Pitching fracturing well selection method, treatment method and device for coal bed gas low-yield well

Abstract

The invention discloses a coal bed gas low-yield well pitching fracturing well selection method, treatment method and device, and the method comprises the steps: building a burial depth-construction pressure value fitting curve of a target block based on the burial depth and construction pressure value of a middle-high yield gas well in the coal bed gas target block; on the basis of the burial depth of the low-yield gas well in the target block and the burial depth-construction pressure value fitting curve, determining a pitching fracturing construction pressure value of the low-yield gas well; performing pitching fracturing secondary transformation on the low-yield gas well according to the pitching fracturing construction pressure value, so as to determine the pitching fracturing construction pressure value meeting the pitching fracturing secondary transformation process in the low-yield gas well based on the yield increasing effect of the pitching fracturing secondary transformation; determining a construction pressure difference value range based on the ball fracturing construction pressure value and a primary construction pressure actual value of the low-yield gas well; and selecting the well based on the construction pressure difference value range and the difference value between the one-time construction pressure actual value of the low-yield gas well in the target block and the pitching fracturing construction pressure value of the low-yield gas well.

Description

Technical Field

[0001] The invention relates to the technical field of coalbed methane development, and in particular to a ball-throwing fracturing well selection method, a treatment method and a device for a low-yield coalbed methane well. Background Art

[0002] The development of coalbed methane fields is controlled by insufficient geological knowledge and unsuitable reservoir transformation technology. Low-yield gas wells (daily gas production of vertical wells below 500 cubic meters) will inevitably appear, making it difficult to achieve efficient development of gas wells. At present, secondary transformation measures are mostly used to increase the production of low-yield wells. After years of exploration and research and accumulation of production practice experience, a variety of secondary transformation technologies have been formed, such as ball-throwing fracturing technology. Cai Hua, Zhang Guangbo and others analyzed the technical principles and well selection principles of ball-throwing temporary plugging fracturing technology: ball-throwing temporary plugging technology usually selects coalbed methane wells with strong vertical heterogeneity of coal body structure, uneven first transformation of coal reservoir, and low stability or descending type of primary fracturing curve. The temporary plugging ball temporarily blocks the holes with larger flow, forcing the fracturing fluid to turn to the holes with smaller flow, so as to create new fractures in the same layer vertically and transform the coal seam sections with large differences in mechanical properties, so as to achieve the purpose of uniform transformation of coal seams. The collet-type ball-throwing fracturing sleeve proposed by Ma Shuaibang et al., the ball-throwing fracturing sleeve sandblaster proposed by Hou Haiqiang et al., the drillable ball-throwing fracturing bridge plug proposed by Feng Ding et al., and so on. Summary of the invention

[0003] In order to enrich the process routes and increase the selection space, the embodiments of the present invention provide a method for selecting a coalbed methane low-yield well by ball fracturing, a treatment method and a device.

[0004] In a first aspect, an embodiment of the present invention provides a method for selecting a coalbed methane low-yield well by ball fracturing, which may include:

[0005] Based on the burial depth and operation pressure value of the medium and high-yield gas wells in the target coalbed methane block, a burial depth-operation pressure value fitting curve of the target block is constructed;

[0006] Based on the burial depths of a preset number of low-yield gas wells in the target block and the burial depth-operation pressure value fitting curve, determining the ball fracturing operation pressure values ​​of the preset number of low-yield gas wells;

[0007] The ball-throwing fracturing construction pressure value is used as a ball-throwing fracturing parameter to perform a secondary ball-throwing fracturing transformation on the low-yield gas well, so as to determine the low-yield gas wells that meet the ball-throwing fracturing secondary transformation process and their ball-throwing fracturing construction pressure values ​​among a preset number of low-yield gas wells based on the production increase effect of the secondary ball-throwing fracturing transformation;

[0008] Determine the construction pressure difference range based on the ball fracturing construction pressure value of the low-yield gas well and the actual value of the primary construction pressure of the low-yield gas well;

[0009] Well selection is performed based on the construction pressure difference range and the difference between the actual value of the primary construction pressure of the low-yield gas well in the target block and the ball-dropping fracturing construction pressure value of the low-yield gas well.

[0010] Optionally, based on the production increase effect of the ball-dropping fracturing secondary transformation, determining the low-yield gas wells that meet the requirements of the ball-dropping fracturing secondary transformation process among a preset number of low-yield gas wells may include:

[0011] Based on the production increase effect of the low-yield gas well after the secondary transformation of ball fracturing, the gas production is compared with the gas production of the medium- and high-yield gas wells in the target block;

[0012] The low-yield gas wells whose production increase effect satisfies the preset gas production range of the medium- and high-yield gas wells are determined as low-yield gas wells that meet the requirements of the ball-dropping fracturing secondary transformation process.

[0013] Optionally, the method may further include: preliminarily screening the low-yield gas wells based on the desorption pressure of the low-yield gas wells; if the desorption pressure of the low-yield gas wells is greater than a preset desorption pressure threshold, executing a well selection step; otherwise, the low-yield gas well is no longer selected as a well for ball fracturing.

[0014] In a second aspect, an embodiment of the present invention provides a method for secondary transformation of a low-yield coalbed methane well by ball fracturing, which may include:

[0015] Injecting fracturing fluid into the wellbore of the low-yield gas well at a first displacement rate so that the construction pressure reaches an actual value of the primary construction pressure;

[0016] Throwing nylon balls accounting for a preset proportion of all blastholes into the wellbore of the low-yield gas well at a second displacement;

[0017] After the ball throwing is completed, fracturing fluid with a first sand content ratio and a third displacement is used to perform a first sand addition to the wellbore of the low-yield gas well to a first sand addition amount;

[0018] Using the fracturing fluid with the second sand content ratio, the fourth displacement and the ball-dropping fracturing operation pressure value as the ball-dropping fracturing parameters, adding sand for the second time to the second sand addition amount in the wellbore of the low-yield gas well;

[0019] Wherein, the low-yield gas well is determined according to the coalbed methane low-yield well selection method for ball fracturing described in the first aspect.

[0020] Optionally, the second displacement is smaller than the first displacement, and the third displacement is smaller than the fourth displacement.

[0021] Optionally, the first displacement is smaller than the third displacement.

[0022] Optionally, the third displacement is smaller than the fourth displacement, and the first proportion of sand content is smaller than the second proportion of sand content.

[0023] Optionally, the third displacement is 5-6 cubic meters / min, and the first proportion of sand content is 4%-5%;

[0024] The fourth displacement is 10 to 16 cubic meters per minute, and the second proportion of sand content is 10% to 12%.

[0025] In a third aspect, an embodiment of the present invention provides a device for selecting a well for low-yield coalbed methane wells by ball fracturing, which may include:

[0026] A construction module is used to construct a fitting curve of the burial depth-construction pressure value of the target block based on the burial depth and construction pressure value of the medium and high production gas wells in the target coalbed methane block;

[0027] A ball-dropping fracturing construction pressure value determination module is used to determine the ball-dropping fracturing construction pressure values ​​of a preset number of low-yield gas wells in the target block based on the burial depths of the preset number of low-yield gas wells in the target block and the burial depth-construction pressure value fitting curve;

[0028] A low-yield gas well determination module that meets the requirements of ball-throwing fracturing is used to perform secondary ball-throwing fracturing on the low-yield gas well using the ball-throwing fracturing construction pressure value as a ball-throwing fracturing parameter, so as to determine the low-yield gas wells that meet the requirements of the secondary ball-throwing fracturing process and their ball-throwing fracturing construction pressure values ​​among a preset number of low-yield gas wells based on the production increase effect of the secondary ball-throwing fracturing.

[0029] A construction pressure difference range determination module, used to determine the construction pressure difference range based on the ball fracturing construction pressure value of the low-yield gas well and the actual value of the primary construction pressure of the low-yield gas well;

[0030] The well selection module is used to select wells based on the construction pressure difference range and the difference between the actual value of the primary construction pressure of the low-yield gas well in the target block and the ball fracturing construction pressure value of the low-yield gas well.

[0031] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method for selecting a well for ball-dropping fracturing of a low-yield coalbed methane well as described in the first aspect.

[0032] In a fifth aspect, an embodiment of the present invention provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for selecting a low-yield coalbed methane well by ball fracturing is implemented as described in the first aspect.

[0033] The beneficial effects of the above technical solution provided by the embodiment of the present invention include at least:

[0034] The embodiment of the present invention provides a method, a treatment method and a device for selecting a coalbed methane low-yield well by ball fracturing, which greatly saves the time spent on well selection and improves the accuracy of well selection by quantifying the well selection index. Furthermore, the ability to plug old fractures and create new fractures is greatly improved, which is greatly beneficial to the increase in production of low-yield gas wells.

[0035] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0036] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0038] Figure 1 This is a flow chart of the method for selecting a well for ball fracturing of a low-yield coalbed methane well provided in the first embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of a fitting curve of burial depth-construction pressure value provided in the first embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of the structure of the ball-dropping fracturing well selection device for low-yield coalbed methane wells provided in the first embodiment of the present invention;

[0041] Figure 4 This is a flow chart of the method for secondary transformation of a coalbed methane low-yield gas well by ball fracturing provided in the second embodiment of the present invention;

[0042] Figure 5 A schematic diagram showing the statistical construction displacement when a coal seam rupture occurs during the fracturing of a coal bed methane well in a block provided in the second embodiment of the present invention;

[0043] Figure 6 This is one of the schematic diagrams of the fracturing simulation test provided in Example 2 of the present invention (displacement 8m 3 / min);

[0044] Figure 7 The second schematic diagram of the fracturing simulation test provided in the second embodiment of the present invention (displacement 10m 3 / min);

[0045] Figure 8 The third schematic diagram of the fracturing simulation test provided in the second embodiment of the present invention (displacement 12m 3 / min);

[0046] Fig. 9 The fourth schematic diagram of the fracturing simulation test provided in the second embodiment of the present invention (displacement 12m 3 / min);

[0047] Fig.10 Schematic diagram of the fracturing simulation test provided in Example 2 of the present invention (displacement 16m 3 / min);

[0048] Fig.11 Schematic diagram of the fracturing simulation test provided in Example 2 of the present invention (displacement 18m 3 / min). DETAILED DESCRIPTION

[0049] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0050] Embodiment 1

[0051] The inventors have found that in the prior art, when selecting coalbed methane wells suitable for the ball-dropping fracturing process modification and treatment method, the primary fracturing curve type is required to be a low stable type and a declining type. There is no quantitative concept of what construction pressure is defined as low and how much it declines, which is not convenient for on-site operation; secondly, in the specific construction process, there are currently no specific measures for the ball-dropping fracturing measure to increase production process.

[0052] In view of the above problems, the present invention proposes a method for selecting a coalbed methane low-yield well by ball fracturing to overcome the above problems or at least partially solve the above problems. The method mainly focuses on how to realize the selection of ball fracturing wells, and how to carry out ball fracturing construction in the subsequent treatment of coalbed methane low-yield wells, so as to achieve the purpose of maximizing the single well production effect. Figure 1 As shown, the above-mentioned coalbed methane low-yield well fracturing well selection method in the embodiment of the present invention may include the following steps:

[0053] Step S11: construct a fitting curve of the burial depth-operation pressure value of the target block based on the burial depth and operation pressure value of the medium and high production gas wells in the target coalbed methane block.

[0054] In the embodiment of the present invention, the gas wells of the target block are divided into high-yield gas wells, medium-yield gas wells and low-yield gas wells based on the daily gas production, for example, the division can be performed by a threshold method. According to the actual situation of the target block, for example, the gas wells with a daily gas production of less than 500 cubic meters that do not meet the definition of industrial gas flow can be classified as low-yield gas wells, the gas wells with a daily gas production of 500 to 1000 cubic meters can be classified as medium-yield gas wells, and the gas wells with a daily gas production of more than 1000 cubic meters can be classified as high-yield gas wells.

[0055] This step is to make a scatter plot of the burial depth and construction pressure of all medium and high-yield gas wells in the research block, with the burial depth as the x-axis and the construction pressure as the y-axis. Based on the scatter plot, the burial depth-construction pressure fitting curve of the target block is fitted. This fitting curve can be used as the normal value standard line of the construction pressure of the coalbed methane field (target block). Figure 2 As shown, the greater the burial depth, the greater the weight of the overlying rock strata, and a greater force is required to break the strata. This force is reflected in the construction pressure during fracturing, that is, the construction pressure will increase with the increase of burial depth.

[0056] Step S12: determining the ball fracturing construction pressure values ​​of a preset number of low-yield gas wells in the target block based on the burial depths of the preset number of low-yield gas wells in the target block and the burial depth-construction pressure value fitting curve.

[0057] In this step, some low-yield gas wells are first selected for secondary transformation test of ball fracturing, that is, based on the burial depth of the low-yield gas well and the fitting curve of burial depth-construction pressure value, the corresponding ball fracturing construction pressure value of the low-yield gas well is determined, that is, the burial depth of the low-yield gas well is brought into the above fitting curve, and the ball fracturing construction pressure value can be calculated. However, the secondary transformation of ball fracturing based on the ball fracturing construction pressure value may not always achieve the ideal effect of increasing production, so subsequent steps are required to screen the value. For example, the actual value of the primary pressure construction of a low-yield gas well is 16MPa, and the ball fracturing construction pressure value determined based on its burial depth and fitting curve is 16.5MPa. However, the coal seam is subjected to secondary fracturing transformation with a construction pressure of 16.5MPa, and its coalbed methane production increase may not necessarily achieve a medium-to-high yield effect.

[0058] Step S13, using the ball-throwing fracturing construction pressure value as the ball-throwing fracturing parameter to perform secondary ball-throwing fracturing on the low-yield gas well, so as to determine the low-yield gas wells that meet the ball-throwing fracturing secondary transformation process and their ball-throwing fracturing construction pressure values ​​among a preset number of low-yield gas wells based on the production increase effect of the secondary ball-throwing fracturing.

[0059] This step is to select low-yield gas wells with relatively good production-increasing effects after secondary transformation with ball-throwing fracturing, laying the foundation for calculating the construction pressure difference range (Δf) in the subsequent steps.

[0060] During the specific implementation of this step, the production increase effect after secondary transformation of the low-yield gas wells by ball-dropping fracturing is first compared with the gas production of the medium- and high-yield gas wells in the target block; then, the low-yield gas wells whose production increase effect meets the preset range of the gas production of the medium- and high-yield gas wells are determined as low-yield gas wells that meet the requirements of the secondary transformation process of ball-dropping fracturing.

[0061] Step S14, determining a construction pressure difference range based on the ball-dropping fracturing construction pressure value of the low-yield gas well and the actual value of the primary construction pressure of the low-yield gas well.

[0062] This step uses the calculated ball-throwing fracturing construction pressure value to perform ball-throwing fracturing measures, and finds that some wells have good effects after fracturing, while others have poor effects. By making a scatter plot of the Δf index and the gas increase after fracturing, it is found that wells with high gas increase (>500 cubic meters) are all within the Δf range, so low-yield gas wells within this range are suitable for ball-throwing fracturing measures. The focus of the embodiment of the present invention is to obtain the construction pressure difference range, so that when selecting wells in subsequent steps, low-yield gas wells within the construction pressure difference range can meet the requirements of ball-throwing fracturing secondary transformation to achieve medium and high production effects.

[0063] Step S15, selecting a well based on the construction pressure difference range and the difference between the actual value of the primary construction pressure of the low-yield gas well in the target block and the ball fracturing construction pressure value of the low-yield gas well.

[0064] The method provided by the embodiment of the present invention greatly saves the time spent on well selection and improves the accuracy of well selection by quantifying the well selection index.

[0065] In an optional embodiment, referring to the above Figure 1 As shown, the method may also include the following steps:

[0066] Step S10, preliminarily screening low-yield gas wells based on their desorption pressure; if the desorption pressure of the low-yield gas well is greater than a preset desorption pressure threshold, then executing the well selection step, otherwise the low-yield gas well is no longer selected as a well for ball fracturing.

[0067] In this step, desorption pressure is used as a screening condition. Desorption pressure is a standard for characterizing the gas content of coalbed methane reservoirs and can reflect the amount of coalbed methane methane in the coal reservoir. The reason for limiting this condition is that some wells with a capacity of less than 500 cubic meters have too low methane content in the coal reservoir, and it is difficult to obtain high production even after secondary fracturing.

[0068] In a specific example, the method provided by the present invention is applied in the coalbed methane production process of a certain block, and the operation is specifically performed according to the following steps:

[0069] Step 1: Select all vertical wells in the coalbed methane field with a daily gas production of more than 1,000 cubic meters, and count the burial depth and construction pressure of each well. There are 222 vertical wells in the area with a daily gas production of more than 1,000 cubic meters. Complete the statistics of the burial depth and construction pressure of each well. Figure 2 As shown, a scatter plot of the burial depth and the construction pressure is drawn, and the formula y=0.0129x+9.1573 is obtained.

[0070] Step 2: Select all 196 vertical wells in the area with a daily gas production of less than 500 cubic meters, read the desorption pressure of each well, and select 120 wells with a desorption pressure above 1.5 MPa. Substitute the burial depth of the selected wells into the fitting formula y=0.0129x+9.1573 to obtain the construction pressure fitting value f2. For example, the burial depth of the HG1 well is 542 meters, and its construction pressure fitting f2 is 16.1 MPa, and its actual construction pressure f1 is 13 MPa, and the calculated Δf is 3.1 MPa. The burial depth of the HG2 well is 652 meters, and its construction pressure fitting f2 is 17.6 MPa, and its actual construction pressure f1 is 17 MPa, and the calculated Δf is 0.6 MPa.

[0071] Step 3: Use the construction pressure fitting value f2 as the ball-dropping fracturing parameter to perform secondary ball-dropping fracturing on the low-yield gas well, so as to determine the low-yield gas wells that meet the ball-dropping fracturing secondary transformation process and their ball-dropping fracturing construction pressure value f2 among a preset number of low-yield gas wells based on the production increase effect of the secondary ball-dropping fracturing.

[0072] Step 4: The construction pressure fitting value f2 of the low-yield gas well that meets the ball-throwing fracturing secondary transformation process is subtracted from the actual construction pressure value f1 to obtain Δf. For example, the calculated Δf of the HG1 well is 3.1MPa, and the calculated Δf of the HG2 well is 0.6MPa. After screening, the Δf of this area is 2-4MPa.

[0073] Step 5: compare the difference between the actual value of the primary construction pressure of all low-yield gas wells and the construction pressure value of the ball fracturing of the low-yield gas wells with the above-mentioned construction pressure difference range Δf. If it is within the range of Δf, then select the well as one that can be subjected to secondary reconstruction by ball fracturing.

[0074] Based on the same inventive concept, the present invention also provides a coalbed methane low-yield well ball fracturing well selection device, referring to Figure 3 As shown, the device may include: a construction module 31, a ball-throwing fracturing construction pressure value determination module 32, a low-yield gas well determination module 33 that meets the requirements of ball-throwing fracturing, a construction pressure difference range determination module 34, and a well selection module 35. The working principle is as follows:

[0075] The construction module 31 is used to construct a fitting curve of the burial depth-construction pressure value of the target block based on the burial depth and construction pressure value of the medium and high production gas wells in the target coalbed methane block;

[0076] The ball-dropping fracturing construction pressure value determination module 32 is used to determine the ball-dropping fracturing construction pressure values ​​of a preset number of low-yield gas wells in the target block based on the burial depths of the preset number of low-yield gas wells in the target block and the burial depth-construction pressure value fitting curve;

[0077] The low-yield gas well determination module 33 that meets the requirements of ball-throwing fracturing is used to use the ball-throwing fracturing construction pressure value as a ball-throwing fracturing parameter to perform ball-throwing fracturing secondary transformation on the low-yield gas well, so as to determine the low-yield gas wells that meet the requirements of the ball-throwing fracturing secondary transformation process and their ball-throwing fracturing construction pressure values ​​among a preset number of low-yield gas wells based on the production increase effect of the ball-throwing fracturing secondary transformation;

[0078] The construction pressure difference range determination module 34 is used to determine the construction pressure difference range based on the ball fracturing construction pressure value of the low-yield gas well and the actual value of the primary construction pressure of the low-yield gas well;

[0079] The well selection module 35 is used to determine whether the low-yield gas well meets the ball-dropping fracturing well selection conditions based on the construction pressure difference range and the difference between the actual value of the primary construction pressure of the low-yield gas well in the target block and the ball-dropping fracturing construction pressure value of the low-yield gas well.

[0080] In an alternative embodiment, referring to Figure 3 As shown, the device may also include: a preliminary screening module 30, which is used to perform preliminary screening of low-yield gas wells based on their desorption pressure; if the desorption pressure of the low-yield gas well is greater than a preset desorption pressure threshold, the well selection step is executed; otherwise, the low-yield gas well is no longer selected as a well for ball fracturing.

[0081] Based on the same inventive concept, an embodiment of the present invention further provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the above-mentioned method for selecting a well for low-yield coalbed methane wells by ball fracturing is implemented.

[0082] Based on the same inventive concept, a computer device is also provided in an embodiment of the present invention, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the above-mentioned method for selecting a low-yield coalbed methane well by ball fracturing is implemented.

[0083] The principles of the problems solved by the above-mentioned devices, media, and related equipment in the embodiments of the present invention are similar to those of the above-mentioned methods, so their implementation can refer to the implementation of the above-mentioned methods, and the repeated parts will not be repeated.

[0084] Embodiment 2

[0085] The second embodiment of the present invention also provides a method for secondary transformation of a coalbed methane low-yield gas well by ball fracturing, referring to Figure 4 As shown, the method may include the following steps:

[0086] Step S41, injecting fracturing fluid into the wellbore of the low-yield gas well at a first displacement to make the construction pressure reach an actual value of the primary construction pressure; wherein the low-yield gas well is determined according to the coalbed methane low-yield well ball fracturing well selection method in Example 1.

[0087] In this step, the fracturing fluid is injected at a low displacement (e.g. 4 cubic meters / min), and the injection is stopped when the construction pressure reaches the actual value of the primary construction pressure. For example, the well was started at 3:00 pm, and the formal construction began at 3:05 after the pressure test was completed. The liquid was injected at a low displacement (4 cubic meters / min), and the primary construction pressure of the well reached 15MPa at 3:25, with a total injection volume of 80 cubic meters.

[0088] Because the purpose of this stage is to use liquid to fill the existing old fracture network, increase the pressure of the old fracture network, and reduce the possibility of new fractures entering the old fractures during subsequent fracturing, it is necessary to avoid opening new fractures in this process, such as Figure 5 Statistics show that the construction displacement when the coal seam in this area breaks is above 5 cubic meters per minute. Therefore, the injection displacement in this stage is designed to be 4 cubic meters per minute, which not only ensures that all the liquid enters the old seams, but also shortens the operation time to the greatest extent.

[0089] Step S42, dropping nylon balls accounting for a preset proportion of all blastholes into the wellbore of the low-yield gas well at a second displacement.

[0090] In this step, the second displacement is smaller than the first displacement. In this step, nylon balls are put into the wellbore at a lower displacement (e.g., 2 cubic meters / min). For example, there are 70 blastholes in the well, and a total of 42 nylon balls are put in (accounting for 60% of the total number of blastholes). The ball throwing is completed at 3:27, and a total of 4 cubic meters of liquid are injected.

[0091] Step S43: After the ball throwing is completed, the fracturing fluid with the first sand content ratio and the third displacement are used to add sand to the wellbore of the low-yield gas well for the first time to the first sand addition amount.

[0092] In this step, the first displacement is smaller than the third displacement, for example, at 3:27 the displacement is increased to 6 cubic meters / min, the first sand addition is carried out, 20 cubic meters of sand is added at a low sand ratio of 5%, and the process is completed at 4:30, with a total injection volume of 400 cubic meters.

[0093] Step S44, using the fracturing fluid with the second sand content ratio, the fourth displacement and the ball-dropping fracturing construction pressure value as the ball-dropping fracturing parameters, adding sand to the wellbore of the low-yield gas well for the second time to the second sand addition amount.

[0094] The third displacement in this step is smaller than the fourth displacement, and the first proportion of sand content is smaller than the second proportion of sand content. The third displacement is 5-6 cubic meters / min, and the first proportion of sand content is 4%-5%; the fourth displacement is 10-16 cubic meters / min, and the second proportion of sand content is 10%-12%. For example, at 4:30, the displacement is increased to 14 cubic meters / min, and the second sand addition is carried out. The sand ratio is 10%, and 40 cubic meters of sand are added. It is completed at 5:30, and a total of 400 cubic meters of liquid are injected; the pump is stopped for 30 minutes, and the pressure drop measurement is completed at 6:00. After the pressure drop measurement is completed, the spray is immediately released to return the fracturing fluid.

[0095] Reference Figure 6 to Figure 11 As shown in the figure, through fracturing simulation, it is found that with the increase of displacement, the length of the crack increases first and then decreases. If the construction pressure is too high, the equipment cannot be deployed, which will also cause the cracks in the coal seam to be more uneven, or the coal blocks will be crushed into broken coal, which cannot improve the fracturing effect. Therefore, the advantageous range is 10-16 cubic meters / min. This process method greatly improves the ability to plug old cracks and create new cracks, which is very beneficial to the increase of production of low-yield gas wells.

[0096] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) containing computer-usable program code.

[0097] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0098] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0099] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0100] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for selecting a well for low-yield coalbed methane wells by ball fracturing, characterized in that: include: Based on the burial depth and operation pressure value of the medium and high-yield gas wells in the target coalbed methane block, a burial depth-operation pressure value fitting curve of the target block is constructed; Based on the burial depths of a preset number of low-yield gas wells in the target block and the burial depth-operation pressure value fitting curve, determining the ball fracturing operation pressure values ​​of the preset number of low-yield gas wells; The ball-throwing fracturing construction pressure value is used as a ball-throwing fracturing parameter to perform a secondary ball-throwing fracturing transformation on the low-yield gas well, so as to determine the low-yield gas wells that meet the ball-throwing fracturing secondary transformation process and their ball-throwing fracturing construction pressure values ​​among a preset number of low-yield gas wells based on the production increase effect of the secondary ball-throwing fracturing transformation; Determine the construction pressure difference range based on the ball fracturing construction pressure value of the low-yield gas well and the actual value of the primary construction pressure of the low-yield gas well; Well selection is performed based on the construction pressure difference range and the difference between the actual value of the primary construction pressure of the low-yield gas well in the target block and the ball-dropping fracturing construction pressure value of the low-yield gas well.

2. The method according to claim 1, characterized in that Based on the production increase effect of the secondary transformation of ball-throwing fracturing, determining the low-yield gas wells that meet the requirements of the secondary transformation process of ball-throwing fracturing among a preset number of low-yield gas wells, including: Based on the production increase effect of the low-yield gas well after the secondary transformation of ball fracturing, the gas production is compared with the gas production of the medium- and high-yield gas wells in the target block; The low-yield gas wells whose production increase effect satisfies the preset gas production range of the medium- and high-yield gas wells are determined as low-yield gas wells that meet the requirements of the ball-dropping fracturing secondary transformation process.

3. The method according to claim 1, characterized in that Also includes: Preliminarily screening the low-yield gas wells based on the desorption pressure of the low-yield gas wells; If the desorption pressure of the low-yield gas well is greater than a preset desorption pressure threshold, executing a well selection step; Otherwise, the low-yield gas well will no longer be selected as a well for ball fracturing.

4. A method for secondary transformation of a low-yield coalbed methane well by ball fracturing, characterized in that: include: Injecting fracturing fluid into the wellbore of the low-yield gas well at a first displacement rate so that the construction pressure reaches an actual value of the primary construction pressure; Throwing nylon balls accounting for a preset proportion of all blastholes into the wellbore of the low-yield gas well at a second displacement; After the ball throwing is completed, fracturing fluid with a first sand content ratio and a third displacement is used to perform a first sand addition to the wellbore of the low-yield gas well to a first sand addition amount; Using the fracturing fluid with the second sand content ratio, the fourth displacement and the ball-dropping fracturing operation pressure value as the ball-dropping fracturing parameters, adding sand for the second time to the wellbore of the low-yield gas well to the second sand addition amount; Wherein, the low-yield gas well is determined by the coalbed methane low-yield well selection method by ball fracturing according to any one of claims 1 to 3.

5. The method according to claim 4, characterized in that The second displacement is smaller than the first displacement, and the third displacement is smaller than the fourth displacement.

6. The method according to claim 5, characterized in that The first displacement is smaller than the third displacement.

7. The method according to claim 4, characterized in that The third displacement is smaller than the fourth displacement, and the first proportion of sand content is smaller than the second proportion of sand content.

8. The method according to claim 4, characterized in that The third displacement is 5-6 cubic meters / min, and the first proportion of sand content is 4%-5%; The fourth displacement is 10 to 16 cubic meters per minute, and the second proportion of sand content is 10% to 12%.

9. A ball-throwing fracturing well selection device for low-yield coalbed methane wells, characterized in that: include: A construction module is used to construct a fitting curve of the burial depth-construction pressure value of the target block based on the burial depth and construction pressure value of the medium and high production gas wells in the target coalbed methane block; A ball-dropping fracturing construction pressure value determination module is used to determine the ball-dropping fracturing construction pressure values ​​of a preset number of low-yield gas wells in the target block based on the burial depths of the preset number of low-yield gas wells in the target block and the burial depth-construction pressure value fitting curve; A low-yield gas well determination module that meets the requirements of ball-throwing fracturing is used to perform secondary ball-throwing fracturing on the low-yield gas well using the ball-throwing fracturing construction pressure value as a ball-throwing fracturing parameter, so as to determine the low-yield gas wells that meet the requirements of the secondary ball-throwing fracturing process and their ball-throwing fracturing construction pressure values ​​among a preset number of low-yield gas wells based on the production increase effect of the secondary ball-throwing fracturing. A construction pressure difference range determination module, used to determine the construction pressure difference range based on the ball fracturing construction pressure value of the low-yield gas well and the actual value of the primary construction pressure of the low-yield gas well; The well selection module is used to select wells based on the construction pressure difference range and the difference between the actual value of the primary construction pressure of the low-yield gas well in the target block and the ball fracturing construction pressure value of the low-yield gas well.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method for selecting a coalbed methane low-yield well by ball fracturing is implemented as described in any one of claims 1 to 3.

11. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the method for selecting a coalbed methane low-yield well by ball fracturing according to any one of claims 1 to 3 is implemented.

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