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 coal bed gas reservoir average formation pressure prediction method and device and a storage medium, and the prediction method comprises the steps: recording multiple groups of accumulated gas production rates and corresponding actually measured average formation pressures; the coal rock density, the maximum gas adsorption capacity, the gas quasi-saturated vapor pressure at the reservoir temperature, the model fitting coefficient and the characteristic index of the target coal bed gas reservoir are obtained; introducing the coal rock density, the maximum gas adsorption capacity, the gas quasi-saturated vapor pressure at the reservoir temperature, the model fitting coefficient, the characteristic index, the multiple groups of accumulated gas production rates and the multiple groups of actually measured average formation pressures into a DA model to determine the total gas reserves and the critical desorption pressure; and predicting the average formation pressure corresponding to each accumulated gas production rate according to the total gas reserves, the critical desorption pressure, the model fitting coefficient, the characteristic index and the gas quasi-saturated vapor pressure under the reservoir temperature. 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] 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;

[0007] Obtain the coal rock density, maximum gas adsorption capacity, pseudo-saturated vapor pressure of gas at reservoir temperature, model fitting coefficient, and characteristic index of the target coalbed methane reservoir;

[0008] The coal rock density, maximum gas adsorption, gas pseudo-saturated vapor pressure at reservoir temperature, model fitting coefficient, characteristic index, multiple groups of cumulative gas production and multiple groups of measured average formation pressure are imported into the DA model to determine the total gas reserves and critical desorption pressure of the target coalbed methane reservoir;

[0009] The average formation pressure corresponding to each cumulative gas production is predicted based on the total gas reserves, critical desorption pressure, model fitting coefficient, characteristic index, and pseudo-saturated vapor pressure of gas at reservoir temperature.

[0010] In the embodiment of the present application, the coal rock density, the maximum gas adsorption amount, the pseudo-saturated vapor pressure of the gas at the reservoir temperature, the model fitting coefficient, the characteristic index, multiple groups of cumulative gas production and multiple groups of measured average formation pressures are introduced into the DA model to determine the total gas reserves and critical desorption pressure of the target coalbed methane reservoir. The steps include: constructing a material balance equation for the coalbed methane reservoir based on the coal rock density, the maximum gas adsorption amount, the pseudo-saturated vapor pressure of the gas at the reservoir temperature, the model fitting coefficient, and the characteristic index; constructing a material balance equation for the cumulative gas production and the critical desorption pressure based on the material balance equation. A linear function of , where C is the model fitting coefficient, p0 is the pseudo-saturated vapor pressure of gas at reservoir temperature, p is the average formation pressure, and n is the characteristic index; 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.

[0011] In the embodiment of the present application, the material balance equation of the coalbed methane reservoir is constructed as follows:

[0012]

[0013] Among them, G p is the cumulative production of the target CBM reservoir, 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 coalbed methane reservoir, V0 is the maximum gas adsorption capacity, C is the model fitting coefficient, p0 is the pseudo-saturated vapor pressure of the gas at the reservoir temperature, p d is the critical desorption pressure, p is the average formation pressure, and n is the characteristic index.

[0014] In the embodiment of the present application, the cumulative gas production and The steps of a linear function include:

[0015] Based on the transformation of formula (1), the following formula (2) is obtained:

[0016]

[0017] Based on formula (2), the linear function expression (3) is obtained by further transformation:

[0018]

[0019] 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 production, C is the model fitting coefficient, p0 is the pseudo-saturated vapor pressure of gas at reservoir temperature, p is the average formation pressure, and n is the characteristic index.

[0020] 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):

[0021]

[0022] 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.

[0023] In the embodiment of the present application, the average formation pressure is determined according to the following formula (5):

[0024]

[0025] Among them, p0 is the pseudo-saturated vapor pressure of gas at reservoir temperature, N is the vertical intercept of the linear function, n is the characteristic index, C is the model fitting coefficient, G is the reserves of coalbed methane in the coalbed methane reservoir, G p For cumulative production.

[0026] 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):

[0027]

[0028] Among them, p d is the critical desorption pressure of the target coalbed methane reservoir, p0 is the pseudo-saturated vapor pressure of the gas at the reservoir temperature, C is the model fitting coefficient, N represents the vertical intercept of the linear function, and n is the characteristic index.

[0029] 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):

[0030]

[0031] Among them, A is the controlled area of ​​the target CBM reservoir, h is the coal reservoir thickness of the target CBM reservoir, ρ c is the coal rock density of the target coalbed methane reservoir, V0 is the maximum gas adsorption capacity, and M represents the slope of the linear function.

[0032] 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.

[0033] 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.

[0034] Through the above technical solution, when predicting the average formation pressure for the target coal seam, first obtain multiple sets of cumulative gas production and their corresponding measured average formation pressure recorded during the mining process of the target coalbed methane reservoir, and then obtain the coal rock density, maximum gas adsorption, gas pseudo-saturated vapor pressure at reservoir temperature, model fitting coefficient and characteristic index of the target coalbed methane reservoir. The acquisition of these parameters provides basic data for the subsequent prediction process. After importing these data into the pre-built DA model, the model can analyze and process them based on these data to determine the total gas reserves and critical desorption pressure of the target coalbed methane reservoir. Finally, based on the determined total gas reserves and critical desorption pressure, combined with the model fitting coefficient, characteristic index and gas pseudo-saturated vapor pressure at reservoir temperature, a specific prediction formula can be used to predict the average formation pressure corresponding to each cumulative gas production. The above prediction method does not require the input of multiple sets of cumulative water production and frequent iterative calculation of gas deviation coefficients. It can predict the corresponding average formation pressure by only inputting the cumulative gas production, combined with a small number of parameters such as coal rock density, maximum gas adsorption capacity, gas pseudo-saturated vapor pressure at reservoir temperature, model fitting coefficient and characteristic index, thereby greatly simplifying the calculation process, reducing the calculation difficulty and improving the calculation efficiency.

[0035] 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

[0036] 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:

[0037] 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;

[0038] Figure 2 A 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;

[0039] Figure 3 A schematic diagram of a linear function image provided according to an embodiment of the present application is schematically shown;

[0040] Figure 4 A schematic diagram of a dynamic curve showing the change of average formation pressure with production time provided in an embodiment of the present application is shown schematically. DETAILED DESCRIPTION

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] Figure 1 The 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 1As shown, an embodiment of the present application provides a method for predicting the average formation pressure of a coalbed methane reservoir, which method may include the following steps.

[0046] S101. 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.

[0047] S102. Obtain the coal rock density, maximum gas adsorption capacity, pseudo-saturated vapor pressure of gas at reservoir temperature, model fitting coefficient, and characteristic index of the target coalbed methane reservoir.

[0048] S103. The coal rock density, the maximum gas adsorption amount, the pseudo-saturated vapor pressure of the gas at the reservoir temperature, the model fitting coefficient, the characteristic index, multiple groups of cumulative gas production and multiple groups of measured average formation pressures are introduced into the DA model to determine the total gas reserves and critical desorption pressure of the target coalbed methane reservoir.

[0049] S104. Predict the average formation pressure corresponding to each cumulative gas production according to the total gas reserves, critical desorption pressure, model fitting coefficient, characteristic index, and pseudo-saturated vapor pressure of gas at reservoir temperature.

[0050] 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.

[0051] Specifically, when predicting the average formation pressure for the target coal seam, firstly, according to the multiple groups of cumulative gas production and the corresponding measured average formation pressure recorded during the exploitation of the target coalbed methane reservoir, combined with the coal rock density, maximum gas adsorption, gas pseudo-saturated vapor pressure at reservoir temperature, model fitting coefficient and characteristic index of the target coalbed methane reservoir, these data are imported into the pre-built DA model as input parameters. The DA model can perform complex analysis and calculation based on these input parameters to determine the total gas reserves and critical desorption pressure of the target coalbed methane reservoir. Finally, based on the determined total gas reserves and critical desorption pressure, as well as other known parameters such as model fitting coefficient, characteristic index and gas pseudo-saturated vapor pressure at reservoir temperature, a specific prediction formula is used to accurately predict the average formation pressure corresponding to each cumulative gas production. This process not only avoids the tedious steps of frequently iterating the calculation of gas deviation coefficients in traditional methods, but also significantly improves the prediction efficiency and accuracy. 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.

[0052] 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.

[0053] In one embodiment, the coal rock density, the maximum gas adsorption amount, the pseudo-saturated vapor pressure of the gas at the reservoir temperature, the model fitting coefficient, the characteristic index, multiple groups of cumulative gas production and multiple groups of measured average formation pressures are introduced into the DA model to determine the total gas reserves and critical desorption pressure of the target coalbed methane reservoir. The steps include: constructing a material balance equation for the coalbed methane reservoir based on the coal rock density, the maximum gas adsorption amount, the pseudo-saturated vapor pressure of the gas at the reservoir temperature, the model fitting coefficient, and the characteristic index; constructing a material balance equation for the cumulative gas production and the critical desorption pressure based on the material balance equation. A linear function of , where C is the model fitting coefficient, p0 is the pseudo-saturated vapor pressure of gas at reservoir temperature, p is the average formation pressure, and n is the characteristic index; 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.

[0054] 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 constructed based on the coal rock density, the maximum gas adsorption amount, the pseudo-saturated vapor pressure of the gas at the reservoir temperature, the model fitting coefficient, and the characteristic index. The material balance equation can reflect the dynamic equilibrium relationship of the gas in the coalbed methane reservoir. Subsequently, based on the constructed material balance equation, the cumulative gas production and This step is achieved through mathematical transformation, which aims to simplify the complex material balance equation into a more manageable linear function form. In the linear function expression, the cumulative gas production is used as the independent variable, and As the function part of the dependent variable, the slope and ordinate intercept of the linear function are obtained by fitting multiple groups of measured average formation pressures and multiple groups of cumulative gas production in the production data table. Once the slope and ordinate intercept are determined, the total gas reserves of the target coalbed methane reservoir can be inferred using this information and known parameters such as the model fitting coefficient, the pseudo-saturated vapor pressure of the gas at the reservoir temperature, and the characteristic index. In this process, the determination of the total gas reserves is based on the material balance principle and the comprehensive analysis of experimental data, so it has high accuracy and reliability. 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.

[0055] In one embodiment, the material balance equation of the coalbed methane reservoir is constructed as follows:

[0056]

[0057] Among them, G p is the cumulative production of the target CBM reservoir, 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 coalbed methane reservoir, V0 is the maximum gas adsorption capacity, C is the model fitting coefficient, p0 is the pseudo-saturated vapor pressure of the gas at the reservoir temperature, p d is the critical desorption pressure, p is the average formation pressure, and n is the characteristic index.

[0058] The material balance equation comprehensively considers various parameters and factors of the coalbed methane reservoir and can accurately describe the dynamic balance relationship of the gas in the coalbed methane reservoir. In formula (1), the cumulative production G p As the target variable, it reflects the exploitation of coalbed methane reservoirs. Coal reservoir thickness h, control area A, coal rock density ρ c Parameters such as the maximum adsorption capacity of gas V0 reflect the geological characteristics and gas storage capacity of the coalbed methane reservoir. The pseudo-saturated vapor pressure p0 of the gas at the reservoir temperature, the critical desorption pressure p dParameters such as and average formation pressure p are related to the gas state and pressure distribution in the coalbed methane reservoir. The model fitting coefficient C and characteristic index n are empirical parameters obtained through data fitting, which are used to describe the complex behavior of gas in the coalbed methane reservoir. By comprehensively considering these parameters, formula (1) can more comprehensively reflect the dynamic equilibrium relationship of gas in the coalbed methane reservoir, providing a basis for subsequent analysis and prediction.

[0059] In one embodiment, the cumulative gas production and The steps of a linear function include:

[0060] Based on the transformation of formula (1), the following formula (2) is obtained:

[0061]

[0062] Based on formula (2), the linear function expression (3) is obtained by further transformation:

[0063]

[0064] 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 production, C is the model fitting coefficient, p0 is the pseudo-saturated vapor pressure of gas at reservoir temperature, p is the average formation pressure, and n is the characteristic index.

[0065] In constructing the cumulative output and In the process of converting the linear function of the gas reservoir into a linear function, mathematical transformation is first 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 transforming the equation, making the form of the equation more concise and clear. Further, in formula (3), the equation is completely converted 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. In the process of transforming a linear function, it is necessary to strictly follow the mathematical derivation rules to ensure the correctness and rationality of the equation transformation.

[0066] In one embodiment, the total gas reserves of the target coalbed methane reservoir are determined according to the following formula (4):

[0067]

[0068] 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.

[0069] In one embodiment, the average formation pressure is determined according to the following formula (5):

[0070]

[0071] Among them, p0 is the pseudo-saturated vapor pressure of gas at reservoir temperature, N is the vertical intercept of the linear function, n is the characteristic index, C is the model fitting coefficient, G is the reserves of coalbed methane in the coalbed methane reservoir, G p For cumulative production.

[0072] In formula (5), by comprehensively considering multiple factors such as the geological characteristics, gas storage capacity, gas state and pressure distribution of the coalbed methane reservoir, an accurate prediction of the average formation pressure is achieved. This prediction formula not only takes into account the complexity and diversity of the coalbed methane reservoir, but also improves the accuracy and reliability of the prediction results by introducing empirical parameters such as model fitting coefficients and characteristic indexes. In specific applications, it is only necessary to substitute the known cumulative production, gas pseudo-saturated vapor pressure at reservoir temperature, the vertical axis intercept of the linear function, the characteristic index and the model fitting coefficient into formula (5) to quickly calculate the corresponding average formation pressure. This prediction method not only simplifies the calculation process, but also significantly improves the calculation efficiency, providing strong technical support for the exploitation of coalbed methane reservoirs. In summary, the prediction method for the average formation pressure of the coalbed methane reservoir provided in this application realizes the accurate calculation and efficient prediction of the total gas reserves and average formation pressure of the target coalbed methane reservoir by constructing the coalbed methane reservoir material balance equation and the linear function expression.

[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, p0 is the pseudo-saturated vapor pressure of the gas at the reservoir temperature, C is the model fitting coefficient, N represents the vertical axis intercept of the linear function, and n is the characteristic index. In the above formula (6), it is only necessary to substitute the known pseudo-saturated vapor pressure of the gas at the reservoir temperature, the vertical axis intercept of the linear function, the model fitting coefficient and the characteristic index into formula (6) to quickly solve the critical desorption pressure of the target coalbed methane reservoir. This method not only simplifies the calculation steps, but also significantly improves the calculation efficiency, providing important technical support for the exploitation of coalbed methane reservoirs. The determination of the critical desorption pressure is of great significance to the exploitation of coalbed methane reservoirs. It can help engineers better understand the gas storage capacity and exploitation potential of the gas reservoir, and provide an important basis for formulating a reasonable exploitation plan. By adopting the above prediction method and calculation formula, this application realizes the accurate calculation and efficient prediction of the total gas reserves and critical desorption pressure of the target coalbed methane reservoir, providing strong technical support and reliable data guarantee for the exploitation of coalbed methane reservoirs.

[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] Among them, A is the controlled area of ​​the target CBM reservoir, h is the coal reservoir thickness of the target CBM reservoir, ρ cis the coal rock density of the target coalbed methane reservoir, V0 is the maximum gas adsorption capacity, 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, maximum gas adsorption, 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 maximum gas adsorption capacity is 13.4m 3 / t, the pseudo-saturated vapor pressure of gas at reservoir temperature is 60MPa, the model fitting coefficient is 0.165, and the characteristic index is 1.7. In 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 and corresponding cumulative gas production data of the target coalbed methane reservoir

[0082]

[0083] Take G in Table 1 p is the horizontal axis, As the vertical axis, make a scatter plot 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 -0.066506 (10 6 m 3 ) -1 , the vertical intercept N of the straight line is 0.627178.

[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 cSubstituting the maximum gas adsorption capacity V0 and the slope M of the linear function in Table 1 into the following formula, the control area A of the target coalbed methane reservoir can be calculated:

[0089]

[0090] Taking the cumulative gas production data of 3500 days of production as an example, according to Figure 2 The curve shows that the cumulative output G on the 3500th day is p =3.037102(10 6 m 3 ), substitute the pseudo-saturated vapor pressure of gas at reservoir temperature, model fitting coefficient, characteristic index, and total gas reserves G into the following formula to obtain the average formation pressure p:

[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: 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 coal rock density, maximum gas adsorption capacity, pseudo-saturated vapor pressure of gas at reservoir temperature, model fitting coefficient, and characteristic index of the target coalbed methane reservoir; The coal rock density, the maximum gas adsorption amount, the pseudo-saturated vapor pressure of the gas at the reservoir temperature, the model fitting coefficient, the characteristic index, multiple groups of cumulative gas production and multiple groups of measured average formation pressures are introduced into the DA 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, the critical desorption pressure, the model fitting coefficient, the characteristic index, and the pseudo-saturated vapor pressure of gas at the reservoir temperature.

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 coal rock density, the maximum gas adsorption amount, the pseudo-saturated vapor pressure of the gas at the reservoir temperature, the model fitting coefficient, the characteristic index, multiple groups of cumulative gas production and multiple groups of measured average formation pressures into the DA 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 coal rock density, the maximum adsorption amount of the gas, the pseudo-saturated vapor pressure of the gas at the reservoir temperature, the model fitting coefficient, and the characteristic index; Based on the material balance equation, the cumulative gas production and A linear function of, wherein C is the model fitting coefficient, p0 is the pseudo-saturated vapor pressure of the gas at the reservoir temperature, p is the average formation pressure, and n is the characteristic 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 based on the slope and the vertical axis 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 of the target coalbed methane reservoir, 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, V0 is the maximum adsorption amount of the gas, C is the model fitting coefficient, p0 is the pseudo-saturated vapor pressure of the gas at the reservoir temperature, p d is the critical desorption pressure, p is the average formation pressure, and n is the characteristic 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 used to construct the cumulative gas production and The steps of a linear function include: 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 production, C is the model fitting coefficient, p0 is the pseudo-saturated vapor pressure of the gas at the reservoir temperature, p is the average formation pressure, and n is the characteristic 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, p0 is the pseudo-saturated vapor pressure of the gas at the reservoir temperature, N represents the vertical intercept of the linear function, n is the characteristic index, C is the model fitting coefficient, 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 (6): Among them, p d is the critical desorption pressure of the target coalbed methane reservoir, p0 is the pseudo-saturated vapor pressure of the gas at the reservoir temperature, C is the model fitting coefficient, N represents the vertical intercept of the linear function, and n is the characteristic index.

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, A is the controlled area of ​​the target coalbed methane reservoir, h is the coal reservoir thickness of the target coalbed methane reservoir, and ρ c is the coal rock density of the target coalbed methane reservoir, V0 is the maximum adsorption amount of the gas, 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.

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