head body 1022, and the sixth metal sealing layer and the seventh metal sealing layer of the secondary sealing area are meshed with the first protrusion 1 of the primary casing head body 1022. Through the primary sealing area and the secondary sealing area, and by providing multiple sealing layers in each sealing area, the gas can be effectively sealed.

[0071] In the second aspect of the present application, a gas storage well casing head sealing method is also provided, which is used for the gas storage well casing head sealing device 10 mentioned in the first aspect, see Figure 3 , which is a schematic diagram of the process of a gas storage well casing head sealing method proposed in the present application, the method comprising:

[0072] S210, obtaining a target load of a main sealing region of a casing head of the well to be sealed and a target preload force of bolts of a casing head assembly based on a numerical simulation method;

[0073] Exemplarily, a numerical simulation method is used to determine the target load required in the primary sealing area of ​​the well casing head, which includes considering the physical properties of the hanger seal and casing head assembly, as well as the gas pressure on the casing.

[0074] S220, obtaining the total hanging weight and the buoyancy of the casing string before sealing, wherein the total hanging weight is the sum of the hanging weights of the top drive, the landing joint, the hanger assembly and the casing string;

[0075] Exemplarily, the evaluation of the wellbore condition before sealing includes calculating the total hanging weight, which is composed of the sum of the weights of the top drive, landing joint, hanger assembly and casing string. At the same time, the casing string buoyancy is also considered, which is the force generated by the buoyancy of liquid or gas.

[0076] S230, determining the closing traction force according to the total suspended weight, the target load of the main closed area and the buoyancy of the casing string;

[0077] Exemplarily, the buoyancy f of the casing string connected to the hanger in the drilling fluid;

[0078] f=aG1

[0079] a=(bc) / b

[0080] Where G1 is the hanging weight of the casing string, in kN, a is the buoyancy coefficient, b is the density of the casing string, and c is the density of the drilling fluid. In this embodiment, G1 = 600 kN, b = 7.87 g / cm 3 , the drilling fluid is mud, density c = 1.2g / cm 3 ;

[0081] Calculate the closed traction force F required by the motor based on the calculated optimal load P, buoyancy f and total suspended weight G:

[0082] F=G+Pf

[0083] S240, applying the above-mentioned closing traction force to the end of the above-mentioned hanger seal away from the bottom of the well to make the main sealing area close to the above-mentioned main sealing area target load;

[0084] Exemplarily, an optimal load is applied to the main sealing structure of the hanger seal to completely seal the gap between the casing head body and the hanger.

[0085] S250, connecting the casing head assembly according to the target preload force.

[0086] Exemplarily, the casing head assembly is connected according to the previously calculated bolt target preload force of the casing head assembly. The bolts can be accurately tightened to ensure the safe connection of the casing head and to ensure that the main sealing area forms an effective seal at the correct position. It should be noted that the target preload force is the preload force along the axial direction of the bolt.

[0087] In summary, the gas storage well casing head sealing method proposed in the embodiment of the present application can realize the formation of multi-layer metal seals through sealing grooves and sealing protrusions in a hanger through the hanger seal, greatly improving the sealing effect. The optimal load is calculated by numerical simulation method, and the annular space pressure problem that may occur during the operation of the gas storage well is predicted. The sealing method of the present application can make the main sealing structure of the hanger effectively block the annular space pressure of each layer of casing caused by the annular space pressure, and solve the main sealing structure failure problem that may be caused by emergencies during the actual construction process through the secondary sealing structure of the hanger, reduce the risk of wellhead leakage, and prevent major safety accidents.

[0088] In one embodiment, the above-mentioned method based on numerical simulation to obtain the target load of the main sealing area of ​​the casing head of the well to be sealed and the target bolt preload of the casing head assembly includes:

[0089] Obtain the annular pressure of the well to be sealed based on current working condition information and historical annular pressure data;

[0090] Constructing a first mechanical simulation model and a first fluid simulation model corresponding to the primary sealing area;

[0091] Determine the target load of the primary sealing area according to the annular space pressure, the first mechanical simulation model and the first fluid simulation model;

[0092] Constructing a second mechanical simulation model corresponding to the secondary sealing area;

[0093] The target preload force of the bolt is determined according to the second mechanical simulation model.

[0094] Exemplarily, the annular pressure under different annular pressure conditions under the operating information (annular pressure) of the well to be sealed during operation can be estimated based on the annular pressure data of the operating injection and production wells of a gas storage reservoir. Specifically, the following method can be used: divide the downhole space of the well to be sealed and label the downhole annuli; determine whether there are operating injection and production wells that are geographically close to the well to be sealed. If so, screen the types of annular pressure generated in each annulus during the operation of the operating injection and production wells and their annular pressure data; if there are no operating injection and production wells, the annular pressure data of each annulus takes the designed injection and production pressure of the well to be sealed; store each of the above-mentioned annular pressure data in the form of column vectors according to the label of the annulus in which it is located in the matrix M A 、M B..., where subscript A represents annulus A and subscript B represents annulus B. If there are two or more operating injection and production wells with the same annulus pressure, the data with the larger pressure value is stored in the matrix; the matrix M is calculated using the least squares method. A 、M B ...perform nonlinear fitting on each column element to obtain the annular pressure load Y kj (x), Y kj (x) is used to estimate the annular pressure change when the annulus k produces the jth annular pressure during the operation of the well to be sealed, j = 1, 2...m, where x represents time and k represents the annular number, which can be A, B...

[0095] In order to determine the target load of the main sealing area, it is necessary to establish a mechanical simulation model and a fluid simulation model. The mechanical simulation model can simulate the stress conditions of each component in the sealing system, including the casing head, hanger, seals, etc. The fluid simulation model is used to simulate the flow of liquid or gas in the sealing area in order to understand the effect of annular pressure on sealing performance. Combining the annular pressure data and the results of the first mechanical simulation model and the first fluid simulation model, the target load required for the main sealing area can be determined. This target load is to ensure that the main sealing area can be effectively sealed under different environmental conditions.

[0096] In addition to the primary sealing area, the system may also include a secondary sealing area. In order to ensure the reliability of the entire sealing system, a second mechanical simulation model needs to be established to simulate the stress conditions in the secondary sealing area. This helps determine the mechanical properties and preload required for the secondary sealing area. Using the results of the second mechanical simulation model, the target bolt preload required to connect the casing head assembly can be determined. The goal of this preload is to ensure the safe connection and sealing of the casing head.

[0097] The target load of the main sealing area and the target preload of the bolts of the casing head assembly are measured, and the annulus pressure problem that may occur during the operation of the gas storage well is predicted. The sealing method of the present application can enable the main sealing structure of the hanger to effectively block the annulus pressure of each layer of casing caused by the annulus pressure, and solve the problem of failure of the main sealing structure that may be caused by emergencies during the actual construction process through the secondary sealing structure of the hanger, thereby reducing the risk of wellhead leakage and preventing major safety accidents.

[0098] In one embodiment, determining the target load of the primary sealing area according to the annular space pressure, the first mechanical simulation model and the first fluid simulation model includes:

[0099] Applying an initial load to the first mechanical simulation model to obtain deformation information;

[0100] Applying the deformation information and the annular pressure to the fluid simulation model to obtain a fluid simulation result;

[0101] According to the above fluid simulation results, an adjustment load is applied to perform a first mechanical and fluid mechanics cycle iterative simulation to obtain the above target load corresponding to the sealing area under the pressure judgment condition and the gas flow judgment condition, wherein the above initial load, the above adjustment load and the above target load are axial loads applied to the above hanger seal, and the above target load is the sum of the load values ​​of the above initial load and the above adjustment load.

[0102] Exemplarily, a physical model of the hanger seal and the first-level casing head body (i.e., the first mechanical simulation model) is established in the stress analysis software, the number of the annulus to be sealed is input to determine the corresponding annulus pressure, and the calculation parameters of the hanger seal and the first-level casing head body are input, including Poisson's ratio, density, yield strength, the initial value of the main sealing load P, the single load increase m1, and the initial value of the number of cycles n1.

[0103] Apply the main sealing load P to the hanger seal, and perform stress calculation to obtain the deformation distribution of the hanger seal and the primary casing head body. Import the physical model of the deformed hanger seal and the primary casing head body into the airflow field analysis software, and perform physical modeling of the annulus area to be sealed (i.e., the first mechanical simulation model). The space formed by the boundaries of the deformed hanger seal, the primary casing head body, and the annulus area to be sealed is the calculation area. The area without gas in the calculation area is the sealing area, and the area with gas is the gas area. Enter the airflow parameters in the gas area, including gas density, dynamic viscosity, gas constant, gas temperature, and diffusion coefficient, select the type of turbulence model, and set the annulus pressure load Y. kj In (x), the initial value of j is 1, and k is the number of the annulus to be sealed. According to the actual working conditions, an annulus pressure load Y is applied on the boundary of the gas zone. kj(x), numerical simulation of the calculation area is performed using airflow field analysis software to obtain the pressure distribution and airflow velocity distribution of the calculation area. According to the pressure distribution and airflow velocity distribution of the sealing area in the calculation area, it is judged whether the main sealing structure of the deformed hanger seal can completely seal the annulus. If the pressure in the sealing area is zero and there is no gas flow, it means that the main sealing structure of the deformed hanger seal can completely seal the annulus and can resist the jth annular pressure problem of the k annulus, j=j+1, repeat the first mechanical and fluid mechanical cycle iterative simulation until j>m, and output the target load; if the pressure in the sealing area is not zero and there is gas flow, it means that the main sealing structure of the deformed hanger seal cannot ensure the gap is completely sealed, the number of cycles n1 is increased by 1, and the load applied to the hanger seal becomes P=P+n1m1, until it is completely sealed, the cycle ends, and the target load is output; the output target at this time is the optimal load P that can enable the main sealing structure of the hanger seal to completely seal the annulus, and the output at this time is the ideal deformation of the hanger seal and the secondary casing head body.

[0104] In one embodiment, determining the target preload force of the bolt according to the second mechanical simulation model includes:

[0105] Applying the target load and the initial preload to the second mechanical simulation model to obtain deformation information;

[0106] According to the deformation information, an adjusted preload is applied to perform a second mechanical simulation in a loop iteration, so that the sealing area satisfies the target bolt preload corresponding to the contact judgment condition, wherein the initial load, the adjusted load and the target load are axial loads applied to the hanger seal, and the target load is the sum of the initial load and the adjusted load.

[0107] Exemplarily, in the stress analysis software, the above-mentioned implementation is used to physically model the hanger seal and the first-level casing head body that produce ideal deformation (the first mechanical simulation model), and at the same time, the physical model of the second-level casing head body and the bolts (the second mechanical simulation model) is performed; the annulus number to be sealed (to determine the annulus pressure) and the calculation parameters of the hanger seal, the first-level casing head body, the second-level casing head body, and the bolts are input, including Poisson's ratio, density, yield strength, the initial value of the bolt preload Q, the single preload increase m2, and the initial value of the number of cycles n2; the bolt preload Q is applied to the bolt, and the stress calculation is performed to obtain the deformation distribution of the hanger seal and the second-level casing head body; the above-calculated deformation distribution determines whether the metal sealing layer of the hanger secondary sealing structure is in close contact with the first-level casing head body and the second-level casing head body. If there is tight contact, it means that the secondary sealing structure can completely seal the gap between the hanger and the casing head body; if there is no tight contact, the number of cycles n is increased by 1, and the preload force applied to the hanger seal becomes Q=Q+n2m2. Repeat the steps of loading and simulation until complete sealing. The cycle ends and the target bolt preload force output at this time is the optimal preload force Q.

[0108] In one embodiment, the sealing traction force is determined according to the total suspended weight, the target load of the main sealing area and the buoyancy of the casing string, including:

[0109] The difference between the total hanging weight, the casing string buoyancy and the target load of the main sealing area is used as a reference sealing traction force;

[0110] When the reference closed traction force is greater than or equal to zero, the reference traction force is used as the closed traction force;

[0111] In the case that the reference traction force is less than zero, the weight of the top coupling section and / or the top drive is increased to make the reference closing traction force greater than or equal to zero, and the reference traction force is used as the closing traction force.

[0112] Exemplarily, the total hanging weight G of the unsealed top drive, landing joint, hanger and casing string is measured;

[0113] Calculate the buoyancy f of the casing string connected to the hanger in the drilling fluid during the sealing process;

[0114] f=aG1

[0115] a=(bc) / b

[0116] Where G1 is the hanging weight of the casing string, in kN, a is the buoyancy coefficient, b is the density of the casing string, and c is the density of the drilling fluid. In this embodiment, G1 = 600 kN, b = 7.87 g / cm 3 , the drilling fluid is mud, density c = 1.2g / cm 3;

[0117] Calculate the traction force F that the motor needs to output based on the calculated optimal load P, buoyancy f and total suspended weight G:

[0118] F=G+Pf

[0119] Determine whether F is a non-negative number. If it is a non-negative number, the output traction force F is a closed traction force. If it is a negative number, increase the weight of the top joint and the top drive until F is a non-negative number.

[0120] In one embodiment, applying the closing traction force at the end of the hanger seal away from the bottom hole to make the main sealing area approach the main sealing area target load includes:

[0121] Connecting the load output unit to the end of the hanger seal away from the bottom of the well, wherein the load output unit includes a computer, a controller, a motor, a pull rope, a fixed pulley, a large hook, a tension sensor, a top drive and a top joint;

[0122] The working stroke of the motor is controlled so that the actual load of the tension sensor approaches the closing traction force, so that the main sealing area approaches the main sealing area target load.

[0123] Exemplarily, applying the above-mentioned closing traction force at the end of the above-mentioned hanger seal away from the bottom hole can be achieved by Figure 4 The load output unit shown is applied, and the load output unit includes a computer, a controller, a motor, a pull rope, a fixed pulley, a big hook, a data acquisition card, a tension sensor, a top drive, and a top joint; the output end of the computer is connected to the input end of the controller, the output end of the controller is connected to the motor and then to the pull rope, the pull rope is connected to the big hook through the fixed pulley, the tension sensor is installed on the big hook, the output end of the tension sensor is connected to the computer through the data acquisition card, the big hook is connected to one end of the top drive, the other end of the top drive is connected to one end of the top joint, and the other end of the top joint is connected to one end of the hanger seal through a thread.

[0124] Figure 5 This is a schematic diagram of the principle of a gas storage well casing head sealing device before sealing, proposed in an embodiment of the present application. Figure 6 This is a schematic diagram of the principle of a gas storage well casing head sealing device after closure proposed in an embodiment of the present application. The process of loading and sealing is specifically implemented in the following manner: installing the hanger seal on the primary casing head body and starting the sealing load output unit; adjusting the motor speed through the controller so that the motor outputs a traction force F and keeps it constant; applying the traction force F output by the motor to the hanger seal, at which time the total load on the hanger seal is the optimal load P, which can cause the main sealing structure of the hanger seal to produce an ideal deformation, thereby achieving the purpose of completely sealing the gap;

[0125] In one embodiment, connecting the casing head assembly according to the target preload force comprises:

[0126] disconnecting the load output unit from the hanger seal;

[0127] Remove the protective covers and straps from the gas reservoir seal;

[0128] Sleeve the secondary casing head body on the upper sealing part of the hanger seal;

[0129] The target pre-tightening force applied by the bolt assembly is used to connect the primary casing head body and the secondary casing head body.

[0130] Exemplarily, during the process of connecting the above casing head assembly with the target preload, the sealing load output unit is closed, and the connection between the sealing load output unit and the hanger seal is disconnected; the binding band is loosened, the protective cover of the hanger seal is removed, and the secondary casing head body is installed on the hanger seal;

[0131] The primary casing head body and the secondary casing head body are connected by bolts, and the bolt preload force is gradually increased until the target preload force Q is reached.

[0132] In one embodiment, the computer in the load output unit is used to model and simulate stress of the hanger seal, the first-level casing head body, the second-level casing head body, etc., calculate the optimal load when the main sealing structure of the hanger seal produces an ideal deformation, and the optimal preload of the secondary sealing structure of the hanger seal to completely seal the gap. The computer model can be TG01-155ccn; the tension sensor has a measurement range of 0-200 tons, a model of DAYSENSOR, and can output a 4-20mA analog signal. The tension sensor is used to measure the total hanging weight of the top drive, the top joint, the hanger seal and the casing string before sealing, and transmit the measurement results to the computer through the data acquisition card. The data acquisition card model can be TD-4071; the controller is used to control the output speed of the motor, and the model can be FX2N-128MR-001; the motor is used to output traction so that the big hook generates an upward pulling force on the top drive, and the model can be SERIAL, with a rated power of 720kW; the fixed pulley is used to change the direction of the pulling force, and the maximum load-bearing capacity is 200 tons.

[0133] The hanging structure of the hanger seal is used to hang the casing string. If the hanger seal seals the annulus between the oil pipe and the production casing, the hanger seal hangs the production casing string. If the hanger seal seals the annulus between the production casing and the technical casing, the hanger seal hangs the technical casing string. If the hanger seal seals the annulus between the technical casing and the surface casing, the hanger seal hangs the surface casing string. In this embodiment, the hanger seal hangs the technical casing string.

[0134] The multi-layer metal sealing device for the casing head of the gas storage well is used to seal the annulus between the layers of the casing strings. The optimal load is applied to the main sealing structure of the hanger seal to completely seal the gap between the casing head body and the hanger. At the same time, the hanger secondary sealing structure is used to solve the problem of failure of the main sealing structure that may be caused by unexpected situations during the actual construction process, including:

[0135] S310, estimating the annular pressure under different annular pressure conditions during the operation of the well to be sealed based on the annular pressure data of the injection and production wells in operation in a gas storage facility;

[0136] S3101, divide the underground space of the well to be sealed and label the underground annulus; Figure 1 As shown, in this embodiment, the gap between the oil pipe and the production casing is defined as annulus A, the gap between the production casing and the technical casing is defined as annulus B, and the gap between the technical casing and the surface casing is defined as annulus C;

[0137] S3102. Determine whether there are any operating injection-production wells that are geographically close to the well to be sealed. If so, screen the types of annular pressure generated in each annulus during the operation of the operating injection-production well and its annular pressure data; if there are no operating injection-production wells, the annular pressure data of each annulus shall be the designed injection-production pressure of the well to be sealed; in this embodiment, there are injection-production wells that are geographically close to the well to be sealed, and the types of annular pressure generated in the operation of the well are 11, 1 to 5 represent the types of annular pressure generated in the A annulus, where 1 represents the annular pressure caused by leakage of the tubing joint, 2 represents the annular pressure caused by corrosion and perforation of the tubing, and 3 represents the annular pressure caused by failure of the safety valve. 4 represents the annular pressure caused by the failure of the tubing packer seal, and 5 represents the annular pressure caused by the failure of the tail pipe hanger seal; 6-8 represent the types of annular pressure generated in the B annulus, among which 6 represents the annular pressure caused by the failure of the production casing thread seal, 7 represents the annular pressure caused by the corrosion and perforation of the production casing, and 8 represents the annular pressure caused by the damage of the cement ring of the B annulus; 9-10 represent the types of annular pressure generated in the C annulus, among which 9 represents the annular pressure caused by the failure of the technical casing thread seal, 10 represents the annular pressure caused by the corrosion and perforation of the technical casing, and 11 represents the annular pressure caused by the damage of the cement ring of the C annulus;

[0138] S3103, store each annular space pressure data of step S3102 in the form of column vectors according to the number of the annular space where it is located in the matrix M A 、M B ..., where subscript A represents annulus A and subscript B represents annulus B. If there are two or more operating injection and production wells with the same annulus pressure, the data with the larger pressure value is stored in the matrix, and the matrix MA 、M B ...as shown in formula (1):

[0139]

[0140] Where k = A, B, ..., the element in the i-th row represents the pressure data of the i-th day, the element in the j-th column represents the pressure data of the j-th type of annular pressure, m ij It indicates the pressure value of the jth annular zone pressure on the i-th day, in MPa;

[0141] S320, using the least squares method to calculate the matrix M A 、M B ...perform nonlinear fitting on each column element to obtain the annular pressure load Y kj (x), Y kj (x) is used to estimate the annular pressure change when the annulus k produces the jth annular pressure during the operation of the well to be sealed, j = 1, 2...m, where x represents time, k represents the annular number, which can be A, B...; in this embodiment, the unit of x is day, Y kj The unit of (x) is MPa;

[0142] S330, determining an optimal load of a main sealing structure of a hanger seal through numerical simulation;

[0143] S3301. Establish a physical model of the hanger seal and the primary casing head body in the stress analysis software, input the annulus number to be sealed, and the calculation parameters of the hanger seal and the primary casing head body, including Poisson's ratio, density, yield strength, initial value of the main seal load P, single load increase m1, and initial value of the number of cycles n1; in this embodiment, ANSYS software is used for stress analysis. The material of the primary casing head body is stainless steel, with a Poisson's ratio of 0.247 and a density of 7.7 g / cm 3 , yield strength 240N / mm 2 The material of the hanger seal is nickel-chromium alloy, with a Poisson's ratio of 0.327 and a density of 8.0g / cm 3 , yield strength 180N / mm 2 ; The initial value of the main sealing load is 50kN, the single load increase m1 is 10kN, and the initial value of the number of cycles n1 is 0;

[0144] S3302, applying a main sealing load P to the hanger seal, and performing stress calculation to obtain the deformation distribution of the hanger seal and the primary casing head body;

[0145] S3303, importing the physical models of the deformed hanger seal and the secondary casing head body into the airflow field analysis software, and at the same time, performing physical modeling on the annulus area to be sealed, with the space formed by the boundary of the deformed hanger seal, the boundary of the primary casing head body, and the boundary of the annulus area to be sealed as the calculation area, the area without gas in the calculation area is the sealing area, and the area with gas is the gas area; in this embodiment, the FLUENT airflow field analysis software is used to perform the airflow field analysis;

[0146] S3304. Input gas flow parameters in the gas zone, including gas density, dynamic viscosity, gas constant, gas temperature, diffusion coefficient, select the type of turbulence model, and set the annular pressure load Y. kj In (x), the initial value of j is 1, and k is the number of the annulus to be sealed. In this embodiment, the gas density is 0.75 g / cm 3 , dynamic viscosity 0.105×10 -4 Pa·s, gas constant 8.31 J / (mol·K), gas temperature 293 K, diffusion coefficient D are calculated by formula (2), and the turbulence model is selected as the k-ε model.

[0147]

[0148] Among them, K B is the Boltzmann constant, which is 1.38×10 -23 J / K; T is the gas temperature, unit is K; α is the molecular collision diameter, m α is the molecular mass, n is the molecular number density;

[0149] S3305. According to the actual working conditions, an annular pressure load Y is applied on the boundary of the gas zone. kj (x) Use airflow field analysis software to perform numerical simulation on the calculation area to obtain the pressure distribution and airflow velocity distribution in the calculation area;

[0150] S3306. Determine whether the main sealing structure of the deformed hanger seal can completely seal the annulus according to the pressure distribution of the sealing area and the air flow velocity distribution in the calculation area. If the pressure in the sealing area is zero and there is no gas flow, it means that the main sealing structure of the deformed hanger seal can completely seal the annulus and can resist the jth annular pressure problem of the k annulus. j=j+1. Repeat step S3305 until j>m and proceed to step S3307. If the pressure in the sealing area is not zero and there is gas flow, it means that the main sealing structure of the deformed hanger seal cannot ensure that the gap is completely sealed. The number of cycles n1 is increased by 1, and the load applied to the hanger seal becomes P=P+n1m1. Repeat step S3302 until it is completely sealed. The cycle ends and proceed to step S3307.

[0151] S3307, outputting the load value at this time as the optimal load P that can enable the main sealing structure of the hanger seal to completely seal the annulus, and outputting the deformation of the hanger seal and the primary casing head body at this time as the ideal deformation;

[0152] S340, determining an optimal load of a secondary sealing structure of a hanger seal through numerical simulation;

[0153] S3401. Physically model the hanger seal and the primary casing head body that produce the ideal deformation in step S3307 in the stress analysis software, and establish the physical model of the secondary casing head body and the bolts at the same time; input the number of the annulus to be sealed, as well as the calculation parameters of the hanger seal, the primary casing head body, the secondary casing head body, and the bolts, including Poisson's ratio, density, yield strength, the initial value of the bolt preload Q, the single preload increase m2, and the initial value of the number of cycles n2; in this embodiment, the materials of the primary casing head body and the secondary casing head body are both stainless steel, with a Poisson's ratio of 0.247 and a density of 7.7 g / cm 3 , yield strength 240N / mm 2 ;

[0154] S3402, applying a bolt preload force Q to the bolt, and performing stress calculation to obtain deformation distribution of the hanger seal and the secondary casing head body;

[0155] S3403. According to the deformation distribution calculated in step S3402, determine whether the metal sealing layer of the secondary sealing structure of the hanger is in close contact with the primary casing head body and the secondary casing head body. If so, it means that the secondary sealing structure can completely seal the gap between the hanger and the casing head body. If not, the number of cycles n is increased by 1, and the preload force applied to the hanger seal becomes Q=Q+n2m2. Repeat step S3402 until it is completely sealed, the cycle ends, and step S3404 is performed.

[0156] S3404, outputting the preload force at this time as the optimal preload force Q;

[0157] S350, measuring the total hanging weight G of the unsealed front top drive, top joint, hanger and casing string by means of a tension sensor;

[0158] S360, calculating the buoyancy f exerted on the casing string connected to the hanger in the drilling fluid during the sealing process;

[0159] f=aG1 (3)

[0160] a=(bc) / b (4)

[0161] Where G1 is the hanging weight of the casing string, in kN, a is the buoyancy coefficient, b is the density of the casing string, and c is the density of the drilling fluid. In this embodiment, G1 = 600 kN, b = 7.87 g / cm 3 , the drilling fluid is mud, density c = 1.2g / cm 3 ;

[0162] S370, calculating the traction force F that the motor needs to output based on the calculated optimal load P, buoyancy f and total suspended weight G:

[0163] F=G+Pf (5)

[0164] S380, determining whether F is a non-negative number, if it is a non-negative number, proceeding to step S390, if it is a negative number, increasing the weight of the top joint and the top drive until F is a non-negative number;

[0165] S390, installing the hanger seal on the primary casing head body, and starting the seal load output unit;

[0166] S400, adjusting the motor speed through the controller so that the motor outputs a traction force F and keeps it constant;

[0167] S410, applying the traction force F output by the motor to the hanger seal, at which time the total load on the hanger seal is an optimal load P, which can cause the main sealing structure of the hanger seal to produce an ideal deformation, thereby achieving the purpose of completely sealing the gap;

[0168] S420, closing the sealing load output unit, and disconnecting the sealing load output unit from the hanger seal;

[0169] S430, loosen the binding band, remove the protective cover of the hanger seal, and install the secondary casing head body on the hanger seal;

[0170] S440, connecting the primary casing head body and the secondary casing head body by bolts, and gradually increasing the bolt preload force until the optimal preload force Q is reached.

[0171] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A gas storage well casing head sealing device, characterized in that: include: A hanger seal, one end of which is connected to an end of the casing string close to the wellhead, and at least two sealing grooves are arranged on the outer peripheral side of the hanger; A casing head assembly, wherein the hanger assembly is sleeved in the casing head assembly, wherein at least two sealing protrusions are arranged on the inner circumference of the casing head assembly, and wherein the sealing protrusions and the sealing grooves are used to mesh with each other under the action of an external axial force to form a sealing area.

2. The gas storage sealing device according to claim 1, characterized in that: The hanger sealer comprises an upper sealing part and a lower sealing part, the upper sealing part and the lower sealing part are designed as an integrated whole, at least two first sealing grooves are arranged on the inner circumference of the upper sealing part, at least two second sealing grooves are arranged on the inner circumference of the lower sealing part, and the lower sealing part is connected to one end of the casing string close to the wellhead. The casing head assembly comprises a primary casing head body, a secondary casing head body and a bolt assembly, at least two first sealing protrusions are arranged on the inner circumference of the secondary casing head body, at least two second sealing protrusions are arranged on the inner circumference of the primary casing head body, the first sealing groove and the first sealing protrusion form a secondary sealing area, and the second sealing groove and the second sealing protrusion form a primary sealing area; The primary casing head body and the secondary casing head body are connected by the target pre-tightening force applied by the bolt assembly.

3. The gas storage sealing device according to claim 2, characterized in that: When the secondary casing head body is not installed, the gas storage sealer further comprises a protective cover and a binding belt, wherein the protective cover is sleeved on the upper sealing part, and the binding belt wraps the protective cover and the upper sealing part to form a fixed connection.

4. A gas storage well casing head sealing method, used for the gas storage well casing head sealing device according to any one of claims 1 to 3, characterized in that: include: Based on the numerical simulation method, the target load of the main sealing area of ​​the casing head of the well to be sealed and the target preload force of the bolts of the casing head assembly are obtained; Obtaining the total hanging weight and the buoyancy of the casing string before sealing, wherein the total hanging weight is the sum of the hanging weights of the top drive, the landing joint, the hanger assembly and the casing string; Determine the closing traction force according to the total suspended weight, the target load of the main closing area and the buoyancy of the casing string; Applying the closing traction force at the end of the hanger seal away from the bottom hole to make the main seal area approach the main seal area target load; The casing head assembly is connected according to the target preload force.

5. The method for sealing a casing head of a gas storage well according to claim 4, characterized in that: The method of obtaining the target load of the main sealing area of ​​the casing head of the well to be sealed and the target preload force of the bolts of the casing head assembly based on the numerical simulation method includes: Obtain the annular pressure of the well to be sealed based on current working condition information and historical annular pressure data; Constructing a first mechanical simulation model and a first fluid simulation model corresponding to the primary sealing area; Determining a target load of the primary sealing area according to the annular space pressure, the first mechanical simulation model and the first fluid simulation model; Constructing a second mechanical simulation model corresponding to the secondary sealing area; The target bolt preload force is determined according to the second mechanical simulation model.

6. The method for sealing a casing head of a gas storage well according to claim 5, characterized in that: Determining the target load of the primary sealing area according to the annular space pressure, the first mechanical simulation model and the first fluid simulation model includes: Applying an initial load to the first mechanical simulation model to obtain deformation information; Loading the deformation information and the annular pressure into the fluid simulation model to obtain a fluid simulation result; An adjustment load is applied according to the fluid simulation result to perform a first mechanical and fluid mechanical iterative simulation cycle to obtain the target load corresponding to the sealing area under the pressure judgment condition and the gas flow judgment condition, wherein the initial load, the adjustment load and the target load are axial loads applied to the hanger seal, and the target load is the sum of the initial load and the adjustment load.

7. The method for sealing a casing head of a gas storage well according to claim 5, characterized in that: Determining the target bolt preload according to the second mechanical simulation model includes: Applying the target load and the initial preload to the second mechanical simulation model to obtain deformation information; An adjusted preload is applied according to the deformation information to perform a second mechanical simulation in a cyclic iteration, so that the secondary sealing area satisfies the target bolt preload corresponding to the contact judgment condition, wherein the initial load, the adjusted load and the target load are axial loads applied to the hanger seal, and the target load is the sum of the initial load and the adjusted load.

8. The method for sealing a casing head of a gas storage well according to claim 4, characterized in that: Determining the closing traction force according to the total suspended weight, the target load of the main closing area and the buoyancy of the casing string includes: The difference between the total suspended weight, the casing string buoyancy and the target load of the primary sealing area is used as a reference sealing traction force; In the case where the reference closing traction force is greater than or equal to zero, using the reference traction force as the closing traction force; In the case where the reference traction force is less than zero, the weight of the landing section and / or the top drive is increased to make the reference closing traction force greater than or equal to zero, and the reference traction force is used as the closing traction force.

9. The method for sealing a casing head of a gas storage well according to claim 4, characterized in that: Applying the closing traction force at the end of the hanger seal away from the bottom hole to make the main seal area approach the main seal area target load includes: Connecting the load output unit to the end of the hanger seal away from the bottom of the well, wherein the load output unit includes a computer, a controller, a motor, a pull rope, a fixed pulley, a large hook, a tension sensor, a top drive and a landing joint; The working stroke of the motor is controlled so that the actual load of the tension sensor approaches the closing traction force, so that the main sealing area approaches the main sealing area target load.

10. The method for sealing a casing head of a gas storage well according to claim 4, characterized in that: Connecting the casing head assembly according to the target preload force comprises: disconnecting the load output unit from the hanger seal; Remove the protective covers and straps from the gas reservoir seal; Sleeve the secondary casing head body on the upper sealing part of the hanger seal; The target pre-tightening force applied by the bolt assembly connects the primary casing head body and the secondary casing head body.

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