Swirl generator

Abstract

The present invention discloses a swirl generator, which is mainly composed of a central shaft, a one-way valve, an outer shell, a rotor, a stator, and a flow guide body; wherein: an annular groove is provided on the outer periphery of the central shaft, a bypass hole is provided on the upper part, and a leakage hole is provided on the lower part of the central shaft; the outer shell is wrapped on the annular groove of the central shaft and forms a rotational fit with the central shaft, and an annular driving cavity is formed between the outer shell and the central shaft, and the annular driving cavity is respectively connected with the bypass hole and the leakage hole at the upper and lower parts; the one-way valve is arranged in the bypass hole; the rotor and the stator are arranged in an annular driving cavity formed between the outer shell and the central shaft, and the rotor is fixed on the inner wall of the outer shell, and the stator is fixed on the outer wall of the central shaft; the flow guide body is arranged on the outer surface of the outer shell. The swirl generator can fully meet the cementing process requirements of domestic vertical wells, directional wells, horizontal wells and complex structure wells, and is a new type of tool with simple structure, convenient operation, low cost, safety and reliability.

Description

Technical Field

[0001] The invention relates to a downhole tool in the fields of oil and gas drilling, coal bed gas drilling, geological exploration, mine drilling and the like, in particular to a swirl generator. Background Art

[0002] After the drilling and completion operation is completed, in order to ensure the stability of the wellbore and the safety and smoothness of subsequent construction operations, casing must be lowered into the wellbore and cement must be injected into the annulus between the casing and the well wall. After the cement solidifies, a stable wellbore is formed. During the cementing process, after the casing is lowered into the wellbore, cement slurry is injected from the casing mouth and returned from the bottom of the casing into the annulus between the casing and the wellbore wall. As the cement slurry is continuously injected, the cement slurry displaces the drilling fluid in the annulus out of the wellbore. The traditional method is one-dimensional axial flow displacement. The conventional method has the following shortcomings: (1) The flow velocity in the annulus near the wellbore wall is low, and the drilling fluid has a high adhesion. High adhesion requires high flow rate displacement. High flow rate displacement requires high energy consumption, which is limited by pump pressure and formation pressure bearing capacity; (2) The wellbore is irregular and the wellbore wall is jagged and uneven. Conventional one-dimensional axial flow can easily cause drilling fluid backflow, resulting in drilling fluid retention; (3) The lower casing string is often difficult to replace due to insufficient displacement.

[0003] In response to the above problems, a lot of research work has been carried out at home and abroad, and a variety of displacement methods have been proposed and corresponding tools have been developed. The main purpose is to overcome the shortcomings of one-dimensional axial flow in displacement. The spiral flow displacement method is based on the one-dimensional axial flow displacement and then applies the circumferential shear carrying effect, which is conducive to the clean displacement of the drilling fluid in the wellbore annulus. Conventional methods for generating spiral flow:

[0004] One is to rotate the casing string while injecting cement slurry, but it requires a high rotation torque, which makes on-site construction difficult and risky. For example: the liquid cyclone generator disclosed in Chinese patent publication number CN2406060Y. This cyclone generator consists of a body, a cyclone guide belt, a guide groove and a fixing bolt. Four guide grooves are evenly welded on the body along the circumference, and a cyclone guide belt is embedded in each guide groove. The three screw holes at the upper and lower ends of the body are respectively screwed with fixing bolts. When in use, the upper and lower fixing bolts of the device body are loosened and sleeved on the casing body, and then the bolts are tightened to go down to the lower end of the larger part of the wellbore with the casing string, so that the cyclone sheet contacts the well wall to form a cyclone flow channel. When the liquid passes through, the liquid can form a rotating flow to fully drive the liquid in the wellbore, forming a cyclone effect, so as to achieve the purpose of improving the displacement efficiency. In order to ensure that the cyclone generator is in the center position in the wellbore, it can be equipped with a centralizer at the top and bottom. The swirl generator has two specifications, φ177.8 and φ139.7, and the swirl length that can be formed during operation is generally 20-40m. During cementing operations, 1-6 swirl generators of corresponding specifications can be selected according to the well diameter and the length of the large well diameter section in the wellbore.

[0005] The second is to use a swirl straightener. Although it is easy to use and has low risks, the swirl energy is small, the wellbore length that can produce the swirl effect is short, and the ability to replace drilling fluid is limited. For example: China Patent Publication No. CN109138861A discloses a "Swirl Straightening Tool for Mud Cake Scraping of Cement Slurry Swirl Generator", which includes a rubber spiral wing seat and a rigid spiral wing fixed on the outer wall of the outer sleeve, and a rubber spiral wing fixed on the rubber spiral wing seat. There are 4 rubber spiral wing seats and rigid spiral wings, which are fixed on the outer sleeve at intervals. The rubber spiral wing seat includes a left base and a right base, and the left base and the right base are L-shaped in cross-section, symmetrically welded on the outer sleeve to form a slideway; the rubber spiral wing is T-shaped in cross-section, and its bottom edge is placed in the slideway and fixed by screws.

[0006] Therefore, it is urgent to develop a vortex generator that not only meets the requirements of conventional cementing technology, but also can generate large energy spiral flow, so as to give full play to the technical advantages of spiral flow replacement drilling fluid. At the same time, it must also be safe and reliable, simple in structure and easy to maintain. Summary of the invention

[0007] The purpose of the present invention is to give full play to the technical advantages of spiral flow displacement of drilling fluid, and to provide a vortex generator that can further improve the cementing quality without changing the existing cementing process and equipment, generate a spiral flow with greater energy, and give full play to the role of spiral flow displacement of drilling fluid.

[0008] The technical solution adopted by the present invention to solve its technical problem is:

[0009] A swirl generator is mainly composed of a central shaft, a one-way valve, an outer shell, a rotor, a stator, and a flow guide; wherein: the outer periphery of the central shaft is provided with an annular groove, a bypass hole is provided at the upper part, and a leakage hole is provided at the lower part of the central shaft; the outer shell is wrapped around the annular groove of the central shaft and forms a rotational fit with the central shaft, an annular driving cavity is formed between the outer shell and the central shaft, and the annular driving cavity is respectively connected to the bypass hole and the leakage hole at the upper and lower parts; the one-way valve is arranged in the bypass hole; the rotor and the stator are arranged in an annular driving cavity formed between the outer shell and the central shaft, and the rotor is fixed on the inner wall of the outer shell, and the stator is fixed on the outer wall of the central shaft; the flow guide is arranged on the outer surface of the outer shell.

[0010] The above scheme further comprises:

[0011] A bearing A is installed at a joint between the upper portion of the outer shell and the central shaft, and a bearing B is installed at a joint between the lower portion of the outer shell and the central shaft.

[0012] The bearing A is installed at the radial joint of the outer shell and the central shaft, and the bearing B is installed at the axial joint of the outer shell and the central shaft.

[0013] The bearing A is a rolling bearing, and the bearing B is a thrust bearing.

[0014] The upper section of the annular groove of the central shaft is a tapered surface, and the bypass hole is arranged on the tapered surface section.

[0015] The bottom of the annular groove of the central shaft is a plane, and the leakage hole is axially arranged along the annular driving cavity between the outer shell and the central shaft.

[0016] The bypass holes are multiple and evenly distributed.

[0017] There are multiple leakage holes that are evenly distributed; or the leakage holes are annular hole structures as a whole.

[0018] The guide body is a spiral wing structure.

[0019] There are 2 to 6 spiral wings, which are evenly distributed on the outer shell.

[0020] The working principle of the swirl generator of the present invention:

[0021] The swirl generator is installed at the lower end of the casing string and is lowered into the wellbore with the casing string. During the cementing process, the cementing fluid passes through the bypass hole and the one-way valve of the central axis and enters the driving chamber between the outer shell and the central axis. Since the rotor is installed on the inner wall of the outer shell and the stator is installed on the outer wall of the central axis, under the action of the high-pressure cementing fluid, the rotor starts to rotate and drives the outer shell to rotate at a high speed. The cementing fluid enters the annulus after passing through the leakage hole and returns upward. Due to the high-speed rotation of the outer shell and the processing of the diversion body on the outer wall, the cementing fluid returns from the inside of the annulus to the outside. Under the driving force of the high-speed rotation of the outer shell, a spiral flow will be generated. With the continuous injection of cementing fluid, the cementing fluid in the annulus will return upward in the form of a spiral flow.

[0022] The swirl generator has a high rotation speed, that is, the initial velocity of the spiral flow is high and the energy is high. Therefore, compared with the conventional spiral flow method, it can extend upward for a longer distance, so the efficiency of replacing the original drilling fluid in the annulus is also higher, and the cementing quality is better. The swirl generator converts the liquid kinetic energy of the cementing fluid injected into the casing into the mechanical energy of the high-speed rotation of the outer shell, and then drives the cementing fluid in the annulus to generate a high-speed upward spiral flow, that is, the mechanical energy is converted into liquid kinetic energy. Through the optimized design of the flow channel, rotor, and stator structure, the energy loss can be minimized and the mechanical efficiency of the swirl generator can be improved.

[0023] Field tests have shown that the swirl generator can fully meet the technological requirements of cementing construction. Application data analysis shows that the excellent cementing quality rate is an average of 95.6%-166% higher than that of conventional cementing methods, especially in the cementing process of deep wells, ultra-deep wells, small wellbores and wells with complex structures. The cementing quality has been greatly improved and met the design requirements.

[0024] Compared with the prior art, the beneficial effects of the present invention are: the rotation speed of the swirl generator is high, that is, the initial velocity of the spiral flow is large and the energy is high, the spiral flow extends upward for a longer distance, and the annulus displacement efficiency is higher; the liquid kinetic energy of the cementing fluid injected into the casing string is converted into the mechanical energy of the high-speed rotation of the outer shell, and then the annulus cementing fluid is driven to generate a high-speed upward spiral flow, thereby minimizing energy loss and improving the mechanical efficiency of the swirl generator; it also has the characteristics of simple structural design, reliable performance, convenient operation and low cost, and is convenient for large-scale promotion and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the half-section structure of the swirl generator of the present invention.

[0026] Figure 2 yes Figure 1 Section view along section AA.

[0027] In the figure, 1-central axis, 2-bearing A, 3-bypass hole, 4-check valve, 5-outer casing, 6-rotor, 7-stator, 8-guiding body, 9-bearing B, 10-leakage hole. DETAILED DESCRIPTION

[0028] The present invention will be described in detail below with reference to the accompanying drawings.

[0029] Example 1

[0030] A swirl generator, comprising a central shaft 1, a one-way valve 4, an outer shell 5, a rotor 6, a stator 7, and a guide body 8; wherein: the outer periphery of the central shaft 1 is provided with an annular groove, the upper part is provided with a bypass hole 3, and the lower part of the central shaft 1 is provided with a leakage hole 10. The outer shell 5 is wrapped around the annular groove of the central shaft 1 and forms a rotational fit with the central shaft 1. An annular driving cavity is formed between the outer shell 5 and the central shaft 1, and the annular driving cavity is connected to the bypass hole 3 and the leakage hole 10 respectively. Figure 1 The part of the central axis 1 with the annular groove is a closed structure, ensuring that the fluid can only flow along the bypass hole 3 and the annular drive cavity to the leakage hole 10. The one-way valve 4 is arranged in the bypass hole to prevent the fluid from flowing in the opposite direction. The rotor 6 and the stator 7 are arranged in the annular drive cavity formed between the outer shell 5 and the central axis 1, and the rotor 6 is fixed on the inner wall of the outer shell 5, and the stator 7 is fixed on the outer wall of the central axis 1. The stator and the rotor form a high-speed rotation match under the drive of the fluid. The flow guide 8 is arranged on the outer surface of the outer shell 5, and the outer shell and the flow guide are driven to rotate synchronously by the rotation of the rotor, so that the fluid outside the sleeve generates upward rotational energy.

[0031] Example 2

[0032] Based on Example 1, the invention further comprises:

[0033] A bearing A2 is installed at the joint between the upper portion of the outer shell 5 and the central axis 1 , and a bearing B9 is installed at the joint between the lower portion of the outer shell 5 and the central axis 1 .

[0034] The bearing A2 is installed at the radial joint between the outer shell 5 and the central shaft 1 , and the bearing B9 is installed at the axial joint between the outer shell 5 and the central shaft 1 .

[0035] Bearing A is a rolling bearing and bearing B is a thrust bearing.

[0036] Example 3

[0037] Based on Example 1 or 2, further comprising:

[0038] The upper section of the outer annular groove of the central shaft 1 is a conical surface or an arc surface, and the bypass hole 3 is arranged on the conical surface or the arc surface section. This design better solves the force of the fluid on the rotor.

[0039] The bottom of the annular groove outside the central shaft 1 is a plane, and the leakage hole 10 is axially arranged along the annular driving cavity between the outer shell 5 and the central shaft 1 to increase the patency of the flow channel.

[0040] There are multiple bypass holes 3, which are specifically determined according to factors such as hole size, fluid flow, casing diameter, pressure, etc., and are evenly distributed.

[0041] There are multiple leakage holes 10, and the number and aperture size are specifically set according to needs and are evenly distributed; or the leakage holes 10 directly adopt an integral ring hole structure.

[0042] The flow guide 8 is a spiral wing structure, which can refer to the spiral wing structure in the reference document. The number of the flow guide 8 is 2-6, preferably 2, and is evenly distributed on the outer shell.

[0043] Typical embodiment 4

[0044] See attached Figure 1 and 2 The swirl generator is mainly composed of a central shaft 1, a bearing 2, a bypass hole 3, a one-way valve 4, an outer shell 5, a rotor 6, a stator 7, a guide body 8, and a leakage hole 10. The bypass hole 3 is processed on the upper part of the central shaft 1, and the one-way valve 4 is installed in the bypass hole 3. The rotor 6 is installed on the inner wall of the outer shell 5, and the stator 7 is installed on the outer wall of the central shaft 1. The bearing 2 is installed between the upper part of the outer shell 5 and the central shaft 1, the guide body 8 is processed on the outer wall of the outer shell 5, the leakage hole 10 is processed on the lower part of the central shaft 1, and the bearing 9 is installed between the lower part of the outer shell 5 and the lower part of the central shaft 1.

[0045] Furthermore, in order to increase the airtightness between the outer shell 5 and the central shaft 1 , a seal is added to the joint portion thereof, or a sealed bearing is used.

[0046] The swirl generator is installed at the bottom of the casing string and is lowered into the wellbore with the casing string. During the cementing process, the cementing fluid passes through the bypass hole 3 and the one-way valve 4 of the central axis 1 and enters the chamber between the outer shell 5 and the central axis 1. The swirl generator has a screw or turbine drive structure. Since the rotor 6 is installed on the inner wall of the outer shell 5 and the stator 7 is installed on the outer wall of the central axis 1, under the action of the high-pressure cementing fluid, the rotor 6 starts to rotate and drives the outer shell 5 to rotate at a high speed. The cementing fluid passes through the leakage hole 10 and enters the annulus and returns upward. Since the outer shell 5 rotates at a high speed and the guide body 8 is processed on the outer wall, while the cementing fluid returns upward in the annulus, a spiral flow will be generated under the driving force of the high-speed rotation of the outer shell 5. With the continuous injection of cementing fluid, the cementing fluid in the annulus will return upward in the form of a spiral flow.

[0047] The swirl generator has a high rotation speed, that is, the initial velocity of the spiral flow is high and the energy is high. Therefore, compared with the conventional spiral flow method, it can extend upward for a longer distance, so the efficiency of replacing the original drilling fluid in the annulus is also higher, and the cementing quality is better. The swirl generator converts the liquid kinetic energy of the cementing fluid injected into the casing into the mechanical energy of the high-speed rotation of the outer shell, and then drives the cementing fluid in the annulus to generate a high-speed upward spiral flow, that is, the mechanical energy is converted into liquid kinetic energy. Through the optimized design of the flow channel, rotor, and stator structure, the energy loss can be minimized and the mechanical efficiency of the swirl generator can be improved.

Claims

1. A swirl generator, mainly composed of a central shaft (1), a one-way valve (4), an outer shell (5), a rotor (6), a stator (7), and a guide body (8); characterized in that: The central shaft (1) is provided with an annular groove on its outer periphery, a bypass hole (3) on its upper portion, and a leakage hole (10) on its lower portion; the outer shell (5) is wrapped around the annular groove of the central shaft (1) and forms a rotational fit with the central shaft (1); an annular drive cavity is formed between the outer shell (5) and the central shaft (1), and the annular drive cavity is connected to the bypass hole (3) and the leakage hole (10) at the upper and lower portions, respectively; the one-way valve (4) is arranged in the bypass hole (3); the rotor (6) and the stator (7) are provided with An annular driving cavity is formed between the outer shell (5) and the central shaft (1), and the rotor (6) is fixed on the inner wall of the outer shell (5), and the stator (7) is fixed on the outer wall of the central shaft (1); the guide body (8) is arranged on the outer surface of the outer shell (5); the upper section of the annular groove of the central shaft (1) is a conical inclined surface, and the bypass hole (3) is arranged on the conical inclined surface section; the bottom of the annular groove of the central shaft (1) is a plane, and the leakage hole (10) is arranged along the axial direction of the annular driving cavity between the outer shell (5) and the central shaft (1).

2. The swirl generator according to claim 1, characterized in that: A bearing A (2) is installed at the junction between the upper part of the outer shell (5) and the central shaft (1), and a bearing B (9) is installed at the junction between the lower part of the outer shell (5) and the central shaft (1).

3. The swirl generator according to claim 2, characterized in that: The bearing A (2) is mounted on a radial joint between the outer shell (5) and the central shaft (1), and the bearing B (9) is mounted on an axial joint between the outer shell (5) and the central shaft (1).

4. The swirl generator according to claim 3, characterized in that: The bearing A (2) is a rolling bearing, and the bearing B (9) is a thrust bearing.

5. The swirl generator according to claim 4, characterized in that: The bypass holes (3) are multiple and evenly distributed.

6. The swirl generator according to claim 5, characterized in that: The leakage holes (10) are multiple and evenly distributed; or the leakage holes (10) are of an overall ring hole structure.

7. The swirl generator according to claim 6, characterized in that: The guide body (8) is a spiral wing structure.

8. The swirl generator according to claim 7, characterized in that: There are 2 to 6 spiral wings, which are evenly distributed on the outer shell (5).

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