Method and device for evaluating proportions of different gas contents in coal bed gas reservoir

Abstract

The invention discloses a coal bed gas reservoir different gas content ratio evaluation method and device, and the method comprises the steps: calculating the initial values of coal bed porosity and coal bed water saturation when a target coal bed just starts to be put into production after fracturing flowback according to the physical parameters of the target coal bed and the initial value of the control volume after fracturing flowback; according to the physical property parameters, the coal seam porosity and the initial value of the coal seam water saturation, a production dynamic data table, the coal seam water saturation, free gas original reserves, adsorbed gas original reserves and dissolved gas original reserves are obtained; and finally, calculating the original free gas content, the original adsorbed gas content and the original dissolved gas content according to the original reserves of the three gases so as to obtain the content ratio of the three original gases. The method for evaluating the content and proportion of different gases in the coal bed gas reservoir is provided by considering the pressure difference between the adsorption gas pores and the free gas pores, the influence of fracturing transformation on the change of physical property parameters of the coal bed and the dissolved gas, the measurement process of actual measurement of the gas content and pressure maintaining coring is avoided, and the cost is saved.

Description

Technical Field

[0001] The present application relates to the technical field of coalbed methane reservoir development, and specifically relates to a method and device for evaluating the proportion of different gas contents in a coalbed methane reservoir. Background Art

[0002] As one of the important unconventional resources, coalbed methane has attracted wide attention globally as it can alleviate energy shortages, reduce coal mine safety accidents, and relieve environmental pressure. In recent years, target coalbed methane has developed rapidly, and high-yield breakthroughs have been achieved in multiple target coalbed methane blocks. The reason is that the gas types in target coalbed methane not only include adsorbed gas, but also are rich in free gas and contain a certain amount of dissolved gas. Studying the proportion of different types of gas contents in a target coalbed methane reservoir has important theoretical and practical significance for the evaluation of target coalbed methane reservoir reserves, prediction of geological sweet spots, etc.

[0003] Currently, there are many methods for the proportion of different types of gas contents (i.e., reserve proportion) in target coalbed methane, but most of them are based on measured gas content and isothermal adsorption and desorption experimental data. The measured gas content includes lost gas, desorbed gas, and residual gas. Among them, lost gas cannot be directly measured and can only be predicted using a correlation formula, and the result error is relatively large. Of course, in recent years, for target coalbed methane reservoirs, a method of pressure-maintaining coring has been proposed, which eliminates the influence of lost gas prediction error on the measured gas content. However, the cost of pressure-maintaining coring is expensive, and it is impossible to ensure that pressure-maintaining coring is carried out for each well. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a method and device for evaluating the proportion of different gas contents in a coalbed methane reservoir, so as to solve the technical problems of large evaluation error and relatively high prediction cost for the proportion of different gas contents in a coalbed methane reservoir.

[0005] To achieve the above purpose, the first aspect of the present application provides a method for evaluating the proportion of different gas contents in a coalbed methane reservoir. The method for evaluating the proportion of different gas contents in a coalbed methane reservoir includes the steps of:

[0006] Obtain the physical property parameters of the target coal seam and the initial value of the control volume of the target coal seam;

[0007] After fracturing flowback, calculate the initial values of the coal seam porosity and coal seam water saturation when the target coal seam just starts production according to the physical property parameters of the target coal seam and the initial value of the control volume of the target coal seam;

[0008] Obtain the production dynamic data table of the target coalbed methane reservoir, the control volume of the target coal seam, the coal seam porosity and coal seam water saturation when the target coal seam just starts production after fracturing flowback according to the physical property parameters, the coal seam porosity and coal seam water saturation when the target coal seam just starts production after fracturing flowback;

[0009] Calculate the original free gas reserves, original adsorbed gas reserves, and original dissolved gas reserves of the target coalbed methane reservoir based on physical property parameters, the controlled volume of the target coal seam, the coal seam porosity and coal seam water saturation at the beginning of production when the target coal seam starts production after fracturing and flowback, and the production performance data table.

[0010] Calculate the original free gas content, original adsorbed gas content, and original dissolved gas content in the target coalbed methane reservoir based on the original free gas reserves, original adsorbed gas reserves, and original dissolved gas reserves.

[0011] Calculate the proportion of the content of the three original gases in the target coalbed methane reservoir based on the original free gas content, original adsorbed gas content, and original dissolved gas content.

[0012] In the embodiment of the present application, after fracturing and flowback, the steps of calculating the initial values of the coal seam porosity and coal seam water saturation at the beginning of production when the target coal seam starts production based on the physical property parameters of the target coal seam and the initial value of the controlled volume of the target coal seam include:

[0013] Obtain the capillary pressure between the micropores and mesopores of the target coal seam.

[0014] Calculate the original pressure in the micropores of the target coal seam based on the original target coal seam pressure and the capillary pressure.

[0015] Obtain the net fracturing injection volume during the fracturing and flowback process.

[0016] Calculate the initial value of the coal seam porosity at the beginning of production when the target coal seam starts production after fracturing and flowback based on the net fracturing injection volume, the initial value of the controlled volume of the target coal seam, the original porosity of the target coal seam, and the volume coefficient of water.

[0017] Calculate the initial value of the coal seam water saturation based on the initial value of the controlled volume of the target coal seam, the original porosity of the target coal seam, the original water saturation, the net fracturing injection volume, the volume coefficient of water, and the initial value of the coal seam porosity at the beginning of production when the target coal seam starts production after fracturing and flowback.

[0018] In the embodiment of the present application, the steps of obtaining the production performance data table of the target coalbed methane reservoir based on the physical property parameters, the initial values of the coal seam porosity and coal seam water saturation at the beginning of production when the target coal seam starts production after fracturing and flowback include:

[0019] During the mining process, obtain multiple sets of average coal seam pressures, cumulative gas production, and cumulative water production of the target coal seam.

[0020] Calculate the dimensionless equivalent pressure drop corresponding to each production date based on the initial value of the coal seam porosity at the beginning of production when the target coal seam starts production after fracturing and flowback, the initial value of the coal seam water saturation, the physical property parameters of the target coal seam, and the average coal seam pressure.

[0021] Calculate the equivalent cumulative gas production corresponding to each production date based on the physical property parameters, cumulative gas production, cumulative water production, and cumulative water invasion volume data of the target coal seam.

[0022] Organize multiple groups of measured average coal seam pressure, cumulative gas production, cumulative water production, dimensionless equivalent pressure drop, and equivalent cumulative gas production into a table, which is the production performance data table.

[0023] In the embodiment of the present application, the steps of obtaining the control volume of the target coal seam, the coal seam porosity, and the coal seam water saturation at the beginning of production after fracturing flowback based on the physical property parameters, the initial values of the coal seam porosity and the coal seam water saturation at the beginning of production of the target coal seam after fracturing flowback include:

[0024] Use the equivalent cumulative gas production as the Y-axis and the dimensionless equivalent pressure drop as the X-axis for a linear function fitting. According to the linear function relationship, obtain the slope of the linear function and the Y-axis intercept of the linear function.

[0025] Calculate the control volume of the target coal seam according to the slope of the linear function.

[0026] Calculate the original free gas reserves of the target coal seam gas reservoir according to the Y-axis intercept of the linear function.

[0027] Calculate the coal seam porosity at the beginning of production of the target coal seam after fracturing flowback based on the control volume of the target coal seam, the net fracturing injection volume, the original porosity of the target coal seam, and the volume coefficient of water.

[0028] Calculate the first calculated value of the coal seam water saturation at the beginning of production of the target coal seam after fracturing flowback based on the control volume of the target coal seam, the original porosity of the target coal seam, the original water saturation, the net fracturing injection volume, the volume coefficient of water, and the coal seam porosity at the beginning of production of the target coal seam after fracturing flowback.

[0029] Calculate the second calculated value of the coal seam water saturation at the beginning of production of the target coal seam after fracturing flowback based on the control volume of the target coal seam and the original free gas reserves of the target coal seam gas reservoir.

[0030] Take the average of the coal seam water saturation, the first calculated value, and the second calculated value of the coal seam water saturation as the new coal seam water saturation, update the dimensionless equivalent pressure drop in the production performance data table of the target coal seam gas reservoir, and perform multiple iterations until the difference between the coal seam water saturations of two adjacent times is less than 0.001. Then determine that the control volume of the target coal seam, the coal seam porosity, and the coal seam water saturation at the beginning of production of the target coal seam after fracturing flowback at this time are the final determined values.

[0031] In the embodiment of the present application, the original adsorbed gas reserves in the target coal seam gas reservoir are calculated using the following calculation formula:

[0032]

[0033] Among them, G ai is the original reserve of adsorbed gas in the target coalbed methane reservoir, 10 6 m 3 ; V is the controlled volume of the target coal seam, 10 6 m 3 ; ρ c is the density of coal rock, t / m 3 ; V L is the Langmuir volume of adsorbed gas, m 3 / t; p L is the Langmuir pressure of adsorbed gas, MPa; p mi is the original pressure of the micropores in the target coal seam, MPa; p i is the original pressure of the target coal seam, MPa; p c is the capillary pressure between the micropores and mesopores of the target coal seam, MPa.

[0034] In the embodiment of the present application, the original reserve of dissolved gas in the target coalbed methane reservoir is calculated by the following calculation formula:

[0035] G si =Vφ ip S wip C s p i

[0036] Among them, G si is the original reserve of dissolved gas in the target coalbed methane reservoir, 10 6 m 3 ; V is the controlled volume of the target coal seam, 10 6 m 3 ; φ ip is the porosity of the coal seam at the beginning of production of the target coal seam after fracturing flowback; S wip is the water saturation of the coal seam at the beginning of production of the target coal seam after fracturing flowback; C s is the dissolution coefficient of the target coalbed methane reservoir in water, MPa -1 ; p i is the original pressure of the target coal seam, MPa.

[0037] In the embodiment of the present application, the original adsorbed gas content in the target coalbed methane reservoir is calculated by the following calculation formula:

[0038]

[0039] Among them, V ai is the original adsorbed gas content of the target coalbed methane reservoir, m 3 / t; G aiis the original reserve of adsorbed gas in the target coalbed methane reservoir, 10 6 m 3 ; V is the controlled volume of the target coal seam, 10 6 m 3 ; ρ c is the density of coal rock, t / m 3 ; V L is the Langmuir volume of adsorbed gas, m 3 / t; p L is the Langmuir pressure of adsorbed gas, MPa; p mi is the original pressure of the micropores in the target coal seam, MPa; p i is the original pressure of the target coal seam, MPa; p c is the capillary pressure between the micropores and mesopores of the target coal seam, MPa.

[0040] In the embodiments of the present application, the original free gas content in the target coalbed methane reservoir is calculated by the following calculation formula:

[0041]

[0042] or

[0043]

[0044] wherein, V fi is the original free gas content of the target coalbed methane reservoir, m 3 / t; G fi is the original reserve of free gas in the target coalbed methane reservoir, 10 6 m 3 ; V is the controlled volume of the target coal seam, 10 6 m 3 ; ρ c is the density of coal rock, t / m 3 ; φ ip is the porosity of the coal seam at the beginning of production of the target coal seam after fracturing flowback; S wip is the water saturation of the coal seam at the beginning of production of the target coal seam after fracturing flowback; Z sc is the gas deviation factor under standard conditions, dimensionless, with a value of 1; T sc is the temperature under standard conditions, K, with a value of 293.15; p sc is the pressure under standard conditions, MPa, with a value of 0.101325; p i is the original pressure of the target coal seam, MPa; T is the temperature of the target coal seam, K; Z i is the gas deviation factor at the original pressure of the target coal seam, dimensionless; N is the Y-axis intercept of the linear function, 10 6 m 3 ; M is the slope of the linear function, 106 m 3 。

[0045] In the embodiment of the present application, the original dissolved gas content is calculated by the following calculation formula:

[0046]

[0047] or

[0048]

[0049] wherein, Vsi is the original dissolved gas content of the target coalbed methane reservoir, m 3 / t; Gsi is the original reserve of dissolved gas in the target coalbed methane reservoir, 10 6 m 3 ; V is the controlled volume of the target coal seam, 10 6 m 3 ; ρ c is the density of coal rock, t / m 3 ; φ ip is the porosity of the coal seam at the beginning of production of the target coal seam after fracturing flowback; S wip is the water saturation of the coal seam at the beginning of production of the target coal seam after fracturing flowback; C s is the dissolution coefficient of the target coalbed methane reservoir in water, MPa -1 ; p i is the original pressure of the target coal seam, MPa.

[0050] The second aspect of the present application provides an evaluation device for the proportion of different gas contents in a coalbed methane reservoir, including:

[0051] A memory configured to store instructions; and

[0052] A processor configured to call instructions from the memory and capable of implementing the evaluation method for the proportion of different gas contents in the coalbed methane reservoir as described above.

[0053] Through the above technical solution, physical property parameters of the target coal seam are obtained; after fracturing flowback, based on the physical property parameters of the target coal seam and the initial value of the control volume of the target coal seam, the initial values of the coal seam porosity and the coal seam water saturation at the beginning of production of the target coal seam after fracturing flowback are calculated; according to the physical property parameters, the initial values of the coal seam porosity and the coal seam water saturation at the beginning of production of the target coal seam after fracturing flowback, a production performance data table of the target coalbed methane reservoir, the control volume of the target coal seam, the coal seam porosity and the coal seam water saturation at the beginning of production of the target coal seam after fracturing flowback are obtained; according to the physical property parameters, the control volume of the target coal seam, the coal seam porosity, the coal seam water saturation at the beginning of production of the target coal seam after fracturing flowback, and the production performance data table, the original free gas reserves, the original adsorbed gas reserves and the original dissolved gas reserves of the target coalbed methane reservoir are calculated; according to the original free gas reserves, the original adsorbed gas reserves and the original dissolved gas reserves, the original free gas content, the original adsorbed gas content and the original dissolved gas content in the target coalbed methane reservoir are calculated; according to the original free gas content, the original adsorbed gas content and the original dissolved gas content, the content ratios of the three original gases in the target coalbed methane reservoir are calculated. Based on the material balance principle of the target coalbed methane reservoir, considering the pressure difference between the adsorbed gas pores and the free gas pores, the change of the physical property parameters of the coal seam caused by fracturing transformation and the influence of dissolved gas, the present invention proposes an evaluation method for the adsorbed gas-free gas-dissolved gas reserves of the target coalbed methane reservoir, forms an evaluation method for the content and ratio of the adsorbed gas-free gas-dissolved gas in the target coalbed methane reservoir, avoids the measurement process of the measured gas content by pressure-maintained coring, has small error and saves costs.

[0054] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent specific implementation part. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The drawings are used to provide a further understanding of the embodiments of the present application, and constitute a part of the specification, and are used to explain the embodiments of the present application together with the following specific implementation manners, but do not constitute a limitation to the embodiments of the present application. In the drawings:

[0056] Figure 1 Schematically shows a flow chart of a method for evaluating the content ratio of different gases in a coalbed methane reservoir according to an embodiment of the present application;

[0057] Figure 2 Schematically shows a Y-X diagram during the first trial calculation of a certain deep coalbed methane reservoir;

[0058] Figure 3 Schematically shows the finally determined Y-X diagram of a certain deep coalbed methane reservoir. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0059] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. It should be understood that the specific implementation manners described herein are only used to illustrate and explain the embodiments of this application, and are not used to limit the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope protected by this application.

[0060] It should be noted that the acquisition, transmission, storage, use, processing, etc. of data in the technical solutions of this application all comply with the relevant regulations of laws and regulations. In the embodiments of this application, certain industry-existing solutions such as software, components, models, etc. may be mentioned. They should be regarded as exemplary, and their purpose is only to illustrate the feasibility in the implementation of the technical solutions of this application, but it does not mean that the applicant has already or necessarily used this solution.

[0061] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of this application, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of these features. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0062] As Figure 1 shown, the embodiments of this application provide a method for evaluating the proportion of different gas contents in a coalbed methane reservoir. The method for evaluating the proportion of different gas contents in a coalbed methane reservoir includes the following steps:

[0063] S10: Obtain the physical property parameters of the target coal seam and the initial value of the control volume of the target coal seam;

[0064] Among them, the physical property parameters include: coal rock density ρ c , the original porosity φ of the target coal seam i , the original pressure p of the target coal seam i , coal seam temperature T, the original water saturation S of the target coal seam wi , pore compressibility C p , the average pore diameter d of the coal matrix micropores, the average pore diameter D of the coal matrix mesopores, the coal matrix surface wetting angle θ, the coal matrix shrinkage coefficient C a , adsorbed gas Langmuir volume V L , adsorbed gas Langmuir pressure p L , gas relative density γg 、Coefficient B of water volume w 、Isothermal compressibility C of water w ,Dissolution coefficient C of the target coalbed methane reservoir in water s 、Gas-water interfacial tension σ gw 。

[0065] S20: After pressure return flow, calculate the initial values of the coal seam porosity and coal seam water saturation when the target coal seam starts production for the first time after pressure return flow according to the physical property parameters of the target coal seam and the initial value of the control volume of the target coal seam;

[0066] S30: Obtain the production performance data table of the target coalbed methane reservoir, the control volume of the target coal seam, the coal seam porosity and coal seam water saturation when the target coal seam starts production for the first time after pressure return flow according to the physical property parameters, the coal seam porosity and coal seam water saturation when the target coal seam starts production for the first time after pressure return flow;

[0067] S40: Calculate the original reserves of free gas, adsorbed gas and dissolved gas in the target coalbed methane reservoir according to the physical property parameters, the control volume of the target coal seam, the coal seam porosity, coal seam water saturation when the target coal seam starts production for the first time after pressure return flow, and the production performance data table;

[0068] S50: Calculate the original free gas content, original adsorbed gas content and original dissolved gas content in the target coalbed methane reservoir according to the original reserves of free gas, adsorbed gas and dissolved gas;

[0069] S60: Calculate the proportion of the contents of the three original gases in the target coalbed methane reservoir according to the original free gas content, original adsorbed gas content and original dissolved gas content.

[0070] Based on the material balance principle of the target coalbed methane reservoir, considering the pressure difference between the adsorbed gas pores and free gas pores, the change of coal seam physical property parameters caused by fracturing transformation, and the influence of dissolved gas, the present invention proposes an evaluation method for the reserves of adsorbed gas-free gas-dissolved gas in the target coalbed methane reservoir, forms an evaluation method for the content and proportion of adsorbed gas-free gas-dissolved gas in the target coalbed methane reservoir, avoids the measurement process of pressure-maintained coring for measuring the gas content in-situ, and saves costs.

[0071] In the embodiment of the present application, the step of calculating the initial values of the coal seam porosity and coal seam water saturation when the target coal seam starts production for the first time after pressure return flow according to the physical property parameters of the target coal seam and the initial value of the control volume of the target coal seam after pressure return flow includes:

[0072] Obtain the capillary pressure between the micropores and mesopores of the target coal seam;

[0073] Calculate the original pressure in the micropores of the target coal seam according to the original target coal seam pressure and the capillary pressure;

[0074] Obtain the net fracturing injection volume during the fracturing and flowback processes;

[0075] Calculate the initial value of the coal seam porosity at the beginning of production after fracturing flowback based on the net fracturing injection volume, the initial value of the controlled volume of the target coal seam, the original porosity of the target coal seam, and the volume coefficient of water;

[0076] Calculate the initial value of the coal seam water saturation based on the initial value of the controlled volume of the target coal seam, the original porosity of the target coal seam, the original water saturation, the net fracturing injection volume, the volume coefficient of water, and the initial value of the coal seam porosity at the beginning of production after fracturing flowback.

[0077] Specifically, in this embodiment, the adsorbed gas in the target coal seam mainly exists in the micropores of the coal matrix (pore diameter less than 2 nm), while the free gas, dissolved gas, and water exist in the cleats (pore diameter greater than 1000 nm), macropores (pore diameter between 50 nm and 1000 nm), and mesopores (pore diameter between 2 nm and 50 nm). The original pressure p of the target coal seam i is actually the pressure in the cleats, macropores, and mesopores of the coal seam. Therefore, there is a capillary pressure between the micropores and mesopores of the matrix, which is calculated using the following formula:

[0078]

[0079] In the formula, p c is the capillary pressure between the micropores and mesopores of the target coal seam, in MPa; d is the average pore diameter of the micropores of the coal matrix, in nm; D is the average pore diameter of the mesopores of the coal matrix, in nm; σ gw is the gas-water interfacial tension, in mN / m; θ is the wetting angle of the coal matrix surface, in °.

[0080] Given the original pressure p of the target coal seam i , the original pressure p in the micropores of the coal seam can be calculated according to the following formula mi , that is, the original pressure in the adsorption pores:

[0081] p mi = p i + p c (2)

[0082] In the formula, p mi is the original pressure in the micropores of the coal seam, in MPa; p i is the original pressure of the target coal seam, in MPa; p c is the capillary pressure between the micropores and mesopores of the target coal seam, in MPa.

[0083] Statistically, the total fracturing fluid volume W during the fracturing process of the target coal seam fi and the cumulative flowback volume W during the flowback process fp, and the net fracturing injection volume \(W\) is calculated using the following formula fin :

[0084] \(W\) fin =\(W\) fi - \(W\) fp (3)

[0085] In the formula, \(W\) fin is the net fracturing injection volume, \(10\) 6 \(m\) 3 ; \(W\) fi is the total fracturing fluid volume during the fracturing process of the target coalbed methane reservoir, \(10\) 6 \(m\) 3 ; \(W\) fp is the cumulative fluid production volume during the fluid production process, \(10\) 6 \(m\) 3 .

[0086] When calculating the coal seam porosity, first give an initial value to the control volume \(V\) of the target coal seam, and then substitute the original porosity \(\varphi\) i of the target coal seam, the net fracturing injection volume \(W\) fin and the volume coefficient \(B\) of water w into formula (4) to calculate the initial value of the coal seam porosity \(\varphi\) ip of the target coalbed methane reservoir at the beginning of production after fracturing fluid production.

[0087]

[0088] In the formula, \(\varphi\) ip is the initial value of the coal seam porosity of the target coalbed methane reservoir at the beginning of production after fracturing fluid production; \(\varphi\) i is the original porosity of the target coal seam; \(W\) fin is the net fracturing injection volume, \(10\) 6 \(m\) 3 ; \(B\) w is the volume coefficient of water, \(m\) 3 / \(m\) 3 ; \(V\) is the control volume of the target coal seam, \(10\) 6 \(m\) 3 .

[0089] When calculating the initial value of the coal seam water saturation, substitute the initial value of the control volume \(V\) of the target coal seam, the original porosity \(\varphi\) i of the target coal seam, the original water saturation \(S\) wi of the target coal seam, the net fracturing injection volume \(W\) fin , the volume coefficient \(B\) of water w and the initial value of the coal seam porosity \(\varphi\) ip calculated for the target coalbed methane reservoir at the beginning of production after fracturing fluid production into formula (5) to calculate the coal seam water saturation \(S\) wipInitial value.

[0090]

[0091] In the embodiment of the present application, the steps of obtaining the production performance data table of the target coalbed methane reservoir according to the physical property parameters, the initial values of the coal seam porosity and the coal seam water saturation when the target coal seam just starts production after fracturing flowback include:

[0092] During the mining process, obtain multiple sets of average coal seam pressures, cumulative gas production volumes, and cumulative water production volumes of the target coal seam;

[0093] According to the initial value of the coal seam porosity, the initial value of the coal seam water saturation, the physical property parameters of the target coal seam, and the average coal seam pressure, calculate the dimensionless equivalent pressure drop corresponding to each production date;

[0094] According to the physical property parameters, cumulative gas production volume, cumulative water production volume, and cumulative water influx data of the target coal seam, calculate the equivalent cumulative gas production corresponding to each production date;

[0095] Organize multiple sets of measured average coal seam pressures, cumulative gas production volumes, cumulative water production volumes, dimensionless equivalent pressure drops, and equivalent cumulative gas productions into a table, which is the production performance data table.

[0096] In this embodiment, the initial value of the coal seam porosity φ after fracturing flowback when the gas reservoir just starts production, ip the initial value of the coal seam water saturation S when the target coalbed methane reservoir just starts production after fracturing flowback, wip the initial value, the physical property parameters of the target coal seam, and the measured average coal seam pressure data are substituted into formula (6) to calculate X (dimensionless equivalent pressure drop) corresponding to each date.

[0097]

[0098] In the formula, ρ c is the coal rock density, t / m 3 ; V L is the Langmuir volume, m 3 / t; p L is the Langmuir pressure, MPa; p c is the capillary pressure between the micropores and mesopores of the target coal seam, MPa; φ ip is the coal seam porosity when the target coalbed methane reservoir just starts production after fracturing flowback; S wip is the coal seam water saturation when the target coalbed methane reservoir just starts production after fracturing flowback; Z sc is the natural gas deviation coefficient under standard conditions, dimensionless, with a value of 1; T sc is the temperature under standard conditions, K, with a value of 293.15; p i is the original pressure of the target coal seam, MPa; psc is the standard pressure, in MPa, with a value of 0.101325; T is the coal seam temperature, in K; Z i is the deviation coefficient of the gas under the original pressure of the target coal seam, dimensionless; p is the average coal reservoir pressure, in MPa; Z is the deviation coefficient of the gas under the average coal seam pressure, dimensionless; C p is the pore volume compressibility, in MPa -1 ; C w is the isothermal compressibility of water, in MPa -1 ; C s is the dissolution coefficient of the target coalbed methane reservoir in water, in MPa -1 ; C a is the coal matrix shrinkage coefficient, dimensionless.

[0099] Furthermore, substitute the measured cumulative gas production G p , cumulative water production W p and cumulative water influx W e (usually with a value of 0, unless the aquifer is accidentally fractured during the fracturing process, and during the mining process, as the fluids in the coal seam are produced, the water in the aquifer gradually invades the coal seam) data into formula (7) to calculate the corresponding Y (equivalent cumulative gas production) for each date.

[0100]

[0101] In the formula, G p is the cumulative gas production of the target coalbed methane reservoir, in 10 6 m 3 ; W p is the cumulative water production of the target coalbed methane reservoir, in 10 6 m 3 ; W e is the cumulative water influx during the production process, in 10 6 m 3 ; Z sc is the gas deviation coefficient under standard conditions, dimensionless, with a value of 1; T sc is the temperature under standard conditions, in K, with a value of 293.15; p sc is the standard pressure, in MPa, with a value of 0.101325; T is the temperature of the target coal seam, in K; p is the average coal seam pressure, in MPa; Z is the deviation coefficient of the gas under the average coal seam pressure, dimensionless; C s is the dissolution coefficient of the target coalbed methane reservoir in water, in MPa -1 ; B w is the volume coefficient of water, in m 3 / m 3 .

[0102] Arrange the calculation results of X and Y, as shown in the last two columns of Table 1 below.

[0103] Table 1 Production dynamic data of the target coal seam

[0104]

[0105] Further, taking X as the horizontal axis and Y as the vertical axis, a scatter plot is drawn in a rectangular coordinate graph. By using linear fitting, the slope value M and the Y-axis intercept value N of the oblique line of the obtained linear function are obtained. Then, the control volume V of the target coal seam is equal to the numerical value of the slope M of the oblique line of the linear function obtained by fitting, as shown in formula (8):

[0106] V = M (8)

[0107] In the formula, V is the control volume of the target coal seam, 10 6 m 3 ; M is the slope of the oblique line of the linear function, 10 6 m 3 .

[0108] The Y-axis intercept value N of the oblique line of the linear function obtained by fitting is the numerical value of the original reserve of free gas in the target coalbed methane reservoir, as shown in formula (9):

[0109]

[0110] In the formula, G fi is the original reserve of free gas in the target coalbed methane reservoir, 10 6 m 3 ; V is the control volume of the target coal seam, 10 6 m 3 ; φ ip is the coal seam porosity at the beginning of production of the target coalbed methane reservoir after fracturing flowback, in decimal; S wip is the coal seam water saturation at the beginning of production of the target coalbed methane reservoir after fracturing flowback, in decimal; Z sc is the gas deviation coefficient under standard conditions, dimensionless, with a value of 1; T sc is the temperature under standard conditions, in K, with a value of 293.15; p sc is the standard pressure, in MPa, with a value of 0.101325; p i is the original pressure of the target coal seam, in MPa; T is the coal seam temperature, in K; Z i is the gas deviation coefficient at the original pressure of the target coal seam, dimensionless; N is the Y-axis intercept of the oblique line of the linear function, 10 6 m 3 .

[0111] Combining formula (8) and formula (9) can further solve for the value of S wip The formula is:

[0112]

[0113] In the formula, S wip is the coal seam water saturation at the beginning of production of the target coalbed methane reservoir after fracturing flowback; φ ip is the coal seam porosity at the beginning of production of the target coalbed methane reservoir after fracturing flowback; Z sc is the gas deviation factor under standard conditions, dimensionless, with a value of 1; T sc is the temperature under standard conditions, K, with a value of 293.15; p sc is the standard pressure, MPa, with a value of 0.101325; p i is the original pressure of the target coal seam, MPa; T is the coal seam temperature, K; Z i is the deviation factor of the gas under the original pressure of the target coal seam, dimensionless; N is the Y-axis intercept of the linear function slope, 10 6 m 3 ; M is the slope of the linear function slope, 10 6 m 3 .

[0114] Substitute V obtained by formula (8) into formula (4) to calculate the new φ ip to replace the value of φ ip in the previous step, and then take the average of the calculation results of formula (5) and formula (10) as the new S wip value to replace the value of S wip in the previous step, and repeat the calculation of the values of X and Y, drawing a scatter plot in rectangular coordinates, linear fitting, determining the slope M and intercept N of the linear function slope, calculating the new V, φ ip and S wip , until the difference between S wip calculated in two adjacent times is less than 0.001, and finally determine the coal seam water saturation S wip , the slope M of the linear function slope, the Y-axis intercept N of the linear function slope, the control volume V of the target coal seam, the coal seam porosity φ ip at the beginning of production of the gas reservoir after fracturing flowback, and the original reserve G fi of the free gas in the target coalbed methane reservoir.

[0115] Furthermore, the determined control volume V of the target coal seam, the coal rock density ρ c , the Langmuir volume V L of the adsorbed gas, the Langmuir pressure p L of the adsorbed gas, the original pressure p mi of the micropores of the target coal seam or the original pressure p i of the target coal seam, and the capillary pressure p cSubstitute into Formula (11) and Formula (12) to calculate the original reserves of adsorbed gas and dissolved gas in the target coalbed methane reservoir:

[0116] Among them, the original reserves of adsorbed gas in the target coalbed methane reservoir are calculated using the following formula:

[0117]

[0118] Among them, G ai is the original reserves of adsorbed gas in the target coalbed methane reservoir, 10 6 m 3 ; V is the controlled volume of the target coal seam, 10 6 m 3 ; ρ c is the density of coal rock, t / m 3 ; V L is the Langmuir volume of adsorbed gas, m 3 / t; p L is the Langmuir pressure of adsorbed gas, MPa; p mi is the original pressure of the micropores in the target coal seam, MPa; p i is the original pressure of the target coal seam, MPa; p c is the capillary pressure between the micropores and mesopores of the target coal seam, MPa.

[0119] In the embodiment of the present application, the original reserves of dissolved gas in the target coalbed methane reservoir are calculated using the following formula:

[0120] G si =Vφ ip S wip C s p i (12)

[0121] Among them, G si is the original reserves of dissolved gas in the target coalbed methane reservoir, 10 6 m 3 ; V is the controlled volume of the target coal seam, 10 6 m 3 ; φ ip is the porosity of the coal seam at the beginning of production of the target coal seam after fracturing fluid backflow; S wip is the water saturation of the coal seam at the beginning of production of the target coal seam after fracturing fluid backflow; C s is the dissolution coefficient of the target coalbed methane reservoir in water, MPa -1 ; p i is the original pressure of the target coal seam, MPa.

[0122] In the embodiment of the present application, the original adsorbed gas content in the target coalbed methane reservoir is calculated using the following formula:

[0123]

[0124] Among them, V ai is the original adsorbed gas content of the target coalbed methane reservoir, m 3 / t; G ai is the original reserve of adsorbed gas in the target coalbed methane reservoir, 10 6 m 3 ; V is the controlled volume of the target coal seam, 10 6 m 3 ; ρ c is the density of coal rock, t / m 3 ; V L is the Langmuir volume of adsorbed gas, m 3 / t; p L is the Langmuir pressure of adsorbed gas, MPa; p mi is the original pressure of the micropores in the target coal seam, MPa; p i is the original pressure of the target coal seam, MPa; p c is the capillary pressure between the micropores and mesopores of the target coal seam, MPa.

[0125] In the embodiment of the present application, the original free gas content in the target coalbed methane reservoir is calculated by the following formula:

[0126]

[0127] Or

[0128]

[0129] Among them, V fi is the original free gas content of the target coalbed methane reservoir, m 3 / t; G fi is the original reserve of free gas in the target coalbed methane reservoir, 10 6 m 3 ; V is the controlled volume of the target coal seam, 10 6 m 3 ; ρ c is the density of coal rock, t / m 3 ; φ ip is the porosity of the coal seam at the beginning of production of the target coal seam after fracturing flowback; S wip is the water saturation of the coal seam at the beginning of production of the target coal seam after fracturing flowback; Z sc is the gas deviation coefficient under standard conditions, dimensionless, with a value of 1; T sc is the temperature under standard conditions, K, with a value of 293.15; p sc is the pressure under standard conditions, MPa, with a value of 0.101325; p iis the original pressure of the target coal seam, MPa; T is the temperature of the target coal seam, K; Z i is the deviation coefficient of the gas under the original pressure of the target coal seam, dimensionless; N is the Y-axis intercept of the linear function, 10 6 m 3 ; M is the slope of the linear function, 10 6 m 3 .

[0130] In the embodiment of the present application, the original dissolved gas content is calculated by the following formula:

[0131]

[0132] or

[0133]

[0134] wherein, V si is the original dissolved gas content of the target coalbed methane reservoir, m 3 / t; G si is the original reserve of dissolved gas in the target coalbed methane reservoir, 10 6 m 3 ; V is the controlled volume of the target coal seam, 10 6 m 3 ; ρ c is the density of coal and rock, t / m 3 ; φ ip is the porosity of the coal seam at the beginning of production of the target coal seam after fracturing flowback; S wip is the water saturation of the coal seam at the beginning of production of the target coal seam after fracturing flowback; C s is the dissolution coefficient of the target coalbed methane reservoir in water, MPa -1 ; p i is the original pressure of the target coal seam, MPa.

[0135] When the original adsorbed gas content, original free gas content and original dissolved gas content of the target coal seam are calculated, the content ratios of the following three gases can be obtained:

[0136] (1) Original gas content of the target coalbed methane reservoir:

[0137] V ti = V ai + V fi + V si (18)

[0138] wherein, f ai is the proportion of the original adsorbed gas content in the target coalbed methane reservoir;

[0139] (2) Proportion of the original adsorbed gas content in the target coalbed methane reservoir:

[0140]

[0141] (2) Proportion of original free gas content in the target coalbed methane reservoir:

[0142]

[0143] Among them, f fi is the proportion of original free gas content in the target coalbed methane reservoir;

[0144] (3) Proportion of original dissolved gas content in the target coalbed methane reservoir:

[0145]

[0146] Among them, f si is the proportion of original dissolved gas content in the target coalbed methane reservoir.

[0147] To further illustrate the evaluation process of the evaluation method for the proportion of different gas contents in the coalbed methane reservoir of the present application, the following takes the evaluation process of the gas content proportion of a deep coal reservoir as an example for illustration:

[0148] First, the physical property parameters of the overall deep coal reservoir are referred to Table 2 below:

[0149] Table 2 Statistical Table of Physical Property Parameters of a Certain Deep Coal Reservoir

[0150]

[0151]

[0152] Then, substitute the average pore diameter d = 2 nm of the coal matrix micropores, the average pore diameter D = 10 nm of the coal matrix mesopores, the gas-water interfacial tension σ gw = 60 mN / m and the coal matrix surface wetting angle θ = 89° into formula (1) to obtain the capillary pressure pc = 0.8377 (MPa) between the micropores and mesopores of the coal reservoir.

[0153]

[0154] Substitute the original coal reservoir pressure p i = 21 MPa and the capillary pressure p c = 0.8377 MPa between the micropores and mesopores of the coal reservoir into formula (2) to calculate the original pressure p mi = 21.8377 (MPa) of the adsorbed gas in the adsorbed pores of the coal reservoir.

[0155] p mi = p i + p c = 21 + 0.8377 = 21.8377 (MPa)

[0156] Furthermore, the total amount of fracturing fluid W during the fracturing process of the deep coalbed methane well is statistically calculated fi = 0.03 (10 6 m 3 ) and the cumulative fluid production volume W fp = 0.0075 (10 6 m 3 ) during the fluid production process, and the net injection volume W fin = 0.0225 (10 6 m 3 ) is calculated using formula (3).

[0157] W fin = W fi - W fp = 0.03 - 0.0075 = 0.0225 (10 6 m 3 )

[0158] The results are recorded in Table 3.

[0159] Table 3 Statistical Table of Fracturing and Fluid Production Data of a Certain Deep Coalbed Methane Well

[0160]

[0161]

[0162] First, an initial value is given to the control volume V of the coalbed methane reservoir or well according to geological understanding. The horizontal section length of this coalbed methane well is 1000 m, the well spacing of the horizontal well is 350 m, and the thickness of the deep coal reservoir is 10 m. The calculated initial value of the control volume V of this deep coalbed methane well is 3.5 (10 6 m 3 ). Then, the initial value of V, the original porosity φ i = 0.07, the net injection volume W fin = 0.0225 (10 6 m 3 ) and the volume coefficient B w = 1 of water are substituted into formula (4) to calculate the initial value of the porosity φ ip of the coal reservoir when the well just starts production after fracturing fluid production is 0.076429.

[0163]

[0164] The initial value of the control volume V of this coalbed methane well, 3.5 (10 6 m 3 ), the original porosity φ i = 0.07, the original water saturation S wi= 0.60433, the net fracturing injection volume W fin = 0.0225(10 6 m 3 ), the volume coefficient of water B w = 1 and the calculated porosity φ of the coal reservoir at the beginning of gas well production after fracturing backflow ip = 0.076429 are substituted into formula (5) to calculate the initial water saturation S of the coal reservoir at the beginning of gas well production after fracturing backflow wip is 0.63761.

[0165]

[0166] The measured average coal reservoir pressure and the corresponding cumulative gas production and cumulative water production of this deep coalbed methane well are sorted out as shown in Table 4. Among them, using the Dranchuk-Abou-Kassem method, according to the relative density γ of natural gas g and reservoir temperature T, the average gas deviation coefficient Z at any formation pressure can be obtained.

[0167] Table 4 Measured average coal reservoir pressure and corresponding cumulative gas production and cumulative water production of deep coalbed methane well

[0168]

[0169]

[0170] Through the overall X and Y, the production dynamic data of this coal reservoir are obtained as shown in Table 5 below

[0171] Table 5 Related reservoir production dynamic data

[0172]

[0173] Taking X as the horizontal axis and Y as the vertical axis, a scatter plot is drawn in the rectangular coordinate graph, as Figure 2 shown. By using linear fitting, the slope value M = 3.37998 and the Y-axis intercept value N = 19.56917 of the obtained linear trend line are obtained.

[0174] Then the control volume V of this deep coalbed methane reservoir or gas well is equal to the value of the slope M of the fitted linear trend line:

[0175] V = M = 3.37998(10 6 m 3 )

[0176] The Y-axis intercept value N of the fitted linear trend line is the value of the original free gas reserve in the deep coalbed methane reservoir:

[0177]

[0178] Substitute the slope value M = 3.37998 and the Y-axis intercept value N = 19.56917 of the linearly fitted trend line and some parameters in Table 1 into formula (10) to solve for S wip The value of is:

[0179]

[0180] Substitute the calculated V = 3.37998 into formula (4) to calculate the new φ ip :

[0181]

[0182] Substitute the calculated V = 3.37998 and the calculated new φ ip = 0.07666 into formula (5) to calculate S wip The value of is:

[0183]

[0184] Take the average value of S wip = 0.63866 calculated by formula (5) and S wip = 0.61943 calculated by formula (10) as the new S wip = 0.62905 to replace the previous value of S wip to calculate the new φ ip = 0.07666 to replace the previous value of φ ip Repeat the above steps to calculate the values of X and Y, draw the scatter plot in the rectangular coordinate system, perform linear fitting, determine the slope M and intercept N of the linear trend line, calculate the new V, φ ip and S wip until the difference between the S wip calculated in two adjacent times is less than 0.001, and finally determine the water saturation S of the coal reservoir when the gas well just starts production after fracturing and flowing back wip The value of is 0.63755, the value of the slope M of the linear trend line is 3.50706, and the value of the Y-axis intercept N of the linear trend line is 19.33471, as Figure 3 shown

[0185] Then, the control volume V of this deep coalbed methane well is 3.50706 (10 6 m 3 ), the porosity φ of the coal reservoir when the gas well just starts production after fracturing and flowing back ip = 0.076416, and the original reserve G of the free gas in the deep coalbed methane reservoir fi = 19.33471 (10 6 m 3 )

[0186] The control volume V = 3.50706 (10 6 m 3 ), the coal density ρ c , the Langmuir volume V L of adsorbed gas, the Langmuir pressure p L of adsorbed gas, the original pressure p mi in the micropores of the coal reservoir or the original coal reservoir pressure p i and the capillary pressure p c between the micropores and mesopores of the coal reservoir are substituted into Formula (11) and Formula (12) to calculate the original reserves G ai = 114.6604 (10 6 m 3 ) of adsorbed gas in this deep coalbed methane well, and the original reserves G si = 0.6100 (10 6 m 3 ) of dissolved gas.

[0187]

[0188] G si = Ahφ ip S wip C s p i = 3.50706×0.076416×0.63755×0.17×21 = 0.6100 (10 6 m 3 )

[0189] Using Formula (13), calculate the original adsorbed gas content V ai = 21.7961 (m 3 / t).

[0190]

[0191] Using Formula (14) or Formula (15), calculate the original free gas content V fi = 3.6754 (m 3 / t).

[0192]

[0193] Using Formula (16) or Formula (17), calculate the original dissolved gas content V si = 0.1160 (m 3 / t).

[0194]

[0195] The original gas content V of deep coalbed methane is calculated using formula (18) ti = 25.5875 (m 3 / t).

[0196] V ti = V ai + V fi + V si = 21.7961 + 3.6754 + 0.1160 = 25.5875 (m 3 / t)

[0197] The proportion f of the original adsorbed gas content in the deep coalbed methane reservoir is calculated using formula (19) ai = 85.183%.

[0198]

[0199] The proportion f of the original free gas content in the deep coalbed methane reservoir is calculated using formula (20) fi = 14.364%.

[0200]

[0201] The proportion f of the original dissolved gas content in the deep coalbed methane reservoir is calculated using formula (21) si = 0.453%.

[0202]

[0203] The second aspect of the present application provides an evaluation device for the proportion of different gas contents in a coalbed methane reservoir, including:

[0204] A memory configured to store instructions; and

[0205] A processor configured to call instructions from the memory and capable of implementing the above-mentioned evaluation method for the proportion of different gas contents in a coalbed methane reservoir when executing the instructions.

[0206] Among them, 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, for example, read-only memory (ROM) or flash memory (flash RAM). The memory is an example of a computer-readable medium.

[0207] 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.

[0208] 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.

[0209] 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 evaluating the proportion of different gas contents in a coalbed methane reservoir, characterized in that: The method for evaluating the proportion of different gas contents in a coalbed methane reservoir comprises the following steps: Obtaining the physical property parameters of the target coal seam and the initial value of the control volume of the target coal seam; After fracturing and flowback, the initial values ​​of the coal seam porosity and coal seam water saturation when the target coal seam is just put into production after fracturing and flowback are calculated according to the physical property parameters of the target coal seam and the initial value of the control volume of the target coal seam; According to the physical property parameters, the initial values ​​of the coal seam porosity and the coal seam water saturation when the target coal seam is just put into production after fracturing and flowback, a production dynamic data table of the target coal seam gas reservoir, a controlled volume of the target coal seam, and the coal seam porosity and the coal seam water saturation when the target coal seam is just put into production after fracturing and flowback are obtained; Calculate the original free gas reserves, the original adsorbed gas reserves and the original dissolved gas reserves of the target coalbed methane reservoir according to the physical property parameters, the controlled volume of the target coal seam, the coal seam porosity and the coal seam water saturation of the target coal seam when it is first put into production after fracturing and flowback, and the production performance data table; Calculating the original free gas content, the original adsorbed gas content and the original dissolved gas content in the target coalbed methane reservoir according to the original free gas reserves, the original adsorbed gas reserves and the original dissolved gas reserves; The content ratios of the three original gases in the target coalbed methane reservoir are calculated according to the original free gas content, the original adsorbed gas content and the original dissolved gas content.

2. The method according to claim 1, characterized in that The step of calculating the initial values ​​of the coal seam porosity and the coal seam water saturation of the target coal seam when it is just put into production after fracturing and flowback according to the physical property parameters of the target coal seam and the initial value of the control volume of the target coal seam after fracturing and flowback comprises: Obtaining capillary pressure between micropores and mesopores of the target coal seam; Calculate the original pressure in the micropores of the target coal seam according to the original target coal seam pressure and the capillary pressure; Obtain the net injection volume during fracturing and flowback; Calculate the initial value of the coal seam porosity of the target coal seam when it is just put into production after fracturing flowback according to the net injection volume of fracturing, the initial value of the control volume of the target coal seam, the original porosity of the target coal seam and the volume coefficient of water; The initial value of the water saturation of the target coal seam when it is first put into production after fracturing and flowback is calculated based on the initial value of the control volume of the target coal seam, the original porosity of the target coal seam, the original water saturation, the net fracturing injection volume, the volume coefficient of water, and the initial value of the coal seam porosity when the target coal seam is first put into production after fracturing and flowback.

3. The method according to claim 1, characterized in that The step of obtaining the production dynamic data table of the target coalbed methane reservoir according to the physical property parameters, the initial values ​​of the coal seam porosity and the coal seam water saturation when the target coal seam is just put into production after fracturing and flowback includes: During the mining process, the average coal seam pressure, cumulative gas production and cumulative water production of multiple target coal seams are obtained; According to the initial value of coal seam porosity, initial value of coal seam water saturation, physical property parameters of target coal seam and average coal seam pressure at the beginning of production after fracturing flowback, the dimensionless equivalent pressure drop corresponding to each production date is calculated; Calculate the equivalent cumulative gas production corresponding to each production date based on the physical properties, cumulative gas production, cumulative water production and cumulative water intrusion data of the target coal seam; The production dynamic data table is formed by arranging multiple groups of measured average coal seam pressure, cumulative gas production, cumulative water production, dimensionless equivalent pressure drop and equivalent cumulative gas production into a table.

4. The method according to claim 1, characterized in that: The step of obtaining the controlled volume of the target coal seam, the coal seam porosity and the coal seam water saturation when the target coal seam is just put into production after fracturing and flowback according to the physical property parameters, the initial values ​​of the coal seam porosity and the coal seam water saturation when the target coal seam is just put into production after fracturing and flowback comprises: With equivalent cumulative gas production as the Y-axis and dimensionless equivalent pressure drop as the X-axis, a linear function fitting is performed, and the slope of the linear function and the Y-axis intercept of the linear function are obtained according to the linear function relationship; Calculate the control volume of the target coal seam according to the slope of the linear function; Calculate the original free gas reserves of the target coalbed methane reservoir according to the Y-axis intercept of the linear function; Calculating the coal seam porosity of the target coal seam when it is just put into production after fracturing flowback according to the controlled volume of the target coal seam, the net injection volume of fracturing, the original porosity of the target coal seam and the volume coefficient of water; Calculate a first calculated value of the water saturation of the target coal seam when it is just put into production after fracturing flowback according to the controlled volume of the target coal seam, the original porosity of the target coal seam, the original water saturation, the net injection volume of fracturing, the volume coefficient of water, and the coal seam porosity when the target coal seam is just put into production after fracturing flowback; Calculating a second calculated value of the water saturation of the target coal seam when the target coal seam is just put into production after fracturing and flowback according to the controlled volume of the target coal seam and the original free gas reserves of the target coal seam gas reservoir; The average of the first calculated value and the second calculated value of the coal seam water saturation is used as the new coal seam water saturation, the dimensionless equivalent pressure drop in the production dynamic data table of the target coalbed methane reservoir is updated, and multiple iterations are performed until the difference between two adjacent coal seam water saturations is less than 0.

001. The controlled volume of the target coal seam at this time, the coal seam porosity and coal seam water saturation of the target coal seam when it is just put into production after fracturing and flowback are determined as the final determined values.

5. The method according to claim 1, characterized in that The original reserves of adsorbed gas in the target coalbed methane reservoir are calculated using the following formula: Among them, G ai is the original adsorbed gas reserves of the target coalbed methane reservoir, 10 6 m 3 ; V is the control volume of the target coal seam, 10 6 m 3 ρ c is the density of coal rock, t / m 3 ; V L is the Langmuir volume of adsorbed gas, m 3 / t;p L is the Langmuir pressure of adsorbed gas, MPa; p mi is the original pressure of the micropores of the target coal seam, MPa; p i is the original pressure of the target coal seam, MPa; p c is the capillary pressure between the micropores and mesopores of the target coal seam, MPa.

6. The method according to claim 1, characterized in that The original reserves of dissolved gas in the target coalbed methane reservoir are calculated using the following formula: G si =Vφ ip S wip C s p i Among them, G si is the original reserves of dissolved gas in the target coalbed methane reservoir, 10 6 m 3 ; V is the control volume of the target coal seam, 10 6 m 3 ; φ ip S is the coal seam porosity of the target coal seam when it is just put into production after fracturing and flowback; wip C is the water saturation of the target coal seam when it is first put into production after fracturing flowback; s is the solubility coefficient of the target coalbed methane reservoir in water, MPa -1 ;p i is the original pressure of the target coal seam, MPa.

7. The method according to claim 1, characterized in that The original adsorbed gas content in the target coalbed methane reservoir is calculated using the following calculation formula: Among them, V ai is the original adsorbed gas content of the target coalbed methane reservoir, m 3 / t;G ai is the original adsorbed gas reserves of the target coalbed methane reservoir, 10 6 m 3 ; V is the control volume of the target coal seam, 10 6 m 3 ρ c is the density of coal rock, t / m 3 ; V L is the Langmuir volume of adsorbed gas, m 3 / t;p L is the Langmuir pressure of adsorbed gas, MPa; p mi is the original pressure of the micropores of the target coal seam, MPa; p i is the original pressure of the target coal seam, MPa; p c is the capillary pressure between the micropores and mesopores of the target coal seam, MPa.

8. The method according to claim 1, characterized in that The original free gas content in the target coalbed methane reservoir is calculated using the following calculation formula: or Among them, V fi is the original free gas content of the target coalbed methane reservoir, m 3 / t;G fi is the original free gas reserves of the target coalbed methane reservoir, 10 6 m 3 ; V is the control volume of the target coal seam, 10 6 m 3 ρ c is the density of coal rock, t / m 3 ; φ ip S is the coal seam porosity of the target coal seam when it is just put into production after fracturing and flowback; wip Z is the water saturation of the target coal seam when it is first put into production after fracturing flowback; sc is the natural gas deviation coefficient under standard conditions, dimensionless, and its value is 1; T sc is the temperature under standard conditions, K, and its value is 293.15; p sc is the pressure under standard conditions, MPa, and its value is 0.101325; p i is the original pressure of the target coal seam, MPa; T is the temperature of the target coal seam, K; Z i is the deviation coefficient of gas under the original pressure of the target coal seam, dimensionless; N is the Y-axis intercept of the linear function, 10 6 m 3 ; M is the slope of the linear function, 10 6 m 3 .

9. The method according to claim 1, characterized in that: The original dissolved gas content is calculated using the following formula: or Among them, V si is the original dissolved gas content of the target coalbed methane reservoir, m 3 / t;G si is the original reserves of dissolved gas in the target coalbed methane reservoir, 10 6 m 3 ; V is the control volume of the target coal seam, 10 6 m 3 ρ c is the density of coal rock, t / m 3 ; φ ip S is the coal seam porosity of the target coal seam when it is just put into production after fracturing and flowback; wip C is the water saturation of the target coal seam when it is first put into production after fracturing flowback; s is the solubility coefficient of the target coalbed methane reservoir in water, MPa -1 ;p i is the original pressure of the target coal seam, MPa.

10. A device for evaluating the proportion of different gas contents in a coalbed methane reservoir, characterized in that: include: a memory configured to store instructions; and The processor is configured to call the instructions from the memory and to implement the method for evaluating the proportion of different gas contents in a coalbed methane reservoir according to any one of claims 1 to 9 when executing the instructions.

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