A method for determining the dynamic reserves of coalbed methane wells without shutting them in.

Abstract

This invention proposes a method for determining the dynamic reserves of coalbed methane (CBM) wells without shutting them in. The method includes acquiring PVT experimental data of the CBM well and determining a relationship table between pressure and CBM deviation factor, as well as a relationship table between pressure and apparent pressure, based on the CBM PVT experimental data; determining the binomial production capacity equation expression for the CBM well; selecting a time point for stable bottomhole flowing pressure testing under constant production conditions during two different stable production stages of the CBM well, and determining the corresponding daily production, bottomhole flowing pressure, and cumulative gas production at the two time points; determining the apparent pressure of the original formation pressure and the formation pressure and its corresponding apparent pressure at the corresponding stable bottomhole flowing pressure testing time points in the two stable production stages; and determining the dynamic reserves of the CBM well based on the cumulative production, apparent formation pressure, and original apparent formation pressure at the two stable flowing pressure testing time points. This invention aims to determine the dynamic reserves of CBM wells without shutting them in.

Description

Technical Field

[0001] This invention belongs to the field of coalbed methane development research, and specifically relates to a method for determining the dynamic reserves of coalbed methane wells without shutting them in. Background Technology

[0002] Dynamic reserves of coalbed methane wells are a crucial and commonly used indicator in dynamic analysis, closely related to well production potential analysis and the optimization of development technology policies. Currently, there are three main methods for determining dynamic reserves of gas wells: numerical simulation, well testing, and mass balance. Numerical simulation requires numerous and complex input parameters, resulting in a large workload and inconvenient application. Well testing requires shutting in the well for pressure recovery testing, which can affect well production. The mass balance method suffers from unreliable assumptions and insufficient theoretical basis, leading to unreliable results. Details are as follows:

[0003] (a) Proof that the assumptions for applying the fluid balance method cannot be met.

[0004] The binomial productivity equation for a gas well is:

[0005]

[0006] In the formula, A and B are constants.

[0007] Taking the derivative of both sides of equation (1) with respect to time, we get:

[0008]

[0009] When the gas well is producing at a constant rate, due to q sc It is a constant, therefore Therefore, from equation (2), we get

[0010]

[0011] From equation (3), we can further obtain:

[0012]

[0013] The applicable assumptions of the fluid mass balance method are as follows: after a gas well has been producing at a relatively stable rate for a certain period of time, the pressure wave reaches the outer boundary of the formation, and the gas flow enters a quasi-steady state. During the same time period, the decrease in formation pressure is almost equal to the decrease in bottomhole flowing pressure.

[0014]

[0015] From equation (4), we can obtain:

[0016]

[0017] Because gas wells produce q sc For stable production to occur, there must be a production pressure differential between the formation pressure and the bottom hole flowing pressure. Therefore, the formation pressure P R It is impossible to have its bottom hole flowing pressure P wf Equal, that is Therefore, it can be seen from equation (6) that that is Therefore, the applicable assumptions of the fluid balance method described by equation (5) cannot be established.

[0018] Furthermore, there are currently no reports in the literature on how to determine the dynamic reserves of coalbed methane wells under non-shutdown conditions. Therefore, there is an urgent need to propose a new method for determining the dynamic reserves of coalbed methane wells under non-shutdown conditions. Summary of the Invention

[0019] The purpose of this invention is to provide a method for determining the dynamic reserves of coalbed methane wells without shutting them in, aiming to solve the technical problem that the dynamic reserves of coalbed methane wells cannot be determined under existing non-shutdown conditions.

[0020] To achieve the above objectives, the present invention provides a method for determining the dynamic reserves of a coalbed methane well without shutting it in, comprising the following steps:

[0021] Step 1: Obtain basic data of the target coalbed methane well, including PVT experimental data of the coalbed methane and the original formation pressure P. Ri Bottom-hole flowing pressure data P of coalbed methane wells during production process wf and daily production data q sc ;

[0022] Step 2: Based on the coalbed methane PVT experimental data obtained in Step 1, determine the relationship table between pressure P and coalbed methane deviation factor Z, and further determine the relationship between pressure P and apparent pressure P. s A table showing the relationships between P and P. s =P / Z;

[0023] Step 3: Control the coalbed methane well to continuously employ three or more different production rates q, from large to small, during the preset production stage. sc(1) q sc(2) , ..., q sc(n) To achieve stable production, q sc(1) >q sc(2) >…>q sc(n) To test the stable bottom hole flowing pressure P under different stable production conditions. wf(1) P wf(2) , ..., Pw f(n) ;

[0024] Step 4, based on the different production rates q of the coalbed methane wells sc(1) qsc(2) , ..., q sc(n) and its corresponding stable bottom hole flowing pressure test value P wf(1) P wf(2) , ..., P wf(n) Determine the binomial productivity equation for coalbed methane wells The coefficients A and B in the formula; and P in the formula. R For formation pressure, P wf q represents the bottom hole flowing pressure of a coalbed methane well. sc This represents the daily production of coalbed methane wells.

[0025] Step 5: Based on the production data of the coalbed methane well, select two stable production stages. In the first stable production stage, determine the daily output q corresponding to the preset time a. sca Bottom-hole flowing pressure P wfa and cumulative gas production GP a In the second stable production stage, the daily output q corresponding to the preset time b is determined. scb Bottom-hole flowing pressure P wfb and cumulative gas production GP b ;

[0026] Step 6: Based on the coefficients A and B obtained in Step 4 and the daily output q at time a obtained in Step 5. sca and bottom hole flowing pressure P wfa and the daily output q corresponding to time b scb Bottom-hole flowing pressure P wfb , by formula Calculate the formation pressure P corresponding to time a. Ra , by formula Determine the formation pressure P corresponding to time b. Rb ;

[0027] Step 7, based on the pressure P obtained in Step 2 and the apparent pressure P s The relationship table, combined with the original formation pressure P obtained in step 1 Ri The formation pressure P corresponding to time a obtained in step 6 Ra and the formation pressure P corresponding to time b Rb Determine the corresponding apparent formation pressure P Rsi P Rsa and P Rsb ;

[0028] Step 8, based on the cumulative gas production GP corresponding to time a obtained in Step 5. a Cumulative gas production GP at time v b Simultaneously, combined with the apparent formation pressure P obtained in step 7 Rsi P Rsa and P Rsb , by formula Calculate and determine the dynamic reserves G0 of the coalbed methane well.

[0029] Furthermore, in step 4, the steps for determining the coefficients A and B of the binomial productivity equation for coalbed methane wells are as follows:

[0030] make Based on the different production rates q of a coalbed methane well at a certain production stage sc(1) q sc(2) , ..., q sc(n) and the corresponding stable bottom hole flowing pressure test data P wf(1) P wf(2) , ..., P wf(n) A series of observation points (y) were obtained. (i) x (i) If a second-order polynomial is fitted to the observation point data, then A is equal to the negative of the coefficient of the first-order term, and B is equal to the negative of the coefficient of the second-order term.

[0031] Further, in step 7, the step of determining the apparent formation pressure is as follows:

[0032] The result is obtained by interpolation calculation based on the relationship table between apparent pressure and pressure.

[0033] Alternatively, based on data regarding the relationship between apparent pressure and physical pressure, a function fitting can be performed with apparent pressure as the dependent variable and physical pressure as the independent variable to obtain the calculation expression P for apparent pressure. s =f (P) Then according to expression P s =f (P) The apparent pressure corresponding to the relevant formation pressure was calculated.

[0034] Beneficial effects:

[0035] (1) The method of the present invention effectively overcomes the shortcomings of mainstream methods such as numerical simulation, well testing and fluid balance in determining the dynamic reserves of gas wells, fills the gap in "determining the dynamic reserves of coalbed methane wells without shutting down the well", and is simple, highly operable and effective, with great value for promotion and use.

[0036] (2) Determining the dynamic reserves of coalbed methane wells is an essential routine task in the development of coalbed methane wells. Once the dynamic reserves of coalbed methane wells are determined, they can be used to evaluate the development potential of the wells, calculate the recovery rate, assess the formation pressure, and optimize subsequent mining operations, thus having very important practical value in the mining field. Attached Figure Description

[0037] Figure 1 This is a flowchart of an embodiment of a method for determining the dynamic reserves of a coalbed methane well without shutting it in, according to the present invention;

[0038] Figure 2 It is a quadratic polynomial fitting plot of the observation points;

[0039] Figure 3 It is a graph showing the functional relationship between apparent pressure and actual pressure. Detailed Implementation

[0040] Reference Figure 1 This invention provides a flowchart illustrating an embodiment of a method for determining the dynamic reserves of coalbed methane wells without shutting them in. The specific implementation is as follows:

[0041] Step 1: Obtain basic data of the target coalbed methane well, including PVT experimental data of the coalbed methane and the original formation pressure P. Ri Bottom-hole flowing pressure data P of coalbed methane wells during production process wf and daily production data q sc .

[0042] Step 2: Based on the coalbed methane PVT experimental parameter data obtained in Step 1, determine the relationship table between pressure P and coalbed methane deviation factor Z, and further determine the relationship between pressure P and apparent pressure P. s Relationship table, where P s =P / Z.

[0043] Step 3: Control the coalbed methane well to continuously use three or more different production rates q, from large to small, during a certain production stage. sc(1) q sc(2) , ..., q sc(n) To ensure stable production, the stable bottom hole flowing pressure P was tested under different stable production conditions. wf(1) P wf(2) , ..., P wf(n) , where q sc(1) >qsc (2) >…>q sc(n) .

[0044] Step 4: Determine the binomial productivity equation for coalbed methane wells. The coefficients A and B in the equation.

[0045] Specifically, based on the different production rates q of coalbed methane wells sc(1) q sc(2) , ..., q sc(n) and its corresponding stable bottom hole flowing pressure test value P wf(1) P wf(2) , ..., P wf(n) ,make Based on the different production rates q of a coalbed methane well at a certain production stage sc(1) q sc(2) , ..., qsc(n) and the corresponding stable bottom hole flowing pressure test data P wf(1) P wf(2) , ..., P wf(n) A series of observation points (y) can be obtained. (i) x (i) ); Perform a second-order polynomial fitting on the observation point data, where A equals the negative of the coefficients of the first-order term and B equals the negative of the coefficients of the second-order term; where P R For formation pressure, P wf q represents the bottom hole flowing pressure of a coalbed methane well. sc This represents the daily production of a coalbed methane well.

[0046] Step 5: Based on the production data of the coalbed methane well, select two stable production stages. In the first stable production stage, determine the daily output q corresponding to a certain moment 'a'. sca Bottom-hole flowing pressure P wfa and cumulative gas production GP a In the second stable production phase, the daily output q corresponding to a certain moment v is determined. scb Bottom-hole flowing pressure P wfb and cumulative gas production GP b .

[0047] Step 6: Based on the coefficients A and B obtained in Step 4 and the daily output q at time a obtained in Step 5. sca and bottom hole flowing pressure P wfa and the daily output q corresponding to time b scb Bottom-hole flowing pressure P wfb , by formula Calculate the formation pressure P corresponding to time a. Ra , by formula Determine the formation pressure P corresponding to time b. Rb .

[0048] Step 7, determine the relationship with the original formation pressure P Ri The formation pressure P at time a Ra and the formation pressure P at time b Rb The corresponding apparent formation pressure P Rsi P Rsa and P Rsb Based on the pressure P obtained in step 2 and the apparent pressure P s The relationship table, combined with the original formation pressure P obtained in step 1 Ri The formation pressure P corresponding to time a obtained in step 6 Ra and the formation pressure P corresponding to time b Rb The apparent formation pressure P is obtained by interpolation based on the relationship table between apparent pressure and actual pressure. Rsi PRsa and P Rsb Alternatively, based on the relationship data between apparent pressure and physical pressure, a function fitting can be performed with apparent pressure as the dependent variable and physical pressure as the independent variable to obtain the calculation expression P for apparent pressure. s =f (P) Then, the apparent pressure corresponding to the relevant formation pressure is calculated using this expression.

[0049] Step 8, based on the cumulative gas production GP corresponding to time a obtained in Step 5. a Cumulative gas production GP at time v b Simultaneously, combined with the apparent formation pressure P obtained in step 7 Rsi P Rsa and P Rsb , by formula Calculate and determine the dynamic reserves G0 of the coalbed methane well.

[0050] In this embodiment, basic data of coalbed methane wells are acquired, and a relationship table between pressure and coalbed methane deviation factor is determined based on coalbed methane PVT experimental data. Furthermore, a relationship table between pressure and apparent pressure (apparent pressure equals pressure divided by the deviation factor) is further determined. Based on different production rates of coalbed methane wells within a certain time period and their corresponding stable bottomhole flowing pressure test values, a binomial production capacity equation expression for the coalbed methane well is determined. In two different stable production stages of the coalbed methane well, a time point is selected for stable bottomhole flowing pressure testing under constant production conditions, and the corresponding daily production, bottomhole flowing pressure, and cumulative gas production at the two time points are determined. The apparent pressure of the original formation pressure and the formation pressure and corresponding apparent pressure at the corresponding stable bottomhole flowing pressure test times in the two stable production stages are determined. Based on the cumulative production, apparent formation pressure, and original apparent formation pressure at the two selected stable flowing pressure test times, the dynamic reserves of the coalbed methane well are calculated and determined. It is evident that the method of this invention effectively overcomes the shortcomings of mainstream methods such as numerical simulation, well testing, and fluid mass balance in determining the dynamic reserves of gas wells, fills the gap in "determining the dynamic reserves of coalbed methane wells without shutting them in," and is simple, highly operable, effective, and practical, with great value for widespread application.

[0051] Furthermore, the determination of the dynamic reserve calculation model in step 8 is detailed below:

[0052] The expression for the generalized mass balance equation is:

[0053]

[0054] In the formula, P R Z represents the formation pressure, and P represents the formation pressure. R The corresponding gas deviation factor, G PG0 represents cumulative gas production, and P represents dynamic reserves. Ri Z represents the original formation pressure. i The original formation pressure P Ri Deviation factor under certain conditions.

[0055] Formation pressure P R The ratio of its corresponding deviation factor Z is defined as the apparent pressure P. Rs Original formation pressure P Ri Its corresponding deviation factor Z i The ratio is defined as the apparent pressure P. Rsi Right now

[0056]

[0057]

[0058] Then, from equations (7), (8), and (9), we can obtain the mass balance equation based on apparent pressure:

[0059]

[0060] Let P be the apparent formation pressure at time a. Rsa The cumulative gas production at time a is G. Pa The apparent formation pressure at time b is P. Rsb The cumulative gas production at time a is G. Pb Then, from equation (10), we can obtain:

[0061]

[0062]

[0063] Subtracting both sides of equations (11) and (12), we can obtain:

[0064]

[0065] From equation (13), we can obtain:

[0066]

[0067] From equation (14), we can obtain:

[0068]

[0069] Equation (15) is the dynamic reserve calculation model used in this invention.

[0070] Due to the cumulative output G at times a and b Pa and G Pb It is already known; we only need to determine the apparent formation pressure P corresponding to time a.Rsa The apparent formation pressure at time b is P. Rsb and the original apparent formation pressure P Rsi The dynamic reserves G0 can be calculated according to equation (15).

[0071] Furthermore, in step 7, three apparent formation pressures P are obtained. Rsa P Rsb and P Rsi The specific steps are as follows:

[0072] Let the production of coalbed methane well a at time a be q. sca At time a, the bottom hole flowing pressure of the coalbed methane well is P. wfa The production of coalbed methane well b at time b is q. scb At time b, the bottom hole flowing pressure of the coalbed methane well is P. wfb Therefore, according to the binomial productivity equation of a gas well, we can obtain:

[0073]

[0074] From equation (16), we can obtain:

[0075]

[0076] Similarly, we can conclude that:

[0077]

[0078] Based on the gas well production data and the corresponding bottom hole flowing pressure, the formation pressure P can be obtained from equations (17) and (18). Ra P Rb Then, based on the formation pressure P... Ra P Rb and the original formation pressure P Ri (original formation pressure P) Ri Based on mine test data or the relationship between formation depth and original formation pressure coefficient, and combined with the pressure-apparent pressure relationship table obtained from PVT experimental data, the corresponding apparent formation pressure P can be calculated using interpolation or function fitting methods. Rsa P Rsb and P Rsi .

[0079] Furthermore, in step 4, the detailed steps for determining the constant coefficients in the binomial production capacity equation are as follows:

[0080] Specifically, from equation (1), we can obtain:

[0081]

[0082] make

[0083] In the formula, i is the steady-state pressure test point number, i = 1, 2, ..., n; P wf(i) To produce q sc(i) The stable bottom hole flowing pressure corresponding to fixed-production; q sc(i) Let be the daily gas production corresponding to the i-th stable flow pressure test point.

[0084] Substituting equation (20) into equation (19), we get:

[0085]

[0086] With different outputs q sc(i) When producing at a constant output for (i = 1, 2, ..., n), if the corresponding stable flow pressure P is... wf(i) If the testing work for (i = 1, 2, ..., n) is completed within a relatively short period of time, then the formation pressure P during this period can be approximated. R Basically unchanged, that is, P R It can be considered a constant.

[0087] Therefore, based on the different production rates q of coalbed methane wells during a certain production period... sc(1) q sc(2) , ..., q sc(n) and the corresponding stable bottom hole flowing pressure test data P wf(1) P wf(2) , ..., P wf(n) A series of observation points (y) can be obtained from equation (21). (i) x (i) ); Perform a second-order polynomial fitting on the above observation point data. According to equation (21), A is equal to the negative of the coefficient of the first-order term obtained by fitting, and B is equal to the negative of the coefficient of the second-order term obtained by fitting.

[0088] Explanation of symbol meanings:

[0089] P Ri Original formation pressure, MPa; P wf Bottom hole flowing pressure, MPa; q sc Gas well production, 10,000 cubic meters / day; P: Pressure, MPa; Z: Gas deviation factor, dimensionless, decimal; P s (P s =P / Z): Apparent pressure, MPa; q sc(i) P: Daily gas production corresponding to the i-th stable flow pressure test point, in ten thousand cubic meters per day; wf(i) : based on output q sc(i) The stable bottom hole flowing pressure corresponding to constant production; i: stable flowing pressure test point number, i = 1, 2, ..., n; P R : Formation pressure, MPa; qsca : Daily output at time a, in ten thousand cubic meters / day; P wfa : Bottomhole flowing pressure at time a, MPa; GP a : Cumulative gas production at time a, in ten thousand cubic meters; q scb : Daily output at time b, in ten thousand cubic meters / day; P wfb : Bottomhole flowing pressure at time b, MPa; GP b : Cumulative gas production at time b, in ten thousand cubic meters; P Ra : Formation pressure at time a, MPa; P Rb : Formation pressure at time b, MPa; P Rsi P: Apparent formation pressure corresponding to the original formation pressure, in MPa; Rsa : Apparent formation pressure at time a, MPa; P Rsb G0: Apparent formation pressure at time b, MPa; G0: Dynamic reserves, 10,000 cubic meters.

[0090] Furthermore, specific examples are used below to illustrate the technical solution of the present invention, but the scope of protection of the present invention is not limited thereto.

[0091] Verification Example 1:

[0092] A coalbed methane well has a vertical depth of 2880m in the middle of the formation, an original formation pressure of 28MPa, and a formation temperature of 80.6℃; trial production began in March 2023.

[0093] The method for determining the dynamic reserves of coalbed methane wells without shutting them in, as described in this embodiment:

[0094] (1) The basic data of the coalbed methane well collected are as follows: original formation pressure P Ri =28MPa. The relationship between the deviation factor in the PVT parameters and the pressure is shown in Table 1.

[0095] Table 1. Relationship between pressure, deviation factor, and visual pressure.

[0096]

[0097] (2) Based on the experimental data on the relationship between coalbed methane pressure and deviation factor obtained in step (1), the pressure P in the table can be divided by the corresponding deviation factor Z to obtain the pressure P and apparent pressure P. s (P s The relationship table between P and Z is shown in Table 1.

[0098] (3) During the production period, the well used three different production rates q, from large to small, within two weeks. sc(1) = 86,600 cubic meters / day, q sc(2) = 85,900 cubic meters / day, q sc(3)=84,800 cubic meters / day for stable production, the stable bottom hole flowing pressure values ​​under the three production conditions are P wf(1) =9.68MPa,P wf(2) =10.2MPa, P wf(3) =10.96MPa.

[0099] (4) Let Based on the well production and bottom hole flowing pressure data in step (3), a series of observation points (y) are obtained. (i) x (i) (See Table 2); A second-order polynomial fitting was performed on the observation point data (see...). Figure 2 The resulting fitted expression is y = -8.5137x. 2 -0.8528x+739.58, since A is equal to the negative of the coefficient of the first term obtained from the fitting, and B is equal to the negative of the coefficient of the quadratic term obtained from the fitting, A = 8.5173, B = 0.8528.

[0100] Table 2 Data table for constructing observation points

[0101]

[0102] (5) Based on the production data of the coalbed methane well, the well underwent a flowing pressure test under constant production conditions at the end of May 2023, with a production rate q. sca = 82,300 cubic meters / day, measured steady-state bottom hole flowing pressure P wfa =8.76MPa, at which point the cumulative gas production GP a = 2,524,700 cubic meters; Additionally, the well underwent another flowing pressure test under constant production conditions in mid-August 2023, with a production rate q. scb = 74,800 cubic meters / day, measured steady-state bottom hole flowing pressure P wfb =8.85MPa, cumulative gas production GP up to that day b =8,836,300 cubic meters.

[0103] (6) Based on the coefficients A = 8.5173 and B = 0.8528 obtained in step (4), and the daily output q at time a obtained in step (5). sca =8.23 and bottom hole flowing pressure P wfa =8.76 and the daily output q corresponding to time b scb =7.48, Bottom-hole flowing pressure P wfb =8.85, from the formula Calculate the formation pressure P corresponding to time a. Ra =25.70MPa, from the formula Determine the formation pressure P corresponding to time b. Rb =23.69MPa.

[0104] (7) Based on the pressure P and apparent pressure P obtained in step (2), s The relationship table shows the original formation pressure P calculated using linear interpolation. Ri =28MPa corresponds to the apparent pressure P Rsi = 31.869 MPa, the formation pressure P at time a Ra =25.70MPa corresponds to the apparent pressure P Rsa =29.46 MPa, the formation pressure P at time b Rb =23.69MPa corresponds to the apparent pressure P Rsb =27.37MPa.

[0105] Based on the relationship between pressure and apparent pressure in Table 1, let y = P s (Considering pressure as the dependent variable), x = P (pressure as the independent variable), perform function fitting (see...). Figure 3 The expression for calculating apparent pressure is P. s =1.0795*P+0.2863, the original formation pressure P is calculated using this expression. Ri =28MPa corresponds to the apparent pressure P Rsi = 30.51 MPa, the formation pressure P at time a Ra =25.70MPa corresponds to the apparent pressure P Rsa =28.03 MPa, the formation pressure P at time b Rb =23.69MPa corresponds to the apparent pressure P Rsb =25.86MPa.

[0106] (8) Based on the cumulative gas production GP corresponding to time a obtained in step (5), a =2,524,700 cubic meters, cumulative gas production GP at time b b =8,836,300 cubic meters, and simultaneously combined with the apparent formation pressure P obtained by linear interpolation in step (7). Rsi =31.869MPa, P Rsa =29.46MPa and P Rsb =27.37MPa, from the formula The calculated dynamic reserves of coalbed methane wells are G0 = 96,241,300 cubic meters;

[0107] Based on the apparent formation pressure P obtained by the function fitting method in step (7), Rsi =30.51MPa, P Rsa =28.03MPa and P Rsb =25.86MPa, from the formula The calculated dynamic reserves of the coalbed methane well are G0 = 88.7405 million cubic meters.

[0108] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes made without departing from the present invention should be considered as equivalent substitutions and are included within the protection scope of the present invention.

Claims

1. A method for determining the dynamic reserves of a coalbed methane well without shutting it in, characterized in that, The steps of this method are as follows: Step 1: Obtain basic data of the target coalbed methane well, including PVT experimental data of the coalbed methane and the original formation pressure P. Ri Bottom-hole flowing pressure data P of coalbed methane wells during production process wf and daily production data q sc ; Step 2: Based on the coalbed methane PVT experimental data obtained in Step 1, determine the relationship table between pressure P and coalbed methane deviation factor Z, and further determine the relationship between pressure P and apparent pressure P. s A table showing the relationships between P and P. s =P / Z; Step 3: Control the coalbed methane well to continuously employ three or more different production rates q, from large to small, during the preset production stage. sc(1) q sc(2) , ..., q sc(n) To achieve stable production, q sc(1) >q sc(2) >...>q sc(n) To test the stable bottom hole flowing pressure P under different stable production conditions. wf(1) P wf(2) , ..., P wf(n) ; Step 4, based on the different production rates q of the coalbed methane wells sc(1) q sc(2) , ..., q sc(n) and its corresponding stable bottom hole flowing pressure test value P wf(1) P wf(2) , ..., P wf(n) Determine the binomial productivity equation for coalbed methane wells The coefficients A and B in the formula; and P in the formula. R For formation pressure, P wf q represents the bottom hole flowing pressure of a coalbed methane well. sc This represents the daily production of coalbed methane wells. Step 5: Based on the production data of the coalbed methane well, select two stable production stages. In the first stable production stage, determine the daily output q corresponding to the preset time a. sca Bottom-hole flowing pressure P wfa and cumulative gas production GP a In the second stable production stage, the daily output q corresponding to the preset time b is determined. scb Bottom-hole flowing pressure P wfb and cumulative gas production GP b ; Step 6: Based on the coefficients A and B obtained in Step 4 and the daily output q at time a obtained in Step 5. sca and bottom hole flowing pressure P wfa and the daily output q corresponding to time b scb Bottom-hole flowing pressure P wfb , by formula Calculate the formation pressure P corresponding to time a. Ra , by formula Determine the formation pressure P corresponding to time b. Rb ; Step 7, based on the pressure P obtained in Step 2 and the apparent pressure P s The relationship table, combined with the original formation pressure P obtained in step 1 Ri The formation pressure P corresponding to time a obtained in step 6 Ra and the formation pressure P corresponding to time b Rb Determine the corresponding apparent formation pressure P Rsi P Rsa and P Rsb ; Step 8, based on the cumulative gas production GP corresponding to time a obtained in Step 5. a The cumulative gas production GP at time b b Simultaneously, combined with the apparent formation pressure P obtained in step 7 Rsi P Rsa and P Rsb , by formula Calculate and determine the dynamic reserves G0 of the coalbed methane well.

2. The method for determining the dynamic reserves of a coalbed methane well without shutting it in, as described in claim 1, is characterized in that... In step 4, the steps for determining the coefficients A and B of the binomial productivity equation for coalbed methane wells are as follows: make Based on the different production rates q of a coalbed methane well at a certain production stage sc(1) q sc(2) , ..., q sc(n) and the corresponding stable bottom hole flowing pressure test data P wf(1) P wf(2) , ..., P wf(n) A series of observation points (y) were obtained. (i) x (i) If a second-order polynomial is fitted to the observation point data, then A is equal to the negative of the coefficient of the first-order term, and B is equal to the negative of the coefficient of the second-order term.

3. The method for determining the dynamic reserves of a coalbed methane well without shutting it in, as described in claim 1, is characterized in that... In step 7, the steps for determining the apparent formation pressure are as follows: The result is obtained by interpolation calculation based on the relationship table between apparent pressure and pressure. Alternatively, based on data regarding the relationship between apparent pressure and physical pressure, a function fitting can be performed with apparent pressure as the dependent variable and physical pressure as the independent variable to obtain the calculation expression P for apparent pressure. s =f (P) Then according to expression P s =f (P) The apparent pressure corresponding to the relevant formation pressure was calculated.

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