Track-changing fracturing sliding sleeve

Abstract

The present invention belongs to the technical field of oil drilling, and particularly relates to a downhole fracturing rail-changing fracturing sleeve, which comprises an upper joint, a sealing block, a disc spring limiting mechanism, a rail-changing NPT screw, a spring retainer, a lower inner sleeve, an annular joint, an annular slider, a lower joint, a limiting bushing, a fracturing sleeve, a spring, a rail-changing sleeve, a thrust needle bearing, an upper inner sleeve, and a special-shaped ball. The technical solution is as follows: When the special-shaped ball enters the fracturing sleeve, first, the ball is limited and stuck by the spring limiting mechanism, and the ground pressurizes the internal flow channel. At this time, the ball is limited, driving the central pipe column to move axially downward, and the rail-changing sleeve enters the rail-changing stage at this time. When the track is in the short track, the central pipe column will reset and release the special-shaped ball; when the track is in the long track, the central pipe column is locked after moving downward, the lower annular slider is compressed and contracted, the special-shaped ball is stuck after sliding down, and the upper layer pressurizes the wellbore, entering the fracturing state. The downhole fracturing rail-changing fracturing sleeve of the present invention effectively improves the fracturing counting efficiency and the counting is more accurate. It adopts a full-metal structure, enhancing the stability of downhole use.

Description

Technical Field

[0001] The present invention relates to a fracturing tool for the exploitation of geological resources such as oil and natural gas, and particularly to a rail-changing fracturing sleeve, belonging to the technical field of downhole fracturing. Background Art

[0002] In China's oil and gas resources, unconventional oil and gas resources are large in quantity, with dense reservoirs, strong heterogeneity, and great exploitation difficulty. Only by forming as many artificial fractures as possible in the formation through the staged fracturing technology can economic and effective development be carried out. The staged fracturing technology has become an effective technical measure to increase the oil and gas production of low-permeability and tight oil and gas reservoirs. In the actual exploitation process, especially when dealing with oil and gas reservoirs with a multi-layer structure, large interlayer differences, and the need for targeted transformation, it has shown remarkable effects. This technology effectively improves the permeability and recovery rate of the reservoir by precisely controlling the fracturing operations between layers. In oilfield production, for the infinite-stage staged fracturing of unconventional reservoirs in deep wells, it effectively improves the seepage conditions in the oil well and increases the single-well production.

[0003] The fracturing sleeve is the key technology in the staged fracturing tool, which greatly affects the fracturing operation of unconventional reservoirs. The number of fracturing stages depends on the number of downhole fracturing sleeves installed. The more the installation number, the more the number of staged fracturing layers. The currently commonly used sleeve form is the ball-drop type, which controls the fracturing stages by changing the ball size, and there is a strict operation of holding pressure and dropping balls in the order from small to large for the ball-drop sequence. Therefore, this method will result in a limited number of sleeves that can be installed downhole, affecting the fracturing operation efficiency. Currently, the mature rail-changing fracturing sleeve technology is divided into hydraulic type and mechanical type. Among them, for the hydraulic rail-changing fracturing sleeve, the opening and closing of the sleeve are controlled by the hydraulic principle, but it is difficult to control the downhole pressure, and the fracturing accuracy is not high. For the mechanical rail-changing fracturing sleeve, the opening and closing of the sleeve are realized through a specific mechanical structure, but a specific mechanical device is required to control the opening and closing of the sleeve, with cumbersome operation and low efficiency. Summary of the Invention

[0004] Aiming at the above technical defects, the present invention provides a rail-changing fracturing sleeve, which while realizing the fracturing pressure holding, designs a simple mechanical counting mechanism, improves the stability of the counting function in a complex downhole environment, can achieve precise counting switching between the long and short rails of the sleeve, and precisely hold pressure for fracturing.

[0005] Technical solution of the present invention: The rail-changing fracturing sleeve has a simple internal structure design, a sensitive sleeve triggering method, and clear triggering feedback obtained through pressure feedback data, realizing the full-bore function of multiple ball injections and achieving an infinite-stage fracturing effect; the rail-changing fracturing sleeve includes a sleeve part, a core shaft part, and a special-shaped ball part; the sleeve part includes an upper joint, a rail-changing NPT screw, a lower joint, and a fracturing sleeve; the core shaft part includes a sealing retaining ring, a disc spring limiting mechanism, a spring retaining ring, a lower inner sleeve, a ring groove joint, a ring-shaped slider, a limiting bushing, a spring, a rail-changing sleeve, a thrust needle bearing, and an upper inner sleeve; the disc spring limiting mechanism includes a limiting head, a disc spring, a limiting baffle, a limiting bolt, and a sealing ring; the special-shaped ball part includes a ball head, a ball tail, a connecting bolt, and a washer.

[0006] For the sleeve part, the upper joint and the fracturing sleeve are connected by an NC50 taper thread, and the fracturing sleeve and the lower joint are also connected by an NC50 taper thread to achieve the purpose of sealing through the taper thread connection. Three installation holes for the rail-changing NPT screws are provided on the fracturing sleeve, and the rail-changing NPT screws are also connected to the fracturing sleeve by threads. Three NPT screws are circumferentially distributed on the fracturing sleeve to ensure the stability of the rail-changing structure. Six fracturing drilling fluid pressure relief ports are evenly distributed on the fracturing sleeve for fracturing operations.

[0007] The sleeve core shaft part includes a sealing retaining ring, a disc spring limiting mechanism, a spring retaining ring, a lower inner sleeve, a ring groove joint, a ring-mounted slider, a limiting bushing, a spring, a track changing sleeve, a thrust needle roller bearing, and an upper inner sleeve. The disc spring limiting mechanism includes a limiting head, a disc spring, a limiting baffle, a limiting bolt, and a sealing ring. The upper part of the upper inner sleeve is provided with three installation holes for the disc spring limiting mechanism, and the disc spring limiting mechanism is installed and limited. The limiting head in the disc spring limiting mechanism limits the position at the stepped hole in the upper inner sleeve hole, the limiting baffle applies pre-pressure to the lower disc spring, and the limiting bolt axially limits the limiting baffle in the stepped hole. The upper and lower thrust needle roller bearings axially limit the track changing sleeve, and the lower ring of the upper thrust needle roller bearing and the upper ring of the lower thrust needle roller bearing rotate synchronously with the track changing sleeve to complete the track changing function of the track changing mechanism. The track changing slot on the outside of the track changing sleeve cooperates with the track changing NPT screw to realize the internal limiting function of the track changing. The spring retaining ring is squeezed with the lower ring of the lower thrust needle roller bearing to preload the axial limit of the lower spring. The lower end of the spring in the sleeve core shaft squeezes the stepped shaft part in the fracturing sleeve to achieve axial limit. The upper end of the lower inner sleeve is connected to the upper inner sleeve through a tapered thread NC26 to ensure sealing. The bottom of the lower inner sleeve is also processed with an inclined step to buffer the instantaneous reset impact during the track change process. The bottom of the lower sleeve is connected to the ring groove joint through a thread to fix the ring groove joint. Three dovetail grooves are evenly distributed on the lower part of the ring groove joint, which cooperates with the ring-mounted slider to ensure the stability of the axial limit and radial movement trajectory of the ring-mounted slider. After being squeezed, the ring-mounted slider shrinks along the dovetail groove at the lower part of the ring-mounted joint to axially limit the special-shaped ball and perform pressure-holding fracturing operations. A limit bushing is installed between the ring groove joint and the lower inner sleeve to radially limit the ring-mounted slider.

[0008] The special-shaped ball throwing part comprises a ball head, a ball tail, a connecting bolt and a washer. The ball tail is connected to the ball head through the connecting bolt, and the washer is arranged between the connecting bolt and the ball tail.

[0009] The beneficial effects of the present invention are as follows: (1) The design of the disc spring limit mechanism enables the shaped ball part to pass through the fracturing sleeve above the fracturing layer before entering the fracturing stage. The shaped ball has the same size and realizes the full-diameter function. (2) In the design of the track-changing mechanism, the track-changing sleeve cooperates with the track-changing NPT screw to drive the fracturing mandrel to move up and down by switching the long and short tracks to trigger the fracturing function. (3) Except for some necessary rubber seals, the fracturing sleeve is a mechanical trigger structure with stable performance and little impact from the high temperature and high pressure environment underground. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Attached Figure 1 It is a structural diagram of the track-changing fracturing sleeve of the present invention;

[0011] Attached Figure 2 It is a schematic diagram of the structure and arrangement of the disc spring limit mechanism;

[0012] Attached Figure 3 It is the structural diagram of the track change sleeve;

[0013] Appendix Figure 4 is a schematic diagram of the track layout on the outer surface of the rail-changing sleeve;

[0014] Appendix Figure 5 is a schematic diagram of the layout of the three-stage fracturing rail-changing NPT screws;

[0015] Appendix Figure 6 is a schematic diagram of the circumferential layout of the rail-changing NPT screws;

[0016] Appendix Figure 7 is a schematic diagram of the structure of the special-shaped ball;

[0017] Appendix Figure 8 is a schematic diagram of the structure of the ring-shaped slider;

[0018] Appendix Figure 9 is a schematic diagram of the structure after the installation of the ring-shaped slider and the ring groove joint;

[0019] Appendix Figure 1 The names of the components marked in the figure: the special-shaped ball part; the slip sleeve part includes 1-upper joint, 2-sealing retaining ring, 3-disc spring limiting mechanism, 4-rail-changing NPT screw, 5-spring retaining ring, 6-lower inner slip sleeve, 7-ring groove joint, 8-ring-shaped slider, 9-lower joint, 10-limiting bushing, 11-fracturing sleeve, 12-spring, 13-rail-changing sleeve, 14-thrust needle roller bearing, 15-upper inner slip sleeve, 16-special-shaped ball. Detailed implementation mode

[0020] In the present invention, for the convenience of description, the relative positional relationship of each component is described according to the appendix of the specification Figure 1 in the following manner. For example, the up and down positional relationship is determined according to the direction of the appendix of the specification Figure 1 for illustration.

[0021] Referring to the appendix Figure 1 The rail-changing fracturing slip sleeve includes a slip sleeve part, a slip sleeve mandrel part and a special-shaped ball 16 part; the slip sleeve part includes an upper joint 1, a rail-changing NPT screw 4, a lower joint 9, and a fracturing sleeve 11; the slip sleeve mandrel part includes a sealing retaining ring 2, a disc spring limiting mechanism 3, a spring retaining ring 5, a lower inner slip sleeve 6, a ring groove joint 7, a ring-shaped slider 8, a limiting bushing 10, a spring 12, a rail-changing sleeve 13, a thrust needle roller bearing 14, and an upper inner slip sleeve 15; the disc spring limiting mechanism includes a limiting head, a disc spring, a limiting baffle, a limiting bolt, and a sealing ring; the special-shaped ball 16 part includes a ball head, a ball tail, a connecting bolt, and a washer.

[0022] Before the rail-changing fracturing sleeve is run into the casing, first adjust the positions of the rail-changing sleeve 13 and the rail-changing NPT screw 4 correctly according to the set number of stages, that is, set the initial fracturing stages. After the rail-changing fracturing sleeve is run into the casing, arrange the mechanism bodies without special-shaped ball 16 in sequence at the specified distances in the casing. After the arrangement is completed, enter the fracturing ball-throwing stage.

[0023] Refer to the appendix Figure 5 Taking the setting of three-stage fracturing as an example, the specific implementation method is described below. Before the three-stage fracturing sleeve is lowered into the well, from top to bottom, the positional relationship between the rail-changing NPT screw 4 and the rail-changing sleeve 13 track is set as follows: The first stage is set at the short rail with three rail-changing nodes away from the long rail, that is, at the position label 1; the second stage is set at the position with two rail-changing nodes away from the long rail, that is, at the position label 2; the third stage is set at the position with one rail-changing node away from the long rail, that is, at the position label 3.

[0024] Refer to the appendix Figure 1 Refer to the appendix

[0025] Refer to the appendix Figure 2 Refer to the appendix Figure 6 When the cross-section at the limit position of the rail-changing NPT screw 4 is as shown in the appendix Figure 6 The head of the rail-changing NPT screw 4 is embedded in the track groove arranged on the outer side of the rail-changing sleeve 13 and is circumferentially evenly distributed in 3. Refer to the appendix Figure 8 And the appendix Figure 9, the limiting relationship between the ring-shaped slider 8 and the ring groove joint 7 after installation is as shown in the appendix Figure 9 As shown, they are connected through dovetail grooves, and three ring-shaped sliders are evenly distributed circumferentially.

[0026] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. The rail-changing type fracturing sliding sleeve is characterized in that: The internal structure of the sliding sleeve is simply designed, the triggering method of the sliding sleeve is simple, and clear triggering feedback can be obtained through pressure feedback data. The function of full-bore ball throwing multiple times can be realized, achieving the effect of infinite-stage fracturing. The rail-changing fracturing sliding sleeve includes a sliding sleeve sleeve part, a sliding sleeve mandrel part, and a special-shaped ball-throwing part (16). The sliding sleeve sleeve part includes an upper joint (1), a rail-changing NPT screw (4), a lower joint (9), and a fracturing sleeve (11). The sliding sleeve mandrel part includes a sealing retaining ring (2), a disc spring limiting mechanism (3), a spring retaining ring (5), a lower inner sliding sleeve (6), a ring groove joint (7), a ring-shaped slider (8), a limiting bushing (10), a spring (12), a rail-changing sleeve (13), a thrust needle bearing (14), and an upper inner sliding sleeve (15). The disc spring limiting mechanism includes a limiting head, a disc spring, a limiting baffle, a limiting bolt, and a sealing ring. The special-shaped ball-throwing part includes a ball head, a ball tail, a connecting bolt, and a washer. In the rail-changing mechanism, the rail-changing NPT screw (4) is inserted into the reserved threaded hole of the fracturing sleeve, and three are arranged circumferentially and inserted into the rail-changing groove of the rail-changing sleeve (13). The rail-changing NPT screw (4) realizes the limiting function of the length and short rail switching of the rail-changing sleeve. When the special-shaped ball-throwing part (16) squeezes the disc spring limiting mechanism (3), the rail-changing sleeve moves downward and rotates, compressing the spring (12). The rail-changing NPT screw (4) switches the limiting position on the rail groove of the rail-changing sleeve (13) to complete the rail change. When the rail-changing NPT screw (4) enters the short rail in the rail groove of the rail-changing sleeve (13), fracturing is not carried out, and the special-shaped ball-throwing part (16) enters the next-stage fracturing sliding sleeve through the internal flow channel of the sliding sleeve mandrel. When the rail-changing NPT screw (4) enters the long rail in the rail groove of the rail-changing sleeve (13), the rail-changing NPT screw (4) limits the rail-changing sleeve (13) in the long track, compressing the spring (12). At the same time, the upper inner sliding sleeve (15) and the lower inner sliding sleeve (6) move downward along the inside of the sliding sleeve sleeve, and the ring-shaped slider (8) shrinks under the extrusion inside the lower joint, and the special-shaped ball-throwing part (16) is clamped. After pressure buildup, the fracturing operation is carried out.

2. The rail-changing fracturing sliding sleeve according to claim 1, wherein the through-hole limit of the special-shaped ball-throwing part is completed by the disc spring limiting mechanism (3). The internal central flow channel of the rail-changing fracturing sliding sleeve, the special-shaped ball-throwing part (16) and the disc spring limiting mechanism (3) are squeezed to complete pressure buildup. When the predetermined pressure is reached, the limiting head in the disc spring limiting mechanism (3) squeezes the disc spring, and the special-shaped ball-throwing part (16) completes the through-hole and enters the next stage.

3. The rail-changing fracturing sliding sleeve according to claim 1, during the rail-changing process of the sliding sleeve, the upper and lower thrust needle bearings (14) axially limit the rail-changing sleeve (13), and the lower ring of the upper thrust needle bearing (14) and the upper ring of the lower thrust needle bearing (14) rotate synchronously with the rail-changing sleeve (13) to complete the rotary rail-changing function of the rail-changing mechanism.

4. For the rail-changing fracturing sliding sleeve according to claim 1, after the rail groove on the outer surface of the rail-changing sleeve (13) is changed to a long rail, the rail-changing sleeve (13) rotates to compress the spring (12), driving the sliding sleeve mandrel part to move downward. The upper inner sliding sleeve (15) and the lower inner sliding sleeve (6) move downward, squeezing the ring-shaped slider (8) to contract at the stepped shaft in the lower joint (9). At the same time, the special-shaped ball-throwing part (16) is stuck at the contraction of the ring-shaped slider (8) through the internal central flow channel of the rail-changing fracturing sliding sleeve, entering a pressure-holding state. The upper layer is filled with drilling fluid to increase the pressure for fracturing operations.

5. For the rail-changing fracturing sliding sleeve according to claim 1, in the sliding sleeve mandrel part, the upper sealing retaining ring is limited jointly by the upper joint (1) and the upper step of the upper inner sliding sleeve (15), and the lower sealing retaining ring is limited jointly by the upper inner sliding sleeve (15) and the upper thrust needle bearing (14).

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