A ball seat with two-level pressure

Abstract

The present invention relates to the technical field of downhole operation, and in particular to a ball seat with two-level pressure, comprising a landing short section, a ball seat outer tube detachably connected to the landing short section; a low-pressure ball core, which is assembled to the inner wall of the ball seat outer tube through low-pressure shear nails; a high-pressure ball core, which is assembled to the inner wall of one side end of the low-pressure ball core through high-pressure shear nails; a pressing structure, wherein the pressing structure comprises a first pressing structure arranged on the high-pressure ball core and a second pressing structure on the low-pressure ball core, and the high-pressure ball core and the low-pressure ball core are pressed in sequence by a pressing member, and in the pressing state, the high-pressure shear nails and the low-pressure shear nails are cut off in sequence, so that the high-pressure ball core and the low-pressure ball core fall off in sequence. The present invention can mitigate the water hammer effect caused by the instantaneous impact of high-pressure water flow when the ball seat is knocked down under high pressure, effectively improve the success rate of the tool, and reduce the probability of accidents downhole and at the wellhead.

Description

Technical Field

[0001] The invention relates to the technical field of underground operation, and in particular to a ball seat with two-level pressure. Background Art

[0002] In the completion operation of the underground salt cavern injection and production wells in the gas storage reservoir, a packer is needed to seal the annulus between the production casing and the injection and production casing. The ball seat is a downhole tool used to complete the hydraulic packer setting in the injection and production gas completion operation. Its main function is to assist the completion string packer to complete the setting and open the production channel. Before the packer is set, the ball is dropped from the wellhead to the ball seat to seal the injection and production pipe and pressurize the injection and production pipe; after the packer is set, the inner sleeve of the ball seat is pressed down to make the pipe string unobstructed. For traditional ball seats, the pressure required to knock down the ball seat is often higher than the pressure required to set the packer. At the moment the inner sleeve of the ball seat is knocked down, the pressure water flow will generate a water shock wave due to inertia, causing the internal pressure of the pipeline to increase instantly, causing vibration in the pipe string. This is the water hammer effect. In addition, the larger the diameter of the pipeline, the more obvious the water hammer effect, the injection and production tubing will be subjected to instantaneous upward force, and the larger the diameter of the tubing and the smaller the well depth, the greater the effect, which often causes the injection and production tubing to vibrate or surge, and the wellhead and packer seals to fail. Summary of the invention

[0003] 1. Purpose of the invention

[0004] In order to solve the technical problems existing in the background technology, the present invention proposes a ball seat with two-level pressure, which completes the sealing of the packer under high pressure and knocks down the inner sleeve of the ball seat under low pressure. It reduces the water hammer effect while ensuring the completion of the sealing of the packer and solves the influence of complex downhole factors such as tubing expansion and contraction.

[0005] (II) Technical solution

[0006] In order to solve the above problems, the present invention provides a ball seat with two-level pressure, comprising a seating short section, and a ball seat outer cylinder detachably connected to the seating short section;

[0007] A low-pressure ball core is assembled on the inner wall of the outer cylinder of the ball seat through low-pressure shear nails;

[0008] A high-pressure ball core is assembled on the inner wall of one end of the low-pressure ball core through high-pressure shear nails;

[0009] The pressing structure includes a first pressing structure arranged on the high-pressure ball core and a second pressing structure on the low-pressure ball core. The high-pressure ball core and the low-pressure ball core are pressed in sequence by a pressing member. In the pressing state, the high-pressure shear nails and the low-pressure shear nails are cut off in sequence, so that the high-pressure ball core and the low-pressure ball core fall off in sequence.

[0010] As a technical solution of the present invention, it also includes a guide mechanism arranged on the outer wall of the outer tube of the ball seat, and the well entry end of the guide mechanism is streamlined to ensure that the ball seat is centered as a whole during the well entry process.

[0011] As a technical solution of the present invention, the low-pressure ball core is provided with a strip groove, and a locking rod is provided in the strip groove. In one state, two ends of the locking rod are in tight contact with the ball seat outer cylinder and the high-pressure ball core respectively.

[0012] As a technical solution of the present invention, the setting direction of the strip groove forms an angle greater than 90 degrees with the horizontal direction of the outer end wall of the ball seat outer tube, so that when the pressing piece presses the high-pressure ball core, the locking rod is squeezed against the inner wall of the ball seat outer tube.

[0013] As a technical solution of the present invention, O-rings are arranged between the landing nipple and the ball seat outer cylinder, between the low-pressure ball core and the ball seat outer cylinder, and between the low-pressure ball core and the high-pressure ball core.

[0014] As a technical solution of the present invention, the first pressing structure and the second pressing structure are combined into a continuous smooth surface, and the opening is cone-shaped.

[0015] As a technical solution of the present invention, the pressing member has at least one pressing surface that can smoothly fit with the smooth surface.

[0016] As a technical solution of the present invention, the low-pressure ball core is provided with at least one groove structure.

[0017] The above technical solution of the present invention has the following beneficial technical effects:

[0018] The present invention can complete the setting of the packer at high pressure and open the production channel at low pressure through the design of the high-pressure ball core, the low-pressure ball core, the high-pressure and low-pressure shear nails, the locking rod and other structures;

[0019] The addition of O-rings can effectively prevent foreign matter such as salt crystals from invading the mechanism and blocking the lock rod during the well entry process, preventing the limit mechanism from being blocked and unable to unlock normally;

[0020] The groove design can reduce the weight of the parts while balancing and stabilizing the falling posture of the low-pressure ball core, preventing the low-pressure ball core from tilting and blocking the production channel during the falling process;

[0021] The present invention can mitigate the water hammer effect caused by the instantaneous impact of high-pressure water flow when the ball seat is knocked down under high pressure, effectively improve the success rate of the tool, and reduce the probability of accidents occurring downhole and at the wellhead. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the ball seat of the present invention casting high pressure;

[0023] Figure 2 It is a schematic diagram of the ball seat casting low pressure of the present invention.

[0024] Reference numerals

[0025] 1. Seating short section; 2. Ball seat outer tube; 3. Low-pressure ball core; 4. Locking rod; 5. High-pressure ball core; 6. Guide mechanism; 7. Low-pressure shear pin; 8. O-ring; 9. High-pressure shear pin. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0027] Example, reference Figure 1 , Figure 2 .

[0028] The present invention provides a ball seat with two-level pressure, comprising a seating nipple 1 and a ball seat outer tube 2. The ball seat outer tube 2 and the seating nipple 1 are connected by a threaded structure, and can also be detachably fixed by a structure such as screws;

[0029] In order to ensure that the ball seat is centered as a whole during the well entry process, in this embodiment, an inclined guide structure is set on the outer wall of the ball seat outer tube to guide it into the well. Therefore, the inclined guide structure should be designed to be streamlined with a guiding function. In order to facilitate the installation and disassembly of the inclined guide mechanism 6, the inclined guide mechanism 6 and the ball seat outer tube 2 are connected by threads.

[0030] The low-pressure ball core 3 is assembled on the inner wall of the outer tube of the ball seat through low-pressure shear nails 7;

[0031] The high-pressure ball core 5 is assembled on the inner wall of one side end of the low-pressure ball core through high-pressure shear nails 9;

[0032] The low-pressure ball core is provided with a strip groove, and a locking rod 4 is provided in the strip groove. In one state, two ends of the locking rod 4 are in tight contact with the ball seat outer tube 2 and the high-pressure ball core 5 respectively.

[0033] The setting direction of the strip groove forms an angle greater than 90 degrees with the horizontal direction of the outer end wall of the ball seat outer tube, so that when the pressing piece presses the high-pressure ball core, the locking rod is squeezed toward the inner wall of the ball seat outer tube. The purpose is that when the pressing piece presses the high-pressure ball core 5, the high-pressure shear nail 9 is cut off, while the low-pressure shear nail 7 remains intact, so that the high-pressure ball core 5 falls off first.

[0034] After the high-pressure ball core 5 falls off, the end of the locking rod 4 that originally contacted the high-pressure ball core 5 becomes a free end. When the pressing piece presses the low-pressure ball core 3, the extrusion force generated by the locking rod on the inner wall of the outer tube of the ball seat disappears, and then the pressing piece performs the falling-off and pressing operation on the low-pressure ball core 3.

[0035] The pressing structure includes a first pressing structure arranged on the high-pressure ball core and a second pressing structure on the low-pressure ball core. The high-pressure ball core and the low-pressure ball core are pressed in sequence by a pressing piece. In the pressing state, the high-pressure shear nails and the low-pressure shear nails are cut off in sequence, so that the high-pressure ball core and the low-pressure ball core fall off in sequence. The first pressing structure and the second pressing structure are combined into a continuous smooth surface, and the opening is conical. The pressing piece has at least one pressing surface that can smoothly fit with the smooth surface. In this embodiment, the pressing piece is composed of two spheres of different diameters, and the two spheres correspond to the inner wall shapes of the high-pressure ball core and the low-pressure ball core, respectively, so as to perform high and low pressing.

[0036] In the actual operation process, foreign matter such as salt crystals intrudes into the strip groove, which will cause the lock rod 4 to be in a blocked state, resulting in it being unable to be unlocked, affecting the pressure effect. Therefore, O-rings 8 are arranged between the landing nipple and the outer cylinder of the ball seat, between the low-pressure ball core and the outer cylinder of the ball seat, and between the low-pressure ball core and the high-pressure ball core. Figure 1 Figure 2 The location is shown and no further elaboration is given here.

[0037] It should be noted that a groove structure is provided in the low-pressure ball core, which can reduce the weight of the parts while balancing and stabilizing the falling posture of the low-pressure ball core to prevent the low-pressure ball core from tilting and blocking the production channel during the falling process.

[0038] After the packer and the ball seat are put into the well, a high-pressure steel ball is thrown into the wellhead, and the ball falls on the high-pressure ball core 5, and the packer is set by pressure. After the setting is completed, pressure is continued to cut the high-pressure shear nails. After the shear nails are cut, the high-pressure ball core 5 falls off downward, and the locking rod limit mechanism in the low-pressure ball core is unlocked, and the locking rod loses its fixation and is in a free state;

[0039] By throwing a low-pressure steel ball, the low-pressure steel ball falls on the low-pressure ball core, pressurizing and shearing the low-pressure shear nails. After the low-pressure shear nails are sheared off, the low-pressure ball core 3 moves downward and falls off, and the production channel is safely opened. In this way, the water hammer effect caused by the instantaneous impact of high-pressure water flow when the ball seat is knocked down under high pressure can be slowed down, effectively improving the success rate of the tool and reducing the probability of accidents underground and at the wellhead.

[0040] The basic principle, main features and advantages of the present invention are shown and described. It should be understood by those skilled in the art that the present invention is not limited by the above-mentioned embodiments, and the above-mentioned embodiments and descriptions are only preferred examples of the present invention, and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A ball seat with two-level pressure, characterized in that: It includes a seating short section and a ball seat outer cylinder detachably connected to the seating short section; A low-pressure ball core is assembled on the inner wall of the outer cylinder of the ball seat through low-pressure shear nails; A high-pressure ball core is assembled on the inner wall of one end of the low-pressure ball core through high-pressure shear nails; A pressing structure, wherein the pressing structure comprises a first pressing structure provided on the high-pressure ball core and a second pressing structure on the low-pressure ball core, wherein the high-pressure ball core and the low-pressure ball core are pressed in sequence by a pressing member, and in a pressing state, the high-pressure shear nails and the low-pressure shear nails are cut off in sequence, so that the high-pressure ball core and the low-pressure ball core fall off in sequence; The low-pressure ball core is provided with a strip groove, and a locking rod is provided in the strip groove. In one state, two ends of the locking rod are respectively in close contact with the outer cylinder of the ball seat and the high-pressure ball core; The arrangement direction of the strip groove forms an angle greater than 90 degrees with the horizontal direction of the outer end wall of the ball seat outer tube, so that when the pressing piece presses the high-pressure ball core, the locking rod is pressed against the inner wall of the ball seat outer tube.

2. A ball seat with two-level pressure according to claim 1, characterized in that: It also includes a guide mechanism arranged on the outer wall of the outer tube of the ball seat, and the well-entering end of the guide mechanism is streamlined to ensure that the ball seat is centered as a whole during the well-entering process.

3. A ball seat with two-level pressure according to claim 2, characterized in that: O-rings are arranged between the landing short joint and the ball seat outer cylinder, between the low-pressure ball core and the ball seat outer cylinder, and between the low-pressure ball core and the high-pressure ball core.

4. A ball seat with two-level pressure according to claim 1, characterized in that: The first pressing structure and the second pressing structure are combined to form a continuous smooth surface, and the opening is cone-shaped.

5. A ball seat with two-level pressure according to claim 4, characterized in that: The pressing member has at least one pressing surface that can smoothly fit with the smooth surface.

6. A ball seat with two-level pressure according to claim 1, characterized in that: The low-pressure ball core is provided with at least one groove structure.

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