A completion casing string and method based on coal bed methane horizontal communication wells

Abstract

The application discloses a completion casing string based on a coal bed gas horizontal communication well, which can be directly lowered through a vertical well section, and a casing is cut in the vertical well by a milling method to realize protection of a communication section of the horizontal well and the vertical well, thereby avoiding blockage of a throat section of the well. In the use method of the completion casing string based on the coal bed gas horizontal communication well, after the horizontal well and the vertical well are communicated, eccentricity verification is performed through a workover pipe column to determine whether the communication point is a direct communication or eccentric communication, and if the communication point is the eccentric communication, the direct communication can be realized through repeated eye cutting, and the direct communication relationship between the horizontal well casing string and the communicated vertical well and the specific communication well depth are more convenient to determine.

Description

Technical Field

[0001] This invention belongs to the field of coalbed methane drilling and completion technology, and specifically relates to a completion casing string and method for horizontal interconnected coalbed methane wells. Background Technology

[0002] Coalbed methane development in soft, low-permeability coal seams typically employs a wellbore structure that connects horizontal and vertical wells. Casing cementing and completion are performed, followed by staged fracturing in the horizontal section to connect to a larger reservoir area. Gas production is then achieved through drainage and depressurization via the vertical well. Horizontal well cementing often involves filling the vertical well with sand and installing a screen pipe and blind plug at the end of the horizontal well. A 1.5–3 m gap is maintained between the horizontal well casing and the vertical well casing to prevent interference from the horizontal well casing with the vertical well pump.

[0003] This method has shortcomings in cementing and drainage processes. Because the cement slurry in the cementing section of a horizontal well has a higher specific gravity, if leakage occurs to varying degrees in the vertical well, the cement slurry can enter the vertical well cavity, causing the horizontal and vertical wells to be unable to connect under eccentric connection conditions. Simultaneously, due to the distance between the horizontal well casing and the vertical well cavity, this section is an open-hole section, serving as the throat section for connecting wells. Blockage in this section will significantly impact gas production, requiring horizontal well workover, which is extremely costly and causes considerable damage to the wellbore.

[0004] Although the technology for connecting horizontal and vertical wells has improved, enabling precise connection between them by drilling through cement plugs to achieve connection after cementing, it does not solve the problem of unprotected open holes in the connecting section between horizontal and vertical wells, and blockages in the throat section still occur frequently. Summary of the Invention

[0005] The purpose of this invention is to provide a completion casing string and method for horizontally connected coalbed methane wells, so as to solve the problem of open hole blockage in the connecting section between horizontal and vertical wells in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A completion casing string based on a horizontally connected coalbed methane well includes a hydraulically rotating guide shoe, and the rear of the hydraulically rotating guide shoe is sequentially connected to a milled casing sub, a float collar, a pressure-blocking and plugging mechanism, a packer, a differential pressure grading collar, and the casing.

[0008] The pressure-blocking mechanism includes a pressure-blocking seat and a sealing plug;

[0009] The front and rear parts of the pressure-holding seat are respectively connected to the floating hoop and the packer; a mounting groove is opened around the front part of the pressure-holding seat, and a spring clamp is installed in the mounting groove. The spring clamp is an open spring ring.

[0010] The inner diameter of the middle part to the rear part of the pressure holding seat gradually increases to form a sealing slope; the front part of the sealing plug is a connecting part, and the middle part is a sealing part; the sealing part of the sealing plug is matched with the sealing slope; a hoop groove is formed on the outer wall of the connecting part of the sealing plug in the circumferential direction, and the spring hoop can enter the hoop groove when the spring hoop is in a natural state;

[0011] The sealing plug can enter the inside of the pressure holding seat, and at this time, the spring hoop enters the hoop groove, and the sealing part of the sealing plug is sealingly attached to the sealing slope of the pressure holding seat.

[0012] The application also has the following characteristics:

[0013] Further, the front and rear parts of the pressure holding seat are respectively screwed with the float collar and the packer.

[0014] Further, at least one sealing washer is arranged on the sealing part of the sealing plug.

[0015] The rear part of the sealing plug is provided with a plurality of reinforcing skirts; the plurality of reinforcing skirts are uniformly distributed along the circumferential direction and the axial direction of the sealing plug and are all inclined rearward.

[0016] The reinforcing skirt is made of elastic material.

[0017] Further, the reinforcing skirt is made of rubber material, and the reinforcing skirt is fixed on the rear part of the sealing plug through nitrile rubber vulcanization.

[0018] The outer diameter of the reinforcing skirt in a free state is at least 10% larger than the inner diameter of the casing, and the reinforcing skirt does not overturn when the pressure is not greater than 5MPa.

[0019] Further, the length of the sealing plug is not less than 2 times the inner diameter of the casing.

[0020] Further, a snap spring retainer is arranged in the mounting groove; and the spring hoop is fixedly installed in the mounting groove through the snap spring retainer.

[0021] A use method of the completion casing string based on the coalbed methane horizontal communication well, which is based on the completion casing string based on the coalbed methane horizontal communication well, and comprises the following steps:

[0022] Step 1, drilling the horizontal well by using a horizontal well drilling tool, and when drilling to a distance of 100-120m from the vertical well, lowering a strong magnetic joint and a communication instrument into the horizontal well and the vertical well respectively;

[0023] When drilling to a distance of 5-8m from the vertical well, the communication instrument in the vertical well is recovered, and the communication operation is carried out until the communication sign appears at the wellhead of the vertical well.

[0024] Step 2, after drilling 5-8m of the horizontal well, a communication verification pipe string is lowered into the vertical well, wherein the lower end of the communication verification pipe string is lowered to 5m below the communication point of the horizontal well and the vertical well;

[0025] Step 3, after adjusting the facing angle of the horizontal well drilling tool, drilling is continued, and it is determined whether the horizontal well drilling tool collides with the communication verification pipe string;

[0026] If not, it indicates that the horizontal well and the vertical well are eccentrically communicated, and slotting operation is performed until the horizontal well drilling tool collides with the communication verification pipe string, so that the horizontal well and the vertical well are directly communicated; after the accurate well depth is determined through the collision position of the communication verification pipe string, step 4 is entered;

[0027] If collision occurs, it indicates that the horizontal well and the vertical well are directly communicated; after the accurate well depth is determined through the collision position of the communication verification pipe string, step 4 is entered;

[0028] Step 4, a casing string is formed by connecting a hydraulic rotary shoe, a milling casing sub, a float collar, a pressure holding plugging mechanism, a packer, a differential pressure grading collar and a casing;

[0029] The casing string is lowered into the horizontal well to the accurate well depth determined in step 3, so that the milling casing sub enters the overlapping well section of the vertical well and the horizontal well;

[0030] Step 5, an external circulating pump is used to circulate the annular area in the casing string until the annular area in the casing string is unobstructed, and then a sealing plug is put into the casing string; the sealing plug continues to move under the pump pressure of the external circulating pump until the spring clamp enters the inside of the clamp groove, and the sealing part of the sealing plug is sealed and fitted with the sealing inclined surface of the pressure holding seat, so that the inner passage of the sealing plug is blocked, and pressure holding is realized;

[0031] Step 6, the external pump truck is used to continuously hold pressure in the casing string until the injection port of the injection mechanism of the packer is opened when the opening pressure of the packer is reached; clean water is injected into the packer, and the pressure in the casing string is continuously held until the closing pressure of the packer is reached, the injection port of the injection mechanism of the packer is closed, and the sealing of the packer is realized;

[0032] Step 7, the external pump truck is used to continuously hold pressure in the casing string until the opening pressure of the differential pressure grading collar is reached; cement slurry is injected into the horizontal well, and the closing plug is lowered into the casing string and then water is injected until it contacts the differential pressure grading collar, and then the pressure is continuously held to the closing pressure of the differential pressure grading collar, so that cementing is completed and setting is waited;

[0033] Step 8, the horizontal well is drilled to remove the hydraulic rotary shoe, the float collar, the pressure holding plugging mechanism, the packer and the differential pressure grading collar, so that the vertical well bore and the horizontal well bore are communicated.

[0034] Further, the outer diameter of the communication verification pipe string in step 2 is not less than the outer diameter of the external drainage pump.

[0035] Further, in step 3, the facing angles of the horizontal well drilling tool are adjusted to 90° and 270° respectively, and then drilling is continued.

[0036] Compared with the prior art, the present application has the following technical effects:

[0037] (I) The completion casing string based on the coalbed methane horizontal communication well of the present application can be directly lowered through the vertical well section, the casing is cut in the vertical well by milling, the horizontal well and the vertical well are communicated, the throat section is protected, and the plugging of the throat section is avoided.

[0038] (II) In the use method of the completion casing string based on the coalbed methane horizontal communication well of the present application, after the horizontal well and the vertical well are communicated, eccentricity verification is performed by the workover string to determine whether the communication point is the direct communication or the eccentric communication, if the communication point is the eccentric communication, the direct communication can be achieved by repeatedly reaming, and the direct relationship between the horizontal well casing string and the vertical well and the specific communication depth are determined.

[0039] (III) The completion casing string based on the coalbed methane horizontal communication well of the present application does not contain a screen pipe in the casing string for achieving the direct communication, and the lower end is connected with a rotating guide shoe; in the process of lowering the casing, the pump circulation and the bottom stirring are achieved, and the problem that the circulation is impossible due to the existence of the screen pipe section in the conventional communication well and the difficulty in lowering the casing are avoided.

[0040] (IV) The completion casing string based on the coalbed methane horizontal communication well of the present application can be directly lowered through the vertical well section, the vertical well is cut by milling, the horizontal section is protected, the lower part of the completion casing string is connected with a drillable packer and a differential pressure grading collar, the cementing above the packer in the horizontal section is achieved, the cement slurry is prevented from entering the vertical well, and the present application is suitable for large-scale use and promotion in industry. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a schematic diagram of the overall structure of the completion casing string based on the coalbed methane horizontal communication well of the present application;

[0042] Figure 2 is a schematic diagram of the cementing effect of the completion casing string based on the coalbed methane horizontal communication well of the present application;

[0043] Figure 3 is a schematic diagram of the pressure holding seat structure in the present application;

[0044] Figure 4 is a schematic diagram of the spring clamp structure in the present application;

[0045] Figure 5is a sealing plug structure schematic diagram in the present application;

[0046] Figure 6 is the overall structure schematic diagram of the casing string adopting the row of the casing short section in one embodiment of the present application.

[0047] The meaning of each reference numeral in the figure is as follows:

[0048] 1, hydraulic rotary shoe; 2, milling casing short section; 3, float collar; 4, packer; 5, differential pressure grading collar; 6, casing; 7, pressure holding seat; 8, sealing plug; 9, mounting groove; 10, spring clamp; 11, sealing bevel; 12, clamp groove; 13, sealing washer; 14, reinforcing skirt; 15, snap spring stop ring. DETAILED DESCRIPTION

[0049] It should be noted that all components in the present application, such as without special instructions, all adopt the components known in the prior art. For example, the hydraulic rotary shoe adopts the commonly known hydraulic rotary shoe.

[0050] The following gives a specific embodiment of the present application, it should be noted that the present application is not limited to the following specific embodiments, any equivalent transformation made on the basis of the technical solutions of the present application falls within the protection scope of the present application.

[0051] As shown in Figure 1 , 3 , 4 and 5, a well completion casing string based on coalbed methane horizontal communication well, comprising a hydraulic rotary shoe 1, the rear of the hydraulic rotary shoe 1 is connected with a milling casing short section 2, a float collar 3, a pressure holding plugging mechanism, a packer 4, a differential pressure grading collar 5 and a casing 6 in sequence;

[0052] The pressure holding plugging mechanism comprises a pressure holding seat 7 and a sealing plug 8;

[0053] The front and rear of the pressure holding seat 7 are connected with the float collar 3 and the packer 4 respectively; a circle of mounting grooves 9 is formed in the front part of the pressure holding seat 7 along the circumference, and a spring clamp 10 is mounted in the mounting groove 9, the spring clamp 10 being an open spring ring;

[0054] The inner diameter of the middle part to the rear part of the pressure holding seat 7 gradually increases, forming a sealing bevel 11; the front part of the sealing plug 8 is a connecting part, and the middle part is a sealing part; the shape of the sealing part of the sealing plug 8 matches the sealing bevel 11; a circle of clamp grooves 12 is formed in the outer wall of the front part of the sealing plug 8 along the circumference, and the spring clamp 10 can enter the inside of the clamp groove 12 when in a natural state;

[0055] The sealing plug 8 can enter the inside of the pressure holding seat 7, at this time the spring clamp 10 enters the inside of the clamp groove 12, and the sealing part of the sealing plug 8 is sealingly attached to the sealing bevel 11 of the pressure holding seat 7.

[0056] In use, the diameter of the clamp groove 12 in the pressure containment seat 7 is larger than the inner diameter of the pressure containment seat 7, and the spring clamp 10 is installed in the clamp groove 12. Since the spring clamp 10 is an open spring ring, it can expand when subjected to impact force and shrink to the natural state when the impact force disappears. In actual work, when the sealing plug 8 enters the pressure containment seat 7, the front part of the sealing plug 8 opens the spring clamp 10. As the sealing plug 10 continues to move forward, the spring clamp 10 enters the clamp groove 12. When the impact force disappears, the spring clamp 10 returns to the natural state and tightens until it completely enters the inside of the clamp groove 12, thereby achieving fixation.

[0057] At this time, since the sealing part and the sealing slope 11 have the same shape, the sealing part of the sealing plug 8 is sealed and attached to the sealing slope 11 of the pressure containment seat 7, and sealing can be achieved under pressure.

[0058] As a preferred solution, the front and rear parts of the pressure containment seat 7 are respectively screwed with the float collar 3 and the packer 4. This can ensure the sealing and connection strength while achieving detachable installation.

[0059] As a preferred solution, a sealing gasket 13 is arranged on the sealing part of the sealing plug 8.

[0060] The rear part of the sealing plug 8 is provided with a plurality of reinforcing skirts 14; the plurality of reinforcing skirts 14 are uniformly distributed along the circumferential direction and the axial direction of the sealing plug 8 and are all inclined rearward.

[0061] The reinforcing skirt 14 is made of elastic material.

[0062] Further preferably, the reinforcing skirt 14 is made of rubber material and is vulcanized and fixed on the rear part of the sealing plug 8 by nitrile rubber.

[0063] The outer diameter of the reinforcing skirt 14 in the free state is at least 10% larger than the inner diameter of the casing 6, and the reinforcing skirt 14 does not overturn when the pressure is not greater than 5 MPa.

[0064] The sealing gasket 13 enhances the sealing performance of the sealing plug 8, and in cooperation with the plurality of reinforcing skirts 14, the sealing plug 8 is not easy to move after entering the pressure containment seat 7, thereby further improving the sealing performance while ensuring the fastening of the connection.

[0065] As a preferred solution, the length of the sealing plug 8 is not less than 2 times the inner diameter of the casing 6, and the angle between the axis of the sealing plug 8 and the axis of the pressure containment seat is not greater than 10° on the premise of meeting the safety through the inner through hole of the grading collar. After the sealing plug 8 moves to the sealing slope 11, the sealing plug 8 can be guided by the sealing slope 11, and then tightly attached to achieve sealing; and the problem of blocking of the sealing plug 8 and the sealing slope 11 caused by the too large angle is avoided.

[0066] Further preferably, the mounting groove 9 is further provided with a snap spring retainer 15; the spring clamp 10 is fixedly installed inside the mounting groove 9 through the snap spring retainer 15.

[0067] The snap spring retainer 15 is connected with the pressure blocking seat 7 through threads, and is axially locked together with the clamp groove 12 to prevent axial movement of the snap spring retainer 15 under axial force.

[0068] A use method of the completion casing string based on the horizontal communication well of coal bed gas, which is based on the completion casing string based on the horizontal communication well of coal bed gas, and comprises the following steps:

[0069] Step 1, drilling the horizontal well by using a horizontal well drilling tool, and drilling to a distance of 100-120 m from the vertical well, and then lowering a strong magnetic joint and a communication instrument into the horizontal well and the vertical well respectively to guide the communication between the horizontal well and the vertical well;

[0070] Wherein, when drilling to a distance of 40-50 m from the vertical well, the inclination and azimuth need to be adjusted in place;

[0071] When drilling to a distance of 5-8 m from the vertical well, the communication instrument in the vertical well is recovered, and the communication operation is carried out until the communication sign appears at the wellhead of the vertical well; wherein, the communication sign includes water spraying, gas spraying and the like, and those skilled in the art can determine the communication sign in combination with the related knowledge in the field and the actual situation on the spot.

[0072] Step 2, after drilling the horizontal well for 5-8 m, a communication verification pipe string is lowered into the vertical well, wherein the lower end of the communication verification pipe string is lowered to a position 5 m downward from the communication point of the horizontal well and the vertical well;

[0073] Step 3, adjusting the facing angle of the horizontal well drilling tool and then continuing to drill, and determining whether the horizontal well drilling tool collides with the communication verification pipe string;

[0074] If not, it indicates that the horizontal well and the vertical well are eccentrically communicated, and the slotting operation is carried out until the horizontal well drilling tool collides with the communication verification pipe string, so as to realize the direct communication between the horizontal well and the vertical well; after determining the accurate well depth through the collision position of the communication verification pipe string, step 4 is entered;

[0075] If yes, it indicates that the horizontal well and the vertical well are directly communicated; after determining the accurate well depth through the collision position of the communication verification pipe string, step 4 is entered;

[0076] Wherein, when adjusting the facing angle of the horizontal well drilling tool, the facing angle of the horizontal well drilling tool is adjusted to 90° and 270° respectively;

[0077] Before the slotting operation, the horizontal well continues to drill for 5-8 m, and the last measuring point is measured, and the communication data is recalculated to determine the positional relationship between the actual well trajectory and the straight well axis. If the straight well axis increases in the azimuth direction, the tool face is adjusted to 220-230°, and repeated slotting operations are performed to use the weight of the drilling tool to reduce the well inclination while rapidly reducing the azimuth until the drilling tool string collides with the verification pipe string; if the straight well axis increases in the azimuth direction, the tool face is adjusted to 130-140°, and repeated slotting operations are performed to use the weight of the drilling tool to reduce the well inclination while rapidly increasing the azimuth until the drilling tool string collides with the verification pipe string.

[0078] Step 4, connecting the hydraulic rotary leading shoe 1, the milling casing short section 2, the float collar 3, the pressure holding plugging mechanism, the packer 4, the differential pressure grading collar 5 and the casing 6 to form a casing string;

[0079] The casing string is lowered into the horizontal well to the accurate well depth determined in step 3, and the milling casing short section 2 enters the straight well and the horizontal well overlapping well section;

[0080] When the casing string encounters resistance during the lowering process, according to the conventional selection, the external circulating pump is started to clean the sand at the bottom of the horizontal well;

[0081] Step 5, using the external circulating pump to circulate for 1-2 cycles, making the annulus in the casing unobstructed, then putting the sealing plug 8, making the sealing plug 8 continue to move under the action of pump pressure until the spring clamp 10 enters the clamp groove 12, the sealing part of the sealing plug 8 and the sealing inclined surface 11 of the pressure holding seat 7 are sealed and fitted, the inner passage of the sealing plug 8 is blocked, and the pressure holding is realized;

[0082] Step 6, using the external pump truck to continuously pressurize the inside of the casing string, until the opening pressure of the packer 4 is reached, the injection inlet of the injection mechanism of the packer 4 is opened and clean water is injected into the packer 4; continue to pressurize the inside of the casing string until the closing pressure of the packer 4 is reached, the injection inlet of the injection mechanism of the packer 4 is closed, and the sealing of the packer 4 is realized;

[0083] Step 7, using the external pump truck to continuously pressurize the inside of the casing string until the differential pressure grading collar 5 opening pressure is reached; when injecting cement slurry again, according to the cementing design, cement slurry meeting the requirements of annulus cementing is injected into the horizontal well, and clean water is injected as a post fluid after the closing plug is lowered into the inside of the casing string, until the closing plug contacts the differential pressure grading collar 5, and then the pressure is continuously increased to the closing pressure of the differential pressure grading collar 5, and the cementing is completed;

[0084] The amount and specific gravity of the cement slurry for cementing are the contents of the conventional cementing design, and are not specially studied in this embodiment; the replacement slurry is used because the amount of cement slurry is enough to cement the annulus, and the clean water post fluid is used as the replacement slurry, which can not only assist in the displacement of the cement slurry in the casing, but also can send the closing plug to the predetermined position of the grading collar to realize the closing of the grading collar.

[0085] Step 8: After the condensation is completed, drill into the horizontal well to remove the hydraulic rotary guide shoe 1, float ring 3, pressure-blocking and plugging mechanism, packer 4, and differential pressure grading ring 5, so as to achieve the connection between the vertical well shaft and the horizontal well shaft.

[0086] Specifically, in step 2, the outer diameter of the connectivity verification pipe string is not less than the outer diameter of the external drainage pump hanger.

[0087] The following is an optional implementation method. In actual operation, there may be situations where horizontal wells and vertical wells cannot be directly connected, such as... Figure 6 As shown, at this time, the milled casing short section 2 in the casing string of this application is replaced with the drainage screen pipe short section, and the hydraulic rotating guide shoe 1 is replaced with the self-rotating guide shoe. In this way, after the cement plug is swept in the horizontal well, the horizontal well and the vertical well can be reconnected, and the entire section of the horizontal well is protected by the screen pipe.

Claims

1. A completion casing string for a horizontally interconnected coalbed methane well, characterized in that, It includes a hydraulic rotating guide shoe (1), and the rear of the hydraulic rotating guide shoe (1) is connected in sequence to a milling sleeve short section (2), a float hoop (3), a pressure-blocking mechanism, a packer (4), a differential pressure grading hoop (5) and a sleeve (6); The pressure-blocking mechanism includes a pressure-blocking seat (7) and a sealing plug (8); The front and rear parts of the pressure seat (7) are connected to the floating hoop (3) and the packer (4) respectively; a mounting groove (9) is opened in the front part of the pressure seat (7) along the circumference, and a spring clamp (10) is installed in the mounting groove (9), and the spring clamp (10) is an open spring ring; The inner diameter of the pressure seat (7) gradually increases from the middle to the rear, forming a sealing slope (11); the front part of the sealing plug (8) is a connecting part, and the middle part is a sealing part; the shape of the sealing part of the sealing plug (8) matches the sealing slope (11); a ring of clamp groove (12) is opened along the circumference on the outer wall of the connecting part of the sealing plug (8), and the spring clamp (10) can enter the clamp groove (12) when it is in the natural state; The sealing plug (8) can enter the pressure seat (7), at which time the spring clamp (10) enters the clamp groove (12), and the sealing part of the sealing plug (8) is sealed and fitted with the sealing slope (11) of the pressure seat (7).

2. The completion casing string based on a horizontally interconnected coalbed methane well as described in claim 1, characterized in that, The front and rear parts of the pressure seat (7) are screwed to the floating hoop (3) and the packer (4) respectively.

3. The completion casing string based on a horizontally interconnected coalbed methane well as described in claim 1, characterized in that, The sealing plug (8) is provided with at least one sealing gasket (13) on its sealing part; The rear part of the sealing plug (8) is provided with a plurality of reinforcing skirts (14); the plurality of reinforcing skirts (14) are evenly distributed along the circumference and axial direction of the sealing plug (8) and are all inclined backward. The reinforced skirt (14) is made of elastic material.

4. The completion casing string based on a horizontally interconnected coalbed methane well as described in claim 3, characterized in that, The reinforcing skirt (14) is made of rubber and is fixed to the rear of the sealing plug (8) by vulcanization of nitrile rubber. The outer diameter of the reinforcing skirt (14) in the free state is at least 10% larger than the inner diameter of the sleeve (6), and the reinforcing skirt (14) does not flip when the pressure is not greater than 5MPa.

5. The completion casing string based on a horizontally interconnected coalbed methane well as described in claim 4, characterized in that, The length of the sealing plug (8) is not less than twice the inner diameter of the sleeve (6).

6. The completion casing string based on a horizontally interconnected coalbed methane well as described in claim 5, characterized in that, The mounting groove (9) is also provided with a retaining ring (15); the spring clamp (10) is fixedly installed inside the mounting groove (9) by the retaining ring (15).

7. A method for using a completion casing string for a horizontally interconnected coalbed methane well, the method being based on the completion casing string for a horizontally interconnected coalbed methane well as described in claim 6, characterized in that... Includes the following steps: Step 1: Use a horizontal well drilling tool to drill the horizontal well. When the drilling reaches 100-120m from the vertical well, lower a strong magnetic connector and a connecting instrument into the horizontal well and the vertical well respectively. When drilling to a distance of 5-8m from the vertical well, retrieve the communication instrument inside the vertical well and carry out the communication operation until the vertical wellhead shows signs of communication. Step 2: After drilling the horizontal well for another 5-8m, run the connection verification string into the vertical well. The lower end of the connection verification string is run 5m below the connection point between the horizontal and vertical wells. Step 3: After adjusting the facing angle of the horizontal well drilling tool, continue drilling and determine whether the horizontal well drilling tool collides with the connection verification string. If not, it indicates that the horizontal well and the vertical well are eccentrically connected. The grooving operation is carried out until the horizontal well drilling tool collides with the connection verification string, realizing the direct connection between the horizontal well and the vertical well. After determining the precise well depth by the collision position of the connection verification string, proceed to step 4. If a collision occurs, it indicates that the horizontal well and the vertical well are directly connected. After verifying the collision location of the pipe string through the connection and determining the precise well depth, proceed to step 4. Step 4: Connect the hydraulic rotary guide shoe (1), milled sleeve short section (2), floating hoop (3), pressure sealing mechanism, packer (4), differential pressure classification hoop (5) and sleeve (6) to form a sleeve string; Run the casing into the horizontal well to the precise well depth determined in step 3, and let the milled casing section (2) enter the overlapping section of the vertical and horizontal wells; Step 5: Use an external circulation pump to circulate the annular area in the bushing string until the annular area in the bushing string is unobstructed, then insert the sealing plug (8); let the sealing plug (8) continue to move forward under the pump pressure of the external circulation pump until the spring clamp (10) enters the clamp groove (12), and the sealing part of the sealing plug (8) seals against the sealing slope (11) of the pressure-blocking seat (7), so that the channel inside the sealing plug (8) is blocked, and pressure is blocked; Step 6: Use an external pump truck to continuously pressurize the inside of the casing string until the opening pressure of the packer (4) is reached, and then the injection port of the injection mechanism of the packer (4) is opened; inject clean water into the packer (4) and continue to pressurize the inside of the casing string until the closing pressure of the packer (4) is reached, and then the injection port of the injection mechanism of the packer (4) is closed, thus achieving the sealing of the packer (4); Step 7: Use an external pump truck to continuously pressurize the casing string until the differential pressure classifier (5) opens; inject cement slurry into the horizontal well, insert the closing plug into the casing string and then inject water until it contacts the differential pressure classifier (5), then continue to pressurize until the differential pressure classifier (5) closes, complete the cementing and wait for it to solidify; Step 8: Drill down into the horizontal well to remove the hydraulic rotating guide shoe (1), float collar (3), pressure sealing mechanism, packer (4) and differential pressure classifying collar (5) to achieve the connection between the vertical well shaft and the horizontal well shaft.

8. The method of using the completion casing string in a horizontally interconnected coalbed methane well as described in claim 7, characterized in that, In step 2, the outer diameter of the connection verification pipe string is not less than the outer diameter of the external drainage pump hanger.

9. The method of using the completion casing string in a horizontally interconnected coalbed methane well as described in claim 7, characterized in that, In step 3, the facing angle of the horizontal well drilling tool is adjusted to 90° and 270° respectively before drilling continues.

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