Prediction method and device for average formation pressure of coal bed gas reservoir and storage medium

Abstract

The invention relates to the technical field of coal bed gas exploitation, in particular to a prediction method and device for the average formation pressure of a coal bed gas reservoir and a storage medium. The prediction method comprises the steps that the pressure index of a target coal bed gas reservoir is determined according to the gas reservoir temperature and the pore size of the target coal bed; in the target coal bed gas reservoir exploitation process, multiple groups of accumulated gas production rates and corresponding actually measured average formation pressures are recorded; acquiring Langmuir volume and Langmuir pressure of the target coal bed gas reservoir; introducing the Langmuir volume, the Langmuir pressure, the pressure index, the multiple groups of accumulated gas production rates and the multiple groups of actually measured average formation pressures into a Langmuir-Frandhi model so as to determine the total gas reserves and the critical desorption pressure of the target coal bed gas reservoir; and according to the total gas reserves, the critical desorption pressure, the Langmuir pressure and the pressure index of the target coal bed gas reservoir, predicting the average formation pressure corresponding to each accumulated gas production rate. By adopting the method, the average formation pressure of the target coal bed gas reservoir can be efficiently predicted.

Description

Technical Field

[0001] The present application relates to the technical field of coalbed methane exploitation, and in particular to a method, device and storage medium for predicting average formation pressure of a coalbed methane reservoir. Background Art

[0002] As one of the key unconventional resources, coalbed methane has attracted great attention worldwide because it helps to ease energy shortages, reduce coal mine accidents and reduce environmental burdens. The exploitation of undersaturated coalbed methane reservoirs is affected by reserves and average formation pressure, which are crucial for estimating the original geological reserves, remaining reserves and evaluating the interference between wells of coalbed methane reservoirs. They are of great theoretical and practical significance for analyzing the production performance of gas wells and evaluating production capacity.

[0003] At present, the method for calculating the average formation pressure of undersaturated coalbed methane reservoirs not only considers the production of gas, but also includes the production of water. This requires understanding many parameters such as the relative density of gas, the temperature of the coal reservoir, the initial porosity, the original water saturation, the pore compressibility coefficient and the water phase compressibility coefficient. In the process of calculating the average formation pressure of coalbed methane reservoirs, in addition to the need to input the cumulative gas production, the cumulative water production must also be input, and the gas deviation coefficient needs to be calculated iteratively, which makes the calculation process complicated. Especially for medium and shallow coalbed methane reservoirs and deep coalbed methane reservoirs without free gas, the formation structure is simple and does not actually require so many parameters. Frequent measurement and calculation will not only affect the production capacity and output of coalbed methane, but also increase the cost of coalbed methane mining. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a method, device and storage medium for predicting the average formation pressure of a coalbed methane reservoir, so as to solve the technical problem of difficulty in calculating the average formation pressure of an undersaturated coalbed methane reservoir existing in the prior art.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a method for predicting the average formation pressure of a coalbed methane reservoir, the prediction method comprising:

[0006] Determine the pressure index of the target coal seam gas reservoir according to the gas reservoir temperature and pore size of the target coal seam;

[0007] During the mining process of the target coalbed methane reservoir, multiple groups of cumulative gas production and their corresponding measured average formation pressures are recorded;

[0008] Obtain the Langmuir volume and Langmuir pressure of the target coalbed methane reservoir;

[0009] The Langmuir volume, Langmuir pressure, pressure index, multiple sets of cumulative gas production and multiple sets of measured average formation pressures are imported into the Langmuir-Freundrich model to determine the total gas reserves and critical desorption pressure of the target coalbed methane reservoir;

[0010] The average formation pressure corresponding to each cumulative gas production is predicted based on the total gas reserves, critical desorption pressure, Langmuir pressure and pressure index of the target coalbed methane reservoir.

[0011] In the embodiment of the present application, the steps of importing the Langmuir volume, Langmuir pressure, pressure index, multiple groups of cumulative gas production and multiple groups of measured average formation pressure into the Langmuir-Friedrich model to determine the total gas reserves and critical desorption pressure of the target coalbed methane reservoir include: constructing a material balance equation for the coalbed methane reservoir based on the Langmuir volume, Langmuir pressure and pressure index; constructing a material balance equation for the cumulative production and p based on the material balance equation m / (p L m +p m ), where p is the average formation pressure, pL is the Langmuir pressure, and m is the pressure exponent; the slope and vertical intercept of the linear function are determined according to multiple groups of measured average formation pressures and multiple groups of cumulative gas production; the total gas reserves of the target coalbed methane reservoir are determined according to the slope and vertical intercept of the linear function.

[0012] In the embodiment of the present application, the material balance equation of the coalbed methane reservoir is constructed as follows:

[0013]

[0014] Among them, G p is the cumulative production, h is the coal reservoir thickness of the target CBM reservoir, A is the controlled area of ​​the target CBM reservoir, ρ c is the coal rock density of the target CBM reservoir, V L is the Langmuir volume, p d is the critical desorption pressure of the target coalbed methane reservoir, p L is the Langmuir pressure, p is the average formation pressure, and m is the pressure index.

[0015] In the embodiment of the present application, the cumulative output and p are constructed based on the material balance equation. m / (p L m +p m ) includes the following steps:

[0016] Based on the transformation of formula (1), the following formula (2) is obtained:

[0017]

[0018] Based on formula (2), the linear function expression (3) is obtained by further transformation:

[0019]

[0020] Where N represents the vertical intercept of the linear function. M represents the slope of a linear function. G is the reserves of coalbed methane in the coalbed methane reservoir, G p is the cumulative output, p d is the critical desorption pressure of the target coalbed methane reservoir, p L is the Langmuir pressure, p is the average formation pressure, and m is the pressure index.

[0021] In the embodiment of the present application, the total gas reserves of the target coalbed methane reservoir are determined according to the following formula (4):

[0022]

[0023] Among them, G is the reserves of coalbed methane in the coalbed methane reservoir, N is the vertical intercept of the linear function, and M is the slope of the linear function.

[0024] In the embodiment of the present application, the average formation pressure is determined according to the following formula (5):

[0025]

[0026] Where p is the average formation pressure, p L is the Langmuir pressure, m is the pressure index, N is the vertical intercept of the linear function, G is the reserves of coalbed methane in the coalbed methane reservoir, G p For cumulative production.

[0027] In the embodiment of the present application, the critical desorption pressure of the target coalbed methane reservoir is determined according to the following formula (6):

[0028]

[0029] Among them, p d is the critical desorption pressure of the target coalbed methane reservoir, p L is the Langmuir pressure, m is the pressure exponent, and N is the vertical intercept of the linear function.

[0030] In the embodiment of the present application, the prediction method further includes determining the control area of ​​the target coalbed methane reservoir according to the following formula (7):

[0031]

[0032] Where h is the coal reservoir thickness of the target coalbed methane reservoir, A is the control area of ​​the target coalbed methane reservoir, ρ cis the coal rock density of the target CBM reservoir, V L is the Langmuir volume, and M represents the slope of the linear function.

[0033] A second aspect of the present application provides a device for determining the average formation pressure of an undersaturated coalbed methane reservoir, comprising: a memory configured to store instructions; and a processor configured to call instructions from the memory and to implement the above-mentioned method for predicting the average formation pressure of a coalbed methane reservoir when executing the instructions.

[0034] A third aspect of the present application provides a machine-readable storage medium having instructions stored thereon, the instructions being used to enable a machine to execute the above-mentioned method for predicting the average formation pressure of a coalbed methane reservoir.

[0035] In the above technical scheme, when predicting the average formation pressure of the target coal seam, the pressure index of the target coal seam gas reservoir is first determined according to the gas reservoir temperature and pore size of the target coal seam. Through this pressure index, the physical properties of the coal seam gas reservoir can be described more accurately, thereby improving the accuracy of the prediction. Then, multiple groups of cumulative gas production and corresponding measured average formation pressures recorded during the exploitation of the target coal seam gas reservoir, as well as the Langmuir volume and Langmuir pressure of the target coal seam gas reservoir are obtained. After determining these key parameters, they are imported into the Langmuir-Freundrich model. The model can comprehensively consider the complex characteristics of the coal seam gas reservoir, output the total gas reserves and critical desorption pressure of the target coal seam gas reservoir, and predict the average formation pressure corresponding to each cumulative gas production according to the total gas reserves, critical desorption pressure, Langmuir pressure and pressure index. Through the above prediction method, not only the calculation process is simplified, but also the accuracy and reliability of the prediction are improved, providing strong technical support for the exploitation of coal seam gas reservoirs. In addition, this method can also determine relevant parameters based on the specific conditions of the target coalbed methane reservoir and the actual data during the mining process, thereby improving the pertinence and accuracy of the prediction.

[0036] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present application, but do not constitute a limitation on the embodiments of the present application. In the accompanying drawings:

[0038] Figure 1 A schematic diagram of a process flow of a method for predicting average formation pressure of a coalbed methane reservoir according to an embodiment of the present application is schematically shown;

[0039] Figure 2A schematic diagram of a dynamic curve showing the cumulative gas production and daily gas production changing with production time according to an embodiment of the present application is shown;

[0040] Figure 3 A schematic diagram of a linear function image provided according to an embodiment of the present application is schematically shown;

[0041] Figure 4 A schematic diagram of a dynamic curve of average formation pressure and production time provided according to an embodiment of the present application is schematically shown. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme 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. It should be understood that the specific implementation methods described herein are only used to illustrate and explain the embodiments of the present application, and are not used to limit the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0043] It should be noted that the acquisition, transmission, storage, use, and processing of data in the technical solution of this application are in compliance with the relevant provisions of national laws and regulations. In the embodiments of this application, some existing solutions in the industry such as certain software, components, and models may be mentioned, which should be considered as exemplary. Their purpose is only to illustrate the feasibility of implementing the technical solution of this application, but it does not mean that the applicant has or will necessarily use the solution.

[0044] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0045] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0046] Figure 1The following schematically shows a flow chart of a method for predicting the average formation pressure of a coalbed methane reservoir according to an embodiment of the present application. Figure 1 As shown, the embodiment of the present application provides a method for predicting the average formation pressure of a coalbed methane reservoir, and the prediction method may include the following steps:

[0047] S101, determining a pressure index of a target coalbed methane reservoir according to a gas reservoir temperature and a pore size of the target coalbed.

[0048] S102, during the mining process of the target coalbed methane reservoir, multiple groups of cumulative gas production and their corresponding measured average formation pressures are recorded.

[0049] S103, obtaining the Langmuir volume and Langmuir pressure of the target coalbed methane reservoir.

[0050] S104, importing the Langmuir volume, Langmuir pressure, pressure index, multiple groups of cumulative gas production and multiple groups of measured average formation pressure into the Langmuir-Freundrich model to determine the total gas reserves and critical desorption pressure of the target coalbed methane reservoir.

[0051] S105, predicting an average formation pressure corresponding to each cumulative gas production according to the total gas reserves, critical desorption pressure, Langmuir pressure and pressure index of the target coalbed methane reservoir.

[0052] In the process of coalbed methane exploitation, it is necessary to calculate the average formation pressure of the coalbed methane reservoir in order to analyze the production dynamics, production capacity, remaining reserves and other data of the gas well. However, the method of determining the average formation pressure in the prior art is not convenient to measure, resulting in a long interval between each measurement of the average formation pressure in the production data table. The present application can predict the measured average formation pressure corresponding to other cumulative gas production based on the cumulative gas production and the corresponding measured average formation pressure in the production cycle table, thereby better guiding the production process.

[0053] Specifically, when predicting the average formation pressure of the target coal seam, the pressure index of the target coal seam is first determined according to the gas reservoir temperature and pore size of the target coal seam. During the mining process of the target coal seam, the cumulative gas production and its corresponding measured average formation pressure data are recorded, which are the key inputs in the subsequent prediction process. By accurately measuring and recording these data, the accuracy and reliability of the prediction results can be ensured. Subsequently, these data and key parameters such as the Langmuir volume and Langmuir pressure of the target coal seam are imported into the Langmuir-Freundrich model. This model is a verified mathematical model that can comprehensively consider the complex characteristics of coal seam gas reservoirs, including the physical properties of the gas reservoir, fluid properties, and dynamic changes during the mining process. Through the calculation of this model, important parameters such as the total gas reserves and critical desorption pressure of the target coal seam gas reservoir can be obtained. Finally, based on these parameters and the pressure index, the average formation pressure corresponding to each cumulative gas production can be predicted using a specific prediction formula. This prediction result can provide important technical support for the exploitation of coalbed methane reservoirs, help engineers better understand the dynamic changes of gas reservoirs, formulate reasonable exploitation plans, and improve exploitation efficiency and economic benefits.

[0054] The above prediction method can effectively overcome the problem of inconvenient calculation of the average formation pressure method in the prior art, making the average formation pressure prediction of coalbed methane reservoirs more accurate and efficient. In addition, the application of this method can also shorten the interval time for calculating the average formation pressure in the production data table, providing more timely and reliable data support for the exploitation of coalbed methane reservoirs. This not only helps to improve the exploitation efficiency of coalbed methane reservoirs, but also further reduce the exploitation cost and improve economic benefits.

[0055] In one embodiment, the steps of importing the Langmuir volume, Langmuir pressure, pressure index, multiple groups of cumulative gas production and multiple groups of measured average formation pressure into the Langmuir-Friedrich model to determine the total gas reserves and critical desorption pressure of the target coalbed methane reservoir include: constructing a material balance equation for the coalbed methane reservoir based on the Langmuir volume, Langmuir pressure and pressure index; constructing a material balance equation for the cumulative production and p based on the material balance equation m / (p L m +p m ), where p is the average formation pressure, pL is the Langmuir pressure, and m is the pressure exponent; the slope and vertical intercept of the linear function are determined according to multiple groups of measured average formation pressures and multiple groups of cumulative gas production; the total gas reserves of the target coalbed methane reservoir are determined according to the slope and vertical intercept of the linear function.

[0056] In the process of determining the total gas reserves and critical desorption pressure of the target coalbed methane reservoir, the material balance equation of the coalbed methane reservoir can be first constructed based on the Langmuir volume, Langmuir pressure and pressure index, and then this equation can be used to describe the dynamic equilibrium state of gas flow in the coalbed methane reservoir. The material balance equation is an important theoretical basis for the exploitation of coalbed methane reservoirs. It takes into account multiple factors such as the geometric shape of the gas reservoir, fluid characteristics and exploitation conditions, and can more accurately reflect the gas flow inside the gas reservoir. After constructing the material balance equation, the cumulative production and p can be further derived based on this equation. m / (p L m +p m ). The key to this step is to simplify the complex material balance equation into a linear function form through mathematical transformation, so as to facilitate subsequent calculation and analysis. The slope and ordinate intercept of the linear function are key parameters for determining the total gas reserves of the target coalbed methane reservoir. These parameters can be obtained by fitting multiple sets of measured average formation pressure and corresponding cumulative gas production data. After determining the slope and ordinate intercept of the linear function, the total gas reserves of the target coalbed methane reservoir can be calculated based on these parameters and the expression of the linear function. The determination of the total gas reserves is of great significance to the exploitation of coalbed methane reservoirs. It can help engineers better understand the reserve scale of the gas reservoir, formulate a reasonable exploitation plan, and ensure the smooth progress of the exploitation process. At the same time, the accurate calculation of the total gas reserves is also the basis for the subsequent prediction of parameters such as average formation pressure. It is worth noting that the prediction method in the embodiment of the present application is not only applicable to undersaturated coalbed methane reservoirs, but can also be extended to other types of coalbed methane reservoirs or oil and gas reservoirs.

[0057] In one embodiment, the material balance equation of the coalbed methane reservoir is constructed as follows:

[0058]

[0059] Among them, G p is the cumulative production, h is the coal reservoir thickness of the target CBM reservoir, A is the controlled area of ​​the target CBM reservoir, ρ c is the coal rock density of the target CBM reservoir, V L is the Langmuir volume, p d is the critical desorption pressure of the target coalbed methane reservoir, p L is the Langmuir pressure, p is the average formation pressure, and m is the pressure index. The material balance equation comprehensively considers the geometric parameters of the coalbed methane reservoir (such as coal reservoir thickness h, control area A), physical parameters (such as coal rock density ρ c 、Langmuir volume V L , Langmuir pressure p L , critical desorption pressure p d) and pressure index m and other factors can more comprehensively reflect the flow and storage status of gas in coalbed methane reservoirs.

[0060] In one embodiment, the cumulative production and p are constructed based on the material balance equation. m / (p L m +p m ) includes the following steps:

[0061] Based on the transformation of formula (1), the following formula (2) is obtained:

[0062]

[0063] Based on formula (2), the linear function expression (3) is obtained by further transformation:

[0064]

[0065] Where N represents the vertical intercept of the linear function. M represents the slope of a linear function. G is the reserves of coalbed methane in the coalbed methane reservoir, G p is the cumulative output, p d is the critical desorption pressure of the target coalbed methane reservoir, p L is the Langmuir pressure, p is the average formation pressure, and m is the pressure index.

[0066] In constructing the cumulative output and p m / (p L m +p m), firstly, mathematical transformation is performed based on the material balance equation of the coalbed methane reservoir, and the complex equation form is gradually simplified into a linear function form. The key to this step is to express the various parameters and variables in the equation in a linear relationship through reasonable mathematical deduction, so as to facilitate subsequent calculation and analysis. Formula (2) introduces new variables and parameters by deforming the equation, making the form of the equation more concise and clear. Furthermore, in formula (3), the equation is completely transformed into an expression of a linear function, where N and M represent the vertical intercept and slope of the linear function respectively. These two parameters are the key to determining the linear function and the basis for the subsequent calculation of the total gas reserves. After determining the expression of the linear function, the specific values ​​of the slope and the vertical intercept can be determined by fitting multiple sets of measured data. After obtaining the slope and the vertical intercept, the total gas reserves of the target coalbed methane reservoir can be calculated based on these parameters and the expression of the linear function. The determination of the total gas reserves is of great significance to the exploitation of coalbed methane reservoirs. It can help engineers better understand the reserve scale of the gas reservoir and provide an important basis for formulating a reasonable exploitation plan. At the same time, accurate calculation of total gas reserves is also the basis for subsequent analysis such as average formation pressure prediction. m / (p L m +p m ), it is necessary to strictly follow the mathematical derivation rules to ensure the correctness and rationality of the equation transformation.

[0067] In one embodiment, the total gas reserves of the target coalbed methane reservoir are determined according to the following formula (4):

[0068]

[0069] Among them, G is the reserves of coalbed methane in the coalbed methane reservoir, N represents the vertical intercept of the linear function, and M represents the slope of the linear function. The above method for calculating the total reserves of the target coal seam achieves accurate calculation of the total gas reserves of the target coalbed methane reservoir by constructing a linear function about the ratio of cumulative production to specific pressure and cleverly using the slope and vertical intercept of the function. This method not only simplifies the complex calculation steps, but also significantly improves the accuracy and efficiency of the calculation.

[0070] In one embodiment, the average formation pressure is determined according to the following formula (5):

[0071]

[0072] Where p is the average formation pressure, p L is the Langmuir pressure, m is the pressure index, N is the vertical intercept of the linear function, G is the reserves of coalbed methane in the coalbed methane reservoir, G pis the cumulative production. The above prediction method is used to determine the average formation pressure, which can more accurately reflect the dynamic changes of the coalbed methane reservoir during the mining process. In formula (5), by comprehensively considering multiple parameters such as Langmuir pressure, pressure index, vertical axis intercept of the linear function, total gas reserves of the target coalbed methane reservoir, and cumulative production, a mathematical relationship between the average formation pressure and these parameters is established. The establishment of this relationship enables engineers to accurately predict the average formation pressure of the coalbed methane reservoir based on known mining data and parameters. By adopting the above prediction method, engineers can more scientifically guide the mining process of the coalbed methane reservoir, optimize the mining strategy, and ensure the smooth progress of mining activities. At the same time, the application of this prediction method can also provide strong technical support for the subsequent development of coalbed methane reservoirs and promote the continuous progress and development of coalbed methane mining technology.

[0073] In one embodiment, the critical desorption pressure of the target coalbed methane reservoir is determined according to the following formula (6):

[0074]

[0075] Among them, p d is the critical desorption pressure of the target coalbed methane reservoir, p L is the Langmuir pressure, m is the pressure index, and N represents the vertical intercept of the linear function. In the above formula (6), by comprehensively considering the Langmuir pressure, pressure index and vertical intercept of the linear function of the coalbed methane reservoir, the critical desorption pressure is accurately calculated. This step is a key link in the process of predicting the average formation pressure of the coalbed methane reservoir, because the critical desorption pressure is one of the important parameters reflecting the mining characteristics of the coalbed methane reservoir. By accurately calculating the critical desorption pressure, the mining dynamics of the coalbed methane reservoir can be more deeply understood, providing a strong basis for formulating a reasonable mining strategy. This prediction result can provide important technical support for the mining of coalbed methane reservoirs, help engineers better grasp the dynamic changes of gas reservoirs, optimize mining plans, and improve mining efficiency and economic benefits. In summary, the prediction method for the average formation pressure of the coalbed methane reservoir provided in the embodiment of the present application not only overcomes the problem of inconvenient calculation of the average formation pressure method in the prior art, but also provides more accurate and efficient technical support for the mining of coalbed methane reservoirs by accurately calculating key parameters such as total gas reserves and critical desorption pressure.

[0076] In one embodiment, the prediction method further includes determining the controlled area of ​​the target coalbed methane reservoir according to the following formula (7):

[0077]

[0078] Where h is the coal reservoir thickness of the target coalbed methane reservoir, A is the control area of ​​the target coalbed methane reservoir, ρ cis the coal rock density of the target CBM reservoir, V L is the Langmuir volume, and M represents the slope of the linear function.

[0079] The above prediction method is used to determine the control area of ​​the target coalbed methane reservoir, which can more accurately reflect the geometric characteristics of the coalbed methane reservoir and provide an important basis for subsequent mining plans and resource development. In formula (7), by comprehensively considering multiple parameters such as coal reservoir thickness, coal rock density, Langmuir volume, and the slope of the linear function, a mathematical relationship between the control area and these parameters is established. The establishment of this relationship enables engineers to accurately predict the control area based on the known coalbed methane reservoir characteristics.

[0080] In a specific embodiment, the Langmuir volume of the target coal seam is 12.5 m 3 / t, Langmuir pressure is 2.75MP a , the pressure index is 1.1. During the mining process of the target coalbed methane reservoir, the following is obtained: Figure 2 The following is a dynamic curve diagram of the cumulative gas production and daily gas production changing with production time and the following production data table:

[0081] Table 1 The measured average formation pressure of the target coalbed methane reservoir and the corresponding cumulative gas production data table

[0082]

[0083] Take G in Table 1 p is the horizontal axis, p m / (p L m +p m ) is the vertical axis, and a scatter plot is made in the rectangular coordinate graph, such as Figure 3 As shown, a linear function is applied to fit these data points, and the slope M of the linear function is -0.059535 (10 6 m 3 ) -1 , the vertical intercept N of the linear function is 0.779649.

[0084] Then, the total gas reserves of the target coalbed methane reservoir can be calculated using the following formula:

[0085]

[0086] Critical desorption pressure of coalbed methane reservoir d It can be calculated by the following formula:

[0087]

[0088] Since the coal reservoir thickness of the target CBM reservoir is h = 11m, the coal rock density ρ c=1.5t / m 3 , the coal reservoir thickness h, coal rock density ρ c , Langmuir V L Substituting the linear function slope M into the following formula, the controlled area A of the coalbed methane reservoir can be calculated:

[0089]

[0090] Taking the cumulative gas production data of 3000 days of production as an example, according to Figure 2 The curve in the figure shows that the cumulative output Gp in 3000 days is Gp = 2.507165 (10 6 m 3 ), substituting the Langmuir pressure, pressure index, reserves of the target coalbed methane reservoir and critical desorption pressure into the above formula (5) yields:

[0091]

[0092] By adopting the above calculation steps, the average formation pressure corresponding to each cumulative production of the target coalbed methane reservoir can be obtained, thereby realizing the accurate prediction of the formation pressure change during the coalbed methane reservoir exploitation process. This prediction method not only improves the accuracy of the calculation, but also provides a scientific basis for the rational exploitation of coalbed methane reservoirs. Engineers can formulate more reasonable mining plans and optimize mining strategies based on these prediction results to ensure efficient and safe mining of coalbed methane reservoirs. At the same time, the application of this method can also help reduce mining costs, improve economic benefits, and provide support for the sustainable utilization of coalbed methane resources. In addition, this prediction method also has strong adaptability and flexibility, and can be adjusted and optimized according to different coalbed methane reservoir characteristics and mining conditions to meet the needs of the actual mining process. Therefore, this prediction method has broad application prospects and important practical significance in the field of coalbed methane reservoir exploitation.

[0093] Furthermore, according to the above prediction method, it can be predicted that Figure 2 The corresponding dynamic curve of the average formation pressure of the target coalbed methane reservoir changing with production time is shown in the following figure: Figure 4 shown.

[0094] In one embodiment, a device for determining the average formation pressure of an undersaturated coalbed methane reservoir is provided, comprising: a memory configured to store instructions; and a processor configured to call instructions from the memory and to implement the above-mentioned method for predicting the average formation pressure of the coalbed methane reservoir when executing the instructions.

[0095] In one embodiment, a machine-readable storage medium is provided, on which instructions are stored, and the instructions are used to enable a machine to execute the above-mentioned method for predicting the average formation pressure of a coalbed methane reservoir.

[0096] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0097] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0098] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0099] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0100] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0101] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0102] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0103] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0104] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for predicting average formation pressure of a coalbed methane reservoir, characterized in that: The prediction method comprises: Determine the pressure index of the target coal seam gas reservoir according to the gas reservoir temperature and pore size of the target coal seam; During the mining process of the target coalbed methane reservoir, multiple groups of cumulative gas production and their corresponding measured average formation pressures are recorded; Obtain the Langmuir volume and Langmuir pressure of the target coalbed methane reservoir; Importing the Langmuir volume, the Langmuir pressure, the pressure index, multiple groups of the cumulative gas production and multiple groups of the measured average formation pressures into the Langmuir-Freundrich model to determine the total gas reserves and critical desorption pressure of the target coalbed methane reservoir; The average formation pressure corresponding to each cumulative gas production is predicted based on the total gas reserves of the target coalbed methane reservoir, the critical desorption pressure, the Langmuir pressure and the pressure index.

2. The method for predicting average formation pressure of a coalbed methane reservoir according to claim 1, characterized in that: The step of importing the Langmuir volume, the Langmuir pressure, the pressure index, multiple groups of the cumulative gas production and multiple groups of the measured average formation pressures into the Langmuir-Freundrich model to determine the total gas reserves and critical desorption pressure of the target coalbed methane reservoir includes: Constructing a material balance equation for a coalbed methane reservoir based on the Langmuir volume, the Langmuir pressure and the pressure index; Based on the material balance equation, the cumulative production and p m / (p L m +p m ), where p is the average formation pressure, p L is the Langmuir pressure, m is the pressure index; Determine the slope and the vertical intercept of the linear function according to the multiple groups of measured average formation pressures and the multiple groups of cumulative gas production; The total gas reserves of the target coalbed methane reservoir are determined according to the slope of the linear function and the vertical intercept.

3. The method for predicting the average formation pressure of a coalbed methane reservoir according to claim 2, characterized in that: The material balance equation of the coalbed methane reservoir is constructed as follows: Among them, G p is the cumulative production, h is the coal reservoir thickness of the target coalbed methane reservoir, A is the controlled area of ​​the target coalbed methane reservoir, ρ c is the coal rock density of the target coalbed methane reservoir, V L is the Langmuir volume, p d is the critical desorption pressure of the target coalbed methane reservoir, p L is the Langmuir pressure, p is the average formation pressure, and m is the pressure index.

4. The method for predicting the average formation pressure of a coalbed methane reservoir according to claim 3, characterized in that: The material balance equation is based on the cumulative output and p m / (p L m +p m ) includes the following steps: Based on the above formula (1), the following formula (2) is obtained: Based on the formula (2), the linear function expression (3) is obtained by further deformation: Wherein, N represents the vertical intercept of the linear function, M represents the slope of the linear function, G is the reserves of coalbed methane in the coalbed methane reservoir, G p is the cumulative output, p d is the critical desorption pressure of the target coalbed methane reservoir, p L is the Langmuir pressure, p is the average formation pressure, and m is the pressure index.

5. The method for predicting average formation pressure of a coalbed methane reservoir according to claim 4, characterized in that: The total gas reserves of the target coalbed methane reservoir are determined according to the following formula (4): Wherein, G is the reserves of coalbed methane in the coalbed methane reservoir, N represents the vertical intercept of the linear function, and M represents the slope of the linear function.

6. The method for predicting average formation pressure of a coalbed methane reservoir according to claim 5, characterized in that: The average formation pressure is determined according to the following formula (5): Wherein, p is the average formation pressure, p L is the Langmuir pressure, m is the pressure index, N represents the vertical intercept of the linear function, G is the reserves of coalbed methane in the coalbed methane reservoir, G p is the cumulative output.

7. The method for predicting average formation pressure of a coalbed methane reservoir according to claim 4, characterized in that: The critical desorption pressure of the target coalbed methane reservoir is determined according to the following formula (5): Among them, p d is the critical desorption pressure of the target coalbed methane reservoir, p L is the Langmuir pressure, m is the pressure index, and N represents the vertical intercept of the linear function.

8. The method for predicting average formation pressure of a coalbed methane reservoir according to claim 4, characterized in that: The prediction method further includes determining the controlled area of ​​the target coalbed methane reservoir according to the following formula (7): Wherein, h is the coal reservoir thickness of the target coalbed methane reservoir, A is the controlled area of ​​the target coalbed methane reservoir, and ρ c is the coal rock density of the target coalbed methane reservoir, V L is the Langmuir volume, and M represents the slope of the linear function.

9. A device for determining the average formation pressure of an undersaturated coalbed methane reservoir, characterized in that: include: a memory configured to store instructions; as well as A processor is configured to call the instructions from the memory and implement the method for predicting the average formation pressure of a coalbed methane reservoir according to any one of claims 1 to 8 when executing the instructions.

10. A machine-readable storage medium, characterized in that: The machine-readable storage medium stores instructions for causing a machine to execute a method for predicting an average formation pressure of a coalbed methane reservoir according to any one of claims 1 to 8.

Images