Coal bed gas well repeated fracturing method, device, electronic equipment and storage medium

Abstract

This invention relates to a method, apparatus, electronic device, and storage medium for repeated fracturing of coalbed methane wells, comprising the following steps: determining target construction parameters for a target coalbed methane well in a soft coalfield; based on the target construction parameters, pumping pre-fracturing fluid into the target coalbed methane well; pumping proppant-carrying fluid into the target coalbed methane well until the proppant content in the proppant-carrying fluid reaches the target proppant content; pumping fracturing fluid into the target coalbed methane well until the total pumped amount of pre-fracturing fluid, proppant-carrying fluid, and fracturing fluid reaches the target total fluid usage; shutting down the pump, shutting in the well, and not allowing expansion or venting the target coalbed methane well; repeating the above steps to reach a target number of cycles when the formation pressure decreases to less than the fracture closure pressure of the target coalbed methane well, wherein the target number of cycles is greater than or equal to 2; and performing constant-pressure venting on the target coalbed methane well. This method achieves the maximum modification of coalbed methane wells in soft coalfields through multiple rounds of large-scale fracturing, thereby increasing gas production.

Description

Technical Field

[0001] This invention relates to the field of coalbed methane extraction technology, specifically to measures for the treatment and production enhancement of low-yield coalbed methane wells, and more specifically to a method, apparatus, electronic equipment, and storage medium for repeated fracturing of coalbed methane wells. Background Technology

[0002] Currently, the most common fracturing technology for coalbed methane wells is active water fracturing. The fracturing fluid aims to reduce coal seam damage and increase flowback. The fluid system formulation typically includes water, potassium chloride, and flowback aids. During operation, a 6-8m... 3 Pumping flow rate of / min, sand addition of 35-50m³ 3 Construction scale 600-800m 3 The fracturing technology achieved some improvement in areas with good coal structure and hard coal quality, but the output was lower than expected in areas with well-developed soft coal, with an average increase of only 300m³ after repeated fracturing. 3 This cannot effectively meet the needs of efficient coalbed methane development, and seriously restricts the large-scale development of coalbed methane.

[0003] Compared to the development of conventional high-quality coalbed methane, the coal quality of crushed soft coal is softer, the coal body structure is more fragmented, the proppant is severely embedded, and it is difficult to create long fractures. Given the common problems in coalbed methane development, the difficulty of profitable development is even greater. Summary of the Invention

[0004] This invention provides a method, apparatus, electronic equipment, and storage medium for repeated fracturing of coalbed methane wells to solve the technical problem of the difficulty in modifying soft coal due to its soft coal quality and fragmented coal body structure.

[0005] In a first aspect, the present invention provides a method for repeated fracturing of a coalbed methane well, comprising: S1, determining target construction parameters for a target coalbed methane well in a soft coal zone, wherein the target construction parameters include at least one of a target construction pressure and a target construction displacement, wherein the target construction pressure is greater than the primary construction pressure of the target coalbed methane well, and the target construction displacement is greater than a first preset value; S2, based on the target construction parameters, pumping pre-fracturing fluid into the target coalbed methane well; S3, pumping proppant-carrying fluid into the target coalbed methane well until the amount of proppant added in the proppant-carrying fluid reaches a target amount of proppant added, wherein the target... S4, pump fracturing fluid into the target coalbed methane well until the total amount of pre-fracturing fluid, proppant-carrying fluid, and fracturing fluid pumped reaches the target total amount of fluid used, which is greater than the third preset value; S5, shut down the pump, close the well, and prevent pressure expansion and blowout at the target coalbed methane well; S6, if the pressure acting on the formation decreases to less than the fracture closure pressure of the target coalbed methane well, repeat steps S2 to S5 to reach the target number of cycles, which is greater than or equal to 2; S7, perform constant pressure blowout treatment on the target coalbed methane well.

[0006] In some embodiments, S2 includes: when the pre-fluid is pumped into the target coalbed methane well to a predetermined multiple of the wellbore volume, the construction discharge rate is gradually increased in a stepwise manner until the construction pressure reaches the target construction pressure and the construction discharge rate reaches the target construction discharge rate.

[0007] In some embodiments, the target sand addition amount includes fine sand, medium sand, and coarse sand set according to a preset ratio; the injection of sand-carrying fluid into the target coalbed gas well in step S3 includes: injecting sand-carrying fluid into the target coalbed gas well in the order of fine sand, medium sand, and coarse sand.

[0008] In some embodiments, while performing the pumping of proppant-carrying fluid into the target coalbed methane well in step S3, the method further includes at least one of the following: injecting a soluble temporary plugging agent into the target coalbed methane well at least once to form a fracture network; monitoring the construction pressure in real time, and supplementing the proppant-carrying fluid with fine sand when the construction pressure drops below the target construction pressure to reduce fracturing fluid loss.

[0009] In some embodiments, the fracturing fluid is a viscosity-modifying system with preset low-temperature gel breaking properties and preset low-damage properties.

[0010] In some embodiments, S7 includes: when the pressure acting on the formation decreases to less than the fracture closure pressure of the target coalbed methane well, releasing the gas at a first velocity; and when the pressure acting on the formation decreases to less than a fourth preset value, releasing the gas at a second velocity, wherein the second velocity is greater than the first velocity.

[0011] In some embodiments, before step S1, the method further includes: determining that the reservoir is a brittle soft coal based on a first target parameter of the reservoir area, wherein the first target parameter includes at least one of the following: rock mechanics parameters, logging parameters, and structural development parameters; and determining a target coalbed methane well based on a second target parameter of each candidate coalbed methane well in the brittle soft coal, wherein the second target parameter includes at least one of the following: the distance parameter between the gas content and the fault or collapse column.

[0012] Secondly, the present invention provides a coalbed methane well repeated fracturing device, comprising: a determining module, configured to determine target construction parameters for a target coalbed methane well in a soft coal zone, the target construction parameters including at least one of a target construction pressure and a target construction displacement, wherein the target construction pressure is greater than the primary construction pressure of the target coalbed methane well, and the target construction displacement is greater than a first preset value; and a pumping module, configured to perform the following steps: S2, based on the target construction parameters, pumping pre-fracturing fluid into the target coalbed methane well; S3, pumping sand-carrying fluid into the target coalbed methane well until the sand-carrying fluid reaches the target sand-carrying fluid. S4, injecting fracturing fluid into the target coalbed methane well until the total amount of pre-fracturing fluid, sand-carrying fluid, and fracturing fluid injected reaches the target total amount of fluid used, which is greater than the third preset value; S5, shutting down the pump, closing the well, and not allowing pressure expansion or venting the target coalbed methane well; S6, when the pressure on the formation decreases to less than the fracture closure pressure of the target coalbed methane well, repeating S2 to S5 to reach the target number of cycles, which is greater than or equal to 2; venting module, used to perform constant pressure venting treatment on the target coalbed methane well.

[0013] Thirdly, the present invention provides an electronic device, including a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; the memory is used to store computer programs; and the processor is used to implement the steps of the repeated fracturing method for coalbed methane wells as described in any one of the first aspects when executing the program stored in the memory.

[0014] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the repeated fracturing method for coalbed methane wells as described in any of the first aspects.

[0015] The coalbed methane well repeated fracturing method, apparatus, electronic equipment and storage medium provided in this invention achieve large-scale fracturing of coalbed methane wells in multiple rounds through high construction pressure, high construction discharge, and large-scale sand addition and liquid consumption, thereby maximizing the transformation of broken and soft coal and increasing gas production. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic flowchart of a repeated fracturing method for coalbed methane wells provided in an embodiment of the present invention;

[0019] Figure 2 Schematic diagrams of various pressures provided for embodiments of the present invention;

[0020] Figure 3 A schematic flowchart of another method for repeated fracturing of coalbed methane wells provided in an embodiment of the present invention;

[0021] Figure 4 This is a schematic diagram of a coalbed methane well repeated fracturing device provided in an embodiment of the present invention;

[0022] Figure 5 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Currently, the most common fracturing technology for coalbed methane wells is active water fracturing. The fracturing fluid aims to reduce coal seam damage and increase flowback. The fluid system formulation typically includes water, potassium chloride, and flowback aids. During operation, a 6-8m... 3 Pumping flow rate of / min, sand addition of 35-50m³ 3 Construction scale 600-800m 3 The fracturing technology achieved some improvement in areas with good coal structure and hard coal quality, but the output was lower than expected in areas with well-developed soft coal, with an average increase of only 300m³ after repeated fracturing. 3 This cannot effectively meet the needs of efficient coalbed methane development, and seriously restricts the large-scale development of coalbed methane.

[0025] Compared to the development of conventional high-quality coalbed methane, the coal quality of crushed soft coal is softer, the coal body structure is more fragmented, the proppant is severely embedded, and it is difficult to create long fractures. Given the common problems in coalbed methane development, the difficulty of profitable development is even greater.

[0026] To address the aforementioned technical problems, the present invention provides a method for repeated fracturing of coalbed methane wells in areas with fine and soft coal formations. By conducting large-scale, multi-round fracturing, the resource utilization of coalbed methane wells in areas with fine and soft coal formations is improved, thereby significantly increasing the production of a single well and realizing the efficient development of fine and soft coal seams.

[0027] Figure 1 This is a schematic flowchart illustrating a method for repeated fracturing of coalbed methane wells provided in an embodiment of the present invention. Figure 1 As shown, the repeated fracturing method for coalbed methane wells includes the following steps:

[0028] S1. Determine the target construction parameters for the target coalbed methane well in the soft coal area. The target construction parameters include at least one of the target construction pressure and the target construction discharge rate. The target construction pressure is greater than the primary construction pressure of the target coalbed methane well, and the target construction discharge rate is greater than a first preset value.

[0029] Specifically, for target coalbed methane wells in soft coalfields, the target construction parameters for repeated fracturing (or secondary fracturing) are determined, mainly including construction pressure and flow rate. Parameters such as construction pressure and flow rate during the primary fracturing process can be obtained. Based on changes in production conditions, the production conditions of adjacent wells, and the distance between wells, these parameters provide a basis for optimizing the next step of construction. Generally, the target construction pressure for repeated fracturing should be higher than the primary construction pressure. A higher pressure allows for the creation of more new fracture networks. The construction pressure can be increased by increasing the flow rate, thereby increasing the net construction pressure. The target flow rate for repeated fracturing should be greater than a first preset value, which can be 15m³. 3 / min, meaning the target construction discharge volume is 15m³ / min. 3 A high flow rate of over / min can increase the net pressure within the fracture and open more microcracks; it can also determine the target construction scale for repeated fracturing, which is usually 5 or 6 times the scale of a single construction operation.

[0030] In addition, the single sand addition amount (i.e., the target sand addition amount) can be determined. The single sand addition amount is greater than a second preset value, which can be 200m³. 3 That is, the amount of sand added at one time is 200m³. 3 The above also allows for the determination of the total amount of pre-flush fluid, proppant-carrying fluid, and fracturing fluid used in a single operation (i.e., the target total amount of fluid used). The total amount of fluid used in a single operation must be greater than a third preset value, which can be 2000m³. 3 That is, the total amount of liquid used in a single application is 2000m. 3above.

[0031] Optionally, the target total fluid volume can be adjusted appropriately based on the distance between this well and adjacent wells. For example, less fluid is needed between closer wells, while more fluid is needed between more distant wells to ensure good fracture propagation.

[0032] Optionally, before fracturing, the production tubing of the adjacent well within a preset range to the target coalbed methane well can be retrieved and a fracturing wellhead installed to prevent fracturing channeling.

[0033] S2. Based on the target construction parameters, inject pre-flush fluid into the target coalbed gas well.

[0034] S3. Pump sand-carrying fluid into the target coalbed methane well until the amount of sand added in the sand-carrying fluid reaches the target amount of sand added, and the target amount of sand added is greater than the second preset value.

[0035] S4. Pump fracturing fluid into the target coalbed methane well until the total amount of pre-fracturing fluid, sand-carrying fluid and fracturing fluid pumped reaches the target total amount of fluid used, and the target total amount of fluid used is greater than the third preset value.

[0036] S5. The target coalbed methane well is shut down, pumps are stopped, the well is closed, and pressure is not increased or vented.

[0037] Specifically, after determining the target construction parameters, multiple rounds of fracturing will be carried out. The pumping procedure for each round of fracturing is based on the target construction parameters, sequentially injecting pre-fracturing fluid, proppant-carrying fluid, and fracturing fluid into the target coalbed methane well, followed by pump shutdown and well closure without diffusion or blowout release. First, pre-fracturing fluid is injected. Pre-fracturing fluid is usually a clean liquid, possibly water or other specially formulated liquid. Injecting pre-fracturing fluid ensures wellbore cleanliness, reduces the impact of the formation on the fracturing fluid, and prepares for subsequent fracturing operations. Then, proppant-carrying fluid is injected until the single proppant injection volume reaches 200m³. 3 Propane-carrying fluid is a liquid containing sand particles. These particles can fill the voids in fractures, support and reinforce them, help form stable fractures in the formation, and prevent the fractures from closing rapidly after pressure release. Preferably, quartz sand is used in this embodiment. Finally, fracturing fluid is injected until the total amount of pre-fracturing fluid, proppane-carrying fluid, and fracturing fluid used in a single injection reaches 2000m³. 3 In summary, the injection of fracturing fluid helps to form and enlarge fractures in the formation.

[0038] In some embodiments, the fracturing fluid employs a variable viscosity system, which has low-temperature gel breaking performance and low damage performance, can reduce the filtration loss of fracturing fluid in soft coal seams, improve the migration efficiency of quartz sand, expand the sand spreading range, and the variable viscosity system can be naturally degraded, reducing reservoir damage.

[0039] In some embodiments, S2 includes: when the pre-fluid is pumped into the target coalbed methane well to a predetermined multiple of the wellbore volume, the construction discharge rate is gradually increased in a stepwise manner until the construction pressure reaches the target construction pressure and the construction discharge rate reaches the target construction discharge rate.

[0040] Specifically, the pumping procedure involves gradually increasing the flow rate in stages, by 2 cubic meters per minute each time. Once 3-5 times the wellbore volume has been injected, the flow rate should be increased further to ensure smoother fracture propagation. It should be noted that the flow rate and pressure can generally be increased to the target value during the pre-fluidization stage, and then the sand-carrying fluid and fracturing fluid are continuously pumped into the target coalbed methane well at the target value.

[0041] In some embodiments, the target sand addition amount includes fine sand, medium sand, and coarse sand set according to a preset ratio; the injection of sand-carrying fluid into the target coalbed gas well in step S3 includes: injecting sand-carrying fluid into the target coalbed gas well in the order of fine sand, medium sand, and coarse sand.

[0042] Specifically, the particles contained in the sand-carrying fluid are quartz sand, which is a combination of fine sand, medium sand, and coarse sand. If the target sand addition is 200m³... 3 The preset ratio of fine sand, medium sand, and coarse sand can be 20:150:30. During the proppant-carrying stage, proppant-carrying fluid is pumped into the target coalbed gas well in the order of fine sand, medium sand, and coarse sand. Among them, medium sand accounts for a large proportion, which means that medium sand is used as the main proppant for fracturing, which can solve the problem of severe embedding of quartz sand in soft coal.

[0043] In addition, a small amount of fine sand can be added during the pre-fracturing stage to reduce the filtration coefficient of the fracturing fluid and create more fracture networks; a small amount of coarse sand, generally 10-20 cubic meters, is added before the sand-carrying fluid ends to improve the conductivity of fractures near the wellbore.

[0044] In some embodiments, while performing the pumping of the sand-carrying fluid into the target coalbed methane well in step S3, the method further includes at least one of the following: injecting a soluble temporary plugging agent into the target coalbed methane well at least once to form a fracture network; monitoring the construction pressure in real time, and adding fine sand to the sand-carrying fluid to reduce fracturing fluid loss when the construction pressure drops below the target construction pressure.

[0045] Specifically, during the sand-carrying fluid stage, soluble temporary plugging balls can be added multiple times according to the construction pressure to increase the net construction pressure, which is conducive to creating more new complex fracture networks. During the sand-carrying fluid stage, the construction pressure will also be monitored in real time. When the construction pressure decreases, fine sand can be added to the sand-carrying fluid and pumped into the target coalbed methane well, because fine sand can reduce the fracturing fluid loss coefficient.

[0046] S6, when the pressure applied to the formation is reduced to less than the fracture closure pressure of the target coalbed methane well, repeat S2 to S5 to reach the target number of rounds, the target number of rounds being greater than or equal to 2.

[0047] Specifically, in this embodiment, at least two target cycles are set. After the first cycle of fracturing is completed according to the pumping procedure (i.e., pumping pre-fracturing fluid, proppant-carrying fluid, and fracturing fluid), the pump is stopped, the well is shut down, and pressure is increased without blowout. After the pressure acting on the formation drops below the fracture closure pressure, the second cycle of fracturing begins. The pump is stopped, the well is shut down, and pressure is increased without blowout. After the pressure acting on the formation drops below the fracture closure pressure, the third cycle of fracturing begins. The pump is stopped, the well is shut down, and pressure is increased without blowout. This process is repeated until the target cycle is reached.

[0048] Figure 2 A schematic diagram of the various pressures provided in the embodiments of the present invention, such as... Figure 2 As shown, wellhead pressure can be understood as the real-time pressure monitored at the fracturing wellhead, construction pressure can be understood as the pressure monitored at the wellhead during fracturing construction, and pressure acting on the formation can be understood as the resultant force of construction pressure and injection pressure, which is approximately equal to the wellbore injection pressure plus wellhead pressure. Fracture closure pressure is the pressure when the fracture is just able to open or just not closed, which can be calculated based on fracturing data from adjacent wells or predicted based on pressure drop data from previous wells.

[0049] S7, perform constant pressure venting treatment on the target coalbed methane well.

[0050] Specifically, after the target round of fracturing operations, constant pressure blowout treatment is carried out. Constant pressure blowout has the following functions: First, it stabilizes the fractures. By controlling the injection pressure and the speed of the injected fluid, the open state of the fractures can be maintained, preventing excessive closure or diffusion after pressure release and maintaining fracture stability. Second, it removes residual liquid and solid particles. It removes fracturing fluid and sand particles remaining in the wellbore and fractures, helping to reduce wellbore blockage, maintain fracture permeability, and ensure smooth permeation of coalbed methane. Third, it promotes coalbed methane flow. Removing residual materials and stabilizing the fractures provides more channels and space for coalbed methane, allowing the gas to be released and flow more smoothly from the coal seam to the wellhead, improving production efficiency. Fourth, it protects the wellbore and equipment. Constant pressure blowout also helps clean the wellbore and related equipment, reducing damage to the wellbore and equipment from residual materials, extending their service life, and ensuring the smooth progress of subsequent production operations.

[0051] In some embodiments, S7 includes: when the pressure acting on the formation decreases to less than the fracture closure pressure of the target coalbed methane well, releasing the gas at a first velocity; and when the pressure acting on the formation decreases to less than a fourth preset value, releasing the gas at a second velocity, wherein the second velocity is greater than the first velocity.

[0052] Specifically, after fracturing is completed, the well is shut in for pressure expansion. This means that when the pressure applied to the formation is reduced to the well fracture closure pressure, the fluid is slowly released. When the pressure applied to the formation is reduced to less than the fourth preset value, the valve is opened to release the fluid, maximizing the backflow of fracturing fluid and minimizing the backflow of proppant.

[0053] The coalbed methane well repeated fracturing method provided in this invention can create more new fracture networks by using a target construction pressure higher than the first construction pressure. By using a target construction displacement higher than the first preset value, the complexity of the fractures can be increased, and the proppant migration efficiency can be increased. Furthermore, the large-scale sand addition volume higher than the second preset value and the large-scale fluid volume higher than the third preset value can ensure the length of fracture extension and the radius of effective support when the complex fracture network is opened. In addition, by fracturing at least twice or more, the soft coal seam can be massively modified, and the coal seam can be densely broken and compressed to maximize the modification of the coal seam and form an artificial volume fracture network.

[0054] Based on the above embodiments, Figure 3 This is a schematic flowchart of another method for repeated fracturing of coalbed methane wells provided in an embodiment of the present invention. Figure 3 As shown, the method includes:

[0055] S31. The reservoir is determined to be a soft coal seam based on the first target parameter of the reservoir area. The first target parameter includes at least one of the following: rock mechanics parameters, well logging parameters, and structural development parameters.

[0056] S32. Determine the target coalbed methane well based on the second target parameters of each candidate coalbed methane well in crushed soft coal, wherein the second target parameters include at least one of the following: gas content, distance parameter between the well and the fault or collapse column.

[0057] S33. Determine the target construction parameters for the target coalbed methane well in the soft coal area. The target construction parameters include at least one of the target construction pressure and the target construction discharge rate. The target construction pressure is greater than the primary construction pressure of the target coalbed methane well, and the target construction discharge rate is greater than a first preset value.

[0058] S34. Based on the target construction parameters, pump pre-flush fluid into the target coalbed methane well;

[0059] S35. Pump sand-carrying fluid into the target coalbed gas well until the amount of sand added in the sand-carrying fluid reaches the target amount of sand added, and the target amount of sand added is greater than the second preset value.

[0060] S36. Pump fracturing fluid into the target coalbed methane well until the total amount of pre-fracturing fluid, sand-carrying fluid and fracturing fluid pumped reaches the target total amount of fluid used, and the target total amount of fluid used is greater than a third preset value.

[0061] S37. Perform pump shutdown, well shut-in, no diffuser, and no blowout treatment on the target coalbed methane well;

[0062] S38. When the pressure applied to the formation is reduced to less than the fracture closure pressure of the target coalbed methane well, S2 to S5 are repeated to reach the target number of cycles, wherein the target number of cycles is greater than or equal to 2.

[0063] S39. Perform constant pressure venting treatment on the target coalbed methane well.

[0064] It should be noted that steps S33-S39 in this embodiment are similar to steps S1-S7 in the previous embodiment, and will not be described again here.

[0065] The difference from the previous embodiments lies in that, in order to improve the extraction efficiency of secondary fracturing of coalbed methane in soft coal areas, it is necessary to select good coalbed methane wells as targets for process modification. In this embodiment, the reservoir is determined to be soft coal based on the first target parameters of the reservoir area, and the first target parameters include at least one of the following: rock mechanics parameters, logging parameters, and well logging parameters; the target coalbed methane well is determined based on the second target parameters of each candidate coalbed methane well in the soft coal area, and the second target parameters include at least one of the following: gas content, structural parameters, and distance parameters between the well and the fault or collapse column.

[0066] Specifically, the determination of whether a reservoir is a fragmented soft rock formation is first based on a comprehensive assessment of rock mechanical parameters (Poisson's ratio, elastic modulus, compressive strength, etc.), logging parameters (density logging, sonic logging, resistivity logging, etc.), and well logging parameters (based on descriptions of cuttings returned during drilling). Generally, fragmented soft rock formations typically have a high Poisson's ratio because fractured rocks are more prone to deformation; their elastic modulus is usually low because fractured rocks lose some stiffness; their compressive strength is relatively low because fractured rocks are more likely to break; density logging data can determine the density of the rock, and fragmented soft rock formations typically have low density; sonic logging data can provide information about the rock's pore structure and fracture characteristics, which is helpful in identifying fragmented soft rock formations; resistivity logging data reflects the rock's electrical conductivity and also provides some guidance in identifying fragmented soft rock formations; fragmented soft rock formations are generally more common in tectonically active areas because tectonic activity can lead to rock fracturing and fragmentation. Therefore, the above factors can be considered comprehensively to determine the location of fragmented soft rock formations.

[0067] After identifying the area of ​​crushed and soft coal, a gas content greater than a certain value (such as greater than 10 m³) is usually selected. 3The target coalbed methane (CBM) wells are those located at a certain distance from faults, collapse columns, etc. This is because the gas content of a CBM well is a crucial indicator for assessing the abundance of CBM resources. Selecting CBM wells with a gas content exceeding a certain value for secondary fracturing ensures sufficient natural gas reserves within the coal seam, thereby improving the effectiveness and economic benefits of secondary fracturing. Furthermore, structural geological factors such as faults and collapse columns can impact CBM extraction, potentially leading to concentrated natural gas emissions or affecting the permeability of CBM. Selecting CBM wells at a certain distance from these structural geological elements for secondary fracturing reduces interference with these elements and lowers the extraction risks caused by geological structures.

[0068] Based on the aforementioned embodiments, the method first comprehensively determines whether the reservoir is a fractured soft coal by considering rock mechanics parameters, logging parameters, and structural development. Then, by comprehensively considering the gas content of the coalbed methane well and its distance from structural geological elements, it is possible to more effectively select coalbed methane wells suitable for secondary fracturing, thereby improving the production capacity and extraction efficiency of coalbed methane.

[0069] To further understand the embodiments of the present invention, the following description is based on a coalbed methane well with soft coal seam development, a vertical coal seam depth of 800m (800m injection pressure of 8MPa), and a perforated section thickness of 4m, illustrating the implementation of large-scale secondary fracturing, including the following steps:

[0070] 1) Before construction, remove the production tubing within 300m of the adjacent well and install the fracturing wellhead to prevent blowout caused by pressure channeling;

[0071] 2) The average construction pressure of the first fracturing of this well was 15MPa. The construction pressure of this fracturing is higher than 15MPa. If the construction pressure is not reached, continue to increase the construction flow rate, add fine sand to reduce filtration loss, and increase the net pressure in the fracture.

[0072] 3) This well employs three rounds of large-scale fracturing, with a maximum fracturing rate of 15 cubic meters per minute, increasing by 2 cubic meters per minute each time, and a single sand addition of 200 m³. 3 The solution consists of a quartz sand mixture of 30 cubic meters of fine sand, 150 cubic meters of medium sand, and 20 cubic meters of coarse sand, with a total single-use volume of 2000 m³. 3 In summary, the fracturing fluid uses a viscosity-modifying system, and soluble temporary plugging agents are added multiple times during the sand addition process.

[0073] 4) After completing the first round of fracturing according to the pumping procedure, stop the pump, shut in the well, and allow the pressure to rise without releasing any fluid. Once the pressure acting on the formation (wellhead pressure + 8MPa) drops to less than 12MPa below the fracture closure pressure, begin the second round of fracturing. After completing the fracturing according to the pumping procedure, stop the pump, shut in the well, and allow the pressure to rise without releasing any fluid. Once the pressure acting on the formation (wellhead pressure + 8MPa) drops to less than 12MPa below the fracture closure pressure, begin the third round of fracturing.

[0074] 5) Pressure-controlled release. After the third round of fracturing is completed, the well is shut in and pressure is increased. When the pressure applied to the formation (wellhead pressure + 8MPa) is 12MPa lower than the fracture closure pressure, slow release begins. When the wellhead pressure drops to 1MPa, the valve is opened to release the proppant, minimizing proppant backflow.

[0075] In summary, large-scale quartz sand support is implemented in areas with soft coal development to solve the problem of adaptive sand embedding caused by the soft coal quality; large-volume, large-scale, variable-viscosity fracturing fluid is used to create a complex fracture network to achieve remote support; multiple rounds of fracturing overcome the adverse effects of existing fractures on fracturing, densely breaking up and opening up the coal seam, and maximizing the transformation of the coal seam.

[0076] Figure 4 This is a schematic diagram of a coalbed methane well repeated fracturing device provided in an embodiment of the present invention, as shown below. Figure 4 As shown, the coalbed methane well re-fracture device includes:

[0077] Module 401 is used to determine the target construction parameters of the target coalbed methane well in the soft coal area. The target construction parameters include at least one of the target construction pressure and the target construction displacement. The target construction pressure is greater than the primary construction pressure of the target coalbed methane well, and the target construction displacement is greater than a first preset value. Module 402 is used to perform the following steps: S2, based on the target construction parameters, pumping pre-flush fluid into the target coalbed methane well; S3, pumping sand-carrying fluid into the target coalbed methane well until the sand-carrying fluid reaches the target sand-addition amount, where the target sand-addition amount is greater than a certain value. S4, pumping fracturing fluid into the target coalbed methane well until the total amount of pre-fracturing fluid, proppant-carrying fluid, and fracturing fluid pumped reaches the target total amount of fluid used, which is greater than the third preset value; S5, stopping the pump, shutting in the well, not expanding the pressure, and not releasing the flow in the target coalbed methane well; S6, when the pressure applied to the formation decreases to less than the fracture closure pressure of the target coalbed methane well, repeating S2 to S5 to reach the target number of cycles, which is greater than or equal to 2; the flow release module 403 is used to perform constant pressure flow release treatment on the target coalbed methane well.

[0078] In some embodiments, the pumping module 402 is specifically used to: when the pre-fluid is pumped into the target coalbed methane well to a preset multiple of the wellbore volume of the target coalbed methane well, gradually increase the construction discharge rate in a stepwise manner until the construction pressure reaches the target construction pressure and the construction discharge rate reaches the target construction discharge rate.

[0079] In some embodiments, the target sand addition amount includes fine sand, medium sand, and coarse sand set according to a preset ratio; the pumping module 402 is specifically used to pump sand-carrying fluid into the target coalbed gas well in the order of fine sand, medium sand, and coarse sand.

[0080] In some embodiments, while performing the pumping of the sand-carrying fluid into the target coalbed methane well in step S3, the pumping module 402 is also used for at least one of the following: injecting at least one soluble temporary plugging agent into the target coalbed methane well to form a fracture network; monitoring the construction pressure in real time, and adding fine sand to the sand-carrying fluid to reduce fracturing fluid loss when the construction pressure drops below the target construction pressure.

[0081] In some embodiments, the fracturing fluid is a viscosity-modifying system with preset low-temperature gel breaking properties and preset low-damage properties.

[0082] In some embodiments, the venting module 403 is specifically configured to: vent at a first speed when the pressure acting on the formation decreases to less than the fracture closure pressure of the target coalbed methane well; and vent at a second speed, wherein the second speed is greater than the first speed, when the pressure acting on the formation decreases to less than a fourth preset value.

[0083] In some embodiments, the apparatus further includes a well selection module 404, which is used to determine that the reservoir is a broken soft coal based on a first target parameter of the reservoir area, the first target parameter including at least one of the following: rock parameters, logging parameters, and structural parameters; and to determine a target coalbed methane well based on a second target parameter of each candidate coalbed methane well in the broken soft coal, the second target parameter including at least one of the following: gas content and distance parameter between the well and the fault or collapse column.

[0084] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process and corresponding beneficial effects of the coalbed methane well repeated fracturing device described above can be referred to the corresponding process in the aforementioned method example, and will not be repeated here.

[0085] like Figure 5 As shown, this embodiment of the invention provides an electronic device, including a processor 501, a communication interface 502, a memory 503, and a communication bus 504, wherein the processor 501, the communication interface 502, and the memory 503 communicate with each other via the communication bus 504.

[0086] Memory 503 is used to store computer programs;

[0087] In one embodiment of the present invention, when the processor 501 executes the program stored in the memory 503, it implements the steps of the repeated fracturing method for coalbed methane wells provided in any of the foregoing method embodiments.

[0088] The electronic device provided in this embodiment of the invention has a similar implementation principle and technical effect to the above embodiments, and will not be described again here.

[0089] The aforementioned memory 503 may be an electronic memory such as flash memory, EEPROM (Electrically Erasable Programmable Read-Only Memory), EPROM, hard disk, or ROM. Memory 503 has storage space for program code used to perform any of the method steps described above. For example, the storage space for program code may include individual program codes for implementing the various steps in the methods described above. This program code can be read from or written to one or more computer program products. These computer program products include program code carriers such as hard disks, optical discs (CDs), memory cards, or floppy disks. Such computer program products are typically portable or fixed storage units. The storage unit may have storage segments or storage spaces arranged similarly to memory 503 in the aforementioned electronic device. The program code may be compressed, for example, in a suitable form. Typically, the storage unit includes programs for performing the method steps according to embodiments of the invention, i.e., code that can be read by a processor such as 501, which, when run by the electronic device, causes the electronic device to perform the various steps in the methods described above.

[0090] Embodiments of the present invention also provide a computer-readable storage medium. The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the coalbed methane well repeated fracturing method described above.

[0091] The computer-readable storage medium may be included in the device / apparatus described in the above embodiments; or it may exist independently and not assembled into the device / apparatus. The computer-readable storage medium carries one or more programs that, when executed, implement the method according to the embodiments of the present invention.

[0092] According to embodiments of the present invention, the computer-readable storage medium may be a non-volatile computer-readable storage medium, such as including, but not limited to: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In the present invention, the computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0093] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0094] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for repeated fracturing of coalbed methane wells, characterized in that, include: S1, determine the target construction parameters of the target coalbed methane well in the soft coal area. The target construction parameters include at least one of the target construction pressure and the target construction discharge rate. The target construction pressure is greater than the primary construction pressure of the target coalbed methane well, and the target construction discharge rate is greater than a first preset value. S2, Based on the target construction parameters, inject pre-flush fluid into the target coalbed methane well; S3, pump sand-carrying fluid into the target coalbed gas well until the amount of sand added in the sand-carrying fluid reaches the target amount of sand added, and the target amount of sand added is greater than the second preset value; S4, pump fracturing fluid into the target coalbed methane well until the total amount of pre-fracturing fluid, sand-carrying fluid and fracturing fluid pumped reaches the target total amount of fluid used, and the target total amount of fluid used is greater than the third preset value; S5, perform pump shutdown, well shut-in, no pressure expansion, and no blowout treatment on the target coalbed methane well; S6, when the pressure on the formation is reduced to less than the fracture closure pressure of the target coalbed methane well, S2 to S5 are repeated to reach the target number of rounds, the target number of rounds being greater than or equal to 2; S7, perform constant pressure venting treatment on the target coalbed methane well.

2. The method according to claim 1, characterized in that, S2 includes: When the pre-fluid is pumped into the target coalbed methane well to a predetermined multiple of the wellbore volume, the construction discharge rate is gradually increased in a stepwise manner until the construction pressure reaches the target construction pressure and the construction discharge rate reaches the target construction discharge rate.

3. The method according to claim 1, characterized in that, The target sand addition amount includes fine sand, medium sand, and coarse sand set according to a preset ratio; the injection of sand-carrying fluid into the target coalbed gas well pump in step S3 includes: The sand-carrying fluid is pumped into the target coalbed methane well in the order of fine sand, medium sand, and coarse sand.

4. The method according to claim 3, characterized in that, While performing step S3, the method further includes at least one of the following: At least one soluble temporary plugging agent is injected into the target coalbed methane well to form a fracture network; Real-time monitoring of construction pressure, and when the construction pressure drops below the target construction pressure, adding fine sand to the sand-carrying fluid to reduce fracturing fluid loss.

5. The method according to claim 1, characterized in that, The fracturing fluid is a viscosity-modifying system with preset low-temperature gel breaking performance and preset low-damage performance.

6. The method according to any one of claims 1-5, characterized in that, S7 includes: When the pressure on the formation is reduced to less than the fracture closure pressure of the target coalbed methane well, it is released at the first velocity. When the pressure applied to the formation decreases to less than a fourth preset value, the material is released at a second velocity, which is greater than the first velocity.

7. The method according to any one of claims 1-5, characterized in that, Before S1, it also includes: The reservoir is determined to be a soft coal based on the first target parameter of the reservoir area. The first target parameter includes at least one of the following: rock mechanics parameters, well logging parameters, and structural development parameters. The target coalbed methane well is determined based on the second target parameters of each candidate coalbed methane well in crushed soft coal, wherein the second target parameters include at least one of the following: gas content and distance parameters between the well and the fault or collapse column.

8. A re-fracture device for coalbed methane wells, characterized in that, include: The determination module is used to determine the target construction parameters of the target coalbed methane well in the crushed soft coal area. The target construction parameters include at least one of the target construction pressure and the target construction discharge rate. The target construction pressure is greater than the primary construction pressure of the target coalbed methane well, and the target construction discharge rate is greater than a first preset value. The pumping module is used to perform the following steps: S2, Based on the target construction parameters, inject pre-flush fluid into the target coalbed methane well; S3, pump sand-carrying fluid into the target coalbed gas well until the amount of sand added in the sand-carrying fluid reaches the target amount of sand added, and the target amount of sand added is greater than the second preset value; S4, pump fracturing fluid into the target coalbed methane well until the total amount of pre-fracturing fluid, sand-carrying fluid and fracturing fluid pumped reaches the target total amount of fluid used, and the target total amount of fluid used is greater than the third preset value; S5, perform pump shutdown, well shut-in, no pressure expansion, and no blowout treatment on the target coalbed methane well; S6, when the pressure on the formation is reduced to less than the fracture closure pressure of the target coalbed methane well, S2 to S5 are repeated to reach the target number of rounds, the target number of rounds being greater than or equal to 2; The venting module is used to perform constant pressure venting treatment on the target coalbed methane well.

9. An electronic device, characterized in that, It includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; The processor, when executing a program stored in memory, implements the steps of the repeated fracturing method for coalbed methane wells according to any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the repeated fracturing method for coalbed methane wells as described in any one of claims 1-7.

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