A ball drill for shale gas horizontal wells

Abstract

The present invention discloses a ball drill tool for shale gas horizontal wells, which includes a drill pipe formed by connecting a number of drill pipe bodies. Drill pipe male couplings and drill pipe female couplings are respectively arranged at both ends of the drill pipe body. A plurality of ball mounting positions are provided on each drill pipe body, and multiple rows of balls are arranged at each ball mounting position. Each row of balls has at least 10 balls, and each row of balls is spirally ascending along the axial direction of the drill pipe body; the diameters of the balls in each row have two specifications, namely large-diameter balls and small-diameter balls, and the large-diameter balls and the small-diameter balls are alternately arranged. The hardness of the ball material is less than the hardness of the drill tool body material; there are multiple spirally ascending protrusions on the drill pipe body, and flow channels are formed between adjacent protrusions, and multiple rows of balls are respectively arranged on the protrusions. The present invention has the advantages of small friction, easy tripping in and out, and safe use when in use.

Description

Technical Field

[0001] The present invention relates to the technical field of shale gas extraction equipment, and particularly relates to a ball drill for horizontal shale gas wells. Background Art

[0002] Shale gas refers to natural gas extracted from shale formations and is an important unconventional natural gas resource. The global resource reserve is approximately 456 trillion m3, which is twice that of conventional natural gas resources. According to expert estimates, the recoverable shale gas resources in China are approximately 26 trillion m3, mainly distributed in oil and gas bearing basins such as Sichuan, Ordos, Turpan-Hami, Tarim, and Junggar. The development of shale gas in China is still in its initial stage, and the current investment scale is not very large.

[0003] According to the prediction of the Ministry of Land and Resources, by 2020, the annual output of domestic shale gas will reach 15 - 30 billion m3, and by 2030, it will reach 110 billion m3. By then, shale gas will account for 25% of China's total natural gas production. Shale gas mainly faces problems in extraction technology. Due to the good compactness and very low permeability of shale gas, the production of shale gas is very low under the same wellbore extraction conditions as conventional oil and gas. To increase the production of shale gas, horizontal wells are usually used for extraction. The cost of horizontal wells is 1.5 - 2.5 times that of vertical wells, but the initial extraction rate, controlled reserves, and ultimately evaluated recoverable reserves are 3 - 4 times that of vertical wells. Horizontal wells have a greater chance of intersecting with natural fractures and artificially induced fractures (mainly vertical fractures) in the shale formation, and can better keep the fractures in the target section of the reservoir. Statistical results show that when the horizontal section is 200 m or longer, the chance of encountering fractures is dozens of times more than that of vertical wells, significantly improving the flow condition of reservoir fluids. The application of horizontal well technology can effectively and economically develop shale gas reservoirs with few or no fracture channels.

[0004] In actual extraction, during the drilling process of horizontal shale gas wells and extended reach wells, the drill pipe lies flat on the lower wellbore wall. The friction between the drill pipe and the wellbore wall is sliding friction. During the drilling process of the drill pipe, the transfer of drilling pressure is insensitive, with large fluctuations, difficult to feed the drill, and low drilling speed. During the directional process, due to the reduced efficiency of drilling pressure transfer, it is difficult to position the directional tool face, and the drill string needs to be repeatedly moved up and down. During the tripping process, the drill string closely adheres to the lower wellbore wall with large friction, making it difficult to trip in and out, and prone to sticking accidents. Summary of the Invention

[0005] The purpose of the present invention is to overcome the disadvantages in the prior art that the friction between the drill pipe and the wellbore wall is prone to occur, resulting in insensitive transfer of drilling pressure, large fluctuations, difficult feed of the drill, low drilling speed, and large friction between the drill string and the lower wellbore wall during the tripping process, difficult tripping in and out, and prone to sticking accidents, and to provide a ball drill for horizontal shale gas wells, which has the advantages of small friction, easy tripping in and out, and safe use when in use.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A ball drill for shale gas horizontal wells includes a drill pipe composed of a plurality of drill pipe bodies connected. Drill pipe male collars and drill pipe female collars are respectively arranged at both ends of the drill pipe body. A plurality of ball mounting positions are arranged on each drill pipe body. Multiple rows of balls are arranged at each ball mounting position. Each row of balls has at least 10 balls. Each row of balls spirally ascends along the axial direction of the drill pipe body; there are two specifications for the diameters of the balls in each row, namely large-diameter balls and small-diameter balls. The large-diameter balls and the small-diameter balls are arranged alternately. The hardness of the ball material is less than the hardness of the drill tool body material; the drill pipe body has a plurality of spirally ascending protrusions, and flow channels are formed between adjacent protrusions. Multiple rows of balls are respectively arranged on the protrusions.

[0008] Further optimization: There are four ball mounting positions, two of which are respectively located near the drill pipe male collar and the drill pipe female collar, and the other two are located at the thickened parts of the drill pipe body.

[0009] Further optimization: The large-diameter balls protrude 2 - 5 mm above the protrusions, and the diameter ratio of the large-diameter balls to the small-diameter balls is 2:1.7 - 1.9.

[0010] Among them, the large-diameter balls protrude 3 mm above the protrusions, and the diameter ratio of the large-diameter balls to the small-diameter balls is 2:1.8.

[0011] Among them, the drill pipe body is provided with an installation groove. The installation groove spirally ascends along the axial direction of the drill pipe body. A spirally ascending mounting seat is installed in the installation groove. After the mounting seat is installed, it forms the protrusion. A ball mounting groove is arranged on the mounting seat. An arc surface that fits the surface of the large-diameter ball is arranged on the side wall of the ball mounting groove. The large-diameter balls and the small-diameter balls are installed in the ball mounting groove.

[0012] Among them, the mounting seat is installed in the installation groove by means of bolts or welding.

[0013] Further optimization: A diversion groove is arranged on the arc surface on the side wall of the ball mounting groove.

[0014] Among them, the drill pipe bodies are connected by a flexible connector. The flexible connector is provided with a female thread and a male thread for connecting with the drill pipe male collar and the drill pipe female collar.

[0015] Further defined: The flexible connector is a vulcanized rubber elastic joint.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] When the present invention comes into contact with the downhole wall of a horizontal well, the ball bearings replace the sliding friction between a common drill pipe and the downhole wall with rolling friction, greatly reducing the frictional resistance of the drill pipe in the wellbore, enabling smooth tripping in a long horizontal shale gas well section, sensitive and efficient weight-on-bit during drilling, and achieving the purpose of accelerating shale gas drilling and reducing downhole risks in horizontal wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0020] Figure 2 For the present invention Figure 1 It is a partial enlarged view at location A in the present invention.

[0021] Figure 3 It is a schematic diagram of the structure of the drill pipe body described in the present invention.

[0022] Figure 4 It is an exploded view of the drill pipe body and the flexible connector described in the present invention.

[0023] Figure 5 It is a schematic diagram of the structure of the mounting groove on the drill pipe body described in the present invention.

[0024] Figure 6 It is an exploded view of the drill pipe body and the mounting seat described in the present invention.

[0025] Reference numerals: 1 - drill pipe body, 2 - male drill pipe coupling, 3 - female drill pipe coupling, 4 - ball bearing installation position, 5 - ball bearing, 6 - large-diameter ball bearing, 7 - small-diameter ball bearing, 8 - mounting groove, 9 - mounting seat, 10 - ball bearing mounting groove, 11 - flexible connector, 12 - female thread, 13 - male thread. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The present invention will be further described below in conjunction with embodiments. The described embodiments are only a part of the embodiments of the present invention, not all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0027] Embodiment 1

[0028] This embodiment discloses a ball drill for shale gas horizontal wells, which includes a drill pipe composed of a plurality of drill pipe bodies 1 connected. Drill pipe male collars 2 and drill pipe female collars 3 are respectively arranged at both ends of the drill pipe body 1. A plurality of ball mounting positions 4 are arranged on each drill pipe body 1. Multiple rows of balls 5 are arranged at each ball mounting position 4. Each row of balls has at least 10 balls 5. Each row of balls 5 is spirally ascending along the axial direction of the drill pipe body 1. The diameters of the balls 5 in each row have two specifications, namely large-diameter balls 6 and small-diameter balls 7. The large-diameter balls 6 and the small-diameter balls 7 are alternately arranged. The hardness of the material of the balls 5 is less than the hardness of the material of the drill tool body. The drill pipe body 1 has a plurality of spirally ascending protrusions, and a flow channel is formed between adjacent protrusions. Multiple rows of balls 5 are respectively arranged on the protrusions.

[0029] By arranging the balls 5 on the drill pipe body 1, the friction between the drill pipe body 1 and the drilling well wall can be greatly reduced. Moreover, in the present invention, by arranging protrusions on the drill pipe body 1, a flow channel is formed between adjacent protrusions. In this way, not only can the contact area between the drill pipe body 1 and the drilling well wall be reduced, but also the mud formed during the early drilling process can flow in the flow channel, which can cool the contact part between the drill pipe body 1 and the drilling. When the mud flows between the drill pipe body 1 and the drilling well wall, it can also play a certain protective role for the drill pipe body 1.

[0030] In the present invention, a plurality of ball mounting positions 4 are arranged on the drill pipe body 1. Multiple rows of balls 5 are arranged at each ball mounting position 4. Each row of balls 5 has at least 10 balls 5. Each row of balls 5 is spirally ascending along the axial direction of the drill pipe body 1. When the drill pipe body 1 is in the well, a plurality of support points will be formed, which can disperse the pressure between the drill pipe body 1 and the drilling well wall. At the same time, the balls 5 can provide good support for the drill pipe body 1. Multiple rows of balls 5 are arranged in a spirally ascending manner on the drill pipe body 1. In this way, during the drilling process, it is convenient for the slurry to be discharged and will not affect the flow of the slurry, which can effectively reduce the pressure of the slurry on the drill pipe body 1. More importantly, the slurry can flow spirally in the formed flow channel, which can reduce the resistance of the balls 5 to the mud after adding the balls 5, making the drill pipe body 1 more stable during use and reducing the fluctuation of the drill pipe. At the same time, it can also avoid reducing the rotation speed of the drill pipe body 1.

[0031] The diameters of the balls 5 in each row have two specifications, namely large-diameter balls 6 and small-diameter balls 7. The large-diameter balls 6 and the small-diameter balls 7 are alternately arranged. The hardness of the material of the balls 5 is less than the hardness of the material of the drill tool body. In this way, it can be ensured that the small-diameter balls 7 can play a transitional role when the present invention is in use, making the large-diameter balls 6 easier to roll and reducing the situation of the large-diameter balls 6 getting stuck.

[0032] In this embodiment, there are four ball mounting positions 4, two of which are located near the male coupling 2 and the female coupling 3 of the drill rod, and the other two are located at the thickened part of the drill rod body 1; the force can be dispersed, and a better supporting effect can be provided to the drill rod body.

[0033] Further optimization, the large diameter ball 6 is 2-5 mm higher than the protrusion, and the diameter ratio of the large diameter ball 6 to the small diameter ball 7 is 2:1.7-1.9; in this embodiment, the large diameter ball 6 is 3 mm higher than the protrusion, and the diameter ratio of the large diameter ball 6 to the small diameter ball 7 is 2:1.8.

[0034] In this way, in actual use, the distance between the large diameter ball 6 and the borehole wall can be made more appropriate; at the same time, the diameter ratio of the large diameter ball 6 to the small diameter ball 7 is 2:1.8, which further ensures the smooth rotation of the large diameter ball 6 during use.

[0035] Example 2

[0036] This embodiment is further optimized on the basis of embodiment 1. In this embodiment, the drill rod body 1 is provided with a mounting groove 8, which rises in a spiral along the axial direction of the drill rod body 1. A mounting seat 9 in a spiral shape is installed in the mounting groove 8. After the mounting seat 9 is installed, the protrusion is formed. A ball mounting groove 10 is provided on the mounting seat 9. The side wall of the ball mounting groove 10 is provided with an arc surface that fits the surface of the large diameter ball 6. The large diameter ball 6 and the small diameter ball 7 are installed in the ball mounting groove 10. The small diameter ball 7 is installed in the ball mounting groove 10 in an active state, but it will not fall out of the ball mounting groove 10.

[0037] The small-diameter ball 7 can move in the ball installation groove 10 but will not escape from the ball installation groove 10 .

[0038] The mounting seat 9 is mounted in the mounting groove 8 by means of bolts.

[0039] In this way, in actual use, the mounting seat 9 is installed in the mounting groove 8, and then fixed to the drill rod body 1 by bolts; when the mounting seat 9 or the ball 5 is worn, the drill rod body 1 can be reused. In actual use, only the mounting seat 9 needs to be replaced. The disassembly and assembly process is convenient, which facilitates the reuse of the drill rod body 1.

[0040] Example 3

[0041] This embodiment is further optimized on the basis of the embodiment 2. In this embodiment, a guide groove is provided on the arc surface on the side wall of the ball mounting groove 10; the guide groove is a groove or a strip groove provided on the arc surface.

[0042] In actual use, it is possible to avoid the large-diameter ball 6 from tightly fitting with the arc surface after getting wet, and the diversion groove provided can ensure that the contact area between the large-diameter ball 6 and the arc surface is small, enabling the large-diameter ball 6 to rotate normally.

[0043] In actual use, the drill pipe bodies 1 are connected through a flexible connector 11, and the flexible connector 11 is provided with a female thread 12 and a male thread 13 for connecting with the drill pipe male collar 2 and the drill pipe female collar 3.

[0044] Among them, the flexible connector 11 is a vulcanized rubber elastic joint; the vulcanized rubber elastic joint has the property of high temperature resistance and will not change the advancing direction of the drill tool due to the influence of the high-temperature downhole environment.

[0045] The present invention realizes the connection of the drill pipe bodies 1 through the provided flexible connector 11, which can enable the drill pipe bodies 1 to have better steering performance after connection; thereby enabling the drill tool to deflect at any angle; and ensuring the torque transmission between adjacent drill pipe bodies 1.

[0046] Embodiment 4

[0047] This embodiment is basically the same as Embodiment 2, and the difference lies in that the mounting seat 9 is installed in the mounting groove 8 by welding.

[0048] In this way, the mounting seat 9 can be fixed more tightly and will not fall off during the drilling process.

[0049] Embodiment 5

[0050] This embodiment is a further optimization based on Embodiment 3. In this embodiment, the inside of the large-diameter ball 6 is in a hollow state; this can reduce the weight of the large-diameter ball 6, and then when the drill tool body is in the horizontal section, the weight of the drill pipe body 1 pressing on the drilling wellbore is lighter, which can effectively reduce the friction between the large-diameter ball 6 and the drilling wellbore, and can effectively slow down the wear degree of the large-diameter ball 6; and extend the service life of the drill tool.

[0051] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention. The above description is only for the preferred embodiments of the present invention and is not intended to limit the present invention. It should be noted that any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A ball drill for shale gas horizontal wells, comprising drill pipes connected by a number of drill pipe bodies. Characterized in that: Drill pipe male collars and drill pipe female collars are respectively arranged at both ends of the drill pipe body. A number of ball installation positions are arranged on each drill pipe body. Multiple rows of balls are arranged at each ball installation position. Each row of balls has at least 10 balls. Each row of balls is spirally rising along the axial direction of the drill pipe body. The diameters of the balls in each row have two specifications, namely large-diameter balls and small-diameter balls. The large-diameter balls and small-diameter balls are alternately arranged. The hardness of the ball material is less than the hardness of the drill tool body material. The drill pipe body has multiple spirally rising protrusions. Flow channels are formed between adjacent protrusions. Multiple rows of balls are respectively arranged on the protrusions. The drill pipe body is provided with an installation groove. The installation groove spirally rises along the axial direction of the drill pipe body. A spirally rising mounting seat is installed in the installation groove. After the mounting seat is installed, it forms the protrusion. A ball installation groove is arranged on the mounting seat. An arc surface that fits the surface of the large-diameter ball is arranged on the side wall of the ball installation groove. The large-diameter balls and small-diameter balls are installed in the ball installation groove. The small-diameter balls are installed in the ball installation groove in a movable state and will not fall out of the ball installation groove. The mounting seat is installed in the installation groove, and then the mounting seat is fixed to the drill pipe body by bolts. When the mounting seat or the balls are worn, the drill pipe body can be reused. A diversion groove is arranged on the arc surface on the side wall of the ball installation groove. The diversion groove is a groove or strip groove arranged on the arc surface. To prevent the large-diameter balls from being tightly attached to the arc surface after getting wet, the arranged diversion groove can ensure that the contact area between the large-diameter balls and the arc surface is small, so that the large-diameter balls can rotate normally. The inside of the large-diameter ball is in a hollow state, reducing the weight of the large-diameter ball. When the drill tool body is in the horizontal section, the weight of the drill pipe body pressing on the drilling well wall is lighter, which can effectively reduce the friction between the large-diameter balls and the drilling well wall and effectively slow down the wear degree of the large-diameter balls. Extend the service life of the drill tool.

2. A ball drill for shale gas horizontal wells according to claim 1, Characterized in that: There are four ball installation positions, two of which are respectively located near the drill pipe male collar and the drill pipe female collar, and the other two are located at the thickened parts of the drill pipe body.

3. A ball drill for shale gas horizontal wells according to claim 1, Characterized in that: The large-diameter balls protrude 2 - 5 mm above the protrusions. The diameter ratio of the large-diameter balls to the small-diameter balls is 2:1.7 - 1.

9.

4. A ball drill for shale gas horizontal wells according to claim 3, Characterized in that: The large-diameter balls protrude 3 mm above the protrusions. The diameter ratio of the large-diameter balls to the small-diameter balls is 2:1.

8.

5. A ball drill for shale gas horizontal wells according to claim 1, Characterized in that: The mounting seat is installed in the installation groove by bolts or welding.

6. A ball drill for shale gas horizontal wells according to any one of claims 1 - 5, Characterized in that: The drill pipe bodies are connected by a flexible connector, and the flexible connector is provided with female and male threads for connecting with the drill pipe male coupling and the drill pipe female coupling.

7. A ball drill tool for shale gas horizontal wells according to claim 6, characterized in that: The flexible connector is a vulcanized rubber elastic joint.

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