Mandrel removable soluble bridge plug and fishing tool

Abstract

The present invention belongs to the technical field of well completion engineering for unconventional oil and gas reservoirs such as petroleum and natural gas, and specifically relates to a mandrel-removable soluble bridge plug and a salvage tool used to replace the wellhead after the fracturing construction of the oil and gas well is completed, aiming to solve the problem that the existing bridge plug cannot be used for wellhead replacement operations without injecting liquid into the wellbore. The present invention provides a mandrel-removable soluble bridge plug, including a soluble bridge plug body and a mandrel arranged in the bridge plug body; the bridge plug body and the mandrel are positioned at a locking position by a limiting mechanism, and the limiting mechanism can be disengaged from the locking position under a squeezing force. The present invention is suitable for wellhead replacement operations, and there is no need to pump liquid into the well. The fracturing wellhead can be replaced with a gas production wellhead in a manner that does not pollute the reservoir and does not affect the production, thereby saving operation costs and time.

Description

Technical Field

[0001] The invention belongs to the technical field of well completion engineering of unconventional oil and gas reservoirs such as petroleum and natural gas, and specifically relates to a mandrel-removable soluble bridge plug and a fishing tool used for replacing a wellhead after the fracturing construction of an oil and gas well is completed. Background Art

[0002] In the process of using bridge plug and perforation for fracturing, in order to meet the needs of pressure bearing and wellhead fracturing tools, a special fracturing wellhead is generally selected as the construction wellhead. After the construction is completed, some wells with sufficient gas volume and good production are often directly produced using casing. When the pressure drops and the liquid carrying capacity is insufficient, the production tubing is started under pressure. When the production tubing is under construction, the fracturing wellhead is replaced with a conventional gas production wellhead. This method causes the fracturing wellhead to be occupied for a long time, with low utilization efficiency and increased construction costs.

[0003] There are two main ways to replace the fracturing wellhead with a conventional gas production wellhead. One is to replace the wellhead by pressure reduction, and the other is to insert a temporary plugging bridge plug made of soluble materials to achieve temporary plugging. After replacing the wellhead, liquid is pumped into the wellbore, and the temporary plug is removed by pressure reduction to achieve wellbore connectivity. Both of the above methods require the injection of liquid into the wellbore, which causes certain pollution to the formation and affects production.

[0004] At present, the existing mechanically set and mechanically unsealed bridge plugs can be used for temporary plugging of reservoirs without pumping liquid. This temporary plugging can only be used in conventional operations and cannot be used in wellhead replacement operations because the bridge plug is large in size and can only pass through the fracturing wellhead smoothly, but cannot pass through the replaced gas wellhead. In addition, the current cable cannot provide a large enough unsealing force to realize the unsealing of the bridge plug. Summary of the invention

[0005] The invention provides a mandrel-removable soluble bridge plug and a fishing tool to alleviate the problem that the existing bridge plug cannot be used for wellhead replacement operations without injecting liquid into the wellbore.

[0006] In order to alleviate the above technical problems, the technical solution provided by the present invention is:

[0007] A mandrel-removable soluble bridge plug comprises a soluble bridge plug body and a mandrel arranged in the bridge plug body; the bridge plug body and the mandrel are positioned at a locking position through a limiting mechanism, and the limiting mechanism can be separated from the locking position under a squeezing force.

[0008] Furthermore, the limiting mechanism includes a fixed locking block, an opening is provided on the bridge plug body, a first insertion hole is provided on the core shaft, and the fixed locking block passes through the opening and the first insertion hole at the same time to lock the bridge plug body and the core shaft in the locking position; two fixed locking blocks are symmetrically arranged along the central axis of the bridge plug body, and the opposite end faces of the two fixed locking blocks are arranged as inclined surfaces, and the inclined surfaces approach each other from top to bottom.

[0009] Furthermore, the upper end of the core shaft is set as a first beveled surface, and a longitudinal groove is set on the side wall of the core shaft along the lowest end of the first beveled surface pointing to the lower part of the core shaft; the core shaft is provided with a hollow section and a solid section, the hollow section is a section of the cross section from the first beveled surface to the bottom surface of the longitudinal groove, and the solid section is a section from the cross section to the bottom surface of the core shaft; the first insertion hole is located on the side wall of the hollow section core shaft and is symmetrically arranged with the longitudinal groove as the axis.

[0010] Furthermore, the limiting mechanism also includes a clamping portion symmetrically arranged with respect to the central axis of the bridge plug body, the clamping portion is arranged above the fixed locking block, and the upper end surface of the fixed locking block is laterally provided with a first positioning hole and a second positioning hole located outside the first positioning hole; when the bridge plug body and the core shaft are in the locking position, the clamping portion is clamped in the first positioning hole; when the bridge plug body and the core shaft are unlocked, the clamping portion is clamped in the second positioning hole.

[0011] Furthermore, the pressing portion is provided with a spring and a locking pin arranged below the spring, and the spring always has a tendency to drive the locking pin to move downward so that the locking pin is fixed in the first positioning hole or the second positioning hole.

[0012] Furthermore, the pressing part also includes a fixing sleeve and a pressure cap which are sequentially arranged above the spring, and the pressure cap applies a downward pressure to the fixing sleeve so that the spring always has a downward pressure.

[0013] Furthermore, the bridge plug body includes an axially hollow center tube and a seating sleeve mounted on the upper end of the center tube, and the core shaft is located inside the center tube; before performing the seating process, the outer end of the fixed locking block is locked by the seating sleeve, and after performing the seating process, the seating sleeve releases the lock on the fixed locking block.

[0014] A salvage tool for salvaging the core shaft of a core shaft removable soluble bridge plug such as the above-mentioned core shaft removable type, the salvage tool comprises an outer tube, an unsealing block and a driving mechanism; a second insertion hole is opened on the side wall of the outer tube, and the unsealing block is laterally slidably connected to the second insertion hole; the driving mechanism is arranged inside the outer tube, and is configured to be able to drive the inner end of the unsealing block to move outward so that the unsealing block drives the fixed locking block to release the locking state between the bridge plug body and the core shaft.

[0015] Furthermore, the salvage tool and the mandrel are limited by a longitudinal connection mechanism, which includes a longitudinal boss arranged on the salvage tool and a longitudinal groove arranged on the mandrel; when the longitudinal boss is inserted into the longitudinal groove, the second insertion hole is opposite to the first insertion hole.

[0016] Furthermore, the driving mechanism includes a core rod, a retaining ring, a conical slider, a connecting rod and a slider arranged from top to bottom; the retaining ring is arranged as an annular structure and is connected to the upper part of the inner wall of the outer cylinder by bolts; the core rod passes through the center hole of the retaining ring and is connected to the conical slider; the diameter of the lower end face of the conical slider is smaller than the diameter of the upper end face, and the lower end face of the conical slider is connected to the slider through a connecting rod; two unsealing blocks are symmetrically arranged on both sides of the connecting rod, and the gap between the two unsealing blocks is larger than the outer diameter of the connecting rod and smaller than the outer diameter of the lower end face of the conical slider.

[0017] The beneficial effects of the mandrel-removable soluble bridge plug of the present invention are analyzed as follows:

[0018] A mandrel-removable soluble bridge plug comprises a soluble bridge plug body and a mandrel arranged in the bridge plug body; the bridge plug body and the mandrel are positioned at a locking position through a limiting mechanism, and the limiting mechanism can be separated from the locking position under a squeezing force.

[0019] After the fracturing construction of the oil and gas well is completed, the reservoir is sealed by using a core-removable soluble bridge plug. After sealing, the fracturing wellhead is replaced with a conventional gas production wellhead. After the wellhead is replaced, the limit mechanism can be separated from the locking position under a certain extrusion pressure, and the bridge plug body and the core shaft are unlocked. The separated core shaft is fished out of the wellbore to achieve wellbore connection and normal production. During the production process, the soluble bridge plug body remaining in the well gradually degrades to achieve full bore of the wellbore, so there is no need to pump liquid into the well. The fracturing wellhead can be replaced with a gas production wellhead in a way that does not pollute the reservoir and does not affect the production, saving operation costs and time. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the related technologies, the drawings required for use in the specific embodiments or the related technical descriptions will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic structural diagram of a mandrel-removable soluble bridge plug provided in an embodiment of the present invention;

[0022] Figure 2 A schematic structural diagram of a mandrel provided in an embodiment of the present invention;

[0023] Figure 3Schematic diagram of setting of a mandrel-removable soluble bridge plug provided in an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of a salvage tool provided by an embodiment of the present invention being inserted into a mandrel;

[0025] Figure 5 A schematic diagram of a salvage tool and a mandrel in a locked state provided by an embodiment of the present invention;

[0026] Figure 6 A schematic diagram of a bridge plug body after unsealing provided by an embodiment of the present invention;

[0027] Figure 7 A schematic structural diagram of a salvage tool provided in an embodiment of the present invention;

[0028] Figure 8 A schematic structural diagram of a salvage tool outer barrel provided in an embodiment of the present invention.

[0029] Fig. 9 A schematic diagram of a salvaging tool for salvaging a mandrel provided in an embodiment of the present invention.

[0030] icon:

[0031] 100-bridge plug body; 200-core shaft; 300-fishing tool; 10-seating joint; 11-lower joint; 12-sealing ring; 13-lower slip; 14-lower cone; 15-rubber cylinder; 16-center tube; 17-upper cone; 18-upper slip; 19-seating sleeve; 20-fixed locking block; 110-tightening part; 111-locking pin; 112-spring; 113-fixing sleeve; 114-pressure cap; 210-first bevel; 220-longitudinal groove; 230-first insertion hole; 310-outer tube; 320-slider; 330-unsealing block; 331-protrusion; 340-connecting rod; 350-conical slider; 360-retaining ring; 370-core rod; 311-second bevel; 312-longitudinal boss; 313-second insertion hole. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described implementation is a part of the implementation of the present invention, not all of the implementation. Based on the implementation of the present invention, all other implementations obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. Physical quantities in formulas, if not separately marked, should be understood as basic quantities of the base units of the International System of Units, or derived quantities derived from the basic quantities through mathematical operations such as multiplication, division, differentiation or integration.

[0034] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] In the process of using bridge plug and perforation for fracturing, in order to meet the needs of pressure bearing and wellhead fracturing tools, a special fracturing wellhead is generally selected as the construction wellhead. After the construction is completed, some wells with sufficient gas volume and good production are often directly produced using casing. When the pressure drops and the liquid carrying capacity is insufficient, the production tubing is started under pressure. When the production tubing is under construction, the fracturing wellhead is replaced with a conventional gas production wellhead. This method causes the fracturing wellhead to be occupied for a long time, with low utilization efficiency and increased construction costs.

[0036] There are two main ways to replace the fracturing wellhead with a conventional gas production wellhead. One is to replace the wellhead by pressure reduction, and the other is to insert a temporary plugging bridge plug made of soluble materials to achieve temporary plugging. After replacing the wellhead, liquid is pumped into the wellbore, and the temporary plug is removed by pressure reduction to achieve wellbore connectivity. Both of the above methods require the injection of liquid into the wellbore, which causes certain pollution to the formation and affects production.

[0037] At present, the existing mechanically set and mechanically unsealed bridge plugs can be used for temporary plugging of reservoirs without pumping liquid. This temporary plugging can only be used in conventional operations and cannot be used in wellhead replacement operations because the bridge plug is large in size and can only pass through the fracturing wellhead smoothly, but cannot pass through the replaced gas wellhead. In addition, the current cable cannot provide a large enough unsealing force to realize the unsealing of the bridge plug.

[0038] In view of this, the present invention provides a mandrel removable soluble bridge plug, please refer to Figure 1 The mandrel-removable soluble bridge plug comprises a soluble bridge plug body 100 and a mandrel 200 disposed in the bridge plug body 100; the bridge plug body 100 and the mandrel 200 are positioned at a locking position by a limiting mechanism, and the limiting mechanism can be disengaged from the locking position under a squeezing force.

[0039] After the fracturing construction of the oil and gas well is completed, the reservoir is sealed by using a core-removable soluble bridge plug. After sealing, the fracturing wellhead is replaced with a conventional gas production wellhead. After the wellhead is replaced, the limit mechanism can be separated from the locking position under an extrusion force, and the bridge plug body 100 and the core shaft 200 are unlocked, and the separated core shaft 200 is fished out of the wellbore to achieve wellbore connectivity and normal production. During the production process, the soluble bridge plug body 100 remaining in the well is gradually degraded to achieve full bore of the wellbore, so there is no need to pump liquid into the well. The fracturing wellhead is replaced with a gas production wellhead in a way that does not pollute the reservoir and does not affect production, saving operating costs and time.

[0040] In an optional solution of this embodiment, the limiting mechanism includes a fixed locking block 20, an opening is provided on the bridge plug body 100, and a first insertion hole 230 is provided on the mandrel 200. The fixed locking block 20 passes through the opening and the first insertion hole 230 at the same time to lock the bridge plug body 100 and the mandrel 200 in the locking position; two fixed locking blocks 20 are symmetrically arranged along the central axis of the bridge plug body 100, and the opposite end faces of the two fixed locking blocks 20 are arranged as inclined surfaces, and the inclined surfaces are close to each other from top to bottom. When an outward extrusion force is applied to the fixed locking block 20, the fixed locking block 20 moves outward and disengages from the mandrel 200, and the mandrel 200 and the bridge plug body 100 are unlocked. The opposite end faces of the fixed locking block 20 are arranged as inclined surfaces to reduce the resistance when the fixed locking block 20 is inserted into the opening and the first insertion hole 230, so that the fixed locking block 20 is easier to insert into the opening and the first insertion hole 230.

[0041] In the optional solution of this embodiment, please refer to Figure 2 The upper end of the mandrel 200 is provided with a first chamfer 210, and a longitudinal groove 220 is provided on the side wall of the mandrel 200 along the lowest end of the first chamfer 210 pointing to the lower part of the mandrel 200; the mandrel 200 is provided with a hollow section and a solid section, the hollow section is a section of the cross section from the first chamfer 210 to the bottom surface of the longitudinal groove 220, and the solid section is a section from the cross section to the bottom surface of the mandrel 200; the first insertion hole 230 is located on the side wall of the hollow section mandrel 200 and is symmetrically arranged with the longitudinal groove 220 as an axis. The solid section mandrel 200 at the lower part is used to plug the central tube of the soluble bridge plug, and the hollow section mandrel 200 at the upper part is used to realize the locking of the mandrel 200 and the bridge plug body 100.

[0042] In the optional solution of this embodiment, please refer to Figure 1 and Figure 5 The limiting mechanism also includes a tightening portion 110 symmetrically arranged with respect to the central axis of the bridge plug body 100, the tightening portion 110 is arranged above the fixed locking block 20, and the upper end surface of the fixed locking block 20 is laterally provided with a first positioning hole and a second positioning hole located outside the first positioning hole; when the bridge plug body 100 and the core shaft 200 are in the locking position, the tightening portion 110 is clamped in the first positioning hole so that the fixed locking block 20 passes through the opening and the first insertion hole 230 at the same time; when the bridge plug body 100 and the core shaft 200 are unlocked, the tightening portion 110 is clamped in the second positioning hole so that the fixed locking block 20 only passes through the opening and is separated from the first insertion hole 230.

[0043] In an optional solution of this embodiment, the pressing portion 110 is provided with a spring 112 and a locking pin 111 provided below the spring 112. The spring 112 always has a tendency to drive the locking pin 111 to move downward so that the locking pin 111 is fixed in the first positioning hole or the second positioning hole.

[0044] In an optional solution of this embodiment, the pressing portion 110 further includes a fixing sleeve 113 and a pressure cap 114 which are sequentially arranged above the spring 112 . The pressure cap 114 applies a downward pressure to the fixing sleeve 113 so that the spring 112 always has a downward pressure.

[0045] Furthermore, the abutting portion 110 also includes a cylinder with an axial hollow structure, and the lock pin 111, the spring 112, the fixing sleeve 113 and the pressure cap 114 are sequentially arranged in the cylinder from bottom to top, and the lock pin 111 includes a main plate body, an insertion portion arranged below the main plate body, and an insertion portion arranged above the plate body and extending into the spring, and the insertion portion is inserted into the first positioning hole or the second positioning hole so that the abutting portion 110 fixes the fixed locking block 20. The fixing sleeve 113 includes a limit plate and an insertion block arranged below the limit plate, the insertion block extends into the spring, and the upper part of the limit plate abuts against the lower part of the pressure cap. The pressure cap 114 is connected to the side wall of the cylinder by bolts, and the pressure cap 114 always applies a downward pressure to the fixing sleeve 113, so that the spring 112 is always in a compressed state, so that the spring 112 always has a tendency to drive the lock pin 111 to move downward, so that the lock pin 111 is inserted into the first positioning hole or the second positioning hole on the upper end surface of the fixed locking block 20.

[0046] In an optional solution of this embodiment, the bridge plug body 100 includes an axially hollow central tube 16 and a seating sleeve 19 sleeved on the upper end of the central tube 16, and the mandrel 200 is located in the central tube 16; further, the inner lower part of the central tube 16 is connected with a circular ring-shaped seating joint 10, and the lower part of the mandrel 200 abuts against the upper end surface of the seating joint 10. When the lower part of the mandrel 200 abuts against the upper end surface of the seating joint 10, the first insertion hole 230 is directly opposite to the opening, and the seating joint 10 limits the mandrel 200, and when the mandrel 200 and the bridge plug body 100 are unlocked, the mandrel 200 is prevented from falling down into the well. Furthermore, a sealing ring 12 is sleeved on the outer lower part of the mandrel 200 inside the central tube 16, so that the mandrel 200 and the bridge plug body 100 are sealed.

[0047] In an optional solution of this embodiment, the bridge plug body 100 further includes a lower joint 11 connected to the lower outer side of the central tube 16 and a setting sleeve 19, an upper slip 18, an upper cone 17, a rubber sleeve 15, a lower cone 14 and a lower slip 13 which are sequentially sleeved on the central tube 16 from top to bottom; the lower joint 11 is fixed to the central tube 16 by threads, and the lower slip 13 abuts against the upper part of the lower joint 11; before the setting process is performed, the outer end of the fixed locking block 20 is locked by the setting sleeve 19, and the fixed locking block 20 is restricted by the setting sleeve 19 and cannot move, so the core shaft 200 will not be separated from the bridge plug body 100 before the setting process. After the setting process is performed, the locking of the fixed locking block 20 by the setting sleeve 19 is released.

[0048] Please refer to Figure 3 and Figure 6 The setting and unsealing process of the mandrel removable soluble bridge plug is described as follows:

[0049] The bridge plug and perforation combined fracturing technology is used to perform fracturing construction on several reservoirs in the well. After the construction is completed, the fluid is discharged through the fracturing wellhead. After the discharge is completed, when entering the normal production process, the electric sealing tool and the mandrel removable soluble bridge plug are lowered together with the cable. After being lowered to the predetermined position, the cable is energized to start the electric sealing tool. The electric sealing tool pushes the sealing sleeve 19 on the bridge plug to move downward and releases the lock of the fixed locking block 20. The sealing sleeve 19 pushes the upper slip 18, the upper cone 17, the lower cone 14 and the lower slip 13 to squeeze the rubber cylinder 15, and the rubber cylinder 15 expands and seals, thereby realizing the setting of the mandrel removable soluble bridge plug, and the bridge plug is completed. After sealing, the reservoir and the wellbore above the bridge plug are isolated, and the wellhead can be replaced at this time; after the wellhead is replaced, an outward squeezing force is applied to the limiting mechanism to make the fixed locking block 20 move outward and disengage from the core shaft 200, so that the core shaft 200 and the bridge plug body 100 are unlocked, and the separated core shaft 200 is fished out of the wellbore to achieve wellbore connectivity and normal production. During the production process, the soluble bridge plug body 100 remaining in the well gradually degrades to achieve full bore of the wellbore, so that there is no need to pump liquid into the well, and the fracturing wellhead can be replaced with a gas production wellhead in a way that does not pollute the reservoir and does not affect production, thereby saving operating costs and time.

[0050] Embodiment 2

[0051] After the bridge plug is set and the wellhead is replaced, there are two ways to achieve wellbore connectivity. One is a temporary bridge plug made of soluble material, which requires pumping liquid into the wellbore and knocking out the core shaft in the temporary plugging head embodiment 1 by pressure. The liquid injected into the wellbore causes certain pollution to the formation and affects the production. The other is the existing mechanically set and mechanically unsealed bridge plug, which is large in size and cannot be used in the operation of replacing the wellhead.

[0052] In view of this, the present invention provides a fishing tool 300 for fishing the mandrel of the mandrel-retrievable soluble bridge plug described in Example 1. Please refer to Figures 4 to 9 The salvage tool 300 includes an outer cylinder 310, an unsealing block 330 and a driving mechanism; a second insertion hole 313 is provided on the side wall of the outer cylinder 310, and the unsealing block 330 is slidably connected to the second insertion hole 313 in a transverse direction; the driving mechanism is arranged inside the outer cylinder 310, and is configured to drive the inner end of the unsealing block 330 to move outward so that the unsealing block 330 drives the fixed locking block 20 to release the locking state between the bridge plug body 100 and the mandrel 200. The unsealing block 330 moves outward under the action of the driving mechanism, thereby pushing the fixed locking block 20 to move outward and disengage from the first insertion hole 230, and then the unsealing block 330 is inserted into the first insertion hole 230, thereby releasing the locking between the bridge plug body 100 and the mandrel 200, and at the same time, the locking between the salvage tool 300 and the mandrel 200 is realized to facilitate the subsequent salvage of the mandrel 200.

[0053] In an optional scheme of this embodiment, the salvage tool 300 and the core shaft 200 are limited by a longitudinal connecting mechanism, which includes a longitudinal boss arranged on the salvage tool 300 and a longitudinal groove 220 arranged on the core shaft 200; when the longitudinal boss is inserted into the longitudinal groove 220 and is in place, the second insertion hole 313 is opposite to the first insertion hole 230, which means that the lowest points of the first insertion hole 230 and the second insertion hole 313 are located on the same horizontal line and the two are connected to each other, so that the unsealing block 330 can slide outward from the second insertion hole 313 through the first insertion hole 230, thereby pushing the fixed locking block 20 to move outward, thereby releasing the locking state between the bridge plug body 100 and the core shaft 200.

[0054] Preferably, the lower end of the outer cylinder 310 is provided with a second chamfered surface 311, and the second chamfered surface 311 has the same inclination angle as the first chamfered surface 210. A longitudinal boss 312 having a structure corresponding to the longitudinal groove 220 is provided on the outer wall of the outer cylinder 310 along the lowermost end of the second chamfered surface 311 pointing to the upper part of the outer cylinder 310. The second chamfered surface 311 and the first chamfered surface 210 match each other, and when the fishing tool 300 is inserted into the mandrel 200, the lowest end of the second chamfered surface 311 slides to the lowest end of the first chamfered surface 210 under the action of gravity, so that the lowest end of the longitudinal boss 312 is aligned with the uppermost end of the longitudinal groove 220, and then under the action of gravity, the lowest end of the longitudinal boss 312 slides to the uppermost end of the longitudinal groove 220, thereby achieving positioning.

[0055] In an optional scheme of this embodiment, the driving mechanism includes a core rod 370, a retaining ring 360, a conical slider 350, a connecting rod 340 and a slider 320 arranged from top to bottom; the retaining ring 360 is arranged as an annular structure and the retaining ring 360 is connected to the upper part of the inner wall of the outer cylinder 310 by bolts; the core rod 370 passes through the center hole of the retaining ring 360 and is connected to the conical slider 350; the diameter of the lower end face of the conical slider 350 is smaller than the diameter of the upper end face, and the lower end face of the conical slider 350 is connected to the slider 320 by the connecting rod 340; the two unsealing blocks 330 are symmetrically arranged on both sides of the connecting rod 340, and the gap between the two unsealing blocks 330 is larger than the outer diameter of the connecting rod 340 and smaller than the outer diameter of the lower end face of the conical slider 350, so when the conical slider 350 moves downward, it will contact and push the unsealing block 330 to move outward.

[0056] Preferably, the two unsealing blocks 330 are respectively provided with protrusions 331 of a triangular plate structure near the upper end surface of the connecting rod 340, one right-angled side of the protrusion 331 is connected to the upper end surface of the unsealing block 330, the other right-angled side of the protrusion 331 faces the inner wall of the outer cylinder 310, and the hypotenuse of the protrusion 331 faces the connecting rod 340. The protrusion 331 can prevent the unsealing block 330 from falling from the second insertion hole 313 during the outward movement under the push of the conical slider 350, and the inclined surface of the protrusion 331 increases the contact area between the unsealing block 330 and the conical slider 350, which helps to push the unsealing block 330 to move outward when the conical slider 350 moves downward.

[0057] Preferably, the lower end surface of the unsealing block 330 is provided with a groove; the bottom of the side wall of the second insertion hole 313 on the outer cylinder 310 is provided with a protrusion corresponding to the groove structure, and the protrusion and the groove match to prevent the unsealing block 330 from rotating.

[0058] The process of fishing the mandrel 200 of the mandrel-retrievable soluble bridge plug using the fishing tool 300 is described in detail as follows:

[0059] After the bridge plug is sealed and the wellhead is replaced, a cable-belt salvage tool 300 is lowered, and the second beveled surface 311 of the outer cylinder 310 contacts the first beveled surface 210 of the core shaft 200. The salvage tool 300 is gradually inserted into the core shaft 200. Under the action of gravity, the lowest point of the longitudinal boss 312 on the outer cylinder 310 slides to the lowest point of the longitudinal groove 220 of the core shaft 200, thereby achieving positioning, that is, the first insertion hole 230 is opposite to the second insertion hole 313, and the unsealing block 330 on the salvage tool 300 is opposite to the fixed locking block 20 on the bridge plug body 100. Continue to lower the cable to allow the slider 320, the connecting rod 340, the tapered slider 350, the core rod 370, etc. to be in a free state. Under the action of the gravity of the core rod 370, the salvage tool 300 continues to move downward. When the tapered slider 350 contacts the unsealing block 330, the unsealing block 330 is pushed to move outward. During the unsealing block 330's outward movement, the fixed locking block 20 is pushed. The fixed locking block 20 transmits the force to the locking pin 111, pushing the locking pin 111 to overcome the force of the spring 112 and move upward, so that The locking pin 111 is disengaged from the first positioning hole and inserted into the second positioning hole, at which time, the mandrel 200 loses the control of the fixed locking block 20 and releases the locking state with the bridge plug body 100. At the same time, the unblocking block 330 slides outward from the second insertion hole 313 through the first insertion hole 230 to lock the mandrel 200 and the fishing tool 300. Then the lifting cable drives the fishing tool 300 to move upward, thereby lifting the mandrel 200 together, achieving wellbore connection and normal production. During the production process, the soluble bridge plug body 100 left in the well gradually degrades to achieve full bore of the wellbore, so that there is no need to pump liquid into the well. The fracturing wellhead is replaced with a gas production wellhead in a way that does not pollute the reservoir and does not affect the production, saving operation costs and time.

[0060] In combination with the first and second embodiments, the beneficial effects of the mandrel-retrievable soluble bridge plug and fishing tool 300 provided in the present invention are as follows:

[0061] 1. Solve the problem of using fracturing wellhead for production, which leads to the occupation of fracturing wellhead resources and increases construction costs;

[0062] 2. The wellhead can be replaced without killing the well, avoiding the pollution of the formation and the impact on production during the killing process;

[0063] 3. Solve the problem of contamination of the formation by the liquid pumped during the plugging process of the soluble bridge plug with plug.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A mandrel-removable soluble bridge plug, characterized in that: It comprises a soluble bridge plug body (100) and a core shaft (200) arranged in the bridge plug body (100); The bridge plug body (100) and the core shaft (200) are positioned at a locking position through a limiting mechanism, and the limiting mechanism can be separated from the locking position under a pressing force; The limiting mechanism comprises a fixed locking block (20), an opening is provided on the bridge plug body (100), a first insertion hole (230) is provided on the mandrel (200), and the fixed locking block (20) passes through the opening and the first insertion hole (230) at the same time to lock the bridge plug body (100) and the mandrel (200) in a locking position; Two fixed locking blocks (20) are symmetrically arranged along the central axis of the bridge plug body (100), and the opposite end surfaces of the two fixed locking blocks (20) are arranged as inclined surfaces, and the inclined surfaces are close to each other from top to bottom; The upper end of the mandrel (200) is provided with a first chamfered surface (210), and a longitudinal groove (220) is provided on the side wall of the mandrel (200) along the lowest end of the first chamfered surface (210) and pointing to the lower part of the mandrel (200); The core shaft (200) is provided with a hollow section and a solid section, the hollow section is a section of the cross section from the first chamfered surface (210) to the bottom surface of the longitudinal groove (220), and the solid section is a section from the cross section to the bottom surface of the core shaft (200); The first insertion hole (230) is located on the side wall of the hollow section core shaft (200) and is symmetrically arranged with the longitudinal groove (220) as an axis.

2. The mandrel removable soluble bridge plug according to claim 1, characterized in that: The limiting mechanism further comprises a pressing portion (110) symmetrically arranged with respect to the central axis of the bridge plug body (100), wherein the pressing portion (110) is arranged above the fixed locking block (20), and a first positioning hole and a second positioning hole located outside the first positioning hole are transversely arranged on the upper end surface of the fixed locking block (20); When the bridge plug body (100) and the core shaft (200) are in a locking position, the abutting portion (110) is fixed to the first positioning hole; When the bridge plug body (100) and the core shaft (200) are unlocked, the abutment portion (110) is fixed to the second positioning hole.

3. The mandrel removable soluble bridge plug according to claim 2, characterized in that: The abutting portion (110) is provided with a spring (112) and a locking pin (111) arranged below the spring (112); the spring (112) always has a tendency to drive the locking pin (111) to move downward so that the locking pin (111) is fixed in the first positioning hole or in the second positioning hole.

4. The mandrel removable soluble bridge plug according to claim 3, characterized in that: The pressing portion (110) further comprises a fixing sleeve (113) and a pressure cap (114) which are sequentially arranged above the spring (112); the pressure cap (114) applies a downward pressure to the fixing sleeve (113) so that the spring (112) always has a downward pressure.

5. The mandrel removable soluble bridge plug according to claim 1, characterized in that: The bridge plug body (100) comprises an axially hollow central tube (16) and a setting sleeve (19) sleeved on the upper end of the central tube (16), and the core shaft (200) is located in the central tube (16); Before the setting process is performed, the outer end of the fixed locking block (20) is locked by the setting sleeve (19), and after the setting process is performed, the locking of the fixed locking block (20) by the setting sleeve (19) is released.

6. A fishing tool for fishing the mandrel of the mandrel-retrievable soluble bridge plug according to any one of claims 1 to 5, characterized in that: The salvaging tool (300) comprises an outer cylinder (310), a deblocking block (330) and a driving mechanism; A second insertion hole (313) is formed on the side wall of the outer cylinder (310), and the unsealing block (330) is laterally slidably connected to the second insertion hole (313); The driving mechanism is disposed inside the outer cylinder (310) and is configured to be able to drive the inner end of the unsealing block (330) to move outward so that the unsealing block (330) drives the fixed locking block (20) to release the locking state between the bridge plug body (100) and the core shaft (200).

7. The fishing tool according to claim 6, characterized in that: The salvaging tool (300) and the mandrel (200) are limited by a longitudinal connection mechanism, and the longitudinal connection mechanism comprises a longitudinal boss (312) provided on the salvaging tool (300) and the longitudinal groove (220) provided on the mandrel (200); When the longitudinal boss (312) is inserted into the longitudinal groove (220) and in place, the second insertion hole (313) faces the first insertion hole (230).

8. The fishing tool according to claim 7, characterized in that: The driving mechanism comprises a core rod (370), a retaining ring (360), a conical slider (350), a connecting rod (340) and a slider (320) arranged from top to bottom; The retaining ring (360) is configured as a ring-shaped structure and the retaining ring (360) is connected to the upper portion of the inner wall of the outer cylinder (310) by means of bolts; The core rod (370) passes through the central hole of the retaining ring (360) and is connected to the conical slider (350); The diameter of the lower end surface of the tapered slider (350) is smaller than the diameter of the upper end surface, and the lower end surface of the tapered slider (350) is connected to the slider (320) via the connecting rod (340); The two unsealing blocks (330) are symmetrically arranged on both sides of the connecting rod (340), and the gap between the two unsealing blocks (330) is larger than the outer diameter of the connecting rod (340) and smaller than the outer diameter of the lower end surface of the conical sliding block (350).

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