Coal bed gas straight well deepening wellbore completion device and method

Abstract

This invention belongs to the field of coalbed methane extraction, specifically relating to a well completion device and method for deepening vertical coalbed methane wells. It aims to solve the problems of small casing diameter in deepening old wells, which makes subsequent fracturing and pump installation difficult. The invention includes a bell-shaped inlet, a first short section, a small casing, a check valve, and a second short section. These components are sequentially connected by threads to form a tubular structure. Multiple circulation holes are provided on the first and second short sections. This invention eliminates the traditional hanger structure and adopts a double-layer packer fracturing structure, reducing the risk of sand burial. The construction method is scalable and has good application prospects.

Description

Technical Field

[0001] This invention belongs to the field of coalbed methane extraction, and specifically relates to a wellbore completion device and method for deepening vertical coalbed methane wells. Background Technology

[0002] As development continues, the extraction rate of some major coal seams increases, necessitating the mining of new strata to compensate for the decline in production. Since the lower coal seams also have development potential, the technology of deepening old wells to increase production capacity is adopted to develop the lower potential coal seams, thereby increasing the production of single wells.

[0003] The main reasons for the decline in production or even depletion of production capacity in old wells are the high degree of coalbed methane extraction and the reduction of gas content due to gas drainage during coal mining. Developing potential coal seams by deepening old wells can increase the production capacity of old wells and achieve the goal of increasing single-well production. Furthermore, drilling using old wells can solve the problem of difficult construction in mountainous areas, while saving drilling costs and reducing pollution risks.

[0004] The production casing of coalbed methane vertical wells generally uses an outer diameter of D139.7mm and an inner diameter of 124.2mm. In the existing deep well construction process, it is necessary to first seal the already produced section, but this will cause a loss of production. The completion structure uses devices such as hangers, small casings and check valves. Due to the structural limitations of the hanger, the outer diameter of the small casing can only reach 89mm, which increases the difficulty of fracturing and pumping in the later stage. Summary of the Invention

[0005] To address the challenges of small casing diameter and subsequent fracturing and pumping difficulties in deepening old wells using existing technologies, this invention provides a well completion device for deepening the borehole of a vertical coalbed methane well, comprising a bell mouth, a first short section, a small casing, a check valve, and a second short section.

[0006] The bell mouth, the first short section, the small sleeve, the check valve and the second short section are connected sequentially by threads to form a tubular structure;

[0007] The outer diameter of the flared mouth is not less than 118mm, and the outer diameter of the small sleeve is not less than 110mm;

[0008] The first and second short sections are provided with a plurality of circulation holes, the diameter of which is not less than 1 cm.

[0009] According to some embodiments of this application, a coalbed methane vertical well deepening well completion device is provided, wherein the outer diameter of the bell mouth is 118-120mm.

[0010] According to some embodiments of this application, a well completion device for deepening the borehole of a vertical coalbed methane well is provided, wherein the outer diameter of the small casing is 110-114 mm.

[0011] According to some embodiments of this application, a coalbed methane vertical well deepening well completion device is provided, wherein the first short section and the second short section are provided with 2-3 circulation holes with a diameter of 1-2 cm.

[0012] On the other hand, a method for deepening the borehole of a vertical coalbed methane well is also provided, which uses the aforementioned completion device for deepening the borehole of a vertical coalbed methane well, and specifically includes the following steps:

[0013] S1. Wellbore cleaning: Remove the old wellbore drainage tubing string, clean the old wellbore, the wellbore gauge outer diameter should be no less than 118mm and the length should be 10m, the wellbore should be unobstructed and the sand flushing tubing string should be lowered to flush the sand to the bottom of the original artificial well, so as to achieve a thorough well cleaning.

[0014] S2. Temporary plugging and sealing: Inject soluble temporary plugging agent into the original perforated section to seal the near-wellbore fractures and blast holes, and pass the pressure test;

[0015] The original perforated section of the well is temporarily plugged. A soluble plugging agent is prepared to temporarily plug the upper coal seam. The well washing tubing is then lowered and the soluble plugging agent is injected into the upper coal seam to plug the perforation and near-wellbore fractures. After the pressure test is passed, the next step is carried out.

[0016] S3. Deepening Drilling: Deepening drilling is carried out using a drill bit with an integrated drill-reamerization bit. The outer diameter of the drill bit is ≥116mm, and the well diameter after reaming is 135-140mm. Cuttings logging is carried out during drilling, and logging is carried out after drilling is completed.

[0017] S4. Well completion construction: Run in the well completion equipment. The well completion equipment, from top to bottom, consists of the bell mouth, the first short section, the small casing, the check valve, and the second short section.

[0018] S5. Cementing construction: Run in the cementing string, pressurize and set the packer, slowly inject cement slurry, and after the cement slurry injection is completed, pull out the cementing string and check the cementing quality after it has set.

[0019] S6. Fracturing Operation: A double-layer packer structure is used for fracturing to reduce the risk of sand burial.

[0020] S7. Pump Completion: Run in tubing with an outer diameter of 73mm. The tubing couplings are chamfered to improve maneuverability.

[0021] According to some embodiments of this application, a method for deepening the borehole of a vertical coalbed methane well is provided. In step S3, the drill string assembly used is a 116mm drill bit with integrated drilling and reaming, a 73mm heavy-duty drill pipe, and a 73mm drill pipe.

[0022] According to some embodiments of this application, a method for deepening the borehole of a vertical coalbed methane well is provided. In S5, the cementing string includes tubing and a packer, and the packer is disposed between the circulation holes of the first short section and the circulation holes of the second short section.

[0023] According to some embodiments of this application, a method for deepening the borehole of a coalbed methane vertical well is provided. The fracturing string structure in S6, from top to bottom, consists of: D89mm tubing, hydraulic anchor, K341 packer, D73mm tubing sub, K344 packer, and lower direct injection device.

[0024] The beneficial effects of this invention are:

[0025] This invention solves the problems of small casing diameter and difficult fracturing and pump installation in old wells when deepening the wellbore. It eliminates the traditional hanger structure without affecting the cementing effect, increases the small casing diameter, adopts a double packer fracturing structure to reduce the risk of sand burial, and uses a corresponding wellbore deepening construction method based on the unique completion device. It is scalable and has good application prospects. Attached Figure Description

[0026] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0027] Figure 1 This is a schematic diagram of the overall structure of some embodiments of this application.

[0028] In the diagram: 1. Bell mouth; 2. First short section; 3. Small sleeve; 4. Check valve; 5. Second short section. Detailed Implementation

[0029] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] like Figure 1 As shown, the present invention provides a well completion device for deepening the borehole of a vertical coalbed methane well, comprising a bell mouth 1, a first short section 2, a small casing 3, a check valve 4, and a second short section 5;

[0032] The bell mouth 1, the first short section 2, the small sleeve 3, the check valve 4, and the second short section 5 are connected sequentially by threads to form a tubular structure;

[0033] The outer diameter of the flared mouth 1 is not less than 118mm, and the outer diameter of the small sleeve 3 is not less than 110mm;

[0034] Multiple circulation holes are provided on the first short section 2 and the second short section 5, and the diameter of the circulation holes is not less than 1 cm.

[0035] In practice, the flared end 1 is threaded to the upper part of the first short section, the lower part of the first short section 2 is threaded to the upper part of the small sleeve 3, the lower part of the small sleeve 3 is threaded to the upper part of the check valve 4, the lower part of the check valve 4 is threaded to the upper part of the second short section 5, and the second short section 5 is located at the bottom of the artificial well.

[0036] In practice, the top of the funnel 1 is designed as a funnel to prevent the tubing string from scraping the upper end face of the small casing during later tripping. The circulation hole on the first short section 2 is the upper circulation hole, which is the channel through which cement slurry circulates from the outer annulus of the casing to the inside of the casing during cementing. The small casing 3 provides a stable space for the production tubing string. The circulation hole on the second short section 5 is the lower circulation hole, which is the channel through which cement slurry circulates from the inside of the casing to the outer annulus of the casing during cementing.

[0037] In some embodiments, the outer diameter of the flared mouth 1 is 118-120 mm.

[0038] In some embodiments, the outer diameter of the small sleeve 3 is 110-114 mm.

[0039] In some embodiments, the first short section 2 and the second short section 5 are provided with 2-3 circulation holes with a diameter of 1-2 cm.

[0040] In practice, the outer diameter of the bell mouth is 118-120mm. The purpose is to prevent the casing from scraping the upper end face of the small casing during the later running-in and running-out of the tubing string. The outer diameter of the small casing is D110-114mm. The length of the small casing is determined according to the actual deepening situation. The first short section 2 and the second short section 5 are provided with 2-3 circulation holes with a diameter of 1-2cm to increase the circulation channel of cement slurry during cementing and avoid the problem of pressure buildup caused by the small gap between the two casings during cement slurry circulation.

[0041] On the other hand, a method for deepening the borehole of a vertical coalbed methane well is also provided, which employs a well completion device for deepening the borehole of a vertical coalbed methane well, specifically including the following steps:

[0042] S1. Wellbore cleaning: Remove the old wellbore drainage tubing string, clean the old wellbore, the wellbore gauge outer diameter should be no less than 118mm and the length should be 10m, the wellbore should be unobstructed and the sand flushing tubing string should be lowered to flush the sand to the bottom of the original artificial well, so as to achieve a thorough well cleaning.

[0043] S2. Temporary plugging and sealing: Inject soluble temporary plugging agent into the original perforated section to seal the near-wellbore fractures and blast holes, and pass the pressure test;

[0044] The original perforated section of the well is temporarily plugged. A soluble plugging agent is prepared to temporarily plug the upper coal seam. The well washing tubing is then lowered and the soluble plugging agent is injected into the upper coal seam to plug the perforation and near-wellbore fractures. After the pressure test is passed, the next step is carried out.

[0045] S3. Deepening Drilling: Deepening drilling is carried out using a drill bit with an integrated drill-reamerization bit. The outer diameter of the drill bit is ≥116mm, and the well diameter after reaming is 135-140mm. Cuttings logging is carried out during drilling, and logging is carried out after drilling is completed.

[0046] S4. Well completion construction: Run in the well completion equipment. The well completion equipment, from top to bottom, consists of bell mouth 1, first short section 2, small casing 3, check valve 4, and second short section 5.

[0047] S5. Cementing construction: Run in the cementing string, pressurize and set the packer, slowly inject cement slurry, and after the cement slurry injection is completed, pull out the cementing string and check the cementing quality after it has set.

[0048] S6. Fracturing Operation: A double-layer packer structure is used for fracturing to reduce the risk of sand burial.

[0049] S7. Pump Completion: Run in tubing with an outer diameter of 73mm. The tubing couplings are chamfered to improve maneuverability.

[0050] In some embodiments, the drill string assembly used in S3 is a 116mm drill-reamer integrated drill bit, a 73mm weighted drill pipe, and a 73mm drill pipe.

[0051] In some embodiments, the cementing string in S5 includes tubing and a packer, the packer being disposed between the circulation port of the first sub-section 2 and the circulation port of the second sub-section 5.

[0052] In some embodiments, the fracturing string structure in S6, from top to bottom, consists of: a D89mm tubing, a hydraulic anchor, a K341 packer, a D73mm tubing stub, a K344 packer, and a lower direct injection device.

[0053] In practice, the wellbore is flushed, the old well discharge tubing is pulled out, and the old wellbore is flushed. The wellbore gauge has an outer diameter of 118mm or more and a length of 10m to ensure that the wellbore is unobstructed and to facilitate the lowering of the tubing for the next step. The sand flushing tubing is then lowered to flush the sand to the bottom of the original artificial well, so as to achieve a thorough well flush.

[0054] Temporary plugging and sealing: Although the production capacity of the old coal seam in the upper part of the well is exhausted, a small amount of coalbed methane will still be produced in the coal seam. After fracturing and drainage, the coal seam has developed fractures, which can easily cause well leakage during drilling. In order to prevent the coalbed methane produced by the coal seam from causing safety hazards to subsequent construction, and to avoid drilling fluid from entering the coal seam and causing well leakage and pollution, the blast holes in the original perforated section need to be temporarily plugged before deepening the well. A soluble plugging agent is prepared. The soluble plugging agent is water-soluble. The coal seam is temporarily plugged, and the water-soluble plugging agent is injected into the coal seam by running the well washing string to seal the blast holes and near-wellbore fractures. Only after the pressure test is qualified can the next step be carried out.

[0055] Deepening Drilling: To ensure the smooth completion of subsequent cementing and casing installation, a drill-and-reamer integrated bit with a maximum outer diameter of 116mm or larger is used. After reaming in the deepening section, the wellbore diameter can reach 135-140mm. The drill string assembly consists of a 116mm drill-and-reamer integrated bit, 73mm heavy-duty drill pipe, and 73mm drill pipe. During construction, measures must be taken to prevent collapse and leakage to ensure smooth progress. Cuttings logging will be implemented during drilling, and logging will be conducted after drilling is completed.

[0056] Well completion construction: Run in the well completion equipment. The structure from top to bottom is: bell mouth 1, first short section 2 with upper circulation hole, small casing 3, check valve 4, second short section 5 with lower circulation hole. After the well completion equipment is run in, the bell mouth 1 is 1.0-2.0m above the bottom end of the original casing, and the hole is located 0.5-1.0m below the original casing.

[0057] Cementing operation: Run in the cementing string, which includes several tubing and packers. The packers are located between the upper and lower circulation holes. Pressurize and set the packers. Calculate the amount of cement slurry to be injected and the amount of displacement fluid. Slowly inject the cement slurry. After the cement slurry injection is completed, pull out the cementing string and wait 12 hours for it to set before measuring the cementing quality.

[0058] Fracturing operations: When the cementing section is less than 100m, the cementing section above the coal seam is less than 50m, and the cement slurry has a certain degree of water dilution, it is difficult to cement the entire section. In addition, the connection at the bell mouth 1 is not pressure-bearing, and fracturing is prone to cross-layering. Targeted fracturing technology is required.

[0059] The cementing string structure from top to bottom includes: D89mm tubing, hydraulic anchor, K341 packer (outer diameter 114mm), 1m D73mm tubing stub, K344 packer (outer diameter 92mm) and bottom direct injection.

[0060] The upper part is a K341 packer, and the lower part is a K344 packer. This structure can reduce the risk of sand-buried tubing.

[0061] Pump completion: When the inner diameter of the casing is 100mm, it is not possible to run a pressure gauge. Therefore, the outer diameter of the tubing body is 73mm. The tubing coupling is machined with a chamfer to improve the tubing's throughput.

[0062] In the description of this invention, terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate direction or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0063] Furthermore, it should be noted that, in the description of this invention, 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 mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0064] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent in such process, method, article, or apparatus / device.

[0065] The technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features and device dimensions, and the technical solutions resulting from these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A well completion device for deepening the borehole of a vertical coalbed methane well, characterized in that, It includes a bell mouth (1), a first short section (2), a small sleeve (3), a check valve (4), and a second short section (5); The bell mouth (1), the first short section (2), the small sleeve (3), the one-way valve (4), and the second short section (5) are connected by threads in sequence to form a tubular structure; The outer diameter of the flared mouth (1) is not less than 118 mm, and the outer diameter of the small sleeve (3) is not less than 110 mm; The first short section (2) and the second short section (5) are provided with a plurality of circulation holes, the diameter of which is not less than 1 cm.

2. The well completion device for deepening a vertical coalbed methane well according to claim 1, characterized in that, The outer diameter of the flared mouth (1) is 118-120mm.

3. The well completion device for deepening a vertical coalbed methane well according to claim 1, characterized in that, The outer diameter of the small sleeve (3) is 110-114 mm.

4. A well completion device for deepening a vertical coalbed methane well according to claim 1, characterized in that, The first short section (2) and the second short section (5) are provided with 2-3 circulation holes with a diameter of 1-2 cm.

5. A method for constructing a deeper wellbore in a coalbed methane vertical well, characterized in that, The well completion device for deepening a vertical coalbed methane well according to any one of claims 1-4 specifically includes the following steps: S1. Wellbore cleaning: Remove the old wellbore drainage tubing string, clean the old wellbore, the wellbore gauge outer diameter should be no less than 118mm and the length should be 10m, the wellbore should be unobstructed and the sand flushing tubing string should be lowered to flush the sand to the bottom of the original artificial well, so as to achieve a thorough well cleaning. S2. Temporary plugging and sealing: Inject soluble temporary plugging agent into the original perforated section to seal the near-wellbore fractures and blast holes, and pass the pressure test; The original perforated section of the well is temporarily plugged. A soluble plugging agent is prepared to temporarily plug the upper coal seam. The well washing tubing is then lowered and the soluble plugging agent is injected into the upper coal seam to plug the perforation and near-wellbore fractures. After the pressure test is passed, the next step is carried out. S3. Deepening Drilling: Deepening drilling is carried out using a drill bit with an integrated drill-reamerization bit. The outer diameter of the drill bit is ≥116mm, and the well diameter after reaming is 135-140mm. Cuttings logging is carried out during drilling, and logging is carried out after drilling is completed. S4. Well completion construction: Run in the well completion equipment. The well completion equipment consists of the bell mouth (1), the first short section (2), the small casing (3), the check valve (4), and the second short section (5) from top to bottom. S5. Cementing construction: Run in the cementing string, pressurize and set the packer, slowly inject cement slurry, and after the cement slurry injection is completed, pull out the cementing string and check the cementing quality after it has set. S6. Fracturing Operation: A double-layer packer structure is used for fracturing to reduce the risk of sand burial. S7. Pump Completion: Run in tubing with an outer diameter of 73mm. The tubing couplings are chamfered to improve maneuverability.

6. A method for deepening the borehole of a vertical coalbed methane well according to claim 5, characterized in that, The drilling tool combination used in S3 is a 116mm drill bit with integrated drilling and reaming, a 73mm heavy-duty drill pipe, and a 73mm drill pipe.

7. A method for deepening the borehole of a vertical coalbed methane well according to claim 5, characterized in that, The cementing string in S5 includes tubing and a packer, with the packer positioned between the circulation holes of the first subsection (2) and the circulation holes of the second subsection (5).

8. A method for deepening the borehole of a vertical coalbed methane well according to claim 5, characterized in that, The fracturing string structure in S6, from top to bottom, consists of: D89mm tubing, hydraulic anchor, K341 packer, D73mm tubing stub, K344 packer, and lower direct injection unit.

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