Method, device, medium and equipment for expanding capacity of carbon dioxide storage space of offshore depleted gas field

Abstract

The invention relates to an offshore depleted gas field carbon dioxide sequestration space expansion method, device, medium and equipment, and the method comprises the steps: calculating a first space expansion amount of offshore depleted gas field carbon dioxide sequestration by using an empirical formula; acquiring current state information of the exhausted natural gas reservoir; obtaining the mechanical strength of the cover layer; on the basis of the current state information of the depleted natural gas reservoir and the mechanical strength of the cover layer, predicting production dynamic data of the carbon dioxide injected into the offshore depleted gas field, and predicting and calculating a second space expansion amount of the carbon dioxide sequestration of the offshore depleted gas field through the predicted production dynamic data; the production dynamic data are optimized, the carbon dioxide storage amount after the capacity expansion of the carbon dioxide storage space of the offshore depleted gas field is obtained, and the optimized second space capacity expansion amount is obtained; and comparing the first space expansion amount with the optimized second space expansion amount, wherein the minimum value of the first space expansion amount and the optimized second space expansion amount is the offshore exhausted gas field carbon dioxide sequestration space expansion amount.

Description

Technical Field

[0001] The present invention relates to the technical field of geological storage of carbon dioxide, and in particular to a method, device, medium and equipment for expanding the storage space of carbon dioxide in an offshore depleted gas field. Background Art

[0002] Carbon dioxide geological storage is the most effective technical option for reducing greenhouse gas emissions on a large scale. Offshore carbon dioxide geological storage is an important measure to deal with greenhouse gas emissions in eastern China. At present, more than 17 offshore gas fields have been put into production in my country, with an annual oil and gas production of about 2900×10 4 Tons of oil equivalent, some gas fields have been in production for more than 20 years, or even 30 years, and their development and production have entered the late stage and are facing depletion. Offshore depleted gas fields have good sealing properties, and the geological environment is suitable for carbon dioxide storage. At the same time, offshore depleted gas fields have accumulated rich geological data in the long-term exploration and development process, which has laid a strong data foundation for carbon dioxide storage research and application. In addition, some of the original production facilities, such as onshore terminals, submarine pipelines, wellhead platforms and wellbores, can be used to store, transport and inject carbon dioxide, greatly reducing storage costs. Therefore, offshore depleted gas fields are an important place for future offshore carbon dioxide geological storage.

[0003] The unique geological environment and engineering conditions of offshore depleted gas fields bring new opportunities as well as new challenges, mainly reflected in the small space for carbon dioxide storage. Generally speaking, offshore depleted gas fields consist of three parts: the overlying saline water layer, the depleted natural gas layer and the underlying saline water layer. The pore pressure coefficient of the depleted natural gas layer after long-term development is small (for example, the pressure coefficient of a depleted natural gas layer in the East China Sea is about 0.3), while the pore pressure coefficients of the overlying saline water layer and the underlying saline water layer are about 1, which makes the average pore pressure difference between the depleted natural gas layer and the overlying saline water layer, and the depleted natural gas layer and the underlying saline water layer large. If the overlying saline water layer, the depleted natural gas layer and the underlying saline water layer are used at the same time, the average pore pressure difference between the depleted natural gas layer and the overlying saline water layer, and the depleted natural gas layer and the underlying saline water layer may continue to increase, causing the cap rock to be damaged, thereby leading to carbon dioxide leakage. Therefore, the existing offshore depleted gas field carbon dioxide storage projects only use the depleted natural gas layer for carbon dioxide storage, and have not yet used the overlying saline aquifer and underlying saline aquifer, resulting in a small carbon dioxide storage space. At present, the storage of carbon dioxide in offshore depleted gas fields at home and abroad is still in its infancy, and there are few public reports on the expansion of carbon dioxide storage space.

[0004] Therefore, there is an urgent need for a method to expand the carbon dioxide storage space in offshore depleted gas fields to increase the carbon dioxide storage capacity and economic benefits of the project. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a method, device, medium and equipment for expanding the carbon dioxide storage space of offshore depleted gas fields, which can achieve safe and efficient expansion of the carbon dioxide storage space of offshore depleted gas fields and increase the carbon dioxide storage capacity and economic benefits of the project.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The method for expanding the storage space of carbon dioxide in an offshore depleted gas field according to the present invention comprises the following steps:

[0008] Calculate the first space expansion capacity of CO2 storage in offshore depleted gas fields using empirical formulas;

[0009] Obtain information on the current status of depleted natural gas layers;

[0010] Obtaining the mechanical strength of the cap layer;

[0011] Based on the current state information of the depleted natural gas layer and the mechanical strength of the cap rock, the production dynamic data of carbon dioxide injection into the offshore depleted gas field is predicted, and the second space expansion capacity of carbon dioxide storage in the offshore depleted gas field is predicted and calculated through the predicted production dynamic data;

[0012] Optimize production dynamic data, obtain the CO2 storage capacity after the CO2 storage space of offshore depleted gas fields is expanded, and obtain the optimized second space expansion capacity;

[0013] Comparing the first space expansion capacity with the optimized second space expansion capacity, the minimum value between the two is the space expansion capacity for carbon dioxide storage in offshore depleted gas fields.

[0014] The method for expanding the storage space of carbon dioxide in an offshore depleted gas field, preferably, the method of calculating the first space expansion capacity of the storage space of carbon dioxide in an offshore depleted gas field by using an empirical formula specifically comprises the following steps:

[0015] According to the geological characteristics of the offshore depleted gas field, the depleted natural gas layer, the overlying saline water layer, the underlying saline water layer and the cap layer for carbon dioxide storage are determined, a cap layer is provided between the depleted natural gas layer and the overlying saline water layer, and a cap layer is provided between the depleted natural gas layer and the underlying saline water layer, wherein the depleted natural gas layer, the overlying saline water layer and the underlying saline water layer can all be injected with carbon dioxide for storage;

[0016] Determine the depth D of the depleted natural gas layer and the amount of natural gas resources OGIP, and use the following empirical formula to calculate the carbon dioxide storage capacity of the depleted natural gas layer

[0017]

[0018] Where a is the correction factor; is the density of injected carbon dioxide; R f is the gas field recovery factor; is the molar ratio of the same volume of CO2 to CH4 under offshore gas field conditions, calculated using the following formula:

[0019]

[0020] Determine the area A, depth h and average porosity of the overlying saline layer The following empirical formula is used to calculate the carbon dioxide storage capacity of the overlying saline layer:

[0021]

[0022] in, is the density of injected carbon dioxide; E is the storage factor, which is 3%;

[0023] Further clarify the underlying saline layer's coverage area B, depth H, average porosity The following empirical formula is used to calculate the carbon dioxide storage capacity of the underlying saline aquifer:

[0024]

[0025] in, is the density of injected carbon dioxide, E is the storage factor, which is 3%;

[0026] By simultaneously utilizing the depleted natural gas layer, the overlying saline aquifer and the underlying saline aquifer, the CO2 storage space in the offshore depleted gas field has been significantly increased. That is, the first space expansion capacity for carbon dioxide storage in offshore depleted gas fields.

[0027] The method for expanding the storage space of carbon dioxide in an offshore depleted gas field, preferably, the step of obtaining the current state information of the depleted natural gas layer specifically comprises the following steps:

[0028] According to the geological characteristics and production data of the depleted natural gas layer, and through numerical simulation technology, the actual oil production, gas production, water production, bottom hole temperature and pressure are fitted. After the fitting is completed, the current status information of the depleted natural gas layer can be output, including the oil, natural gas and water saturation distribution, pressure distribution and temperature distribution.

[0029] In the method for expanding the storage space of carbon dioxide in an offshore depleted gas field, preferably, obtaining the mechanical strength of the cap rock specifically comprises the following steps:

[0030] The cap rock in the offshore depleted gas field is cored and placed in a triaxial pressure chamber for triaxial strength testing to obtain the mechanical strength W of the cap rock.

[0031] The method for expanding the storage space of carbon dioxide in an offshore depleted gas field preferably predicts the production dynamic data of carbon dioxide injected into the offshore depleted gas field, and predicts and calculates the second space expansion capacity of carbon dioxide storage in the offshore depleted gas field through the predicted production dynamic data, specifically comprising the following steps:

[0032] According to the geomechanical parameters and fluid mechanics parameters of offshore depleted gas fields, the fluid-solid coupling numerical model of offshore depleted gas fields is established as follows:

[0033]

[0034] Among them, K uu is the pore skeleton stiffness of the formation; K uf is the coupling stiffness between formation pores and fluid; K ff is the formation fluid flow stiffness; i is the formation deformation; p is the formation pore pressure; F u is the formation mechanics boundary condition; F p is the formation fluid boundary condition;

[0035] The above numerical model is discretized by finite element method, and the CO2 injection parameters of the depleted natural gas layer, the overlying saline layer and the underlying saline layer are imported, including the injection rate and injection time. After the calculation is completed, the production dynamic data of CO2 injection into the offshore depleted gas field can be output, including the formation pore pressure and formation deformation;

[0036] The amount of carbon dioxide stored in depleted natural gas layers is calculated using the following formula:

[0037]

[0038] where t 11 and t 12 are the start and stop time of carbon dioxide injection into the depleted natural gas layer, respectively; V1(t) is the carbon dioxide injection rate into the depleted natural gas layer;

[0039] The average pore pressure of a depleted gas layer is calculated by the following formula:

[0040]

[0041] Where N1 is the number of finite element grids in the depleted natural gas layer; p1(i) is the pore pressure of the i-th finite element grid in the depleted natural gas layer;

[0042] The amount of carbon dioxide stored in the overlying saline aquifer is calculated using the following formula:

[0043]

[0044] where t 21 and t 22 are the start and stop time of carbon dioxide injection into the overlying saline water layer, respectively; V2(t) is the carbon dioxide injection rate into the overlying saline water layer;

[0045] The average pore pressure of the overlying saline layer is calculated by the following formula:

[0046]

[0047] Where N2 is the number of finite element grids in the overlying saline layer; p2(i) is the pore pressure of the i-th finite element grid in the overlying saline layer;

[0048] The amount of carbon dioxide stored in the underlying saline aquifer is calculated using the following formula:

[0049]

[0050] where t 31 and t 32 are the start and stop time of carbon dioxide injection into the underlying saline aquifer, respectively; V3(t) is the carbon dioxide injection rate into the underlying saline aquifer;

[0051] The average pore pressure of the underlying saline layer 5 is calculated by the following formula:

[0052]

[0053] Where N3 is the number of finite element grids in the underlying saline water layer; p3(i) is the pore pressure of the i-th finite element grid in the underlying saline water layer;

[0054] By simultaneously utilizing the depleted natural gas layer, the overlying saline aquifer and the underlying saline aquifer, the carbon dioxide storage space in the offshore depleted gas field is significantly increased. The carbon dioxide storage space is expanded by C2+C3. C2+C3 is the second space expansion capacity of carbon dioxide storage in the offshore depleted gas field.

[0055] The method for expanding the carbon dioxide storage space of an offshore depleted gas field, preferably, optimizing the production dynamic data, obtaining the carbon dioxide storage capacity after the expansion of the carbon dioxide storage space of the offshore depleted gas field, and obtaining the optimized second space expansion capacity, specifically comprises the following steps:

[0056] The CO2 injection system in the CO2 injection well is equipped with a packer, so as to realize the independent setting of CO2 injection parameters for the depleted natural gas layer, the overlying saline layer and the underlying saline layer;

[0057] The objective function is constructed using the least squares method as follows:

[0058]

[0059] By adjusting the CO2 injection parameters of the depleted natural gas layer, the overlying saline layer and the underlying saline layer, the objective function converges and the optimized production dynamic parameters are obtained. The CO2 storage space expansion C2′+C3′ can be obtained through formulas (8) and (10), and C2′+C3′ is the optimized second space expansion capacity. When the objective function does not converge, the CO2 injection parameters of the depleted natural gas layer, the overlying saline layer and the underlying saline layer are continuously adjusted until the objective function converges.

[0060] The present invention also provides a device for expanding the storage space of carbon dioxide in an offshore depleted gas field, comprising:

[0061] A first processing unit is used to calculate the first space expansion capacity of carbon dioxide storage in an offshore depleted gas field using an empirical formula;

[0062] A second processing unit is used to obtain current status information of the depleted natural gas layer;

[0063] The third processing unit is used to obtain the mechanical strength of the cap layer;

[0064] The fourth processing unit is used to predict the production dynamic data of carbon dioxide injection into the offshore depleted gas field based on the current state information of the depleted natural gas layer and the mechanical strength of the cap rock, and predict and calculate the second space expansion capacity of the offshore depleted gas field carbon dioxide storage through the predicted production dynamic data;

[0065] A fifth processing unit is used to optimize the production dynamic data, obtain the carbon dioxide storage capacity after the carbon dioxide storage space of the offshore depleted gas field is expanded, and obtain the optimized second space expansion capacity;

[0066] The sixth processing unit is used to compare the first space expansion capacity and the optimized second space expansion capacity, and the minimum value between the two is the space expansion capacity of carbon dioxide storage in the offshore depleted gas field.

[0067] The present invention also provides a computer storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method for expanding the capacity of carbon dioxide storage space in an offshore depleted gas field are implemented.

[0068] The present invention also provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method for expanding the capacity of carbon dioxide storage space in an offshore depleted gas field when executing the computer program.

[0069] The present invention adopts the above technical solution, which has the following advantages:

[0070] The present invention comprehensively utilizes the depleted natural gas layer, the overlying saline water layer and the underlying saline water layer, thereby significantly expanding the carbon dioxide storage space of the offshore depleted gas field; the present invention also systematically optimizes the carbon dioxide injection parameters of the depleted natural gas layer, the overlying saline water layer and the underlying saline water layer, ensuring the safety of the depleted natural gas layer, the overlying saline water layer and the underlying saline water layer during the carbon dioxide injection process. Thus, an efficient and safe method for expanding the carbon dioxide storage space of offshore depleted gas fields is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention.

[0072] Throughout the drawings, the same reference numerals are used to denote the same components. In the drawings:

[0073] Figure 1 It is a schematic diagram of the carbon dioxide injection system in the present invention.

[0074] The reference numerals in the figures are as follows:

[0075] 1-CO2 injection well; 11-CO2 integrated injection system; 2-cap rock; 3-overlying saline layer; 4-depleted natural gas layer; 5-underlying saline layer; 6-packer. DETAILED DESCRIPTION

[0076] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0077] The present invention provides a method for expanding the carbon dioxide storage space of an offshore depleted gas field, with the goal that the average pore pressure difference between the overlying saline water layer and the depleted natural gas layer during carbon dioxide injection is less than the cap rock strength, and the average pore pressure difference between the underlying saline water layer and the depleted natural gas layer is less than the cap rock strength. The depleted natural gas layer, the overlying saline water layer and the underlying saline water layer of the offshore depleted gas field are safely and efficiently utilized, thereby increasing the carbon dioxide storage space capacity of the offshore depleted gas field and being able to guide on-site application.

[0078] The method for expanding the storage space of carbon dioxide in an offshore depleted gas field provided by the present invention comprises the following steps:

[0079] (1) Calculate the first space expansion capacity of CO2 storage in offshore depleted gas fields using empirical formulas;

[0080] (2) Obtaining information on the current status of depleted natural gas layers;

[0081] (3) Obtaining the mechanical strength of the cap layer;

[0082] (4) Based on the current state information of the depleted natural gas layer and the mechanical strength of the cap rock, predict the production dynamic data of carbon dioxide injection into the offshore depleted gas field, and predict and calculate the second space expansion capacity of carbon dioxide storage in the offshore depleted gas field through the predicted production dynamic data;

[0083] (5) Optimizing production dynamic data, obtaining the CO2 storage capacity after the CO2 storage space of the offshore depleted gas field is expanded, and obtaining the optimized second space expansion capacity;

[0084] (6) The first space expansion capacity and the optimized second space expansion capacity are compared, and the minimum value between the two is the space expansion capacity of carbon dioxide storage in offshore depleted gas fields.

[0085] In the above embodiment, preferably, the calculation of the first space expansion capacity of carbon dioxide storage in an offshore depleted gas field by using an empirical formula specifically includes the following steps:

[0086] like Figure 1 As shown, according to the geological characteristics of the offshore depleted gas field, the depleted natural gas layer 4, the overlying saline water layer 3, the underlying saline water layer 5 and the cap layer 2 for carbon dioxide storage are determined, the cap layer 2 is provided between the depleted natural gas layer 4 and the overlying saline water layer 3, and the cap layer 2 is provided between the depleted natural gas layer 4 and the underlying saline water layer 5, wherein the depleted natural gas layer 4, the overlying saline water layer 3 and the underlying saline water layer 5 can all be injected with carbon dioxide for storage;

[0087] Determine the depth D and natural gas resource OGIP of depleted natural gas layer 4, and use the following empirical formula to calculate the carbon dioxide storage capacity of depleted natural gas layer 4

[0088]

[0089] Where a is the correction coefficient, which is 1; is the density of injected carbon dioxide; R f is the gas field recovery factor, with a value of 0.60; is the molar ratio of the same volume of CO2 to CH4 under offshore gas field conditions, calculated using the following formula:

[0090]

[0091] Determine the coverage area A, depth h and average porosity of the overlying saline layer 3 The following empirical formula is used to calculate the carbon dioxide storage capacity of the overlying saline layer 3

[0092]

[0093] in, is the density of injected carbon dioxide; E is the storage factor, which is 3%;

[0094] Further clarify the coverage area B, depth H, average porosity of the underlying saline layer 5 The following empirical formula is used to calculate the carbon dioxide storage capacity of the underlying saline aquifer 5

[0095]

[0096] in, is the density of injected carbon dioxide, E is the storage factor, which is 3%;

[0097] By simultaneously utilizing the depleted natural gas layer 4, the overlying saline aquifer 3 and the underlying saline aquifer 5, the CO2 storage space in the offshore depleted gas field has been significantly increased. That is, the first space expansion capacity for carbon dioxide storage in offshore depleted gas fields.

[0098] In the above embodiment, preferably, the obtaining of the current status information of the depleted natural gas layer specifically includes the following steps:

[0099] According to the geological characteristics and production data of the depleted natural gas layer, and through numerical simulation technology, the actual oil production, gas production, water production, bottom hole temperature and pressure are fitted. After the fitting is completed, the current status information of the depleted natural gas layer can be output, including the oil, natural gas and water saturation distribution, pressure distribution and temperature distribution.

[0100] In the above embodiment, preferably, obtaining the mechanical strength of the cover layer 2 specifically includes the following steps:

[0101] The cap layer 2 in the offshore depleted gas field is cored, placed in a triaxial pressure chamber and then subjected to a triaxial strength test to obtain the mechanical strength W of the cap layer.

[0102] In the above embodiment, preferably, predicting the production dynamic data of carbon dioxide injection into an offshore depleted gas field, and predicting and calculating the second space expansion capacity of carbon dioxide storage in the offshore depleted gas field through the predicted production dynamic data, specifically includes the following steps:

[0103] According to the geomechanical parameters and fluid mechanics parameters of offshore depleted gas fields, the fluid-solid coupling numerical model of offshore depleted gas fields is established as follows:

[0104]

[0105] Among them, Kuu is the pore skeleton stiffness of the formation; K uf is the coupling stiffness between formation pores and fluid; K ff is the formation fluid flow stiffness; u is the formation deformation; p is the formation pore pressure; F u is the formation mechanics boundary condition; F p is the formation fluid boundary condition;

[0106] The above numerical model is discretized by finite element method, and the carbon dioxide injection parameters of the depleted natural gas layer 4, the overlying saline water layer 3 and the underlying saline water layer 5 are imported, including the injection rate and injection time. After the calculation is completed, the production dynamic data of carbon dioxide injection into the offshore depleted gas field can be output, including the formation pore pressure and formation deformation;

[0107] The amount of carbon dioxide stored in depleted natural gas layers is calculated using the following formula:

[0108]

[0109] where t 11 and t 12 are the start and stop time of carbon dioxide injection into the depleted natural gas layer 4; V1(t) is the carbon dioxide injection rate into the depleted natural gas layer;

[0110] The average pore pressure of the depleted natural gas layer 4 is calculated by the following formula:

[0111]

[0112] Wherein, N1 is the number of finite element grids in the depleted natural gas layer 4; p1(i) is the pore pressure of the i-th finite element grid in the depleted natural gas layer 4;

[0113] The carbon dioxide storage capacity of the overlying saline layer 3 is calculated using the following formula:

[0114]

[0115] where t 21 and t 22 are the start and stop time of carbon dioxide injection into the overlying saline water layer, respectively; V2(t) is the carbon dioxide injection rate into the overlying saline water layer;

[0116] The average pore pressure of the overlying saline layer 3 is calculated by the following formula:

[0117]

[0118] Wherein, N2 is the number of finite element grids in the overlying saline water layer 3; p2(i) is the pore pressure of the i-th finite element grid in the overlying saline water layer 3;

[0119] The amount of carbon dioxide stored in the underlying saline aquifer 5 is calculated using the following formula:

[0120]

[0121] where t 31 and t 32 are the start and stop time of carbon dioxide injection into the underlying saline water layer 5, respectively; V3(t) is the carbon dioxide injection rate into the underlying saline water layer 5;

[0122] The average pore pressure of the underlying saline layer 5 is calculated by the following formula:

[0123]

[0124] Wherein, N3 is the number of finite element grids in the underlying saline water layer 5; p3(i) is the pore pressure of the i-th finite element grid in the underlying saline water layer 5;

[0125] By simultaneously utilizing the depleted natural gas layer 4, the overlying saline water layer 3 and the underlying saline water layer 5, the carbon dioxide storage space in the offshore depleted gas field is significantly increased, and the carbon dioxide storage space is expanded by C2+C3. C2+C3 is the second space expansion capacity of carbon dioxide storage in the offshore depleted gas field.

[0126] In the above embodiment, preferably, the optimizing production dynamic data, obtaining the carbon dioxide storage capacity after the carbon dioxide storage space of the offshore depleted gas field is expanded, and obtaining the optimized second space expansion capacity specifically includes the following steps:

[0127] The carbon dioxide injection system 11 in the carbon dioxide injection well 1 is provided with a packer 6, so as to realize independent setting of carbon dioxide injection parameters for the depleted natural gas layer 4, the overlying saline water layer 3 and the underlying saline water layer 5;

[0128] The objective function is constructed using the least squares method as follows:

[0129]

[0130] By adjusting the CO2 injection parameters of the depleted natural gas layer, the overlying saline layer and the underlying saline layer, the objective function converges and the optimized production dynamic parameters are obtained. The CO2 storage space expansion C2′+C3′ can be obtained through formulas (8) and (10), and C2′+C3′ is the optimized second space expansion capacity. When the objective function does not converge, the CO2 injection parameters of the depleted natural gas layer, the overlying saline layer and the underlying saline layer are continuously adjusted until the objective function converges.

[0131] The present invention also provides a device for expanding the storage space of carbon dioxide in an offshore depleted gas field, comprising:

[0132] A first processing unit is used to calculate the first space expansion capacity of carbon dioxide storage in an offshore depleted gas field using an empirical formula;

[0133] A second processing unit is used to obtain current status information of the depleted natural gas layer;

[0134] The third processing unit is used to obtain the mechanical strength of the cap layer;

[0135] The fourth processing unit is used to predict the production dynamic data of carbon dioxide injection into the offshore depleted gas field based on the current state information of the depleted natural gas layer and the mechanical strength of the cap rock, and predict and calculate the second space expansion capacity of the offshore depleted gas field carbon dioxide storage through the predicted production dynamic data;

[0136] A fifth processing unit is used to optimize the production dynamic data, obtain the carbon dioxide storage capacity after the carbon dioxide storage space of the offshore depleted gas field is expanded, and obtain the optimized second space expansion capacity;

[0137] The sixth processing unit is used to compare the first space expansion capacity and the optimized second space expansion capacity, and the minimum value between the two is the space expansion capacity of carbon dioxide storage in the offshore depleted gas field.

[0138] The present invention also provides a computer storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method for expanding the capacity of carbon dioxide storage space in an offshore depleted gas field are implemented.

[0139] The present invention also provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method for expanding the capacity of carbon dioxide storage space in an offshore depleted gas field when executing the computer program.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention 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 invention.

Claims

1. A method for expanding the storage space of carbon dioxide in an offshore depleted gas field, characterized in that: The steps include: Calculate the first space expansion capacity of CO2 storage in offshore depleted gas fields using empirical formulas; Obtain information on the current status of depleted natural gas layers; Obtaining the mechanical strength of the cap layer; Based on the current state information of the depleted natural gas layer and the mechanical strength of the cap rock, the production dynamic data of carbon dioxide injection into the offshore depleted gas field is predicted, and the second space expansion capacity of carbon dioxide storage in the offshore depleted gas field is predicted and calculated through the predicted production dynamic data; Optimize production dynamic data, obtain the CO2 storage capacity after the CO2 storage space of offshore depleted gas fields is expanded, and obtain the optimized second space expansion capacity; Comparing the first space expansion capacity with the optimized second space expansion capacity, the minimum value between the two is the space expansion capacity for carbon dioxide storage in offshore depleted gas fields.

2. The method for expanding the storage space of carbon dioxide in an offshore depleted gas field according to claim 1, characterized in that: The method of calculating the first space expansion capacity of carbon dioxide storage in an offshore depleted gas field by using an empirical formula specifically comprises the following steps: According to the geological characteristics of the offshore depleted gas field, the depleted natural gas layer, the overlying saline water layer, the underlying saline water layer and the cap layer for carbon dioxide storage are determined, a cap layer is provided between the depleted natural gas layer and the overlying saline water layer, and a cap layer is provided between the depleted natural gas layer and the underlying saline water layer, wherein the depleted natural gas layer, the overlying saline water layer and the underlying saline water layer can all be injected with carbon dioxide for storage; Determine the depth D of the depleted natural gas layer and the amount of natural gas resources OGIP, and use the following empirical formula to calculate the carbon dioxide storage capacity of the depleted natural gas layer Where A is the correction factor; is the density of injected carbon dioxide; R f is the gas field recovery factor; is the molar ratio of the same volume of CO2 to CH4 under offshore gas field conditions, calculated using the following formula: Determine the coverage area A, depth h and average porosity of the overlying saline layer The following empirical formula is used to calculate the carbon dioxide storage capacity of the overlying saline layer: in, is the density of injected carbon dioxide; E is the storage coefficient; Further clarify the underlying saline layer's coverage area B, depth H, average porosity The following empirical formula is used to calculate the carbon dioxide storage capacity of the underlying saline aquifer: in, is the density of injected carbon dioxide, E is the storage factor, which is 3%; By simultaneously utilizing the depleted natural gas layer, the overlying saline aquifer and the underlying saline aquifer, the CO2 storage space in the offshore depleted gas field has been significantly increased. That is, the first space expansion capacity for carbon dioxide storage in offshore depleted gas fields.

3. The method for expanding the storage space of carbon dioxide in an offshore depleted gas field according to claim 1, characterized in that: The step of obtaining the current state information of the depleted natural gas layer specifically includes the following steps: According to the geological characteristics and production data of the depleted natural gas layer, and through numerical simulation technology, the actual oil production, gas production, water production, bottom hole temperature and pressure are fitted. After the fitting is completed, the current status information of the depleted natural gas layer can be output, including the oil, natural gas and water saturation distribution, pressure distribution and temperature distribution.

4. The method for expanding the storage space of carbon dioxide in an offshore depleted gas field according to claim 1, characterized in that: The obtaining of the mechanical strength of the cap layer specifically comprises the following steps: The cap rock in the offshore depleted gas field is cored and placed in a triaxial pressure chamber for triaxial strength testing to obtain the mechanical strength W of the cap rock.

5. The method for expanding the storage space of carbon dioxide in an offshore depleted gas field according to claim 1, characterized in that: Predicting the production dynamic data of carbon dioxide injection into an offshore depleted gas field, and predicting and calculating the second space expansion capacity of carbon dioxide storage in the offshore depleted gas field through the predicted production dynamic data, specifically includes the following steps: According to the geomechanical parameters and fluid mechanics parameters of offshore depleted gas fields, the fluid-solid coupling numerical model of offshore depleted gas fields is established as follows: Among them, K uu is the pore skeleton stiffness of the formation; K uf is the coupling stiffness between formation pores and fluid; K ff is the formation fluid flow stiffness; u is the formation deformation; p is the formation pore pressure; F u is the formation mechanics boundary condition; F p is the formation fluid boundary condition; The above numerical model is discretized by finite element method, and the CO2 injection parameters of the depleted natural gas layer, the overlying saline layer and the underlying saline layer are imported, including the injection rate and injection time. After the calculation is completed, the production dynamic data of CO2 injection into the offshore depleted gas field can be output, including the formation pore pressure and formation deformation; The amount of carbon dioxide stored in depleted natural gas layers is calculated using the following formula: where t 11 and t 12 are the start and stop time of carbon dioxide injection into the depleted natural gas layer, respectively; V1(t) is the carbon dioxide injection rate into the depleted natural gas layer; The average pore pressure of a depleted gas layer is calculated by the following formula: Where N1 is the number of finite element grids in the depleted natural gas layer; p1(i) is the pore pressure of the i-th finite element grid in the depleted natural gas layer; The amount of carbon dioxide stored in the overlying saline aquifer is calculated using the following formula: where t 21 and t 22 are the start and stop time of carbon dioxide injection into the overlying saline water layer, respectively; V2(t) is the carbon dioxide injection rate into the overlying saline water layer; The average pore pressure of the overlying saline layer is calculated by the following formula: Where N2 is the number of finite element grids in the overlying saline layer; p2(i) is the pore pressure of the i-th finite element grid in the overlying saline layer; The amount of carbon dioxide stored in the underlying saline aquifer is calculated using the following formula: where t 31 and t 32 are the start and stop time of carbon dioxide injection into the underlying saline aquifer, respectively; V3(t) is the carbon dioxide injection rate into the underlying saline aquifer; The average pore pressure of the underlying saline aquifer is calculated by: Where N3 is the number of finite element grids in the underlying saline water layer; p3(i) is the pore pressure of the i-th finite element grid in the underlying saline water layer; By simultaneously utilizing the depleted natural gas layer, the overlying saline aquifer and the underlying saline aquifer, the carbon dioxide storage space in the offshore depleted gas field is significantly increased. The carbon dioxide storage space is expanded by C2+C3. C2+C3 is the second space expansion capacity of carbon dioxide storage in the offshore depleted gas field.

6. The method for expanding the storage space of carbon dioxide in an offshore depleted gas field according to claim 5, characterized in that: The optimization of production dynamic data, obtaining the carbon dioxide storage capacity after the expansion of the carbon dioxide storage space of the offshore depleted gas field, and obtaining the optimized second space expansion capacity specifically includes the following steps: The CO2 injection system in the CO2 injection well is equipped with a packer, so as to realize the independent setting of CO2 injection parameters for the depleted natural gas layer, the overlying saline layer and the underlying saline layer; The objective function is constructed using the least squares method as follows: By adjusting the CO2 injection parameters of the depleted natural gas layer, the overlying saline layer and the underlying saline layer, the objective function converges and the optimized production dynamic parameters are obtained. The CO2 storage space expansion C2′+C3′ can be obtained through formulas (8) and (10), and C2′+C3′ is the optimized second space expansion capacity. When the objective function does not converge, the CO2 injection parameters of the depleted natural gas layer, the overlying saline layer and the underlying saline layer are continuously adjusted until the objective function converges.

7. A device for expanding the storage space of carbon dioxide in an offshore depleted gas field, characterized in that: include: A first processing unit is used to calculate the first space expansion capacity of carbon dioxide storage in an offshore depleted gas field using an empirical formula; A second processing unit is used to obtain current status information of the depleted natural gas layer; The third processing unit is used to obtain the mechanical strength of the cap layer; The fourth processing unit is used to predict the production dynamic data of carbon dioxide injection into the offshore depleted gas field based on the current state information of the depleted natural gas layer and the mechanical strength of the cap rock, and predict and calculate the second space expansion capacity of the offshore depleted gas field carbon dioxide storage through the predicted production dynamic data; A fifth processing unit is used to optimize the production dynamic data, obtain the carbon dioxide storage capacity after the carbon dioxide storage space of the offshore depleted gas field is expanded, and obtain the optimized second space expansion capacity; The sixth processing unit is used to compare the first space expansion capacity and the optimized second space expansion capacity, and the minimum value between the two is the space expansion capacity of carbon dioxide storage in the offshore depleted gas field.

8. A computer storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for expanding the storage space of carbon dioxide in an offshore depleted gas field according to any one of claims 1 to 6 are implemented.

9. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method for expanding the storage space of carbon dioxide in an offshore depleted gas field as described in any one of claims 1-6 are implemented.

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