A small wellbore steering resistance reducing device and its use method

Abstract

The present invention belongs to the field of drilling engineering, and specifically relates to a small-hole steering drag reducer and a method for using the same. The small-hole steering drag reducer comprises a steering cylinder, which is a cylindrical structure with a sealed bottom and a steering port on its side wall. The small-hole steering drag reducer also comprises a main control ball, which is placed at the bottom of the steering cylinder. The present invention is applied to small-hole drilling operations, and can improve the efficiency of small-hole drilling and reduce drilling costs.

Description

Technical Field

[0001] The invention belongs to the field of drilling engineering, and in particular relates to a small wellbore steering drag reducer and a use method thereof. Background Art

[0002] At present, ultra-short radius horizontal well drilling mainly adopts slim hole drilling technology, which is conducive to reducing drilling costs and improving the development benefits of residual oil in old oil fields. It has been widely used in old oil field blocks at home and abroad. In the process of ultra-short radius drilling, this technology has great problems in hole expansion. The turning radius is too small, which makes it easy for cuttings to be deposited at the turning position, resulting in increased friction resistance of the drill pipe. At present, there is no friction reduction equipment for this position at home and abroad.

[0003] The open document "Research on the Matching of Ultra-Short Radius Steering Track and Drill Pipe" (Master's thesis of China University of Petroleum (East China)) is dedicated to the matching research of ultra-short radius steering track and drill pipe for small hole expansion, reducing the traditional hole expansion diameter of 600mm to between 300-450mm, seeking thin-walled drill pipes with an outer diameter of Φ14-25mm and a wall thickness of 1.0-2.5mm, so that it can safely pass through the track with a steering radius of no more than 200mm under high internal pressure and no instability. The basic process of drill pipe bending and steering was studied by theoretical analysis, finite element simulation and indoor experiments. The drill pipe material that meets the downhole working conditions was evaluated and optimized, and a steering track with a steering space in the range of 300mm-450mm was designed. The track and the matching drill pipe were simulated and analyzed by finite element simulation, and the problems of cuttings deposition and large friction at the steering position were found, but no solution was given.

[0004] The public document "Design of Double-Acting Booster Tool for Horizontal Wells with Continuous Tubing in Small Holes" (Master's thesis of Chongqing University of Science and Technology) analyzes the working mechanism of existing hydraulic oscillation drag reduction tools and hydraulic boosters, and uses the principle of drag reduction and pressurization to improve the working efficiency of continuous tubing. A three-cylinder series continuous tubing double-acting booster tool is designed. Although it can increase the driving force of the drill pipe, it has no effect on diverting cuttings deposition.

[0005] The public document "Small-hole window side-drilling horizontal well drilling technology in oil fields" (Smart City) summarizes the basic overview of small-hole window side-drilling horizontal well drilling technology, and discusses the application of small-hole window side-drilling horizontal well drilling technology in oil fields from four aspects: trajectory setting, selection of equipment combination and construction points, wellbore trajectory measurement and friction resistance control, and clarification of relevant precautions. However, it lacks relevant equipment configuration for the control of friction resistance and cuttings deposition problems at specific turning positions. Summary of the invention

[0006] In order to solve the problem that a large amount of rock cuttings are easily deposited at the turning position during the drilling of ultra-short radius small wells, resulting in extremely large friction resistance between the steering cylinder and the drill pipe, improve the efficiency of small well drilling and reduce drilling costs, the present invention proposes a small well steering drag reducer, including a steering cylinder, which is a cylindrical structure with a sealed bottom and a steering port on its side wall. The small well steering drag reducer also includes a main control ball, which is placed at the bottom of the steering cylinder.

[0007] The small-bore steering drag reducer further comprises a plurality of auxiliary control spheres, wherein the plurality of auxiliary control spheres are laid at the bottom of the steering cylinder, and the main control sphere is placed on the auxiliary control spheres.

[0008] Wherein, the secondary control sphere is a solid sphere, and the density of the secondary control sphere is not less than the density of the main control sphere.

[0009] Wherein, the volume of a single main control sphere is greater than the volume of a single auxiliary control sphere.

[0010] Wherein, the steering cylinder is a cylindrical structure, and the diameter of the main control sphere is not greater than the radius of the steering cylinder.

[0011] A hole is opened in the center of the main control sphere, the hole is coaxial with the main control sphere and passes through from one end to the other end of the main control sphere.

[0012] Wherein, the diameter of the hole of the main control sphere is smaller than the diameter of the auxiliary control sphere.

[0013] The contact point between the main control ball and the steering cylinder is lower than the center point of the steering port. After the auxiliary control ball is laid on the bottom of the steering cylinder, the highest point of the auxiliary control ball is lower than the lower edge of the steering port.

[0014] Wherein, the main control sphere and the auxiliary control sphere are both made of high hardness and high density materials.

[0015] The present invention also provides a method for using a small wellbore steering drag reducer, comprising the following steps:

[0016] S1, stop the pump to keep the drilling fluid level still, and lower the slim hole steering drag reducer to the bottom of the well;

[0017] S2, lower the drill pipe;

[0018] S3, the drill rod enters the steering cylinder from above the steering cylinder;

[0019] S4, the drill rod reaches the steering port position and starts to turn toward the steering port and drill out of the steering cylinder through the steering port;

[0020] S5. Turn on the pump to circulate the drilling fluid.

[0021] Compared with the prior art, the present invention has the following beneficial effects.

[0022] The present invention is a high-reliability passive cuttings reducing small borehole steering drag reducer, which is mainly used to control the steering trajectory and slope of small borehole drilling, reduce the friction resistance of the drill pipe, and passively control the cuttings deposition effect according to the cuttings deposition situation while controlling the wellbore steering and reducing the friction resistance of the drill pipe, thereby reducing the cuttings deposition rate.

[0023] The present invention optimizes the performance of the small-bore steering joint by arranging a control ball, can stir up the deposited cuttings at the steering position to flow with the drilling fluid, thereby reducing the cuttings deposition, realizing passive control of the cuttings deposition at the steering position, and reducing the friction resistance of the drill pipe footage; at the same time, in order to improve the efficiency of reducing the cuttings deposition, the number of control balls is increased, and a plurality of auxiliary control balls are laid under the main control ball. The plurality of auxiliary control balls can effectively improve the rotation frequency of the main control ball, increase the efficiency of stirring the cuttings, thereby reducing the cuttings deposition at the steering position and reducing the drilling friction resistance.

[0024] The friction between the main control ball, the auxiliary control ball and the drill pipe is rolling friction, so the sliding friction between the drill pipe and the cuttings, and between the drill pipe and other contact objects is reduced or even eliminated, thereby reducing the friction resistance of the drill pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of the slim wellbore steering drag reducer provided by the present invention in a side view direction;

[0026] Figure 2 A schematic structural diagram of the front view of the slim wellbore steering drag reducer provided by the present invention;

[0027] Figure 3a A schematic diagram of the structure of the main control sphere provided by the present invention in the front view direction;

[0028] Figure 3b A schematic diagram of the structure of the main control sphere provided by the present invention in a side view direction;

[0029] Figure 4 A schematic diagram of the structure of a small wellbore steering drag reducer with a drill pipe provided by the present invention;

[0030] Figure 5 A step diagram of the method for using the small wellbore steering drag reducer provided by the present invention. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention.

[0032] like Figure 1 , Figure 2 , Figure 4 As shown, the slim hole steering drag reducer comprises a steering cylinder 1, a main control ball 3, and an auxiliary control ball 4. The steering cylinder 1 is a cylindrical structure with a sealed bottom and a steering port 2 on its side wall. The steering port is generally circular in shape and has a certain distance from the bottom. The distance depends on the distance between the side drilling position and the bottom of the well when the wellbore structure engineering plan is designed, and should generally be slightly smaller than the distance between the side drilling position and the bottom of the well.

[0033] The slim borehole steering drag reducer provided in this embodiment is a drag reducing device placed at the bottom of a vertical borehole, and is used to solve the problem of excessive friction that often exists at the connection position between the vertical borehole and the lateral borehole during directional well drilling. It is common knowledge in the art that the friction at the connection position between the vertical borehole and the lateral borehole during directional well drilling is large, and will not be elaborated here.

[0034] In this embodiment, the main control sphere 3 and the auxiliary control sphere 4 are placed at the bottom of the inner cavity of the steering cylinder, wherein a plurality of auxiliary control spheres 4 are laid at the bottom of the steering cylinder, the main control sphere 3 is placed on the auxiliary control sphere 4, the density of the main control sphere 3 and the auxiliary control sphere 4 are both greater than the density of the rock debris, and the density of the auxiliary control sphere 4 is not less than the density of the main control sphere 3, and at the same time, the volume of a single main control sphere 3 is greater than the volume of a single auxiliary control sphere 4. The auxiliary control sphere 4 is closely laid at the bottom of the steering cylinder 1, and two layers of auxiliary control spheres 4 can be laid to ensure that the main control sphere 3 will not sink below the auxiliary control sphere 4. The auxiliary control sphere 4 is a solid sphere. The filling of the main control sphere 3 and the auxiliary control sphere 4 can effectively reduce the amount of rock cuttings deposited in the steering cylinder 1. At the same time, the friction between the auxiliary control sphere 4, the main control sphere 3 and the drill rod 5 is rolling friction, which reduces the sliding friction between the drill rod and the rock cuttings, and between the drill rod and other contact objects, thereby reducing the friction resistance of the drill rod 5. Therefore, the setting of the auxiliary control sphere 4 can reduce the friction resistance to a greater extent.

[0035] like Figure 3a , Figure 3bAs shown, a hole is provided at the center of the main control sphere 3 in this embodiment as a circulation channel for the drilling fluid. The hole is coaxial with the main control sphere 3 and runs from one end to the other. The diameter of the hole should be smaller than the diameter of the auxiliary control sphere 3, and should not be too small to ensure the smooth circulation of the drilling fluid. The diameter of the main control sphere 3 is not larger than the radius of the steering cylinder 1 to ensure that the drill rod 5 has enough space to pass through. The main control sphere 3 is placed on the lower side of the steering cylinder 1 and on the opposite side of the steering port 2 in the lateral position, that is, beside the steering position of the drill rod 5. Its center of gravity is slightly higher than the lower edge of the steering port 2, so even if the main control sphere 3 rolls to the right, it will not block the steering port 2, so as to ensure that the drilling fluid can effectively pass through the hole of the main control sphere when it is returned, so as to ensure the normal progress of the drilling operation.

[0036] In this embodiment, the contact point between the main control ball 3 and the steering cylinder 1 should be lower than the center point of the steering port 2 to prevent the main control ball 3 from slipping out of the steering port 2. The auxiliary control ball 4 is a solid sphere, which is placed below the main control ball 3 to help reduce friction resistance. The diameter of the auxiliary control ball 4 is larger than the hole diameter of the main control ball 3, and it can ensure that the highest point of the auxiliary control ball 4 is slightly lower than the lower edge of the steering port 2 of the steering cylinder 1 after laying two layers, so as to prevent the auxiliary control ball 4 from slipping out of the steering port 2 during operation.

[0037] The secondary control sphere 4 and the main control sphere 3 are mainly subjected to rolling friction. The setting of the secondary control sphere 4 reduces the probability of sliding friction between the main control sphere 3 and the cuttings. At the same time, the secondary control sphere 4 is affected by the return drilling fluid and rolls, which can further drive the main control sphere 3 to rotate, thereby increasing the rotation frequency of the main control sphere 3. Therefore, the setting of the secondary control sphere can increase the rotation frequency of the main control sphere 3, thereby reducing the friction resistance of the drill rod 5.

[0038] Each control sphere is made of extremely hard and high-density materials, such as high-strength stainless steel, copper, etc., to prevent excessive wear during use that may cause its function of reducing friction resistance to weaken or even disappear.

[0039] like Figure 4 As shown, during the drilling process, the drill rod enters the steering cylinder 1 from above the steering cylinder 1, and turns to drill out from the steering port 2. After drilling a certain distance, the slope of the drill rod at the steering port 2 gradually increases until an angle close to 90° is formed. That is, the drill rod 5 is a bendable structure, so the drill rod 5 can change direction during the drilling process. After the drill rod head enters the steering cylinder 1 downward, the drill rod 5 is blocked by the main control ball 3 or the auxiliary control ball 4 and then turns to the direction of the steering port 2 and continues to move forward. At this time, the drill rod 5 starts to turn and move right at the steering port 2. At this time, the angle between the downward part and the right part of the drill rod 5 gradually approaches 90°. At this time, the friction between the drill rod 5 and the steering cylinder 1 increases to the maximum.

[0040] When used in a specific drilling process, the pump is stopped to keep the drilling fluid level still, the small hole steering drag reducer is first lowered to the bottom of the well, and then the drill pipe 5 is lowered. After the drill pipe 5 is lowered, the pump is turned on to circulate the drilling fluid. Since the drill pipe 5 occupies space after being lowered into the well, the main control ball 3 can be always pressed below the side of the drill pipe, and the change of the specific position of the main control ball 3 below the side of the drill pipe has little effect on the drag reduction effect.

[0041] like Figure 1 , Figure 2 As shown, the main control ball 3 can support the drill rod 5 and generate friction with the drill rod 5. The friction force causes the main control ball 3 to roll, thereby reducing the sliding friction resistance of the drill rod 5 during drilling. A plurality of auxiliary control balls 4 are laid under the main control ball 3. When the main control ball 3 rotates due to the friction force of the drill rod, the auxiliary control balls 4 rotate synchronously under the force, thereby reducing the sliding friction between the main control ball 3 and the inner interface of the steering cylinder 1.

[0042] like Figure 3a As shown in Figure 3b, there is a hole in the center of the main control sphere 3, which is used to control the circulation of drilling fluid. After the drill pipe 5 is lowered into the well, the pump is turned on to circulate the drilling fluid. After the drill pipe 5 begins to turn and move rightward at the steering port 2, the drilling fluid flows out from the drill pipe 5, and the drilling fluid flows back from the steering port 2 and flows out from the space between the inner wall of the steering cylinder 1 and the drill pipe 5 above the steering port. Due to the presence of cuttings, the instability of the amount of cuttings, and the inconsistency between the size of the lateral wellbore and the vertical wellbore, the drilling fluid flow field at this position is constantly changing. The drilling fluid flows back from the lateral steering port 2 into the steering cylinder 1 and flows out from the annulus formed by the inner wall of the steering cylinder 1 and the drill pipe 5. The change in the flow direction of the drilling fluid in the steering cylinder 1 causes the flow cross-sectional area of ​​the drilling fluid to change, thereby affecting the drilling fluid flow back speed. Therefore, when the main control sphere 3 rotates, the drilling fluid still flows through the hole of the main control sphere 3. Since the direction of the hole and the direction of the drilling fluid flow field are constantly changing, the drilling fluid return speed at this position is constantly changing, generating local disturbances, so as to achieve the purpose of stirring the deposited cuttings and flowing with the drilling fluid, thereby reducing the deposition of cuttings. At the same time, the continuous rotation of the auxiliary control sphere 4 below can also assist in stirring the cuttings, thereby enhancing the effect of reducing the deposition of cuttings and reducing the friction resistance of the drill rod during drilling.

[0043] The detailed process of reducing cuttings deposition and friction resistance during operation of the slim hole steering drag reducer is as follows:

[0044] During the drilling process, the drill rod 5 enters the steering cylinder 1 from above the steering cylinder 1, and turns to drill out from the steering port 2. After drilling a certain distance, the slope of the drill rod 5 at the steering port 2 gradually increases until an angle of approximately 90° is formed. At this time, the friction between the drill rod 5 and the steering cylinder 1 increases to the maximum.

[0045] The reduction of friction is mainly achieved by the following structures and working processes:

[0046] 1. There is a hole in the center of the main control sphere 3, which is used to control the circulation of drilling fluid. After the drill pipe 5 is lowered into the well, it is opened to circulate the drilling fluid. After the drill pipe 5 begins to turn and move to the right at the steering port 2, the drilling fluid flows out from the drill pipe 5, and the drilling fluid flows back from the steering port 2 and flows out from the space between the inner wall of the steering cylinder 1 and the drill pipe 5 above the steering port. Due to the presence of cuttings, the instability of the amount of cuttings and the inconsistency of the size of the lateral wellbore, the drilling fluid flow field at this position is constantly changing. The drilling fluid flows back from the lateral steering port 2 into the steering cylinder 1 and flows out from the annulus formed by the inner wall of the steering cylinder 1 and the drill pipe 5. The change in the flow direction of the drilling fluid in the steering cylinder 1 causes the flow cross-sectional area of ​​the drilling fluid to change, thereby affecting the return speed of the drilling fluid. Therefore, when the main control ball 3 rotates, the drilling fluid still flows through the hole of the main control ball 3. Since the direction of the hole and the direction of the drilling fluid flow field are constantly changing, the drilling fluid return speed at this position is constantly changing, generating local disturbances, so as to achieve the purpose of stirring the deposited cuttings in the steering cylinder 1 and flowing with the drilling fluid, thereby reducing the deposition of cuttings. At the same time, the continuous rotation of the auxiliary control ball 4 below can also assist in stirring the cuttings, thereby enhancing the reduction of cuttings deposition and reducing the friction resistance of the drill rod during drilling.

[0047] 2. The secondary control sphere 4 and the main control sphere 3 are mainly subjected to rolling friction. The setting of the secondary control sphere 4 reduces the probability of sliding friction between the main control sphere 3 and the cuttings. At the same time, the secondary control sphere 4 is affected by the return drilling fluid and rolls, which can further drive the main control sphere 3 to rotate, thereby increasing the rotation frequency of the main control sphere 3. Therefore, the setting of the secondary control sphere can increase the rotation frequency of the main control sphere 3, thereby reducing the friction resistance of the drill rod 5.

[0048] The auxiliary control sphere 4 is a solid sphere. It is placed below the main control sphere 3 to help reduce friction resistance. The filling of the auxiliary control sphere 4 can effectively reduce the amount of rock debris deposited in the steering cylinder 1, so the auxiliary control sphere 4 can reduce friction resistance. At the same time, the friction between the auxiliary control sphere 4, the main control sphere 3 and the drill rod 5 is rolling friction, so the sliding friction between the drill rod and the rock debris, and the drill rod and other contact objects is reduced, thereby reducing the friction resistance of the drill rod 5.

[0049] The main control ball 3 can support the drill rod 5 and generate friction with the drill rod 5. The friction force causes the main control ball 3 to roll, thereby reducing the sliding friction resistance of the drill rod 5 during the drilling process. A plurality of auxiliary control balls 4 are placed under the main control ball 3. When the main control ball 3 rotates due to the friction force of the drill rod, the auxiliary control balls 4 rotate synchronously under the force, thereby reducing the friction between the main control ball and the inner interface of the steering cylinder 1.

[0050] like Figure 5 As shown, the method for using the small hole steering drag reducer includes the following steps:

[0051] S1, stop the pump to keep the drilling fluid level still, and lower the slim hole steering drag reducer to the bottom of the well;

[0052] S2, lowering the drill pipe 5;

[0053] S3, the drill rod 5 enters the steering cylinder from above the steering cylinder;

[0054] S4, the drill rod 5 reaches the position of the steering port 2 and starts to turn toward the steering port 2 and drill out of the steering cylinder 1 through the steering port 2. The slope of the drill rod at the position of the steering port 2 gradually increases until an angle of approximately 90° is formed;

[0055] S5. After drilling a certain distance, turn on the pump to circulate the drilling fluid.

[0056] When the drill rod head enters the steering cylinder 1 downward, the drill rod 5 is blocked by the main control ball 3 and then turns to the direction of the steering port 2 to continue moving forward. At this time, the drill rod 5 begins to turn right at the steering port 2. The main control ball 3 can support the drill rod 5 and generate friction with the drill rod 5. The friction force causes the main control ball 3 to roll, thereby achieving the purpose of reducing the sliding friction resistance of the drill rod 5 during the drilling process.

[0057] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0058] In the description of the present invention, unless otherwise specified, the terms "upper", "lower", "left", "right", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0059] Finally, it should be explained that the above technical solution is only one implementation method of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the application methods and principles disclosed in the present invention, and it is not limited to the method described in the above specific implementation method of the present invention. Therefore, the method described above is only preferred and does not have a restrictive meaning.

Claims

1. A small wellbore steering drag reducer, comprising a steering cylinder, the steering cylinder is a cylindrical structure, the bottom of which is sealed, and a steering port is opened on the side wall, characterized in that: The small hole steering drag reducer also includes a main control sphere, which is placed at the bottom of the steering cylinder; a hole is opened in the center of the main control sphere, which is coaxial with the main control sphere and passes through from one end of the main control sphere to the other end; The small hole steering drag reducer also includes a plurality of auxiliary control balls; wherein the plurality of auxiliary control balls are laid on the bottom of the steering cylinder, and the main control ball is placed on the auxiliary control ball; The diameter of the hole of the main control sphere is smaller than the diameter of the auxiliary control sphere; The contact point between the main control ball and the steering cylinder is lower than the center point of the steering port. After the auxiliary control ball is laid on the bottom of the steering cylinder, the highest point of the auxiliary control ball is lower than the lower edge of the steering port.

2. The slim wellbore steering drag reducer according to claim 1, characterized in that: The secondary control sphere is a solid sphere, and the density of the secondary control sphere is not less than the density of the primary control sphere.

3. The slim wellbore steering drag reducer according to claim 1, characterized in that: The volume of a single main control sphere is greater than the volume of a single auxiliary control sphere.

4. The slim wellbore steering drag reducer according to claim 1, characterized in that: The steering cylinder is a cylindrical structure, and the diameter of the main control sphere is not greater than the radius of the steering cylinder.

5. The slim wellbore steering drag reducer according to claim 1, characterized in that: The main control sphere and the auxiliary control sphere are both made of high-hardness and high-density materials.

6. A method for using the slim wellbore steering drag reducer according to any one of claims 1 to 5, comprising the following steps: S1, stop the pump to keep the drilling fluid level still, and lower the small hole steering resistance reducer to the bottom of the well; S2, lower the drill pipe; S3, the drill rod enters the steering cylinder from above the steering cylinder; S4, the drill rod reaches the steering port position and starts to turn toward the steering port and drill out of the steering cylinder through the steering port; S5. Turn on the pump to circulate the drilling fluid.

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