An adaptive friction-reducing centralizer

Abstract

An adaptive friction reduction straightener comprises an annular outer retaining ring and an annular inner retaining ring, straightening ribs are arranged at equal intervals on the outer side of the outer retaining ring, a groove is provided on the outer retaining ring, a circular through hole is provided on the inner retaining ring, the groove and the circular through hole are arranged correspondingly to each other, a spherical roller is arranged on the groove, the circular through hole is used to limit the radial displacement of the spherical roller in the inner retaining ring, and the spherical roller is in direct contact with the drill rod. The present invention can simultaneously achieve straightening and friction reduction effects on the drill rod body.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield drilling tools, and in particular to an adaptive friction-reducing centralizer. Background Art

[0002] At present, during the drilling of extended reach wells and horizontal wells, the friction torque generated by the friction between the drill pipe and the well wall or casing is a key issue that limits the advancement of drilling technology to deep wells and ultra-deep wells. In addition, maintaining the stability of the bottom hole assembly and the drill pipe nearby is a prerequisite for ensuring the standard of the wellbore structure. The offset wellbore will cause the drill to be subjected to greater lateral force, which will in turn affect the wellbore structure while aggravating the wear of the drill, forming a vicious cycle. The long-term friction between the drill and the well wall or casing will wear through the casing, and in severe cases, the drill will get stuck, or even cause the entire well to be scrapped.

[0003] Installing friction reduction tools is the most commonly used friction reduction method at the drilling site at this stage. However, foreign drilling tools with better friction reduction effects are expensive, and it is difficult for well sites with average benefits to support their costs. There are two main methods for reducing friction and drag in China. One is to spray special materials on the drill bit, but this method is very serious in the harsh downhole environment and causes severe damage to the coating, making it difficult to ensure a good friction reduction effect. The second is to design a friction reduction and drag reduction short section. This type of tool has a complex structure and most of them only have a friction reduction effect in one direction. Although it can play a certain role in reducing friction, the effect is poor and the lifespan is short. In general, there are few downhole tools that can meet the requirements of straightening and friction reduction at the same time, but straightening and friction reduction are key issues in improving the extended drilling capabilities of horizontal wells and directional wells. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, an object of the present invention is to provide an adaptive friction-reducing centralizer, which can simultaneously achieve the effects of centralizing and reducing friction on the drill pipe body.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A self-adaptive friction-reducing straightener comprises an annular outer retaining ring 3 and an annular inner retaining ring 5, straightening ribs 2 are arranged at equal intervals on the outer side of the outer retaining ring 3, a groove is formed on the outer retaining ring 3, a circular through hole is formed on the inner retaining ring 5, the groove and the circular through hole are arranged corresponding to each other, a spherical roller 4 is arranged on the groove, the circular through hole is used to limit the radial displacement of the spherical roller 4 on the inner retaining ring 5, and the spherical roller 4 is in direct contact with the drill pipe.

[0007] The outer retaining ring 3 is composed of two half outer retaining rings, and the joint of the half outer retaining rings is provided with a hexagon socket head screw, a positioning pin, a positioning pin hole, and a stepped threaded hole.

[0008] The outer retaining ring 3 has 4 evenly distributed hemispherical grooves with a diameter of 25 mm on the axis, and 5 evenly distributed hemispherical grooves with a diameter of 25 mm are offset 60 degrees up and down with the axis as the reference.

[0009] The straightening ribs 2 on the outer side of the outer retaining ring 3 are streamlined straightening ribs.

[0010] The inner surface of the outer retaining ring 3 is coated with a ceramic material to form a wear-resistant layer, and the groove is hemispherical.

[0011] The inner retaining ring 5 is a structure of two semicircular rings, and an end cover 1 for fixing is provided at the end of the inner retaining ring 5 .

[0012] The center of the circular through hole provided on the inner retaining ring 5 is on the generatrix of the outer cylindrical surface of the inner retaining ring 5, and 4 circular holes are evenly distributed at the center position. With the line connecting the centers of the central circular holes as a reference, 5 circular through holes are evenly distributed 60 degrees up and down.

[0013] The diameter of the spherical roller 4 is 24 mm.

[0014] Beneficial effects of the present invention:

[0015] The invention is installed on the drill rod body and moves along with the movement of the drill rod, so as to straighten the drill rod and improve the stability of the drill string.

[0016] When the drill pipe cannot move due to excessive friction caused by formation factors, the tool directly contacts the well wall because its diameter is larger than the drill pipe body, thereby releasing the axial movement and axial rotation freedom of the drill pipe, and converting the sliding friction between the drill pipe body and the rock formation or casing into rolling friction, thereby reducing friction.

[0017] The inner surface of the complete retaining ring will have hemispherical grooves distributed in an odd-even pattern (5-4-5, 5-4-5) to avoid fatigue damage to the drill pipe due to stress concentration.

[0018] The circular hole of the inner retaining ring is coaxial with the spherical groove of the outer retaining ring, and plays the role of limiting the spherical roller.

[0019] The streamlined stabilizing ribs have minimal obstruction to the drilling fluid, making it easier for the drilling fluid to carry the cuttings out. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the present invention.

[0021] Figure 2 It is a structural schematic diagram of the semi-outer retaining ring of the present invention.

[0022] Figure 3 It is a front view and a cross-sectional view of the semi-outer retaining ring of the present invention.

[0023] Figure 4It is a structural schematic diagram of the semi-inner retaining ring of the present invention.

[0024] Figure 5 It is a front view and a cross-sectional view of the semi-inner retaining ring of the present invention.

[0025] Figure 6 It is a schematic diagram of the end cover structure of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0027] like Figure 1-Figure 6 As shown in the figure, it is composed of an end cap 1, an outer retaining ring 3, an inner retaining ring 5 and a spherical roller 4. The outer retaining ring 3 is provided with a straightening rib 2, the maximum diameter of which is consistent with the diameter of the wellbore, and plays the role of straightening the drill pipe. The drill pipe body moves in the annular area formed by the roller 4 and the inner retaining ring 5. The drill pipe is in direct contact with the roller 4, which converts the sliding friction between the drill pipe and the well wall or casing into rolling friction, greatly reducing the friction resistance.

[0028] The centralizer has a total length of 1020 mm, a maximum outer diameter of 215.9 mm, and can be adapted to a drill pipe with an outer diameter of 127 mm. The above dimensions only express one dimension of the present invention, but should not be construed as limiting the scope of the present invention.

[0029] The end cover 1 is provided with an internal thread for connecting the two inner half retaining rings to form a complete inner retaining ring 5.

[0030] The outer retaining ring 3 is formed by connecting two half outer retaining rings with hexagon socket head screws. The joint surface is provided with positioning pins, positioning pin holes, and stepped threaded holes. The outer surface is provided with streamlined straightening ribs. The inner surface is coated with ceramic material to form a wear-resistant layer and is provided with hemispherical grooves.

[0031] The hemispherical grooves arranged on the inner surface of the outer retaining ring 3 are distributed as follows: 4 hemispherical grooves with a diameter of 25 mm are evenly distributed on the axis of the half retaining ring, and 5 hemispherical grooves with a diameter of 25 mm are evenly distributed 60 degrees above and below the axis.

[0032] The inner retaining ring 5 is a complete inner retaining ring 5 formed by connecting two half inner retaining rings with an end cover 1, and a positioning pin and a positioning pin hole are provided on the joint surface. Its outer surface is coated with a ceramic material to be wear-resistant and is provided with a circular through hole.

[0033] The center of the circular through hole of the inner retaining ring 5 is on the generatrix of the outer cylindrical surface of the retaining ring, and 4 circular holes are evenly distributed at the center position. With the center line of the central circular hole as the reference, 5 circular through holes are evenly distributed 60 degrees up and down to limit the radial displacement of the roller 4 in the inner retaining ring 5. The diameter of the roller 4 is 24mm.

[0034] Working principle of the present invention:

[0035] The outer retaining ring 3 has a groove for placing the spherical roller 4. The spherical roller 4 is placed in a groove set on the inner surface of a half outer retaining ring. The outer surface of the inner retaining ring 5 with a circular through hole is tightly attached to the inner surface of the outer retaining ring 3, and the spherical roller 3 is confined in the hemispherical groove. Then the other half of the outer retaining ring, the roller and the half inner retaining ring are installed. The two installed halves are assembled and positioned on the drill pipe body with positioning pins, and then the two half outer retaining rings are connected with hexagon socket cylindrical head screws. Then the end cover is connected to the inner retaining ring through threads, and the drill pipe body moves in the annular area formed by the spherical roller 4 and the retaining ring, and the sliding friction between the drill pipe body and the well wall or casing is converted into rolling friction, which plays a role in reducing friction resistance. The outer surface of the outer retaining ring 3 is provided with streamlined straightening ribs 2, which play a role in straightening the drill pipe body and disturbing the drilling fluid, which can speed up the flow rate of the drilling fluid here, prevent the accumulation of cuttings, and improve the drilling efficiency and quality.

Claims

1. An adaptive friction reduction centralizer, characterized in that: It comprises an annular outer retaining ring (3) and an annular inner retaining ring (5), the outer side of the outer retaining ring (3) is provided with straightening ribs (2) at equal intervals, the outer retaining ring (3) is provided with a groove, the inner retaining ring (5) is provided with a circular through hole, the groove and the circular through hole are arranged corresponding to each other, a spherical roller (4) is arranged on the groove, the circular through hole is used to limit the radial displacement of the spherical roller (4) in the inner retaining ring (5), and the spherical roller (4) is in direct contact with the drill rod; The outer retaining ring (3) is composed of two half outer retaining rings, and the joint of the half outer retaining rings is provided with a hexagon socket head screw, a positioning pin, a positioning pin hole, and a stepped threaded hole; Four hemispherical grooves with a diameter of 25 mm are evenly distributed on the axis of the outer retaining ring (3), and five hemispherical grooves with a diameter of 25 mm are evenly distributed at an angle of 60 degrees above and below the axis.

2. The adaptive friction reduction centralizer according to claim 1, characterized in that: The straightening ribs (2) on the outside of the outer retaining ring (3) are streamlined straightening ribs.

3. The adaptive friction reduction centralizer according to claim 1, characterized in that: The inner surface of the outer retaining ring (3) is coated with a ceramic material to form a wear-resistant layer, and the groove is hemispherical.

4. The adaptive friction reducing centralizer according to claim 1, characterized in that: The inner retaining ring (5) is a structure of two semicircular rings, and an end cover (1) for fixing is arranged at the end of the inner retaining ring (5).

5. The adaptive friction reducing centralizer according to claim 1, characterized in that: The center of the circular through hole provided on the inner retaining ring (5) is on the generatrix of the outer cylindrical surface of the inner retaining ring (5), and 4 circular holes are evenly distributed at the center position, and 5 circular through holes are evenly distributed 60 degrees above and below the line connecting the centers of the central circular holes as a reference.

6. The adaptive friction reducing centralizer according to claim 1, characterized in that: The diameter of the spherical roller (4) is 24 mm.

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