G function-based evaluation method for reconstruction effect of middle-deep layer coal bed gas fracturing crack

Abstract

The invention discloses a G-function-based evaluation method for a middle-deep layer coal bed gas fracturing fracture transformation effect, and the method comprises the following steps: S1, carrying out the geological fracture prediction before fracturing construction operation; s2, fracturing construction operation is completed, a fracturing construction curve is obtained after fracturing construction operation is completed, and the type of the fracturing construction curve is determined according to the form of the fracturing construction curve; s3, the obtained fracturing construction data are processed; s4, after fracturing construction, G function analysis is carried out; and S5, evaluating the transformation effect of the middle-deep layer coal bed gas fracturing crack. The method for evaluating the transformation effect of the medium-deep layer coal bed gas fracturing crack based on the G function has the following beneficial effects that 1, the specific geological characteristics of the medium-deep layer coal bed are considered; and 2, economy, accuracy and timeliness are considered.

Description

Technical Field

[0001] This invention relates to the field of medium-deep coal seam stimulation technology, specifically to an evaluation method for the fracturing effect of medium-deep coal seam gas fracturing based on the G function. Background Technology

[0002] Medium-deep coal seams (buried at depths of 1200-1800 meters) have become a key area for coalbed methane exploration and development due to their abundant reserves and wide distribution. However, medium-deep coal seams generally suffer from low permeability (usually less than 1 mD), high geostress, and complex coal and rock mechanical properties, resulting in poor reservoir conductivity. Therefore, fracturing technology is needed to form an effective fracture network to achieve economical extraction of coalbed methane.

[0003] Currently, the evaluation methods for the fracturing effect in medium-deep coalbed methane formations mainly include microseismic monitoring, fiber optic sensing, and production dynamics fitting. However, considering the economic efficiency, accuracy, and timeliness of these evaluation methods, the existing technical solutions all have some shortcomings:

[0004] Microseismic monitoring is highly timely, capable of real-time mapping of three-dimensional fracture distribution and dynamic adjustment of fracturing parameters; however, its accuracy is insufficient and its positioning precision is poor; at the same time, it is not economical, requiring the deployment of downhole geophone arrays or ground networks, resulting in large equipment investment and high costs.

[0005] Fiber optic sensing monitoring is highly accurate with small positioning errors and fracture resolution down to the meter level; however, it is not economical, requiring fiber optic equipment to be installed in advance during well completion, which is costly and makes it difficult to deploy and evaluate comprehensively in large-scale development blocks; at the same time, it lacks timeliness, and fiber optic monitoring of multiple wells needs to be arranged several months in advance.

[0006] The production dynamic fitting method is economical, requiring only historical production data and software analysis, and has the lowest cost; however, it has poor accuracy, relies on model assumptions, and has large errors for complex fracture networks or heterogeneous reservoirs, resulting in multiple solutions; at the same time, it lacks timeliness, requiring long-term production data, and is difficult to guide the fracturing and stimulation of subsequent wells in a timely manner.

[0007] Furthermore, the aforementioned methods cannot effectively assess the unique geological characteristics of medium-deep coal seams, such as coal sensitivity, high ground stress, and uneven fracture development. Therefore, considering the basic situation of large-scale fracturing and stimulation of medium-deep coal seams, there is an urgent need for a fracturing and fracture stimulation effect evaluation method that can comprehensively consider the unique geological characteristics of medium-deep coal seams while simultaneously possessing good economic efficiency, accuracy, and timeliness. Summary of the Invention

[0008] Purpose of the invention: To address the shortcomings of the prior art, this invention provides an evaluation method for the fracturing effect of medium-deep coalbed methane based on the G function.

[0009] This invention combines the geological characteristics of coalbed methane reservoirs with dynamic data from fracturing engineering, employing a dimensionless time function (G-function) to quantitatively analyze fracture propagation capacity and fracture morphology during fracturing. Based on parameters such as fracturing pressure, flow rate, and time, this invention accurately determines the post-fracturing fracture closure point using a G-function theoretical model, obtaining fracturing stimulation parameters such as closure stress, fracturing fluid efficiency, and net pressure. Combined with pre-fracturing geological fracture prediction and fracturing curve morphology evaluation results, this invention achieves an integrated, multi-dimensional, and comprehensive evaluation of the effectiveness of fracturing stimulation in medium-deep coalbed methane formations.

[0010] This invention can evaluate the fracturing effect of a single well as enhance the evaluation of the overall fracturing effect within a block. It is simple to operate, the parameter selection is intuitive and reliable, and the fracturing construction plan can be modified in real time, which greatly improves the speed of evaluating the fracturing effect of a block and enhances the convenience and objectivity of the evaluation.

[0011] Technical solution: An evaluation method for the fracture stimulation effect of medium-deep coalbed methane fracturing based on the G-function, the steps of which are as follows:

[0012] S1. Before hydraulic fracturing operations, geological fracture prediction should be carried out;

[0013] S2. Perform fracturing operation, and obtain the fracturing operation curve after completion. Determine the type of the fracturing operation curve based on its shape.

[0014] S3. Process the acquired fracturing construction data;

[0015] S4. After fracturing, perform G-function analysis;

[0016] S5. Evaluate the effect of fracture modification in medium-deep coalbed methane hydraulic fracturing.

[0017] Beneficial Effects: The evaluation method for fracture stimulation effect in medium-deep coalbed methane fracturing based on the G-function disclosed in this invention has the following beneficial effects:

[0018] 1. Consideration of the unique geological characteristics of medium-deep coal seams: This method combines pre-fracturing geological fracture prediction, fracturing curve morphology evaluation, and post-fracturing G-function analysis to comprehensively evaluate the fracturing effect, realizing the integrated evaluation of the geological engineering of medium-deep coal seams and making up for the shortcomings of single evaluation methods and insufficient combination with the unique geological characteristics of medium-deep coal seams.

[0019] 2. It balances economy, accuracy, and timeliness:

[0020] In terms of economics, this method only requires fracturing construction data for each stage and pressure monitoring data for 1 hour after pump shutdown, without the need for additional equipment or additional costs.

[0021] In terms of accuracy, this method combines pre-fracturing geological prediction, fracturing curve morphology evaluation, and post-fracturing G-function analysis, providing a multi-dimensional and comprehensive approach. The interpretation results are unique and accurate.

[0022] In terms of timeliness, this method can obtain all the necessary data after the pressure drop monitoring is completed, conduct analysis and evaluation, obtain evaluation results before the next stage of construction, and optimize the fracturing construction parameters of the next stage in a timely manner, thus achieving one-stage guidance.

[0023] In summary, this invention overcomes the shortcomings of traditional methods that cannot simultaneously achieve economy, accuracy, and timeliness, and provides an economical, efficient, accurate, and reliable method for evaluating the fracturing effect of large-scale development of medium-deep coal seams. Attached Figure Description

[0024] Figure 1 This is a flowchart of the evaluation method for the fracture modification effect of medium-deep coalbed methane hydraulic fracturing based on the G function disclosed in this invention.

[0025] Figure 2 This is a prediction diagram of geological fractures before compression.

[0026] Figure 3 The diagram shows the fracturing curves for three types of fracturing.

[0027] Figure 4 This is a typical curve for G-function analysis.

[0028] Figure 5 The graph shows the post-fracturing G-function analysis results for the second stage of well XX-Ping 1.

[0029] Figure 6 This is a schematic diagram of the core parameters for fracturing modification based on the G-function analysis results.

[0030] Figure 7 This is a comparison chart of the pump stop pressure and the pump stop pressure gradient for each section.

[0031] Figure 8 This is a diagram showing the evaluation results of the fracturing effect in a horizontal well. Detailed Implementation

[0032] The specific embodiments of the present invention are described in detail below.

[0033] The "range" disclosed in this invention is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 10–50 is listed for a specific parameter, it is also expected that ranges of 10–40 and 20–50 are also included. Furthermore, if the minimum range values ​​are 1 and 2, and the maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0–5" means that all real numbers between "0–5" have been listed herein; "0–5" is merely a shortened representation of these numerical combinations.

[0034] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0035] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0036] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0037] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0038] Unless otherwise specified, the reaction will proceed under normal temperature and pressure conditions.

[0039] Unless otherwise specified, all parts or percentages are by weight or by weight percentage.

[0040] In this invention, all the substances used are known substances that can be purchased or synthesized by known methods.

[0041] In this invention, all the devices or equipment used are conventional devices or equipment known in the art and are readily available.

[0042] The evaluation method for the fracture stimulation effect of medium-deep coalbed methane fracturing based on the G function is as follows:

[0043] S1. Before hydraulic fracturing operations, geological fracture prediction should be carried out;

[0044] S2. Perform fracturing operation, and obtain the fracturing operation curve after completion. Determine the type of the fracturing operation curve based on its shape.

[0045] S3. Process the acquired fracturing construction data;

[0046] S4. After fracturing, perform G-function analysis;

[0047] S5. Evaluate the effect of fracture modification in medium-deep coalbed methane hydraulic fracturing.

[0048] Further, step S1 includes the following steps:

[0049] S11. Conduct three-dimensional seismic surveys on the reservoir of the target block to obtain a predicted map of fracture development and distribution in the reservoir of the target area.

[0050] S12. Using the fracture development and distribution prediction map obtained in step S11, predict the fracture development of the target well and its surrounding area to be fracturing and evaluated, and optimize the fracturing construction plan based on the predicted fracture development of the target well and its surrounding area.

[0051] Furthermore, the types of fracturing operation curves mentioned in step S2 include ascending fracturing operation curves, stable fracturing operation curves, and descending fracturing operation curves.

[0052] When the fracturing operation curve is an ascending fracturing operation curve, the extension of the fracturing fracture is hindered, the proppant accumulates in the fracture, and the fracturing modification effect is limited.

[0053] When the fracturing operation curve is a stable fracturing operation curve, the fracturing fracture extends smoothly, the fracture length increases continuously, and the fracturing modification effect is good.

[0054] When the fracturing operation curve is a descending fracturing operation curve, the fracturing fracture extends smoothly and connects to the natural fractures in the reservoir, resulting in the widest range of fracturing stimulation and the most ideal effect.

[0055] In addition, the types of fracturing operation curves also include secondary types such as fluctuating upward fracturing operation curves (belonging to the upward type of fracturing operation curves) and fluctuating downward fracturing operation curves (belonging to the downward type of fracturing operation curves), all of which should be classified into the three main types mentioned above.

[0056] Furthermore, the fracturing operation data mentioned in step S3 includes fracturing operation time, displacement, and fracturing operation pressure.

[0057] Furthermore, step S3 is as follows:

[0058] S31. Clean the fracturing operation data to remove outliers;

[0059] S32. Align fracturing operation time to ensure consistent units for multiple parameter curve synchronization, with fracturing operation time accurate to the second, fracturing pressure unit converted to MPa, and displacement unit converted to m³. 3 / min.

[0060] Further, step S4 includes the following steps:

[0061] S41. Convert the fracturing operation time after step S3 into G-function time by G-function processing.

[0062] S42. Take the derivative of the time of the fracturing operation after processing in step S3 with the time of the G function obtained in step S42 to obtain the pressure derivative. Multiply the time of the G function obtained in step S42 with the pressure derivative to obtain the superposition derivative of the G function.

[0063] S43. Create graphs showing the relationship between the G-function time and fracturing construction pressure, pressure derivative, and superimposed derivative of the G-function, respectively, determine the pump stop point and closure point, and obtain the core parameters of single-stage fracturing.

[0064] Furthermore, the core parameters for single-stage fracturing described in step S43 include pump shutdown pressure, closure time difference, closure pressure, closure pressure gradient, net pressure, and fluid efficiency. These core parameters can quantitatively evaluate the fracturing effect of a single well and, in conjunction with the results from multiple wells in a block, generate comparative charts of the corresponding parameters, thereby evaluating and selecting superior reservoir areas. By analyzing the curve shape of the G-function time versus fracturing operation pressure, pressure derivative, and superimposed derivative of the G-function, small fluctuations and bulges indicate natural microfractures, thus enabling analysis and judgment of the development of natural fractures in the reservoir.

[0065] Furthermore, the specific steps of step S41 are as follows: The formula for converting the fracturing operation time into the G-function time is:

[0066]

[0067] Where: t—time at a certain moment during fracturing operation, in seconds; t p —Total fracturing operation time, s; G(t) —Time of G function, dimensionless.

[0068] Further, step S5 includes the following steps:

[0069] S51. Combining the fracture development and distribution prediction map of the target area reservoir obtained in step S1, the type of fracturing construction curve determined in step S2, and the curves of G function time versus fracturing construction pressure, pressure derivative, and superimposed derivative of G function obtained in step S4, comprehensively evaluate the fracturing effect of medium and deep coalbed methane.

[0070] S52. By evaluating the complexity and type of fracturing fractures in each section of the horizontal well, statistically analyzing the proportion of each type of fracture complexity in each well, drawing a proportion chart, and comprehensively evaluating the fracturing effect of each well, a multi-level post-fracturing effect evaluation system for medium-deep coalbed methane single-section-single-well-multi-well-block is formed.

[0071] Furthermore, the evaluation results in step S51 include three main categories:

[0072] (1) A main fracture system with relatively simple fracture complexity;

[0073] (2) A system of main fractures plus natural micro fractures with high fracture complexity;

[0074] (3) The main fracture plus large natural large fracture zone system with the highest fracture complexity.

[0075] Example 1

[0076] like Figures 1 to 8 As shown, the evaluation method for the fracture stimulation effect of medium-deep coalbed methane fracturing based on the G function includes the following steps:

[0077] S1. Pre-compression geological fracture prediction;

[0078] S2. Evaluation of fracturing curve morphology;

[0079] S3, Fracturing construction data processing;

[0080] S4. Post-compression G-function analysis;

[0081] S5. Evaluation results of the effect of fracture modification in medium-deep coalbed methane hydraulic fracturing.

[0082] Further, step S1 includes the following steps:

[0083] A three-dimensional seismic evaluation of the reservoir in the block was conducted to obtain a prediction map of the overall fracture development and distribution of the block. For the target well to be fracturing and evaluated, the fracture development of the target well and its surrounding area was predicted based on geological interpretation data before fracturing.

[0084] like Figure 2 As shown, taking well XX-Ping 1 as an example, the location of fracture development around well XX-Ping 1 is predicted before compression. Figure 2 The black lines in the middle represent geologically predicted cracks, thereby reducing the construction discharge and sand addition scale in the latter half of the horizontal section near the geologically predicted crack area, and optimizing the fracturing construction plan.

[0085] Further, step S2 includes the following steps:

[0086] The morphology of the fracturing operation curve was evaluated, including:

[0087] The fracturing operation curves for medium-deep coal seams can be broadly categorized into three types: ascending fracturing operation curves, stable fracturing operation curves, and descending fracturing operation curves. Typical fracturing operation curves for these three types are shown in [reference needed]. Figure 3 .

[0088] The XX-Ping 1 well was constructed in eight sections. Section 5 was an ascending fracturing curve, sections 3, 4, and 7 were stable fracturing curves, and sections 1, 2, 6, and 8 were descending fracturing curves.

[0089] An ascending fracturing operation curve indicates that the fracturing fracture extension is hindered, proppant accumulates within the fracture, and the fracturing modification effect is limited.

[0090] A stable fracturing operation curve indicates that the fracturing fracture extends smoothly, the fracture length increases continuously, and the fracturing modification effect is good.

[0091] A descending fracturing operation curve indicates that the fracturing fracture extends smoothly and connects to the natural fractures in the reservoir, resulting in the widest range of fracturing stimulation and the most ideal effect.

[0092] In addition, fracturing operation curves also have secondary types such as fluctuating upward and fluctuating downward, all of which should be classified into the three main types described in this invention.

[0093] Further, step S3 includes the following steps:

[0094] Fracturing operation data requires time, displacement, and pressure. Outliers caused by fracturing equipment malfunctions must be removed, time must be aligned, and multiple parameter curves must be synchronized with consistent units. Time must be accurate to the second, pressure converted to MPa, and displacement converted to meters. 3 / min;

[0095] Further, step S4 includes the following steps:

[0096] S41. Convert the fracturing operation time after step S3 into G-function time by G-function processing.

[0097] S42. Take the derivative of the time of the fracturing operation after processing in step S3 with the time of the G function obtained in step S42 to obtain the pressure derivative. Multiply the time of the G function obtained in step S42 with the pressure derivative to obtain the superposition derivative of the G function.

[0098] S43. Create graphs showing the relationship between the G-function time and fracturing pressure, pressure derivative, and superimposed derivative of the G-function, respectively. Determine the pump stoppage point and closure point to obtain the core parameters of single-stage fracturing (e.g., ...). Figure 6 As shown in the figure, the core parameters of single-stage fracturing include pump shutdown pressure, closure time difference, closure pressure, closure pressure gradient, net pressure, and fluid efficiency. The G-function analysis results for a single stage are shown in the figure. Figure 5 The G-function analysis parameters for the entire section of Well XX-Ping 1 are shown in Table 1. The core parameters can quantitatively evaluate the fracturing effect of a single well and, combined with the results from multiple wells in the block, generate corresponding parameter comparison charts (as shown in the figure), thereby evaluating and selecting superior reservoir areas. By analyzing the G-function curve morphology, small fluctuations and protrusions represent natural microfractures, allowing for the analysis and judgment of the development of natural fractures in the reservoir. A classic G-function analysis chart is shown below. Figure 4 ;

[0099] Table 1

[0100]

[0101]

[0102]

[0103] Furthermore, step S5 includes the following steps:

[0104] Combining pre-fracturing geological fracture prediction, fracturing construction curve types, G-function analysis parameters and curve types, the fracturing effect of medium-deep coalbed methane formations is comprehensively evaluated. The evaluation results include three categories: main fractures with relatively simple fracture complexity, main fractures with high fracture complexity plus natural microfracture systems, and main fractures with the highest fracture complexity plus large natural fracture zones.

[0105] As shown in Table 1, in the post-compression evaluation results of well XX-Ping 1, there was 1 main fracture, 8 main fractures plus micro fractures, and 7 main fractures plus large fracture bands. A diagram showing the proportion of each fracture type in well XX-Ping 1 is drawn (e.g., ...). Figure 8As shown in the figure); by evaluating the complexity and type of fracturing fractures in a single horizontal well section, the complexity and type ratio of various fractures in a single horizontal well are obtained, thereby enabling the evaluation and comparison of the fracturing effect of multiple horizontal wells. Finally, the overall evaluation of the post-fracturing effect of the block can be obtained, forming a multi-level post-fracturing effect evaluation system for medium-deep coalbed methane single section-single well-multiple wells-block.

[0106] In this embodiment, synchronization is achieved through G-function analysis:

[0107] 1. Consideration of the unique geological characteristics of medium-deep coal seams: This method combines pre-fracturing geological fracture prediction, fracturing curve morphology evaluation, and post-fracturing G-function analysis to comprehensively evaluate the fracturing effect, realizing an integrated evaluation of the geological and engineering aspects of medium-deep coal seams and making up for the shortcomings of single evaluation methods that are insufficient in combining with the unique geological characteristics of medium-deep coal seams.

[0108] 2. This method balances economy, accuracy, and timeliness: Economically, it only requires fracturing operation data for each segment and pressure monitoring data for one hour after pump shutdown, without adding extra equipment or costs. In terms of accuracy, it combines pre-fracturing geological prediction, fracturing curve morphology evaluation, and post-fracturing G-function analysis, providing a multi-dimensional and comprehensive approach with unique and accurate interpretations. In terms of timeliness, it obtains all necessary data for analysis and evaluation immediately after pressure drop monitoring, allowing for timely optimization of fracturing parameters before the next segment's operation, providing guidance for each segment. Therefore, this method overcomes the limitations of traditional methods that cannot simultaneously achieve economy, accuracy, and timeliness, providing an economical, efficient, accurate, and reliable method for evaluating the fracturing effects of large-scale development in medium-deep coal seams.

[0109] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A method for evaluating the fracturing effect of medium-deep coalbed methane based on the G-function, characterized in that, The steps are as follows: S1. Before hydraulic fracturing operations, geological fracture prediction should be carried out; S2. Perform fracturing operation, and obtain the fracturing operation curve after completion. Determine the type of the fracturing operation curve based on its shape. S3. Process the acquired fracturing construction data; S4. After fracturing, perform G-function analysis; S5. Evaluate the effect of fracture modification in medium-deep coalbed methane hydraulic fracturing.

2. The evaluation method for the fracturing effect of medium-deep coalbed methane based on the G-function as described in claim 1, characterized in that, Step S1 includes the following steps: S11. Conduct three-dimensional seismic surveys on the reservoir of the target block to obtain a predicted map of fracture development and distribution in the reservoir of the target area. S12. Using the fracture development and distribution prediction map obtained in step S11, predict the fracture development of the target well and its surrounding area to be fracturing and evaluated, and optimize the fracturing construction plan based on the predicted fracture development of the target well and its surrounding area.

3. The evaluation method for the fracturing effect of medium-deep coalbed methane based on the G-function as described in claim 1, characterized in that, The types of fracturing operation curves mentioned in step S2 include ascending fracturing operation curves, stable fracturing operation curves, and descending fracturing operation curves.

4. The evaluation method for the fracturing effect of medium-deep coalbed methane based on the G-function as described in claim 1, characterized in that, The fracturing operation data mentioned in step S3 includes fracturing operation time, displacement, and fracturing operation pressure.

5. The evaluation method for the fracturing effect of medium-deep coalbed methane based on the G-function as described in claim 4, characterized in that, The steps in step S3 are as follows: S31. Clean the fracturing operation data to remove outliers; S32. Align fracturing operation time to ensure consistent units for multiple parameter curve synchronization, with fracturing operation time accurate to the second, fracturing pressure unit converted to MPa, and displacement unit converted to m³. 3 / min.

6. The evaluation method for the fracturing effect of medium-deep coalbed methane based on the G-function as described in claim 1, characterized in that, Step S4 includes the following steps: S41. Convert the fracturing operation time after step S3 into G-function time by G-function processing. S42. Take the derivative of the time of the fracturing operation after processing in step S3 with the time of the G function obtained in step S42 to obtain the pressure derivative. Multiply the time of the G function obtained in step S42 with the pressure derivative to obtain the superposition derivative of the G function. S43. Create graphs showing the relationship between the G-function time and fracturing construction pressure, pressure derivative, and superimposed derivative of the G-function, respectively, determine the pump stop point and closure point, and obtain the core parameters of single-stage fracturing.

7. The evaluation method for the fracturing effect of medium-deep coalbed methane based on the G-function as described in claim 6, characterized in that, The core parameters for single-stage fracturing mentioned in step S43 include pump shutdown pressure, closure time difference, closure pressure, closure pressure gradient, net pressure, and fluid efficiency.

8. The evaluation method for the fracturing effect of medium-deep coalbed methane based on the G-function as described in claim 6, characterized in that, The specific steps of step S41 are as follows: The formula for converting the fracturing operation time into the G-function time is: Where: t—time at a certain moment during fracturing operation, in seconds; t p —Total fracturing operation time, s; G(t) —Time of G function, dimensionless.

9. The evaluation method for the fracturing effect of medium-deep coalbed methane based on the G-function as described in claim 1, characterized in that, Step S5 includes the following steps: S51. Combining the fracture development and distribution prediction map of the target area reservoir obtained in step S1, the type of fracturing construction curve determined in step S2, and the curves of G function time versus fracturing construction pressure, pressure derivative, and superimposed derivative of G function obtained in step S4, comprehensively evaluate the fracturing effect of medium and deep coalbed methane. S52. By evaluating the complexity and type of fracturing fractures in each section of the horizontal well, statistically analyzing the proportion of each type of fracture complexity in each well, drawing a proportion chart, and comprehensively evaluating the fracturing effect of each well, a multi-level post-fracturing effect evaluation system for medium-deep coalbed methane single-section-single-well-multi-well-block is formed.

10. The evaluation method for the fracturing effect of medium-deep coalbed methane based on the G-function as described in claim 9, characterized in that, The evaluation results in step S51 include three main categories: (1) A main fracture system with relatively simple fracture complexity; (2) A system of main fractures plus natural micro fractures with high fracture complexity; (3) The main fracture plus large natural large fracture zone system with the highest fracture complexity.

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