A high-pressure setting ball seat with double ball cores

Abstract

The present invention relates to the technical field of downhole operation, and in particular to a high-pressure sealing ball seat with double ball cores, comprising a seating short section, a ball seat outer cylinder detachably connected to the seating short section; a low-pressure ball core, which is arranged inside the ball seat outer cylinder and connected to the ball seat outer cylinder by shear nails; a high-pressure ball core, which is arranged inside the ball seat outer cylinder and whose outer wall is in contact with the inner wall of the ball seat outer cylinder; a locking block, one end of which passes through the high-pressure ball core and is embedded in the inner wall groove of the ball seat outer cylinder, and the other end of which is in contact with the outer wall of the low-pressure ball core, wherein the low-pressure ball core can cut off the shear nails under the action of pressure, so that the low-pressure ball core can hit the high-pressure ball core, thereby making the low-pressure ball core and the high-pressure ball core detach from the ball seat outer cylinder together, and has a mode of completing the sealing of the packer at high pressure and opening up the production channel at low pressure, which can mitigate the water hammer effect caused by the instantaneous impact of high-pressure water flow under high pressure, effectively improve the success rate of the tool, and reduce the probability of downhole and wellhead accidents.

Description

Technical Field

[0001] The invention relates to the technical field of downhole operations, and in particular to a high-pressure sealing ball seat with double ball cores. 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 high-pressure sealing ball seat with a double ball core, which can complete the sealing of the packer under high pressure and knock down the inner sleeve of the ball seat under low pressure to open the production channel. On the premise of ensuring the completion of the sealing of the packer, the water hammer effect is reduced, and the influence of complex downhole factors such as tubing expansion and contraction and upward movement is reduced.

[0005] (II) Technical solution

[0006] In order to solve the above problems, the present invention provides a high-pressure setting ball seat with double ball cores, 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 arranged inside the ball seat outer cylinder and connected to the ball seat outer cylinder through shear nails;

[0008] A high-pressure ball core is arranged inside the outer tube of the ball seat and its outer wall is in contact with the inner wall of the outer tube of the ball seat;

[0009] A locking block, one end of which passes through the high-pressure ball core and is embedded in the inner wall groove of the ball seat outer tube, and the other end of which is in contact with the outer wall of the low-pressure ball core. In one state, when one end of the locking block is separated from the outer wall of the low-pressure ball core, the locking block can slide away from the inner wall groove of the ball seat outer tube;

[0010] Furthermore, the low-pressure ball core can cut off the shear pins under pressure, so that the low-pressure ball core can hit the high-pressure ball core, thereby making the low-pressure ball core and the high-pressure ball core detach from the ball seat outer tube together.

[0011] Preferably, one end of the ball seat outer tube away from the seating nipple is connected to a plug tube, and a plurality of pressure discharge holes are distributed around the plug tube for dispersing and discharging the high-pressure water flow.

[0012] Preferably, it also includes a pressing structure, which includes a first hole structure formed at the outer end of the inner wall of the high-pressure ball core and an impact part at the inner end, and a second hole structure formed at the low-pressure ball core, which is used to seal the first hole structure when a soluble ball is thrown in, and to seal the second hole structure when a steel ball is thrown in and make the end of the low-pressure ball core hit the impact part.

[0013] Preferably, the outer wall of the low-pressure ball core is provided with a groove structure for separating the outer wall of the low-pressure ball core from the outer end of the locking block, so that the high-pressure ball core can be transformed into a free state and separated from the outer cylinder of the ball seat.

[0014] Preferably, O-rings are provided on both sides of the shear pin and the locking block to prevent foreign matter from affecting the working state of the shear pin and the locking block during the process of the ball seat entering the well.

[0015] Preferably, the pressure relief holes are evenly distributed on the plug tube wall in the form of multiple rows and columns.

[0016] Preferably, the order of adding the soluble balls and the steel balls is to first add the soluble balls and then add the steel balls after the soluble balls are dissolved.

[0017] Preferably, it also includes an elastic mechanism, which is used to pop the locking block out of the inner wall groove of the ball seat outer tube when the end of the locking block is separated from the outer wall of the low-pressure ball core.

[0018] The above technical solution of the present invention has the following beneficial technical effects:

[0019] 1. It has the function of completing the setting of the packer under high pressure. After the packer and the ball seat are put into the well, a soluble ball is dropped into the wellhead, and the soluble ball falls on the high-pressure ball core to establish the downhole tubing seal. During the pressure-pressurizing process, the high-pressure ball core will not fall off under the action of the locking block within the pressure-bearing range of the tubing, completing the setting of the packer. After 6 hours of setting, the soluble ball dissolves and the downhole liquid pressure balance is re-established.

[0020] 2. It has the function of opening up the production channel at low pressure. After waiting for six hours for the soluble ball to dissolve, a steel ball is thrown in. The diameter of the steel ball is larger than that of the soluble ball. The steel ball falls on the low-pressure ball core and presses to cut the shear nails. After the shear nails are cut, the low-pressure ball core moves downward. At this time, the locking block is separated from the contact surface of the low-pressure ball core, and the locking block changes from a fixed state to a free state. The low-pressure ball core moves downward and hits the high-pressure ball core and falls off together, thus safely opening up the production channel.

[0021] 3. The ball seat uses a soluble ball for high-pressure sealing. The soluble ball surface contacts the low-pressure ball core end face to establish a seal. The sealing process is safe and reliable. After the sealing is completed, wait for six hours for the soluble ball to degrade naturally, avoiding the failure of the lock block to be pressed and unlocked due to the presence of sealing liquid between the two balls when the steel ball is put in later.

[0022] 4. The circumference of the plug tube used in the ball seat is evenly divided into 8 rows and 4 columns of pressure relief holes. During the downward movement of the two ball cores, the high-pressure water flow in the pipe column flows out from multiple pressure relief holes, dispersing the water flow pressure and reducing the impact of the water hammer effect.

[0023] 5. There is an O-ring near the shear pin, which can prevent foreign matter such as salt crystals from invading the shear pin hole during the well entry process, affecting the final shear value, and prevent the pressure liquid from flowing out and causing pressure failure.

[0024] 6. The ball seat has a high-pressure way to complete the sealing of the packer and a low-pressure way to open the production channel. This way can slow down 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the ball stand of the present invention throwing a soluble ball;

[0026] Figure 2 It is a schematic diagram of casting a steel ball into a ball seat of the present invention.

[0027] 1. Seating short section; 2. Ball seat outer tube; 3. Low-pressure ball core; 4. Shear pins; 5. Locking block; 6. High-pressure ball core; 7. Plug tube; 8. O-ring; 9. First hole structure; 10. Impact part; 11. Second hole structure; 12. Trough structure. DETAILED DESCRIPTION

[0028] 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.

[0029] refer to Figure 1 , Figure 2 .

[0030] The present invention provides a high-pressure sealing ball seat with double ball cores, comprising a seating short section 1, a ball seat outer tube 2 detachably connected to the seating short section 1; a low-pressure ball core 3, which is arranged inside the ball seat outer tube 2 and connected to the ball seat outer tube 2 by shear nails 4; a high-pressure ball core 6, which is arranged inside the ball seat outer tube 2 and the outer wall of which is in contact with the inner wall of the ball seat outer tube; a locking block 5, one end of which passes through the high-pressure ball core and is embedded in the inner wall groove of the ball seat outer tube, and the other end of which is in contact with the outer wall of the low-pressure ball core. In one state, when one end of the locking block is separated from the outer wall of the low-pressure ball core, the locking block can slide away from the inner wall groove of the ball seat outer tube; and the low-pressure ball core can shear off the shear nails under pressure, so that the low-pressure ball core can hit the high-pressure ball core, thereby causing the low-pressure ball core and the high-pressure ball core to be separated from the ball seat outer tube together. The end of the ball seat outer tube away from the seating nipple is connected to a plug tube 7, and a plurality of pressure discharge holes are distributed around the plug tube to disperse and discharge the high-pressure water flow. The pressure discharge holes are evenly distributed on the plug tube wall in the form of multiple rows and columns.

[0031] In a specific embodiment of the present invention, the upper end of the landing nipple 1 is a special airtight buckle, the upper end is connected to the matching pipe column through the special airtight buckle, the lower end is connected to the upper end of the ball seat outer tube 2 through a thread, the ball seat outer tube 2 is connected to the plug tube 7 through a thread, and the plug tube 7 has 36 pressure discharge holes distributed in 8 rows and 4 columns around the circumference, which can disperse and discharge the high-pressure water flow and reduce the effect of the high-pressure water flow.

[0032] The present invention also includes a pressure structure, which includes a first hole structure 9 formed at the outer end of the inner wall of the high-pressure ball core and a collision part 10 at the inner end, and a second hole structure 11 formed in the low-pressure ball core, which is used to seal the first hole structure when a soluble ball is put in, and to seal the second hole structure when a steel ball is put in and make the end of the low-pressure ball core hit the collision part. The outer wall of the low-pressure ball core is provided with a groove structure 12, which is used to separate the outer wall of the low-pressure ball core from the outer end of the locking block, so that the high-pressure ball core can be transformed into a free state and can be separated from the outer cylinder of the ball seat. O-rings are provided on both sides of the shear pins and the locking block to prevent foreign matter from affecting the working state of the shear pins and the locking block during the process of the ball seat entering the well.

[0033] The order of adding the soluble balls and the steel balls is to first add the soluble balls, and then add the steel balls after the soluble balls are dissolved.

[0034] It also includes an elastic mechanism, which is used to eject the locking block from the inner wall groove of the ball seat outer tube when the end of the locking block is separated from the outer wall of the low-pressure ball core.

[0035] Working principle: put the soluble ball into the column to pressurize, the soluble ball falls on the high-pressure ball core 6, establish the column seal, and the pressure acts on the high-pressure ball core 6. At this time, the two ends of the locking block 5 in the high-pressure ball core 6 are fixed, and the locking block 5 is stuck in the groove of the outer tube 2 of the ball seat, so that the locking block 5 and the high-pressure ball core 6 are always fixed during the pressurization process. After the pressure is pressed to the pressure required for the packer to be sealed, stop pressing for six hours. The soluble ball dissolves, and the steel ball with a diameter larger than that of the soluble ball is put into the second hole structure of the low-pressure ball core 3. The diameter is larger than the inner diameter of the first hole structure of the high-pressure ball core 6, so the steel ball falls on the low-pressure ball core 3, and continues to pressurize. The pressure acts on the low-pressure ball core 3, and the low-pressure ball core 3 moves downward and falls off to cut the shear nails. The pressure pushes the low-pressure ball core downward. At this time, one end of the locking block 5 in the high-pressure ball core 6 is separated from the contact surface of the low-pressure ball core 3, and the other end of the locking block 5 can slide into the unlocking groove of the low-pressure ball core 3, that is, the slot structure 12 in this application. The low-pressure ball core 3 continues to move and hits the high-pressure ball core 6 and moves downward and falls off together to open the production channel. The present invention has a method of completing the sealing of the packer at high pressure and opening the production channel at low pressure. In this way, the water hammer effect caused by the instantaneous impact of high-pressure water flow under high pressure can be slowed down, effectively improving the success rate of the tool and reducing the probability of accidents downhole and at the wellhead.

[0036] 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 high-pressure setting ball seat with double ball cores, 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 arranged inside the ball seat outer cylinder and connected to the ball seat outer cylinder through shear nails; A high-pressure ball core is arranged inside the outer tube of the ball seat and its outer wall is in contact with the inner wall of the outer tube of the ball seat; A locking block, one end of which passes through the high-pressure ball core and is embedded in the inner wall groove of the ball seat outer tube, and the other end of which is in contact with the outer wall of the low-pressure ball core. When one end of the locking block is separated from the outer wall of the low-pressure ball core, the locking block can slide away from the inner wall groove of the ball seat outer tube; Furthermore, the low-pressure ball core can cut off the shear pins under pressure, so that the low-pressure ball core can hit the high-pressure ball core, thereby making the low-pressure ball core and the high-pressure ball core detach from the ball seat outer tube together.

2. A high pressure setting ball seat with double ball cores according to claim 1, characterized in that: The end of the outer tube of the ball seat away from the seating nipple is connected with a plug tube, and a plurality of pressure discharge holes are distributed around the circumference of the plug tube for dispersing and discharging the high-pressure water flow.

3. The high pressure setting ball seat with double ball cores according to claim 1, characterized in that: It also includes a pressing structure, which includes a first hole structure formed on the outer end of the inner wall of the high-pressure ball core and a collision part on the inner end, and a second hole structure formed on the low-pressure ball core, which is used to seal the first hole structure when a soluble ball is thrown in, and to seal the second hole structure when a steel ball is thrown in and make the end of the low-pressure ball core hit the collision part.

4. The high pressure setting ball seat with double ball cores according to claim 1, characterized in that: The outer wall of the low-pressure ball core is provided with a groove structure, which is used for the outer wall of the low-pressure ball core to be separated from the outer end of the locking block, so that the high-pressure ball core can be transformed into a free state and separated from the outer cylinder of the ball seat.

5. The high pressure setting ball seat with double ball cores according to claim 1, characterized in that: O-rings are arranged on both sides of the shear pin and the locking block to prevent foreign matter from affecting the working state of the shear pin and the locking block during the process of the ball seat entering the well.

6. The high pressure setting ball seat with double ball cores according to claim 2, characterized in that: The pressure relief holes are evenly distributed on the plug tube wall in the form of multiple rows and columns.

7. The high pressure setting ball seat with double ball cores according to claim 3, characterized in that: The order of adding the soluble balls and the steel balls is to first add the soluble balls and then add the steel balls after the soluble balls are dissolved.

8. The high pressure setting ball seat with double ball cores according to claim 1, characterized in that: It also includes an elastic mechanism, which is used to eject the locking block from the inner wall groove of the ball seat outer tube when the end of the locking block is separated from the outer wall of the low-pressure ball core.

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