Reinjection water system for coal seam gas well mining

Abstract

The present application provides a reinjection water system for coalbed methane well exploitation, and relates to the field of coalbed methane exploitation process technology. Among them, the reinjection water system for coalbed methane well exploitation includes an oil pipe arranged underground, and a sucker rod arranged inside the oil pipe, the middle part of the sucker rod is a hollow production water channel, and the annulus formed between the oil pipe and the sucker rod is a reinjection water channel; a reinjection water nipple, the reinjection water nipple is installed at the lower end of the oil pipe, used to communicate with the reinjection water channel and guide the reinjection water in the reinjection water channel; a pump nipple, the pump nipple is installed at the lower end of the reinjection water nipple, the pump nipple is connected to the production water channel, and is used to seal the reinjection water channel; a screw pump, the rotor of the screw pump is connected to the pump nipple; a screen pipe, the screen pipe is installed at the lower end of the screw pump; a tail structure, the tail structure is installed at the lower end of the screw pump.

Description

Technical Field

[0001] The present application relates to the technical field of coalbed methane exploitation technology, and in particular to a water reinjection system for coalbed methane well exploitation. Background Art

[0002] As an unconventional energy source, coalbed methane has developed very rapidly in China. With the continuous improvement of technology, L-type horizontal wells are becoming the main production well type in coalbed methane development, and most L-type horizontal wells use screw pumps for drainage. Since coalbed methane wells produce less water, clean water needs to be injected from the ground to bring the coal powder in the well out of the ground. The traditional reinjection water system is to hang an aluminum-plastic pipe on the outside of the oil pipe, and form an external reinjection water pipe through the aluminum-plastic pipe as a reinjection water channel, and the annulus between the sucker rod and the oil pipe as a channel for produced water. However, due to the large inclination of the trajectory of the L-type horizontal well, during the construction process, the external aluminum-plastic pipe is particularly easy to be worn or flattened, and some joints are also very easy to break, so it is often impossible to perform reinjection water operations. Summary of the invention

[0003] The purpose of the embodiment of the present application is to provide a reinjection water system for coalbed methane well mining, so as to solve the problem that the external reinjection water pipe used in the traditional reinjection water system is easy to be damaged, which affects the normal operation of the reinjection water operation.

[0004] In order to solve the above technical problems, the embodiments of the present application provide the following technical solutions:

[0005] In a first aspect, the present application provides a reinjection water system for coalbed methane well exploitation, the reinjection water system for coalbed methane well exploitation comprising: an oil pipe arranged underground, and a sucker rod arranged inside the oil pipe, the middle part of the sucker rod is a hollow produced water channel, and the annulus formed between the oil pipe and the sucker rod is a reinjection water channel;

[0006] A reinjection water nipple, which is installed at the lower end of the oil pipe and is used to communicate with the reinjection water channel to guide the reinjection water in the reinjection water channel;

[0007] A pump upper nipple, the pump upper nipple being installed at the lower end of the reinjection water nipple, the pump upper nipple being communicated with the produced water channel, and being used to seal the reinjection water channel;

[0008] A screw pump, wherein the rotor of the screw pump is connected to the upper nipple of the pump;

[0009] A screen pipe, the screen pipe being installed at the lower end of the screw pump;

[0010] The tail structure is installed at the lower end of the screen tube to achieve tail sealing.

[0011] In some modified embodiments of the first aspect of the present application, the reinjection water nipple is connected to a reinjection water pipe, the water inlet end of the reinjection water pipe is connected to the reinjection water channel, and the water outlet end of the reinjection water pipe extends to a position lower than the screen tube.

[0012] In some modified implementations of the first aspect of the present application, the water outlet end of the reinjection water pipe is at least 2 meters lower than the screen pipe.

[0013] In some modified implementations of the first aspect of the present application, the reinjection water pipe is connected to at least the pump upper nipple, the screw pump and the screen pipe by welding.

[0014] In some modified implementations of the first aspect of the present application, it also includes: a docking nipple, which is installed between the water reinjection nipple and the pump upper nipple to assist the docking of the sucker rod with the rotor of the screw pump.

[0015] In some modified implementations of the first aspect of the present application, it also includes: a release short section for assisting the separation of the sucker rod and the rotor of the screw pump.

[0016] In some modified embodiments of the first aspect of the present application, a coal powder grinding device is provided inside the short section of the pump and at the place connected to the produced water channel, for grinding the coal powder in the produced water before the produced water enters the produced water channel.

[0017] In some modified implementations of the first aspect of the present application, the method further includes: a Christmas tree disposed at a wellhead, the Christmas tree including a production water inlet connected to the production water channel, and a reinjection water inlet connected to the reinjection water channel.

[0018] In some modified implementations of the first aspect of the present application, the tail structure includes a tail pipe and a tail cone disposed at the tail end of the tail pipe, and the tail pipe is connected to the inner cavity of the screen pipe.

[0019] In some modified implementations of the first aspect of the present application, a guide is provided on the sucker rod, and the produced water channel passes through the guide.

[0020] Compared with the prior art, the reinjection water system for coalbed methane well mining provided by the present application uses a hollow sucker rod as a produced water channel, and uses the annulus between the sucker rod and the oil pipe as a reinjection water channel, which solves the problem that the externally mounted reinjection water pipe is often worn and flattened during well repair operations and cannot be used for reinjection water operations. In addition, the cross-sectional area of ​​the produced water channel is significantly reduced, thereby reducing the flow area after the produced water is discharged from the screw pump, significantly increasing the flow rate of the produced water, increasing the ability of the produced water to carry coal powder, so as to bring the coal powder out of the ground, and also eliminating the possibility of coal powder being deposited in the annulus between the sucker rod and the oil pipe, greatly reducing the risk of the sucker rod being stuck due to coal powder deposition. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] By reading the detailed description below with reference to the accompanying drawings, the above and other purposes, features and advantages of the exemplary embodiments of the present application will become easy to understand. In the accompanying drawings, several embodiments of the present application are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0022] Figure 1 The structure diagram of a water reinjection system for coalbed methane well mining provided by an embodiment of the present invention is schematically shown;

[0023] Figure 2 A schematic diagram of the partial structure of a water reinjection system for coalbed methane well mining provided by an embodiment of the present invention is shown;

[0024] Description of Figure Numbers:

[0025] Oil pipe 1, reinjection water channel 101, sucker rod 2, produced water channel 201, reinjection water short section 3, reinjection water pipe 31, pump upper short section 4, screw pump 5, screen tube 6, tail structure 7, tail pipe 71, tail cone 72, docking short section 8, Christmas tree 9, produced water inlet 91, reinjection water inlet 92. DETAILED DESCRIPTION

[0026] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0027] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by technicians in the field to which this application belongs.

[0028] Embodiment 1

[0029] Reference Figure 1 and attached Figure 2 Embodiment 1 of the present invention provides a water reinjection system for coalbed methane well exploitation, the water reinjection system for coalbed methane well exploitation comprising:

[0030] An oil pipe 1 disposed downhole, and a sucker rod 2 disposed inside the oil pipe 1, wherein the middle portion of the sucker rod 2 is a hollow produced water channel 201, and an annulus formed between the oil pipe 1 and the sucker rod 2 is a reinjection water channel 101;

[0031] A water reinjection nipple 3, which is installed at the lower end of the oil pipe 1 and is connected to a water reinjection pipe, and the water inlet end of the water reinjection pipe is connected to the water reinjection channel 101;

[0032] A pump upper subsection 4, which is installed at the lower end of the reinjection water subsection 3, and is communicated with the produced water channel 201, and is used to seal the reinjection water channel 101;

[0033] A screw pump 5, wherein the rotor of the screw pump 5 is connected to the upper short section 4 of the pump;

[0034] A screen tube 6, wherein the screen tube 6 is installed at the lower end of the screw pump 5;

[0035] The tail structure 7 is installed at the lower end of the screen tube 6 to achieve tail sealing.

[0036] Specifically, the reinjection water system proposed in this embodiment is applied to the drainage process of the L-shaped horizontal well of the coal gas layer, and the screw pump 5 is used for drainage. Due to the small amount of water produced, it is necessary to inject clean water to remove the coal powder. The traditional reinjection water system adopts an external aluminum-plastic reinjection water pipe, which forms an external aluminum-plastic reinjection water pipe as a reinjection water channel 101. The annulus between the sucker rod 2 and the oil pipe 1 is used as a channel for produced water. However, the external aluminum-plastic reinjection water pipe often has problems of wear and flattening, which makes the reinjection water system unable to function properly. The coalbed methane well is usually operated normally, resulting in low water production, and the coal powder discharged from each layer cannot be effectively brought out of the ground. To solve the above problems, this embodiment transforms the traditional reinjection water system. The transformed reinjection water system includes: an oil pipe 1 arranged underground, and a sucker rod 2 inside the oil pipe 1. The sucker rod 2 used in this solution is a hollow sucker rod 2, and the hollow channel of the sucker rod 2 is used as the production water channel 201, and the annular channel formed between the oil pipe 1 and the sucker rod 2 is used as the injection water channel 202. The lower end of the oil pipe 1 is provided with a reinjection water nipple 3, a pump nipple 4, a screw pump 5, a screen tube 6 and a tail structure 7 in sequence, wherein the interior of the pump nipple 4 has a sealing structure for sealing the reinjection water channel 101 below the reinjection water nipple 3, i.e., sealing the annulus between the oil pipe 1 and the sucker rod, so that the reinjection water flowing in the reinjection water channel 101 can only be discharged through the reinjection water nipple 3, so as to discharge the reinjection water to the coal seam and increase the water injection amount; and the pump nipple 4 is also used to fix the screw The rotor of the pump 5 can be specifically fixed to the screw pump 5 through two bearings, and at the same time, it can protect the sealing structure between the sucker rod 2 and the oil pipe 1, avoid the dynamic sealing system from being damaged, and improve the overall stability; a screen pipe 6 is installed at the lower end of the screw pump 5. After the reinjection water is injected into the coal seam through the reinjection water pipe, the water and coal powder produced by the coal seam enter the screen pipe 6, and pass through the pump barrel of the screw pump 5 and the short section 4 on the pump to enter the output water channel 201 of the sucker rod 2, and are discharged from the bottom surface along the output water channel 201, see the attached Figure 2 The arrows in the middle indicate the flow direction of produced water and reinjection water.

[0037] This solution uses a hollow sucker rod 2 as the produced water channel 201, and uses the annulus between the sucker rod 2 and the oil pipe 1 as the reinjection water channel 101, replacing the traditional reinjection water pipe hung outside the oil pipe 1, solving the problem that the external reinjection water pipe is often worn and flattened during well repair operations and cannot be used for reinjection water operations. Secondly, by using the hollow sucker rod 2 as the produced water channel 201, compared with the traditional use of the annulus between the sucker rod 2 and the oil pipe 1 as the produced water channel 201, the cross-sectional area of ​​the produced water channel 201 is significantly reduced, thereby reducing the flow area after the produced water is discharged from the screw pump 5, significantly increasing the flow rate of the produced water, increasing the ability of the produced water to carry coal powder, so as to bring the coal powder out of the ground, and also eliminating the possibility of coal powder being deposited in the annulus between the sucker rod 2 and the oil pipe 1, greatly reducing the risk of the sucker rod 2 being stuck due to coal powder precipitation.

[0038] During the specific implementation, the rotor of the screw pump 5 is first connected to the short section 4 on the pump, and then the reinjection water short section 3, the short section on the pump 4, the screw pump 5, the screen pipe 6 and the tail structure 7 are connected together, and then the reinjection water pipe is led out from the reinjection water short section 3, and the reinjection water pipe is fixed. After the above-mentioned short section connection is completed, it is lowered into the well, and then the docking and disconnecting short sections are connected. The oil pipe 1 is connected to pump into the designed depth, and according to the well inclination trajectory, the sucker rod 2 guide is equipped to lower the sucker rod 2 into the well, and after buckling, the sucker rod 2 is lifted to suspend the weight, so that the bearing of the short section 4 on the pump is free from the pressure of the sucker rod 2, and finally the wellhead big four-way, the sucker rod 2 water outlet system and the screw pump 5 drive head are installed, and the pipeline is connected for production.

[0039] According to the above, the embodiment of the present invention proposes a reinjection water system for coalbed methane well mining, which uses the hollow sucker rod 2 as the output water channel 201, and uses the annulus between the sucker rod 2 and the oil pipe 1 as the reinjection water channel 101, which solves the problem that the external reinjection water pipe is often worn and flattened during the well repair operation and cannot be used for reinjection water operation. In addition, the cross-sectional area of ​​the output water channel 201 is significantly reduced, thereby reducing the flow area after the output water is discharged from the screw pump 5, significantly increasing the flow rate of the output water, increasing the ability of the output water to carry coal powder, so as to bring the coal powder out of the ground, and also eliminating the possibility of coal powder being deposited in the annulus between the sucker rod 2 and the oil pipe 1, greatly reducing the risk of the sucker rod 2 being stuck due to coal powder deposition.

[0040] For further information, see Attachment Figure 1 and attached Figure 2 In a specific implementation, the reinjection water short section 3 is connected to a reinjection water pipe 31 , the water inlet end of the reinjection water pipe 31 is connected to the reinjection water channel 101 , and the water outlet end of the reinjection water pipe 31 extends to a position lower than the screen tube 6 .

[0041] Specifically, the external reinjection water pipe 31 used in the traditional reinjection water system cannot extend to a position lower than the screen tube 6. In order to prevent gas from entering the reinjection water system, in the technical solution adopted by the present invention, when designing the reinjection water system, the reinjection water pipe 31 is led out from the reinjection water short section 3, and the water inlet end of the reinjection water pipe 31 is connected to the reinjection water channel 101, and the water outlet end thereof can be set to extend to a position lower than the screen tube 6. When the screen tube 6 is exposed to the water surface, the screw pump 5 stops working, thereby ensuring that the water outlet end of the reinjection water pipe 31 is lower than the screen tube 6. Even when the screw pump 5 is drained, the liquid level can be maintained above the water outlet end of the reinjection water pipe 31, which can ensure that no gas enters the reinjection water system, so that the reinjection water system has no back pressure, which is conducive to the normal operation of the reinjection water system.

[0042] For further information, see Attachment Figure 1 In a specific implementation, the water outlet end of the reinjection water pipe 31 is at least 2 meters lower than the screen tube 6.

[0043] Specifically, in the technical solution adopted by the present invention, the outlet end of the reinjection water pipe 31 can be set at a position at least two meters lower than the screen tube 6, which can reliably ensure that the outlet end of the reinjection water pipe 31 is always below the liquid surface, but is not limited to this and can be set according to actual conditions.

[0044] For further information, see Attachment Figure 1 and attached Figure 2 In a specific implementation, the reinjection water pipe 31 is connected to at least the pump upper nipple 4, the screw pump 5 and the screen pipe 6 by welding.

[0045] Specifically, in order to achieve the reliability of fixing the reinjection water pipe 31, in the technical solution adopted by the present invention, the reinjection water pipe 31 can be a steel pipe fitting, and its extension trajectory is consistent with the connection and extension trajectory of the reinjection water short section 3, the pump short section 4, the screw pump 5, the screen tube 6, and the tail structure 7, and the reinjection water pipe 31 can be welded to the pump short section 4, the screw pump 5 and the screen tube 6.

[0046] For further information, see Attachment Figure 1 In a specific implementation, the reinjection water system for coalbed methane well exploitation proposed in this embodiment also includes: a docking short section 8, which is installed between the reinjection water short section 3 and the pump upper short section 4, and is used to assist the docking of the sucker rod 2 with the rotor of the screw pump 5. A release short section is also provided at the position of the docking short section 8, which is used to assist the separation of the sucker rod 2 from the rotor of the screw pump 5.

[0047] Specifically, in order to facilitate the construction process, in the technical solution adopted by the present invention, during the specific construction, since the short sections such as the reinjection water short section 3, the pump short section 4 and the screw pump 5 are lowered into the well before the oil pipe 1 and the sucker rod 2, and when the sucker rod 2 is lowered to connect with the rotor of the screw pump 5, it is necessary to use the docking short section 8 to quickly connect the sucker rod 2 and the rotor of the screw pump 5, and to seal well; and when the drainage is completed and the sucker rod 2 needs to be pulled out, the hand-off short section can be used, and the hand-off short section can be two shear pins set at the position of the docking short section 8, so as to pull out the sucker rod 2.

[0048] Furthermore, in a specific implementation, a coal powder grinding device is provided inside the pump upper short section 4 and at the place connected to the produced water channel 201 , for grinding the coal powder in the produced water before the produced water enters the produced water channel 201 .

[0049] Specifically, in order to facilitate the production water to bring the coal powder out of the ground, in the technical solution adopted by the present invention, a coal powder grinding device is also provided inside the pump upper short section 4, and the coal powder grinding device is used to further grind and crush the coal powder, so as to improve the convenience of the production water to bring the coal powder out of the ground. The coal powder grinding device is arranged at the connecting position between the pump upper short section 4 and the production water channel 201, and can be ground and crushed before the coal powder enters the production water channel 201. The production water channel 201 in the middle of the sucker rod 2 is relatively thin. After the coal powder is further ground, the possibility of the coal powder settling in the production water channel 201 and the possibility of the pump being stuck in the subsequent circulation can be reduced. The coal powder grinding device can be realized by using a rotatable grinding screen tube 6 in cooperation with the lower screen tube 6, the external screen tube 6 is fixed, and the grinding screen tube 6 rotates synchronously with the screw pump 5. Through the interaction of the two screen tubes 6, the rotation of the grinding screen tube 6 is utilized to complete the further grinding of the coal powder, so that the coal powder is ground more thoroughly, but the specific structure of the coal powder grinding device is not limited thereto.

[0050] For further information, see Attachment Figure 1 In a specific implementation, the reinjection water system for coalbed methane well exploitation proposed in this embodiment also includes: an oil production tree 9 arranged at the wellhead, and the oil production tree 9 includes a production water inlet 91 connected to the production water channel 201, and a reinjection water inlet 92 connected to the reinjection water channel 101.

[0051] Specifically, since the present solution adopts the hollow sucker rod 2 as the produced water channel 201, and utilizes the annulus between the sucker rod 2 and the oil pipe 1 as the reinjection water channel 101, the circulation mode of the reinjection water and the produced water of the traditional reinjection water system is changed. Therefore, in addition to improving the downhole structure, the technical solution adopted by the present invention also includes improvements to the wellhead Christmas tree 9, specifically, adding a produced water inlet 91 and a reinjection water inlet 92. The produced water inlet 91 is connected to the produced water channel 201, which can facilitate the staff to collect the produced water for subsequent separation, coal powder sedimentation and other operations. The reinjection water inlet 92 is connected to the reinjection water channel 101, so as to control the injection of the reinjection water from the well.

[0052] For further information, see Attachment Figure 1 and attached Figure 2 In a specific implementation, the tail structure 7 includes a tail pipe 71 and a tail cone 72 arranged at the tail end of the tail pipe 71 , and the tail pipe 71 is connected to the inner cavity of the screen pipe 6 .

[0053] Specifically, in the technical solution adopted by the present invention, the tail structure 7 may include a tail pipe 71 and a tail cone 72 at its tail end. The tail cone 72 can seal the entire pipe column. At the same time, since the tail cone 72 itself has a certain curvature, it can also play a guiding role. The tail pipe 71 is connected to the inner cavity of the screen pipe 6, and can receive a portion of the larger particles of precipitated coal powder that are not brought out by the produced water, and can be brought out of the ground in subsequent operations.

[0054] Furthermore, in a specific implementation, a guide is provided on the sucker rod 2, and the produced water channel 201 passes through the guide.

[0055] Specifically, the reinjection water system proposed in this embodiment is applied to the drainage process of the L-shaped horizontal well in the coal gas layer, and the sucker rod 2 has a certain hardness, making it difficult to bend. In the technical solution adopted by the present invention, by setting a guide, on the one hand, the direction of the sucker rod 2 can be changed through the guide so that it can adapt to the horizontal well. On the other hand, the produced water channel 201 can pass through the guide so that the produced water and coal powder can pass through the guide to be brought out of the ground.

[0056] It should be noted that in the description of this specification, the terms "upper", "lower", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention; the terms "connect", "install", "fixed", etc. should be understood in a broad sense, for example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0058] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A water reinjection system for coalbed methane well mining, applied to the drainage process of L-shaped horizontal wells in coalbed methane layers, characterized in that: include: An oil pipe arranged downhole, and a sucker rod arranged inside the oil pipe, the middle part of the sucker rod is a hollow produced water channel, and the annulus formed between the oil pipe and the sucker rod is a reinjection water channel; A reinjection water nipple, which is installed at the lower end of the oil pipe and is used to communicate with the reinjection water channel to guide the reinjection water in the reinjection water channel; A pump upper nipple, the pump upper nipple being installed at the lower end of the reinjection water nipple, the pump upper nipple being connected to the produced water channel and used to seal the reinjection water channel, wherein a coal powder grinding device is provided inside the pump upper nipple and at a location connected to the produced water channel, for grinding coal powder in the produced water before the produced water enters the produced water channel; A screw pump, wherein the rotor of the screw pump is connected to the upper nipple of the pump; A screen pipe, the screen pipe being installed at the lower end of the screw pump; A tail structure, which is installed at the lower end of the screen tube and is used to achieve tail sealing; The reinjection water nipple is connected to a reinjection water pipe, a water inlet end of the reinjection water pipe is in communication with the reinjection water channel, and a water outlet end of the reinjection water pipe extends to a position lower than the screen tube.

2. The water reinjection system for coalbed methane well mining according to claim 1, characterized in that: The water outlet end of the reinjection water pipe is at least 2 meters lower than the screen pipe.

3. The water reinjection system for coalbed methane well mining according to claim 1, characterized in that: The reinjection water pipe is connected to at least the pump upper nipple, the screw pump and the screen pipe by welding.

4. The water reinjection system for coalbed methane well mining according to claim 1, characterized in that: Also includes: A docking nipple is installed between the water reinjection nipple and the pump upper nipple to assist the docking of the sucker rod and the rotor of the screw pump.

5. The water reinjection system for coalbed methane well mining according to claim 4, characterized in that: Also includes: The release nipple is used to assist in separating the sucker rod from the rotor of the screw pump.

6. The water reinjection system for coalbed methane well mining according to claim 1, characterized in that: Also includes: A Christmas tree is arranged at a wellhead, and the Christmas tree comprises a production water inlet connected to the production water channel, and a reinjection water inlet connected to the reinjection water channel.

7. The water reinjection system for coalbed methane well mining according to claim 1, characterized in that: The tail structure includes a tail pipe and a tail cone arranged at the tail end of the tail pipe, and the tail pipe is communicated with the inner cavity of the screen pipe.

8. The water reinjection system for coalbed methane well mining according to claim 1, characterized in that: A guide is provided on the sucker rod, and the produced water channel passes through the guide.

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