Construction method of coal bed gas horizontal well jet flow cavity making device

Abstract

The invention relates to a construction method of a coal bed gas horizontal well jet flow cavity making device. The construction method comprises the following steps that S1, well drilling construction is conducted; s2, cutting the casing pipe; s3, water jet cutting; s4, water jet secondary cutting is conducted, specifically, after the coal seam cavity is partially closed, the jet cavity making device conducts secondary jet cutting cavity making on the coal seam cavity, and a secondary coal seam cavity is formed; according to the construction method, after the high-pressure abrasive slurry is sprayed through the jet flow cavity making device to directly conduct directional reciprocating cutting on the casing pipe, the high-pressure water is sprayed through the jet flow cavity making device to conduct cutting cavity making on the coal seam, coal seam pressure relief and permeability improvement are achieved, secondary cutting is conducted on a coal seam cavity subsequently, a pressure relief area extends outwards, and the permeability of the coal seam is improved. And the coal body around the cavity is subjected to pressure relief and pressure re-relief repeatedly, continuous expansion and communication of microfractures are promoted, the coal seam pressure relief influence range is gradually expanded, the overall infiltration capacity of the coal seam is enhanced, and therefore continuous and stable extraction of the coal-bed gas well is achieved.

Description

Technical Field

[0001] This invention relates to the field of coalbed methane extraction, and more specifically to a construction method for a coalbed methane horizontal well jet cavity-making device. Background Technology

[0002] Coalbed methane (CBM), as an important unconventional natural gas resource, plays a crucial role in ensuring energy security and reducing coal mine gas disasters through its efficient development. However, coal seams generally have complex pore structures, low initial permeability, and high stress sensitivity. Especially in low- and medium-rank coal seams and areas with well-developed geological structures, relying solely on natural desorption and wellbore connectivity makes it difficult to form effective gas flow channels, resulting in long production cycles, low initial production, and insufficient stable production capacity in CBM wells.

[0003] Currently, commonly used permeability enhancement technologies for horizontal coalbed methane wells mainly include hydraulic fracturing, hydraulic slotting, hydraulic perforation, and jet cavity creation. Among these, jet cavity creation technology uses high-pressure fluid to directionally erode the coal seam, forming a cavity structure of a certain volume around the wellbore. This serves to relieve pressure, increase the exposed area, and improve seepage conditions, and has a certain application basis in new well commissioning and secondary stimulation of old wells.

[0004] However, in actual engineering, jet-induced cavity formation often fails to achieve the expected permeability enhancement effect. Coal powder and slag are easily left inside the cavity, affecting the connectivity of subsequent drainage channels. During the extraction process, when the cavity is partially closed and the connectivity is reduced due to the redistribution of ground stress and the creep compaction of coal body, the subsequent gas extraction effect of the cavity is weakened.

[0005] Therefore, to solve the above problems, a construction method for a jet cavity-making device for horizontal wells in coalbed methane is needed. Summary of the Invention

[0006] The construction method of the coalbed methane horizontal well jet cavity-making device of the present invention involves directly cutting the casing by spraying high-pressure abrasive slurry through the jet cavity-making device, followed by cutting and creating a cavity in the coal seam by spraying high-pressure water through the jet cavity-making device. This achieves pressure relief and permeability improvement in the coal seam. By subsequently performing secondary cutting on the coal seam cavity, the pressure relief zone extends outward. The coal body around the cavity repeatedly undergoes pressure relief and re-pressure relief, promoting the continuous expansion and connection of micro-fractures, gradually expanding the pressure relief influence range of the coal seam, enhancing the overall permeability of the coal seam, and thus achieving continuous and stable extraction of coalbed methane from the well.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0008] On the one hand, a construction method for a jet cavity-forming device for horizontal coalbed methane wells includes the following steps:

[0009] S1: Drilling construction: Drill from the surface to form horizontal and vertical wells in the coal seam at the target depth, and install casing in the horizontal well. Install and arrange the jet cavity-making device in conjunction with coiled tubing in the casing.

[0010] S2: Casing cutting: High-pressure abrasive slurry is injected through the coiled tubing. The high-pressure abrasive slurry is sprayed onto the casing at a fixed point through the jet cavity-forming device. The coiled tubing is pulled and the jet cavity-forming device is driven to reciprocate to cut the casing along the horizontal direction of the horizontal well. The cutting is stopped after a casing jet groove of appropriate size is formed on the casing.

[0011] S3: Water jet cutting: High-pressure water is injected through the coiled tubing. The high-pressure water passes through the jet cavity-making device and then through the casing jet groove to perform water jet cutting on the coal seam. The coiled tubing is pulled and the jet cavity-making device is driven to reciprocate along the horizontal direction of the horizontal well. After reciprocating erosion and breaking the coal seam, a coal seam cavity is formed.

[0012] S4: Secondary water jet cutting: After the coal seam cavity is partially closed, the jet cavity-making device performs secondary jet cutting to create a secondary coal seam cavity.

[0013] Furthermore, the jet cavity-forming device includes a jet housing, a straightening connector installed at the end of the jet housing, a jet assembly disposed inside the jet housing, and a jet nozzle arranged on the jet housing; the end of the straightening connector is fitted with a continuous tubing and is used to input fluid into the jet assembly and eject it through the jet nozzle.

[0014] Furthermore, the jet assembly includes a gravity eccentric sleeve and an eccentric swing rod installed inside the jet housing; the gravity eccentric sleeve includes a front eccentric sleeve and a rear eccentric sleeve arranged along the axial direction of the jet housing, and the eccentric swing rod is arranged between the front eccentric sleeve and the rear eccentric sleeve.

[0015] Furthermore, the front eccentric sleeve and the rear eccentric sleeve have the same structure. An eccentric semi-ring is installed inside the front eccentric sleeve. The eccentric swing rod is fixedly installed in conjunction with the eccentric semi-ring. An eccentric sleeve rotating ring is arranged between the front eccentric sleeve and the jet shell.

[0016] Furthermore, the eccentric rocker arm includes a front rocker arm and a rear rocker arm. The rear end of the front rocker arm has a rocker arm wedge block, and the front end of the rear rocker arm has a rocker arm slot. The front end of the rear rocker arm is inclined relative to the axial direction. The rocker arm wedge block is inserted into the rocker arm slot for installation, and after the front rocker arm and the rear rocker arm are connected and installed, a rocker arm opening is formed in the middle.

[0017] Furthermore, the bottom of both the front and rear swing arms is arc-shaped, and the upper end of the front swing arm is concave downward to form a flow guide slope. A flow guide groove is formed at the bottom of the flow guide slope, and the flow guide groove extends from the front end of the front swing arm to the rear end of the front swing arm.

[0018] Furthermore, the jet nozzle includes a radial nozzle and an axial nozzle disposed at the end of the jet housing. An inner protective tube is installed inside the jet housing. The radial nozzle is installed in conjunction with the inner protective tube and is directly opposite the opening of the swing rod. The radial nozzle forms an inclined angle α with the horizontal direction.

[0019] Furthermore, a centralizing ring is installed on the outer casing of the jet, and there are two centralizing rings, which are respectively arranged at both ends of the jet casing.

[0020] Furthermore, a ground pump truck is installed at the ground surface for use in conjunction with the coiled tubing.

[0021] Furthermore, a cemented section is provided inside the vertical shaft.

[0022] The beneficial effects of this technical solution are:

[0023] The construction method of the coalbed methane horizontal well jet cavity-making device of the present invention involves directly cutting the casing by spraying high-pressure abrasive slurry through the jet cavity-making device, followed by cutting and creating a cavity in the coal seam by spraying high-pressure water through the jet cavity-making device. This achieves pressure relief and permeability improvement in the coal seam. By subsequently performing secondary cutting on the coal seam cavity, the pressure relief zone extends outward. The coal body around the cavity repeatedly undergoes pressure relief and re-pressure relief, promoting the continuous expansion and connection of micro-fractures, gradually expanding the pressure relief influence range of the coal seam, enhancing the overall permeability of the coal seam, and thus achieving continuous and stable extraction of coalbed methane from the well. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall invention;

[0025] Figure 2 This is a schematic diagram of the jet cavity-forming device of the present invention;

[0026] Figure 3 This is an exploded schematic diagram of the gravity eccentric sleeve and eccentric pendulum rod of the present invention;

[0027] Figure 4 This is a schematic diagram of the eccentric rocker arm installation of the present invention;

[0028] Figure 5 This is a schematic diagram of the secondary cavity creation method of the present invention;

[0029] Figure 6 This is the overall flowchart of the present invention.

[0030] The attached diagram lists the components represented by each number as follows:

[0031] 1-Jet cavity-forming device; 2-Coal seam; 3-Coal seam roof; 4-Coiled tubing; 5-Annulus zone; 6-Cemented cementing section; 7-Surface pump truck; 11-Centering joint; 12-Centering ring; 13-Eccentric sleeve swivel; 14-Gravity eccentric sleeve; 15-Radial nozzle; 16-Inner casing; 17-Axial nozzle; 18-Eccentric rocker arm; 19-Jet outer shell; 141-Front eccentric sleeve; 142- Rear eccentric sleeve; 143-Eccentric semi-ring; 181-Front swing arm; 182-Rear swing arm; 183-Swing arm wedge block; 184-Swing arm slot; 185-Guiding inclined surface; 186-Guiding groove; 188-Swing arm opening; 31-Coal seam floor; 81-Coal seam cavity; 82-Primary attenuation cavity; 83-Secondary coal seam cavity; 84-Secondary attenuation cavity; 85-Micro fracture; 86-Pressure relief zone. Detailed Implementation

[0032] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0033] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0035] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] like Figure 1 , Figure 6 As shown in the embodiments of this application, one aspect of the construction method for a coalbed methane horizontal well jet cavity-making device includes the following steps:

[0037] S1: Drilling construction: Drill from the surface to the target depth coal seam to form horizontal and vertical wells and install casing in the horizontal well. Install and arrange the jet cavity-making device 1 in conjunction with the coiled tubing 4 in the casing; carry out drilling construction at the designated surface location to drill to the target depth coal seam 2, forming horizontal and vertical wells. Connect and install the jet cavity-making device 1 at the end of the coiled tubing 4 at the designated location in the horizontal well.

[0038] S2: Casing Cutting: High-pressure abrasive slurry is injected through coiled tubing 4. The high-pressure abrasive slurry is then sprayed onto the casing at a fixed point through the jet cavity-forming device 1, pulling the coiled tubing 4 and driving the jet cavity-forming device 1 along the horizontal direction of the horizontal well (i.e., Figure 1 The casing is reciprocated in the horizontal direction to form a casing jet groove of suitable size, and then the cutting is stopped. Homogeneous high-pressure abrasive slurry is transported to the jet cavity-forming device 1 via a continuous tubing. The high-pressure abrasive slurry is ejected through the nozzle of the jet cavity-forming device 1 to perform point-cutting on the casing. Simultaneously, an external drag force is applied to the jet cavity-forming device 1 to control its axial movement (the specific dragging method can use existing technology; here, the continuous tubing 4 can be used to directly drag the jet cavity-forming device 1). The casing cutting is controlled by continuously or intermittently moving the axial direction of the jet cavity-forming device 1, so that the casing cutting process is linear or segmented, along the casing axis (i.e.,...). Figure 1 A sleeve jet groove of predetermined length is formed by horizontal cutting; the abrasive is 60-120 mesh quartz sand with a mass fraction of 5%, the abrasive flow rate of a single nozzle is 280 g / min, and the abrasive jet velocity is 220 m / s; after fixed-point erosion for about 120-180 s, a through hole with a diameter of 8-10 mm is formed on the sleeve (not shown in the figure), and then the sleeve jet groove is formed by repeated grooving along the axial direction at a speed of 200 mm / min.

[0039] S3: Water jet cutting: High-pressure water is injected through coiled tubing 4. The high-pressure water passes through the jet cavity-making device 1 and then through the casing jet groove to perform water jet cutting on the bottom plate 31 of the coal seam 2. This pulls the coiled tubing 4 and drives the jet cavity-making device 1 to move back and forth along the horizontal direction of the horizontal well. After the coal seam 2 is eroded and broken, a coal seam cavity 81 is formed. The high-pressure water jet forms multiple scouring trajectories in the casing jet groove to gradually expand the cavity volume. The cavity-making effect is evaluated by monitoring (the specific monitoring device and method can use existing technology) the debris content in the return fluid, changes in wellbore resistance, or gas production response. When the cavity-making effect does not meet the predetermined transformation requirements, the abrasive casing cutting, water jet cavity-making, and cleaning are repeated to carry out multiple perforation cavity-making transformations on the same well section.

[0040] After the casing cutting is completed, the system switches to high-pressure pure water jet mode. High-pressure water is used to repeatedly flush the tank section to erode and break the coal body outside the casing, forming a cavity connected to the coal seam 2. During the cutting and cavity making process, high-pressure water is continuously sprayed by the jet cavity making device 1 to clean and remove the debris generated by cutting and rock breaking, so that the debris is returned to the wellhead through the wellbore.

[0041] S4: Secondary water jet cutting: After the coal seam cavity is partially closed, the jet cavity-making device performs secondary jet cutting to create a secondary coal seam cavity 83. When the cavity is partially closed and the connectivity is reduced due to the influence of stress redistribution, coal creep compaction, etc., the cavity space and surrounding fractures and pressure relief range can be expanded again by repeating the above operation method, thereby extending the efficient coal seam extraction cycle and increasing the cumulative gas production.

[0042] The continuous decline in gas production indicates a weakening of the connectivity and pressure relief effect of the original cavity-forming area, forming a primary attenuation cavity 82. At this point, based on the primary attenuation cavity 82, the pure water jet erosion cavity-forming and cleaning operations are repeated, thereby forming a larger secondary coal seam cavity 83 on the basis of the original cavity. This causes the pressure relief zone 86 to extend outwards and promotes the continuous development and connectivity of micro-fractures 85 in the surrounding coal body. When the secondary coal seam cavity 83 closes to form a secondary attenuation cavity 84, the above steps are repeated.

[0043] Through repeated cavity-building operations, the coal body around the cavity undergoes repeated depressurization and re-depressurization processes, promoting the continuous expansion and connection of microfractures 85, gradually expanding the influence range of coal seam depressurization, enhancing the overall permeability of the coal seam, and thus achieving continuous and stable extraction of coalbed methane.

[0044] During the multiple perforation and cavity-building processes, the formed cavities are repeatedly flushed and re-eroded by alternating abrasive jets and pure water jets, gradually expanding the cavity volume and removing residual debris, thereby continuously improving the pressure relief of the coal seam and the connectivity of the seepage channels. When phenomena such as a decrease in gas production and a rise in bottom hole pressure occur during extraction, it is judged that the cavity is closed or the connectivity is reduced, and the previous operation method is repeated. Cavities are built according to the pre-set cavity-building distance. After the initial cavity building, coalbed methane can be produced stably for a period of time. After the cavity closes, cavity building is carried out again. Compared with the initial cavity building, the pressure relief range and the extension range of the micro-fractures around the cavity are wider. After a certain number of cycles, the coalbed methane of the extracted strata can be continuously and stably extracted until production stops.

[0045] The construction method of the coalbed methane horizontal well jet cavity-making device of the present invention involves directly cutting the casing by spraying high-pressure abrasive slurry through the jet cavity-making device 1, and then cutting the coal seam 2 by spraying high-pressure water through the jet cavity-making device 1. This achieves coal seam depressurization and permeability improvement. By subsequently cutting the coal seam cavity a second time, the depressurization zone 86 extends outward. The coal body around the cavity repeatedly experiences depressurization and re-depressurization, promoting the continuous expansion and connection of micro fractures 85, gradually expanding the influence range of coal seam depressurization, enhancing the overall permeability of the coal seam, and thus achieving continuous and stable extraction of coalbed methane from the well.

[0046] In this embodiment, the jet cavity device 1 includes a jet housing 19, a straightening connector 11 installed at the end of the jet housing 19, a jet assembly disposed inside the jet housing 19, and a jet nozzle arranged on the jet housing 19; the end of the straightening connector 11 is fitted with a continuous oil pipe 4 and is used to input fluid into the jet assembly and eject it through the jet nozzle.

[0047] like Figure 2 As shown, the left end of the jet housing 19 is connected to the straightening connector 11, which is connected to the continuous oil pipe 4. The installation of the straightening connector 11 reduces wear and ensures that the structure is stable and reliable in use. After passing through the continuous oil pipe 4 and connecting to the straightening connector 11, the liquid enters the jet housing 19 and is ejected from the jet housing 19 after passing through the jet assembly, cutting at the preset position.

[0048] In this embodiment, the jet assembly includes a gravity eccentric sleeve 14 and an eccentric swing rod 18 installed inside the jet housing 19; the gravity eccentric sleeve 14 includes a front eccentric sleeve 141 and a rear eccentric sleeve 142 (the front eccentric sleeve 141 and the rear eccentric sleeve 142) arranged along the axial direction of the jet housing 19. Figure 3 (The left end is the front, and the right end is the rear), the eccentric swing arm 18 is arranged between the front eccentric sleeve 141 and the rear eccentric sleeve 142.

[0049] like Figure 2-4 As shown, the eccentric swing arm 18 is installed in conjunction with the front eccentric sleeve and the rear eccentric sleeve, and the three form an integral eccentric structure, which is arranged inside the jet housing 19. When the fluid enters the jet housing 19, it passes through the front eccentric sleeve 141 and then through the eccentric swing arm 18 and the rear eccentric sleeve 142. The fluid is then ejected from the jet nozzle to cut or flush the preset position.

[0050] In this embodiment, the front eccentric sleeve 141 and the rear eccentric sleeve 142 have the same structure. An eccentric semi-ring 143 is installed inside the front eccentric sleeve 141. The eccentric swing rod 18 is fixedly installed in conjunction with the eccentric semi-ring 143. An eccentric sleeve rotating ring 13 is arranged between the front eccentric sleeve 141 and the jet shell 19.

[0051] like Figure 2-4 As shown, the front eccentric sleeve 141 and the rear eccentric sleeve 142 adopt the same structure. An eccentric semi-ring 143 is installed inside the front eccentric sleeve 141. The length of the eccentric semi-ring 143 can be set to be the same as that of the front eccentric sleeve 141. The two are fixedly connected. The two ends of the eccentric rocker arm 18 are fixedly installed in conjunction with the eccentric semi-ring 143 inside the front eccentric sleeve 141 and the rear eccentric sleeve 142. An eccentric sleeve rotating ring 13 (a bearing can be used here) is set on the outer circumference of the front eccentric sleeve 141, which is rotated in conjunction with the jet housing 19. Of course, a rotation sealing structure is set at the corresponding position. That is, under the action of the gravity of the eccentric semi-ring 143, the opening of the eccentric semi-ring 143 is always facing upward. When the jet cavity device 1 is installed in a suitable position in the horizontal well, the fluid in the jet cavity device 1 is ejected and then ejected in conjunction with the jet nozzle.

[0052] In this embodiment, the eccentric rocker arm 18 includes a front rocker arm 181 and a rear rocker arm 182. The rear end of the front rocker arm 181 is formed with a rocker arm wedge block 183, and the front end of the rear rocker arm 182 is formed with a rocker arm slot 184. The front end of the rear rocker arm is inclined relative to the axial direction. The rocker arm wedge block 183 is inserted and installed in conjunction with the rocker arm slot 184. After the front rocker arm 181 and the rear rocker arm 182 are connected and installed, a rocker arm opening 188 is formed in the middle.

[0053] like Figure 3-4 As shown, the eccentric rocker arm 18 adopts a two-section plug-in structure, including a front rocker arm 181 and a rear rocker arm 182. The rear end of the front rocker arm 181 forms a rocker arm wedge block 183, and the front end of the rear rocker arm 182 forms a rocker arm slot 184. The two are plugged in and installed. After installation, a rocker arm opening 188 structure is formed in the middle, which facilitates the fluid to enter the rocker arm opening 188 and be ejected in conjunction with the corresponding jet nozzle during subsequent use. The eccentric rocker arm 18 can also adopt a one-piece structure, with an opening groove machined in the middle, which does not affect the fluid jetting.

[0054] In this embodiment, the bottom of both the front swing arm 181 and the rear swing arm 182 is arc-shaped. The upper end of the front swing arm 181 is recessed downward to form a flow guiding slope 185. A flow guiding groove 186 is formed at the bottom of the flow guiding slope 185. The flow guiding groove extends from the front end of the front swing arm to the rear end of the front swing arm.

[0055] like Figure 3-4As shown, both the front swing arm 181 and the rear swing arm 182 have downward recessed upper surfaces to form a flow guiding slope 185 structure. A flow guiding groove 186 is formed at the bottom of the slope of the flow guiding slope 185, and the flow guiding groove extends from the front end of the front swing arm to the rear end face, which facilitates the flow of internal fluid. At the same time, the flow guiding groove 186 facilitates the flow of fluid to the swing arm opening 188 and then ejects it from the jet nozzle. The corresponding way in which the front end of the rear swing arm is inclined relative to the axial direction also facilitates the continued export of internal fluid to the rear end of the rear swing arm 182.

[0056] In this embodiment, the jet nozzle includes a radial nozzle 15 and an axial nozzle 17 disposed at the end of the jet housing 19. An inner protective tube 16 is installed inside the jet housing 19. The radial nozzle 15 is installed in conjunction with the inner protective tube 16 and is directly opposite the swing rod opening 188. The radial nozzle 15 forms an inclined angle α with the horizontal direction.

[0057] like Figure 2-4 As shown, the inner protective tube 16 is installed in conjunction with the jet housing 19. The jet nozzle includes a radial nozzle 15 and an axial nozzle 17. There are two radial nozzles 15, symmetrically arranged relative to the axial nozzle 17. The radial nozzles 15 are installed in conjunction with the inner protective tube 16 (installation holes can be made in the inner protective tube 16 to accommodate the radial nozzles 15). The fluid in the front eccentric sleeve 141 enters the guide slope 185 and the guide groove 186 after passing through the front eccentric sleeve 141, and then passes through the swing rod opening 188. The radial nozzles 15 are positioned directly opposite the swing rod opening 188. This arrangement, in conjunction with the guide slope 185, facilitates better direct ejection of the internal fluid to the set position. Simultaneously, the internal fluid flows from the axial nozzle 17. Seven nozzles spray out to flush away residual debris in the axial direction, ensuring that the jet cavity-forming device 1 is not blocked by residual debris accumulation when moving in the axial direction. The radial nozzle 15 forms an inclined angle α with the horizontal direction, preferably set to 85°, so that when the radial nozzle 15 and the axial nozzle 17 spray high-pressure fluid, a certain amount of counter-thrust can be generated in the horizontal direction, which facilitates the reciprocating motion of the jet cavity-forming device 1 in the horizontal direction. Of course, when the jet cavity-forming device 1 moves in the horizontal well, a guide rail or directional slide can be set up (the auxiliary motion device can use the existing technology, and its specific structure and installation method will not be described here) to assist the jet cavity-forming device 1 in horizontal movement and improve its movement stability.

[0058] In this embodiment, a straightening ring 12 is installed on the outer sleeve of the jet shell 19. There are two straightening rings 12, and the two straightening rings are respectively arranged at both ends of the jet shell 19.

[0059] like Figure 2As shown, two identical centralizing rings 12 are installed on the jet casing 19. When used in conjunction with the centralizing connector 11, the overall structure inside the horizontal well is more stable and reliable during use, and the cutting at the set position is more precise and reliable.

[0060] In this embodiment, a ground pump truck 7 is installed at the ground surface for use in conjunction with the continuous tubing 4.

[0061] like Figure 1 As shown, a surface pump truck 7 is installed at the surface. The surface pump truck 7 works with the coiled tubing 4 to input fluid. At the same time, when the internal jet cavity device 1 needs to move along the horizontal well, it can be done by dragging the coiled tubing 4 to drive the jet cavity device 1.

[0062] In this embodiment, a cemented section 6 is provided inside the vertical shaft.

[0063] like Figure 1 As shown, the vertical shaft passes through the top plate 3 of the coal seam. A cemented section 6 is set in the vertical shaft. An annular zone 5 is formed between the coiled tubing 4 and the cemented section 6 (the same method is used for horizontal wells). The annular zone 5 is used to facilitate the discharge of internal fluids and residues after the subsequent fluid cuts through the coal seam, and of course, it is also used for the subsequent extraction and exploitation of coalbed methane.

[0064] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0065] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A construction method for a jet cavity-forming device for horizontal coalbed methane wells, characterized in that: Includes the following steps: S1: Drilling construction: Drill from the surface to the target depth coal seam (2) to form horizontal and vertical wells and install casing in the horizontal well. Install and arrange the jet cavity device (1) in conjunction with the coiled tubing (4) in the casing. S2: Casing cutting: High-pressure abrasive slurry is injected through the coiled tubing (4). The high-pressure abrasive slurry is sprayed onto the casing through the jet cavity device (1). The coiled tubing (4) is pulled and the jet cavity device (1) is driven to reciprocate cutting the casing along the horizontal direction of the horizontal well. After forming a casing jet groove of appropriate size on the casing, the cutting is stopped. S3: Water jet cutting: High-pressure water is injected through the coiled tubing (4). The high-pressure water passes through the jet cavity device (1) and then through the casing jet groove to perform water jet cutting on the coal seam (2). The coiled tubing (4) is pulled and the jet cavity device (1) is driven to move back and forth along the horizontal direction of the horizontal well. After the coal seam is eroded and broken, a coal seam cavity (81) is formed. S4: Secondary water jet cutting: After the coal seam cavity (81) is partially closed, the jet cavity-making device (1) performs secondary jet cutting to create a secondary coal seam cavity (83).

2. The construction method of the coalbed methane horizontal well jet cavity-making device according to claim 1, characterized in that: The jet cavity device (1) includes a jet housing (19), a straightening connector (11) installed at the end of the jet housing (19), a jet assembly disposed inside the jet housing (19), and a jet nozzle arranged on the jet housing (19); the end of the straightening connector (11) is fitted with a continuous oil pipe (4) and is used to input fluid into the jet assembly and eject it through the jet nozzle.

3. The construction method of the coalbed methane horizontal well jet cavity-making device according to claim 2, characterized in that: The jet assembly includes a gravity eccentric sleeve (14) and an eccentric swing rod (18) installed inside the jet housing (19); the gravity eccentric sleeve (14) includes a front eccentric sleeve (141) and a rear eccentric sleeve (142) arranged along the axial direction of the jet housing (19), and the eccentric swing rod (18) is arranged between the front eccentric sleeve (141) and the rear eccentric sleeve (142).

4. The construction method of the coalbed methane horizontal well jet cavity-making device according to claim 3, characterized in that: The front eccentric sleeve (141) and the rear eccentric sleeve (142) have the same structure. An eccentric semi-ring (143) is installed inside the front eccentric sleeve (141). The eccentric swing rod (18) is fixedly installed in conjunction with the eccentric semi-ring (143). An eccentric sleeve swivel (13) is arranged between the front eccentric sleeve (141) and the jet shell (19).

5. The construction method of the coalbed methane horizontal well jet cavity-making device according to claim 3, characterized in that: The eccentric rocker arm (18) includes a front rocker arm (181) and a rear rocker arm (182). The rear end of the front rocker arm (181) is formed with a rocker arm wedge block (183). The front end of the rear rocker arm (182) is formed with a rocker arm slot (184) and the front end of the rear rocker arm is inclined relative to the axial direction. The rocker arm wedge block (183) is inserted and installed in conjunction with the rocker arm slot (184). After the front rocker arm (181) and the rear rocker arm (182) are connected and installed, a rocker arm opening (188) is formed in the middle.

6. The construction method of the coalbed methane horizontal well jet cavity-making device according to claim 5, characterized in that: The bottom of the front swing arm (181) and the bottom of the rear swing arm (182) are both arc-shaped. The upper end of the front swing arm (181) is concave downward to form a flow guide slope (185). A flow guide groove (186) is formed at the bottom of the flow guide slope (185). The flow guide groove (186) extends from the front end of the front swing arm (181) to the rear end of the front swing arm (181).

7. The construction method of the coalbed methane horizontal well jet cavity-making device according to claim 6, characterized in that: The jet nozzle includes a radial nozzle (15) and an axial nozzle (17) disposed at the end of the jet housing (19). An inner protective tube (16) is installed inside the jet housing (19). The radial nozzle (15) is installed in conjunction with the inner protective tube (16) and the radial nozzle (15) is directly opposite the swing rod opening (188). The radial nozzle (15) forms an inclined angle α with the horizontal direction.

8. The construction method of the coalbed methane horizontal well jet cavity-making device according to claim 2, characterized in that: The jet shell (19) is fitted with two straightening rings (12), which are respectively arranged at both ends of the jet shell (19).

9. The construction method of the coalbed methane horizontal well jet cavity-making device according to claim 1, characterized in that: A ground pump truck (7) is installed at the ground surface to work in conjunction with the coiled tubing (4).

10. The construction method of the coalbed methane horizontal well jet cavity-making device according to claim 1, characterized in that: The vertical shaft is equipped with a cement cementing section (6).

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