A friction reducing and resistance reducing device for a drill string

Abstract

The application provides a friction-reducing and resistance-reducing device for a drill string, which comprises an outer cylinder, an inner cylinder inserted into the outer cylinder, a first channel for fluid flow defined in the inner cylinder, a second channel provided in the outer cylinder and communicated with the first channel, the outer cylinder being axially movable along the inner cylinder, and an elastic member for fixing the relative position of the outer cylinder and the inner cylinder. A vane is arranged in the second channel, and the fluid flow can drive the vane to rotate in the second channel, so that a pulse pressure is generated in the second channel when the fluid flows, and the inner cylinder is pushed to reciprocate along the axis to overcome the elastic force of the elastic member.

Description

Technical Field

[0001] This invention relates to the field of oilfield development, and more specifically to a friction-reducing and resistance-reducing device for drill strings. Background Technology

[0002] Improving the drilling efficiency of the drill string is one of the most pressing issues to be addressed during oil well drilling.

[0003] Currently, common approaches and methods for improving drill string drilling efficiency mainly include the following: First, adjusting drilling fluid properties to reduce drilling friction by increasing drilling fluid pressure and cutter carry efficiency. Second, strengthening wellbore stability and wellbore trajectory through cementing measures. Third, improving drilling efficiency by optimizing drill string assembly. Fourth, using various drag-reducing tools to lower drill string friction.

[0004] Currently used drag reduction tools mainly include roller-type drag reduction tools and non-rotating drag reduction joints. These devices have problems such as limited application conditions and insignificant drag reduction effects. Downhole vibration drag reduction tools are needed, but new hydraulic oscillation drag reduction tools can effectively solve these problems, thus gaining field acceptance and widespread application. However, existing hydraulic oscillators have high requirements for hydraulic conditions and are not suitable for oil wells with insufficient hydraulic pressure. They also generate significant pressure loss, making them unsuitable for long, deep wells. Summary of the Invention

[0005] To address the technical problems described above, this invention aims to provide a friction-reducing and drag-reducing device for drill strings. The friction-reducing and drag-reducing device for drill strings of this invention has low pressure loss, making it suitable for deep oil wells, and requires lower pressure conditions, making it suitable for oil wells with insufficient downhole hydraulic pressure.

[0006] According to the present invention, a friction-reducing and resistance-reducing device for a drill string is provided, comprising: an outer cylinder and an inner cylinder inserted into the outer cylinder, a first channel for fluid flow defined in the inner cylinder, a second channel communicating with the first channel in the outer cylinder, the outer cylinder being movable along the axial direction of the inner cylinder, and an elastic member for fixing the relative position of the outer cylinder and the inner cylinder.

[0007] An impeller is provided in the second channel. The impeller can be driven by the fluid to rotate in the second channel, thereby generating pulse pressure in the second channel when the fluid flows through it. This pressure pushes the inner cylinder to overcome the elastic force of the elastic element and reciprocate relative to the outer cylinder along the axial direction.

[0008] In a preferred embodiment, a pressure amplifier is further provided at the end of the outer cylinder away from the inner cylinder, and the pressure amplifier is configured as a Helmholtz resonant cavity.

[0009] In a preferred embodiment, a flow guide is further provided on the side of the impeller near the pressure amplifier, the flow guide being constructed as a boss protruding from the inner wall of the second channel.

[0010] In a preferred embodiment, the guide member is provided with an arc surface adapted to the impeller.

[0011] In a preferred embodiment, an oil injection hole penetrating the outer wall of the outer cylinder is also provided on the outer cylinder body.

[0012] In a preferred embodiment, an exhaust hole penetrating the outer wall of the outer cylinder is also provided on the outer cylinder body.

[0013] In a preferred embodiment, a second step portion is formed on the outer wall of the inner cylinder, and a chamfer is formed on the second step portion.

[0014] In a preferred embodiment, an anti-impact cover is also provided at the end of the outer cylinder near the inner cylinder, and a sealing ring is also provided between the anti-impact cover and the outer wall of the outer cylinder.

[0015] In a preferred embodiment, the outer cylinder and the inner cylinder are connected by a spline.

[0016] In a preferred embodiment, a protective slip ring is further provided between the inner cylinder and the outer cylinder, and the fixed end of the elastic element is connected to the protective slip ring. Attached Figure Description

[0017] The invention will now be described with reference to the accompanying drawings.

[0018] Figure 1 A schematic diagram of a friction-reducing and resistance-reducing device for a drill string according to an embodiment of the present invention is shown.

[0019] In this application, all drawings are schematic and are used only to illustrate the principles of the invention, and are not drawn to scale. Detailed Implementation

[0020] The invention will now be described with reference to the accompanying drawings.

[0021] Figure 1 A friction-reducing and drag-reducing device 100 for a drill string according to an embodiment of the present invention is shown. The friction-reducing and drag-reducing device 100 for a drill string is for connection to a drill string (not shown) and is lowered into the oil well along with the drill string. Figure 1As shown, the friction-reducing and resistance-lowering device 100 for drill strings includes an outer cylinder 10 and an inner cylinder 20. The inner cylinder 20 is inserted into the outer cylinder 10, allowing the outer cylinder 10 to move axially relative to the inner cylinder 20. Simultaneously, an elastic element 22 is provided axially between the outer cylinder 10 and the inner cylinder 20 to keep them relatively fixed.

[0022] like Figure 1 As shown, the inner cylinder 20 is tubular, and a first channel 25 for fluid flow is defined within the inner cylinder 20. Simultaneously, a second channel 15 communicating with the first channel is provided within the outer cylinder 10. Therefore, when the inner cylinder 20 is inserted into the outer cylinder 10, fluid can flow from the first channel 25 to the second channel 15.

[0023] Meanwhile, an impeller 30 is provided in the second channel 15. The impeller 30 can impede the normal flow of fluid in the second channel 25, thereby generating a force in the second channel 15 that is opposite to the direction of fluid flow. When the inner cylinder 20 is inserted into the second channel 15, this force generated by the fluid will overcome the elastic force of the elastic element 22, pushing the inner cylinder 20 to move away from the impeller 30, thereby increasing the length of the entire friction reduction and drag reduction device 100.

[0024] In this invention, the impeller 30 is arranged in the second channel 15 along a direction parallel to the axial direction of the inner cylinder 20. This arrangement allows the impeller 30 to rotate as fluid flows through it. As the impeller 30 rotates within the second channel 15, the effective diameter of the second channel 15 changes periodically. It is easy to understand that as the effective diameter of the second channel 15 changes periodically, the fluid pressure flowing through the second channel 15 also changes periodically. This allows the fluid to generate periodically changing pulse pressures within the second channel 15.

[0025] As the pressure generated by the fluid in the second channel 15 increases, this pressure pushes the inner cylinder 10 in the second channel 15 away from the impeller 30. As this process proceeds, the elastic element 22 is gradually stretched until the elastic force of the elastic element 22 equals the pressure exerted by the fluid on the inner cylinder 20.

[0026] When the pressure exerted by the fluid on the inner cylinder 20 reaches its maximum value, the elastic force of the elastic element 22 also reaches its maximum value. At this time, as the impeller 30 continues to rotate, the effective diameter of the second channel 15 will gradually increase, and the fluid pressure in the second channel 15 will gradually decrease. At this time, the elastic force of the elastic element 22 will be greater than the fluid pressure in the second channel 15, and the elastic element 22 will push the inner cylinder 20 to move closer to the impeller 30 until the fluid pressure in the second channel 15 reaches its minimum value.

[0027] It is easy to understand that as the impeller 30 rotates continuously in the second channel 15 under the drive of the fluid, it will continuously push the inner cylinder 20 to make periodic reciprocating motion along the axial direction, causing the length of the friction reduction and drag reduction device 100 for the drill string of the present invention to change periodically.

[0028] As the length of the friction-reducing and drag-reducing device 100 for the drill string changes periodically, it drives the drill string downhole to reciprocate along the axial direction, causing the drill string to vibrate continuously along the axial direction. With this continuous vibration, the friction between the drill string and the wellbore is effectively reduced, achieving the effect of friction reduction and drag reduction. Compared to traditional hydraulic oscillation devices, the impeller drive method, which generates pulsed pressure in the fluid, has higher transmission efficiency and can effectively reduce fluid pressure loss.

[0029] like Figure 1 As shown, in a preferred embodiment, a pressure amplifier 40 is further provided at the end of the outer cylinder away from the inner cylinder. The pressure amplifier 40 is preferably configured as a Helmholtz resonant cavity. The fluid in the second channel 15 enters the Helmholtz resonant cavity after passing through the impeller 30, causing the fluid to resonate within the cavity. This resonance effect amplifies the alternating pressure generated by the fluid, thereby increasing the fluid pressure on the inner cylinder 20. Thus, through the amplification effect of the pressure amplifier 40, the hydraulic pressure requirements of the friction-reducing and drag-reducing device 100 can be reduced, making the device suitable for applications with lower hydraulic pressure.

[0030] It should be noted that this Helmholtz resonant cavity is a common device in actual production operations, and its detailed description will be omitted here.

[0031] In a preferred embodiment, a flow guide 50 is further provided on the side of the impeller 30 near the pressure amplifier 40. The flow guide 50 is constructed as a boss 52 protruding from the inner wall of the first channel 25. When fluid passes through the impeller 30, it first passes through the flow guide 50 and then flows into the pressure amplifier 40. The flow guide 50 can concentrate the fluid and prevent the fluid from being dispersed by the impeller 30 after flowing through it, thereby reducing the pulse pressure generated by the fluid.

[0032] Meanwhile, the upper end face 55 of the guide member 50 adjacent to the impeller is constructed as an arc surface 55 adapted to the impeller 30. This allows the fluid to enter the pressure amplifier 40 through the arc surface after flowing past the impeller 30, and the arc surface 55 can reduce the energy loss of the fluid when flowing through the guide member 50.

[0033] like Figure 1 As shown, in a preferred embodiment, the outer cylinder 10 is further provided with oil injection holes 12 penetrating the outer wall of the outer cylinder 10. Lubricating oil can be injected into the small radial gap (not shown) between the outer cylinder 10 and the inner cylinder 20 through the oil injection holes 12, thereby reducing the friction between the inner cylinder 20 and the outer cylinder 10, which is more conducive to the axial movement of the inner cylinder 20 and the outer cylinder 10. Simultaneously, injecting lubricating oil also helps to reduce sliding wear between the inner cylinder 20 and the outer cylinder 10, thereby increasing the service life of the inner cylinder 20 and the outer cylinder 10.

[0034] Furthermore, an exhaust port 14 penetrating the outer wall of the outer cylinder 10 is also provided on the outer cylinder body 10. The exhaust port 14 can discharge gas in the small radial gap between the outer cylinder body 10 and the inner cylinder body 20 during the oil injection process, preventing gas from creating pressure and hindering the injection of lubricating oil. At the same time, the discharge of gas by the exhaust port 14 also helps to improve the airtightness of the friction reduction and drag reduction device 100.

[0035] In a preferred embodiment, a second step 24 is formed on the outer wall of the inner cylinder 20. The second step 24 can abut against the outer cylinder 10 after relative movement occurs between the outer cylinder 10 and the inner cylinder 20, thereby providing a limiting effect and hindering relative movement between the outer cylinder 10 and the inner cylinder 20. Simultaneously, a chamfer 241 is also formed on the second step 24. The chamfer 241 can reduce the impact wear on the outer cylinder 10 when the second step 24 collides with it, thereby increasing the service life of the outer cylinder 10.

[0036] In a preferred embodiment, an anti-impact cover 17 is further fitted onto the end of the outer cylinder 10 near the inner cylinder 20. The anti-impact cover 17 is constructed as a cover fitted onto the outer cylinder 10. The anti-impact cover 17 is preferably made of an elastic material, so that when the second step portion 24 collides with the outer cylinder 10, it absorbs the impact load brought by the impact through elastic deformation, thereby reducing the damage to the outer cylinder 10 and the second step portion 24.

[0037] Meanwhile, a sealing ring 19 is also provided between the anti-impact cover 17 and the outer wall of the outer cylinder 10. The sealing ring 19 is sleeved on the outer wall of the outer cylinder 10 to seal the gap between the anti-impact cover 17 and the outer cylinder 10, thereby further improving the sealing performance of the friction reduction and resistance reduction device 100 for drill strings of the present invention.

[0038] In addition, in this invention, the outer cylinder 10 and the inner cylinder 20 are connected by a spline. This spline connection allows the outer cylinder 10 and the inner cylinder 20 to rotate synchronously without affecting their axial movement, thus preventing them from separating during drilling operations due to asynchronous rotation.

[0039] In a preferred embodiment, a protective slip ring 60 is further provided radially between the inner cylinder 20 and the outer cylinder 10. The protective slip ring 60 is constructed as a ring fitted onto the outer wall of the inner cylinder 20, and the fixed end of the elastic element 22 is connected to the protective slip ring 60. The protective slip ring 60 is made of a colloidal material with a certain degree of elasticity, which can generate a buffering effect, reducing the impact on the elastic element 22 during the relative movement of the inner cylinder 20 and the outer cylinder 10 along the axis and during radial vibration, thereby improving the service life of the elastic element 22.

[0040] The working process of the friction reduction and resistance reduction device 100 for drill string according to the present invention is briefly described below.

[0041] During oil drilling, the friction reduction and resistance reduction device 100 for the drill string of the present invention is connected to the drill string and is lowered into the oil well along with the drill string.

[0042] When the high-pressure drilling fluid flows through the drill string to the impeller 30 in the second channel 15, the impeller 30 obstructs the normal flow of fluid within the second channel 15, thereby generating a force opposite to the fluid flow direction within the second channel 15. This force pushes the inner cylinder 20 away from the elastic force of the elastic element 22, moving it away from the impeller 30. Simultaneously, as the fluid flows to the impeller 30, it drives the impeller 30 to rotate, thus periodically changing the effective diameter of the second channel 15.

[0043] As the effective diameter of the second channel 15 changes periodically, the pressure of the fluid also changes continuously, thus generating periodically varying pulse pressure. This pressure overcomes the elastic force of the elastic element 22, causing the inner cylinder 20 to reciprocate axially relative to the outer cylinder 10. When the fluid flows to the pressure amplifier 40, the pressure amplifier 40 also generates a resonance effect, amplifying this pulse pressure.

[0044] As the inner cylinder 20 reciprocates relative to the outer cylinder 10 along the axial direction, the length of the friction reduction and resistance reduction device 100 will also change periodically, thereby causing the drill string connected to the friction reduction and resistance reduction device 100 to vibrate axially and reduce the friction during the drilling process.

[0045] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A friction reducing device (100) for a drill string, comprising: an outer cylinder (10) and an inner cylinder (20) inserted into the outer cylinder, a first channel (25) for fluid flow being defined in the inner cylinder, a second channel (15) being provided in the outer cylinder and communicating with the first channel, the outer cylinder being axially movable along the inner cylinder, and an elastic member (22) for fixing the relative position of the outer cylinder and the inner cylinder, wherein an impeller (30) is provided in the second channel, the impeller being driven by fluid to rotate in the second channel, thereby generating a pulsating pressure in the second channel when fluid flows therethrough, pushing the inner cylinder to reciprocate axially relative to the outer cylinder against the elastic force of the elastic member, a pressure amplifier (40) is further provided at the end of the outer cylinder away from the inner cylinder, the pressure amplifier being configured as a Helmholtz resonator, a flow guide (50) is further provided on the side of the impeller close to the pressure amplifier, the flow guide being configured as a boss protruding from the inner wall of the second channel, when fluid passes through the impeller, it will first pass through the flow guide and then be collected by the flow guide into the pressure amplifier.

2. The friction reducing device (100) for a drill string according to claim 1, characterized in that An arc surface (55) is provided on the flow guide and adapted to the impeller.

3. A friction reducing device (100) for a drill string according to claim 1 or 2, characterized in that, An oil injection hole (12) is further provided in the outer cylinder.

4. A friction reducing device (100) for a drill string according to claim 1 or 2, characterized in that, An exhaust hole (14) is further provided in the outer cylinder.

5. A friction reducing device (100) for a drill string according to claim 1 or 2, characterized in that, A second step portion (24) is configured on the outer wall of the inner cylinder, and a chamfer (241) is configured on the second step portion.

6. A friction reducing device (100) for a drill string according to claim 1 or 2, characterized in that, A pressure-proof cover (17) is further provided on the end of the outer cylinder close to the inner cylinder, and a sealing ring (19) is further provided between the pressure-proof cover and the outer wall of the outer cylinder.

7. A friction reducing device (100) for a drill string according to claim 1 or 2, characterized in that, The outer cylinder and the inner cylinder are connected by splines.

8. A friction reducing device (100) for a drill string according to claim 1 or 2, characterized in that, A protection slip ring (60) is further provided between the inner cylinder and the outer cylinder, and the fixed end of the elastic member is connected to the protection slip ring.

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