Coal bed gas productivity evaluation method and system based on flowing bottomhole pressure and gas production rate

Abstract

The invention relates to a coalbed methane productivity evaluation method and system based on flowing bottomhole pressure and gas production, and the method comprises the steps: obtaining field production data of a target coalbed methane well, the field production data comprising flowing bottomhole pressure and daily gas production; according to the field production data, the output increasing value and the output stabilizing value of the target coal-bed gas well are calculated; according to the output increasing value and the output stabilizing value of the target coal-bed gas well, the productivity coefficient of the target coal-bed gas well is calculated; and obtaining an evaluation result of the productivity of the target coal-bed gas well according to the productivity coefficient. According to the method, the initial data of the flowing bottomhole pressure and the daily output in the control period are obtained and calculated to judge the productivity capacity of the gas production well in the research area, and the productivity of the coal-bed gas well can be evaluated more effectively.

Description

Technical Field

[0001] The present invention relates to the technical field of deep coalbed methane productivity evaluation, and in particular to a coalbed methane productivity evaluation method and system based on bottom hole flow pressure and gas production. Background Art

[0002] Deep coalbed methane (buried depth greater than 1500m) is an important area of ​​coalbed methane exploration and development. Different from shallow coalbed methane, its geological characteristics are complex and its reservoirs are heterogeneous. There are problems such as unclear understanding of the evolution law of coal-forming environment, unclear understanding of gas content distribution law, and unclear understanding of factors controlling the difference in deep coalbed production, which leads to obvious differences in production characteristics during its production process. This makes it difficult to draw clear rules from correlation analysis and it is impossible to effectively and accurately understand the production situation, which restricts the scale of reserve increase and benefit development of deep coalbed methane in the study area. In actual production practice, more accurate and effective production capacity evaluation indicators and methods will play a key role in technological progress. Through scientific production capacity evaluation, problems can be discovered in time, technology can be improved, and the production efficiency of deep coalbed methane development can be improved. Therefore, in-depth research and the proposal of more accurate and effective production capacity evaluation indicators and methods are of great significance for the development of deep coalbed methane.

[0003] The patent "A method, system and electronic equipment for evaluating the productivity of shale gas / coalbed methane wells" is mainly aimed at accurately obtaining the final recoverable reserves of coalbed methane wells, the ratio of adsorbed gas / free gas in daily gas production, fracture conductivity, matrix diffusion coefficient and adsorption capacity and other parameters. However, there are few analyses of production curves during the production process. In the patent "A method for establishing a high-yield mode of coalbed methane wells", the threshold of factors affecting the productivity of coalbed methane wells is determined; the sensitivity of coalbed methane well productivity to different influencing factors is revealed; the main controlling factors affecting the productivity of coalbed methane wells are extracted based on the results of sensitivity analysis. However, there is no complete evaluation system for productivity indicators. Therefore, in view of the special properties of deep coalbed methane, the existing productivity evaluation indicators should be re-examined. Traditional productivity indicators such as production and recovery rate are difficult to fully reflect the complex situation of deep coalbed methane development, so more new indicators need to be introduced to more comprehensively evaluate productivity. Capacity evaluation should also be combined with technical and economic evaluation, considering factors such as investment cost, production cost and income. Through comprehensive consideration, the productivity level of deep coalbed methane development can be more comprehensively evaluated, providing a scientific basis for decision-making. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for evaluating coalbed methane productivity based on bottom hole flow pressure and gas production, which can more effectively evaluate the productivity of coalbed methane wells by comprehensively considering the two key factors of bottom hole flow pressure and gas production.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A coalbed methane productivity evaluation method based on bottom hole flow pressure and gas production, comprising:

[0007] Acquire the on-site production data of the target coalbed methane well, wherein the on-site production data includes bottom hole flow pressure and daily gas production;

[0008] Calculate the production increase value and stable production value of the target coalbed methane well according to the field production data;

[0009] Calculate the production capacity coefficient of the target coalbed methane well according to the production increase value and stable production value of the target coalbed methane well;

[0010] According to the productivity coefficient, an evaluation result of the productivity of the target coalbed methane well is obtained.

[0011] Optionally, according to the field production data, calculating the production increase value and stable production value of the target coalbed methane well includes:

[0012] Draw a production curve based on the field production data of the target coalbed methane well;

[0013] The difference between the maximum gas production flow pressure and the flow pressure before the gas production peak is calculated as the increased production value, and the product of the ratio of the flow pressure after the gas production peak to the maximum flow pressure and the average gas production is calculated as the stable production value.

[0014] Optionally, the calculation method of the output value increase is:

[0015] C i =P max -P b Among them, C i To increase the output value, P max is the maximum flow pressure of gas production, P b is the flow pressure before the gas production peak;

[0016] The method for calculating the stable output value is:

[0017]

[0018] Among them, C S To stabilize the output value, G a is the average gas production, P a is the flow pressure after the gas production peak.

[0019] Optionally, calculating the production capacity coefficient of the target coalbed methane well includes: calculating the production capacity coefficient of the target coalbed methane well according to the ratio of the stable production value to the increased production value.

[0020] Optionally, based on the production capacity coefficient, obtaining the production capacity evaluation result of the target coalbed methane well includes: comparing the production capacity coefficient of the target coalbed methane well with the production capacity coefficient of the gas wells in the study area; if the production capacity coefficient of the target coalbed methane well is greater than the preset value of the production capacity coefficient of the gas wells in the study area, then the gas production capacity of the target coalbed methane well is sufficient; otherwise, the gas production capacity of the target coalbed methane well is insufficient.

[0021] On the other hand, the present invention also provides a coalbed methane productivity evaluation system based on bottom hole flow pressure and gas production, comprising: a data acquisition module, a first calculation module, a second calculation module, and an evaluation module;

[0022] The data acquisition module is used to acquire the on-site production data of the target coalbed methane well, wherein the on-site production data includes bottom hole flow pressure and daily gas production;

[0023] The first calculation module is used to calculate the production increase value and stable production value of the target coalbed methane well according to the field production data;

[0024] The second calculation module is used to calculate the production capacity coefficient of the target coalbed methane well according to the production increase value and the stable production value of the target coalbed methane well;

[0025] The evaluation module is used to obtain the evaluation result of the target coalbed methane well productivity according to the productivity coefficient.

[0026] Optionally, according to the field production data, calculating the production increase value and stable production value of the target coalbed methane well includes:

[0027] According to the field production data, the calculation of the target coalbed methane well's production increase value and stable production value includes:

[0028] Draw a production curve based on the field production data of the target coalbed methane well;

[0029] The difference between the maximum gas production flow pressure and the flow pressure before the gas production peak is calculated as the increased production value, and the product of the ratio of the flow pressure after the gas production peak to the maximum flow pressure and the average gas production is calculated as the stable production value.

[0030] Optionally, calculating the production capacity coefficient of the target coalbed methane well includes: calculating the production capacity coefficient of the target coalbed methane well according to the ratio of the stable production value to the increased production value.

[0031] The beneficial effects of the present invention are as follows: the present invention calculates the production value C of the coalbed methane well i and stable output value (C s), and then calculate the productivity index (GPC) of the coalbed methane well. Among them, the increased production value is calculated by the maximum gas production flow pressure and the flow pressure before the gas production peak, and the stable production value is calculated by the average gas production and the flow pressure after the gas production peak. This innovative method aims to more effectively evaluate the productivity of coalbed methane wells, thereby providing strong support for production practices and technological progress in related fields. By comprehensively considering the two key factors of bottom hole flow pressure and gas production, it can more comprehensively reflect the mining potential and economic benefits of coalbed methane, thereby promoting the sustainable development of the coalbed methane industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 This is a flow chart of a method for evaluating coalbed methane productivity based on bottom hole flow pressure and gas production according to an embodiment of the present invention;

[0034] Figure 2 The graph of daily gas production and bottom hole flow pressure of LXD-26 coalbed methane well in the embodiment of the present invention;

[0035] Figure 3 This is a graph showing daily gas production and bottom hole pressure of the LX1-20-2DM1 coalbed methane well according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Embodiment 1:

[0039] During the production process, although the daily average gas production of some gas wells is good, they face the problem of rapid decline in bottom hole pressure, which leads to a significant lack of power for subsequent gas production, thus affecting the sustainability of high production. This situation is common in the production process. This embodiment can obtain the initial data of bottom hole pressure and daily production within the control period, calculate them, and determine the production capacity of the gas wells in the study area and predict their potential.

[0040] like Figure 1 As shown, this embodiment provides a method for evaluating coalbed methane productivity based on bottom hole flow pressure and gas production, including:

[0041] Obtaining the on-site production data of the target coalbed methane well, wherein the on-site production data includes bottom hole flow pressure and daily gas production;

[0042] Calculate the production increase value and stable production value of the target coalbed methane well according to the field production data;

[0043] Calculate the production capacity coefficient of the target coalbed methane well according to the production increase value and stable production value of the target coalbed methane well;

[0044] According to the productivity coefficient, the evaluation result of the target coalbed methane well productivity is obtained.

[0045] Furthermore, based on the on-site production data, the calculation of the target coalbed methane well's production increase value and stable production value includes:

[0046] Draw a production curve based on the field production data of the target coalbed methane well;

[0047] The difference between the maximum gas production flow pressure and the flow pressure before the gas production peak, that is, the flow pressure drop before the gas production peak, is calculated as the production increase value, and the product of the ratio of the flow pressure after the gas production peak to the maximum flow pressure and the average gas production is calculated as the stable production value.

[0048] Furthermore, the calculation method of the output value is:

[0049] C i =P max -P b

[0050] Among them, C i To increase the output value, P max is the maximum flow pressure of gas production, P b is the flow pressure before the gas production peak;

[0051] The method for calculating the stable output value is:

[0052]

[0053] Among them, C S To stabilize the output value, G a is the average gas production, Pa is the flow pressure after the gas production peak.

[0054] Furthermore, calculating the production capacity coefficient of the target coalbed methane well includes: calculating the production capacity coefficient of the target coalbed methane well according to the ratio of the stable production value to the increased production value.

[0055] Specifically, the ratio of the stable production value to the increased production value is defined as the productivity coefficient (GPC) of deep coalbed methane wells:

[0056]

[0057] Furthermore, according to the production capacity coefficient, the production capacity evaluation result of the target coalbed methane well is obtained, including: comparing the production capacity coefficient of the target coalbed methane well with the production capacity coefficient of the gas wells in the study area; if the production capacity coefficient of the target coalbed methane well is greater than the preset value of the production capacity coefficient of the gas wells in the study area, the gas production capacity of the target coalbed methane well is sufficient; otherwise, the gas production capacity of the target coalbed methane well is insufficient.

[0058] Specifically, the production capacity evaluation result of the target coalbed methane well is obtained, that is, the production capacity type of the coalbed methane well is determined based on the production capacity coefficient. In this embodiment, when it is greater than 20% of the production capacity coefficient of the gas well in the study area, it means that the production capacity efficiency is good and has gas production potential; when it is less than 20% of the production capacity coefficient of the gas well in the study area, it means that the production capacity efficiency is poor and lacks gas production potential.

[0059] Based on the productivity type of CBM wells, the reasons for the low productivity coefficient include:

[0060] Reason 1: Although some gas wells have a high average daily gas production, the bottom hole pressure drops rapidly, resulting in insufficient subsequent gas production power and insufficient sustainability of high production;

[0061] Reason 2: Although the bottom hole flow pressure of some gas wells drops relatively steadily, the gas content of the coal seams is low, resulting in insufficient production.

[0062] Embodiment 2:

[0063] A method for evaluating the production capacity of coalbed methane based on bottom hole flow pressure and gas production includes the following steps: (1) determining the bottom hole flow pressure and daily production of the coalbed methane well; (2) obtaining the difference between the maximum flow pressure of gas production and the flow pressure before the gas production peak; (3) calculating the product of the ratio of the flow pressure after the gas production peak to the maximum flow pressure and the average gas production; (4) determining the gas production type of the coalbed methane well; (5) evaluating the production capacity of the gas producing well and predicting its potential. The present invention can evaluate the gas production capacity of the gas well through simple basic data. The method is simple in practical application and has a strong significance for developing new wells, especially for improving the production of single coalbed methane wells.

[0064] In this embodiment, the daily gas production and bottom hole pressure of the well are as follows: Figure 2As shown in the figure, according to statistics, the maximum bottom hole pressure Pmax of the gas production well is 17.2205Mpa, and the bottom hole pressure at the peak of gas production is 6.5207Mpa. i The calculated value is 10.6998Mpa, which is close to the average gas production of the well G a is 1551.2085m3, and its stable output value is C s The calculated value is 587.3793m3, so the calculated productivity coefficient (GPC) of the well is 54.8963. Comparing the productivity coefficient of the well with other wells in the study area, it is known that the productivity coefficient of the well is less than 20% of the study area, so it is judged that the gas production capacity of the well is insufficient and lacks gas production potential, the reason for which is the low gas content of the coal seam.

[0065] Embodiment three:

[0066] In this embodiment, the daily gas production and bottom hole pressure of the well are as follows: Figure 3 As shown in Figure 2, according to statistics, the maximum bottom hole flow pressure P of the well is max The bottom hole pressure is 17.6798Mpa, and the bottom hole pressure is 12.731Mpa at the peak of gas production. i The calculated value is 4.9488Mpa, which is close to the average gas production of the well G a 3626.0663m 3 , its stable output value C s The calculated value is 2611.0844m 3 Therefore, the productivity coefficient (GPC) of the well is calculated to be 527.6197. Comparing the productivity coefficient of the well with other wells in the study area, it can be seen that the productivity coefficient of the well is much greater than 20% of the study area. Therefore, it is judged that the well has good gas production capacity, sufficient subsequent gas production power, and can maintain high production continuity.

[0067] Embodiment 4:

[0068] A coalbed methane productivity evaluation system based on bottom hole flow pressure and gas production is used in the methods of embodiments 1 to 3, comprising: a data acquisition module, a first calculation module, a second calculation module, and an evaluation module;

[0069] A data acquisition module is used to acquire the on-site production data of the target coalbed methane well, wherein the on-site production data includes bottom hole flow pressure and daily gas production;

[0070] The first calculation module is used to calculate the production increase value and stable production value of the target coalbed methane well according to the on-site production data;

[0071] The second calculation module is used to calculate the production capacity coefficient of the target coalbed methane well according to the production increase value and stable production value of the target coalbed methane well;

[0072] The evaluation module is used to obtain the evaluation result of the target coalbed methane well productivity according to the productivity coefficient.

[0073] Furthermore, based on the on-site production data, the calculation of the target coalbed methane well's production increase value and stable production value includes:

[0074] According to the on-site production data, the calculation of the target CBM well’s production increase value and stable production value includes:

[0075] Draw a production curve based on the field production data of the target coalbed methane well;

[0076] The difference between the maximum gas production flow pressure and the flow pressure before the gas production peak is calculated as the production increase value, and the product of the ratio of the flow pressure after the gas production peak to the maximum flow pressure and the average gas production is calculated as the stable production value.

[0077] Furthermore, calculating the production capacity coefficient of the target coalbed methane well includes: calculating the production capacity coefficient of the target coalbed methane well according to the ratio of the stable production value to the increased production value.

[0078] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for evaluating coalbed methane productivity based on bottom hole flow pressure and gas production, characterized in that: include: Acquire the on-site production data of the target coalbed methane well, wherein the on-site production data includes bottom hole flow pressure and daily gas production; Calculate the production increase value and stable production value of the target coalbed methane well according to the field production data; Calculate the production capacity coefficient of the target coalbed methane well according to the production increase value and stable production value of the target coalbed methane well; According to the productivity coefficient, an evaluation result of the productivity of the target coalbed methane well is obtained.

2. The method for evaluating coalbed methane productivity based on bottom hole flow pressure and gas production according to claim 1, characterized in that: According to the field production data, the calculation of the target coalbed methane well's production increase value and stable production value includes: Draw a production curve based on the field production data of the target coalbed methane well; The difference between the maximum gas production flow pressure and the flow pressure before the gas production peak is calculated as the increased production value, and the product of the ratio of the flow pressure after the gas production peak to the maximum flow pressure and the average gas production is calculated as the stable production value.

3. The method for evaluating coalbed methane productivity based on bottom hole flow pressure and gas production according to claim 2, characterized in that: The calculation method of the production value is: C i =P max -P b Among them, C i To increase the output value, P max is the maximum flow pressure of gas production, P b is the flow pressure before the gas production peak; The method for calculating the stable output value is: Among them, C S To stabilize the output value, G a is the average gas production, P a is the flow pressure after the gas production peak.

4. The method for evaluating coalbed methane productivity based on bottom hole flow pressure and gas production according to claim 1, characterized in that: Calculating the production capacity coefficient of the target coalbed methane well includes: calculating the production capacity coefficient of the target coalbed methane well according to the ratio of the stable production value to the increased production value.

5. The method for evaluating coalbed methane productivity based on bottom hole flow pressure and gas production according to claim 1, characterized in that: According to the production capacity coefficient, obtaining the production capacity evaluation result of the target coalbed methane well includes: comparing the production capacity coefficient of the target coalbed methane well with the production capacity coefficient of the gas wells in the study area; if the production capacity coefficient of the target coalbed methane well is greater than the preset value of the production capacity coefficient of the gas wells in the study area, then the gas production capacity of the target coalbed methane well is sufficient; otherwise, the gas production capacity of the target coalbed methane well is insufficient.

6. A coalbed methane productivity evaluation system based on bottom hole flow pressure and gas production, characterized in that: include: Data acquisition module, first calculation module, second calculation module, evaluation module; The data acquisition module is used to acquire the on-site production data of the target coalbed methane well, wherein the on-site production data includes bottom hole flow pressure and daily gas production; The first calculation module is used to calculate the production increase value and stable production value of the target coalbed methane well according to the field production data; The second calculation module is used to calculate the production capacity coefficient of the target coalbed methane well according to the production increase value and the stable production value of the target coalbed methane well; The evaluation module is used to obtain the evaluation result of the target coalbed methane well productivity according to the productivity coefficient.

7. The coalbed methane productivity evaluation system based on bottom hole flow pressure and gas production according to claim 6 is characterized in that: According to the field production data, the calculation of the production increase value and stable production value of the target coalbed methane well includes: According to the field production data, the calculation of the production increase value and stable production value of the target coalbed methane well includes: Draw a production curve based on the field production data of the target coalbed methane well; The difference between the maximum gas production flow pressure and the flow pressure before the gas production peak is calculated as the increased production value, and the product of the ratio of the flow pressure after the gas production peak to the maximum flow pressure and the average gas production is calculated as the stable production value.

8. The coalbed methane productivity evaluation system based on bottom hole flow pressure and gas production according to claim 6, characterized in that: Calculating the production capacity coefficient of the target coalbed methane well includes: calculating the production capacity coefficient of the target coalbed methane well according to the ratio of the stable production value to the increased production value.

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