Old-age-protecting new-mining layer-checking and hole-patching tubular column and operation method

Abstract

The invention belongs to the technical field of stable production of gas fields, and particularly provides a hole patching tubular column for old-age protection and new-layer mining and an operation method.The hole patching tubular column for old-age protection and new-layer mining comprises a circulating well washing sliding sleeve, a safety connector, an old-layer packing unit, a new-layer packing unit, a drift size gauge tool and a setting matching tool; the circulating well washing sliding sleeve, the safety connector, the old layer packing unit, the new layer packing unit, the drift size gauge tool and the setting matching tool are connected through oil pipes. The method solves the problem that the productivity of a gas well is influenced by interference between a new layer and an old layer in an existing layer checking and hole patching process measure process, isolates the old layer from the new layer, avoids interference of a deficit old layer after pressure on liquid drainage of the new layer, automatically controls the opportunity of old layer gas entering an oil pipe, avoids backflow between a high-pressure layer and a low-pressure layer, and improves the production efficiency of the gas well. And the productivity contribution of the old layer is improved while the productivity of the new layer is effectively exerted.

Description

Technical Field

[0001] The invention belongs to the technical field of gas field stable production, and particularly relates to a production-maintaining, new-layer-producing, layer-checking and hole-compensating string and an operation method thereof. Background Art

[0002] The reservoirs in the Changqing Gas Field are characterized by "low permeability and low pressure", with a rapid pressure decline and low single-well production. With the extension of production time, there are problems such as "rapid decline and difficult stable production". To fully exploit the potential of old wells and improve the ultimate recovery rate of gas reservoirs, a layer-checking and hole-compensating process is carried out in old gas fields. The purpose is to improve the productivity contribution rate of gas layers in layers with insufficient productivity contribution or no contribution in low-yield gas wells through the application of new reservoir stimulation technologies, thereby increasing the gas well production and the degree of reserve utilization and generating economic benefits. Currently, the main stimulation process uses mechanical packer stratified fracturing. When the depleted old layer is at the bottom layer, a temporary plugging process for the lower layer is adopted, and there is no interference between the old layer and the new layer. When the depleted old layer is not the bottom layer, there is interference between layers during the liquid drainage process after fracturing, which affects the productivity of the new layer. When multiple layers produce simultaneously in the later stage, there are differences in interlayer pressures, and there is a phenomenon of "backflow" from high-pressure layers to low-pressure layers during commingled production, which restricts the productivity of gas wells.

[0003] Chinese patent document with publication number CN104213894A and publication date December 17, 2014 discloses an oilfield old well selective refracturing process technology, which performs construction through process steps of assembling, running in the string, dragging the string to complete the perforation operation of the required reformed interval, setting the upper and middle packers, carrying out the fracturing construction of the bottom newly added interval, and releasing and dragging the string to the second newly added reformed interval. This document uses hydraulic jet perforation to form large-aperture and deep-penetration holes, which can effectively reduce the fracture pressure, and uses the advantages of the double-packer single-slotted fracturing process to reduce the requirements for wellhead matching and casing steel grade, effectively solving the problem of repeated reforming of oilfield old wells, and can not only complete the repeated fracturing of the reformed interval but also perform the integrated operation of hole compensation and fracturing of the newly added interval. However, this document does not solve the problem that the interference between new and old layers during the current layer-checking and hole-compensating process measures affects the productivity of gas wells. Summary of the Invention

[0004] The purpose of the production-maintaining, new-layer-producing, layer-checking and hole-compensating string and the operation method provided by the invention is to overcome the problem that the interference between new and old layers during the layer-checking and hole-compensating process measures in the prior art affects the productivity of gas wells.

[0005] To this end, the invention provides a production-maintaining, new-layer-producing, layer-checking and hole-compensating string. A tubing is sleeved inside a casing, and the production-maintaining, new-layer-producing, layer-checking and hole-compensating string is connected between the tubings. The production-maintaining, new-layer-producing, layer-checking and hole-compensating string includes a circulating well-washing sliding sleeve, a safety joint, an old-layer sealing unit, a new-layer sealing unit, a well opener and a setting assembly tool. The circulating well-washing sliding sleeve, the safety joint, the old-layer sealing unit, the new-layer sealing unit, the well opener and the setting assembly tool are connected through the tubing.

[0006] Preferably, the number of the old layer packer units is more than 1. Each old layer packer unit includes 2 hydraulic setting and retrieving packers and 1 reverse pressure differential sliding sleeve. The two hydraulic setting and retrieving packers are spaced up and down and connected by a tubing string. The reverse pressure differential sliding sleeve is connected to the tubing string between two adjacent hydraulic setting and retrieving packers.

[0007] Preferably, the number of the new layer packer units is more than 1. Each new layer packer unit includes a hydraulic setting packer, a ball injection sliding sleeve, a sliding sleeve seating joint and a hydraulic anchor. The hydraulic anchor and the hydraulic setting packer are sleeved on the outer side of the ball injection sliding sleeve in sequence from top to bottom. When the old layer is above the new layer, the lower end of the hydraulic setting packer is connected to the sliding sleeve seating joint. When the old layer is below the new layer, the lower end of the ball injection sliding sleeve is connected to the sliding sleeve seating joint. The ball injection sliding sleeve is provided with a port.

[0008] Preferably, the reverse pressure differential sliding sleeve includes a body one, a sliding sleeve, a sliding sleeve seat and a limit seat. The upper and lower ends of the body one are connected to the tubing string. The sliding sleeve is sleeved on the outer side of the upper part of the body one. The sliding sleeve seat is sleeved between the lower part of the sliding sleeve and the body one. The upper part of the limit seat is sleeved on the outer side of the lower part of the sliding sleeve, and the lower part of the limit seat is sleeved on the outer side of the body one, and the lower part of the sliding sleeve seat is located inside the limit seat and the body one.

[0009] Preferably, the inside and outside of the body one are both provided with threads. The upper part of the body one is provided with a port and a liquid passing hole in sequence from top to bottom.

[0010] Preferably, the lower part of the sliding sleeve has an enlarged diameter. A first cavity is formed among the sliding sleeve, the sliding sleeve seat and the body one. A second cavity is formed among the limit seat, the sliding sleeve and the sliding sleeve seat.

[0011] Preferably, the sliding sleeve and the body one are connected by a first shear pin and a first sealing ring, and both the first shear pin and the first sealing ring are located above the port. The sliding sleeve seat and the body one are connected by a second sealing ring and a second shear pin. A third sealing ring is connected between the sliding sleeve seat and the sliding sleeve.

[0012] Preferably, the length of the second cavity is not less than that of the first cavity, and the length of the first cavity is greater than the length of the upper sealing surface of the port.

[0013] Preferably, the setting matching tool includes a body two and a plugging core, and the plugging core is connected inside the body two.

[0014] An operation method for a tubing string for protecting old layers, producing new layers, inspecting layers and filling holes includes the following steps:

[0015] S1. Lower the old-layer-preserving, new-layer-exploiting, layer-checking and hole-filling string into the target position. Among them, the hydraulic-setting and upward-unsetting packer above is located above the old layer, the hydraulic-setting and upward-unsetting packer below is located below the old layer, and the hydraulic-setting packer of the new-layer isolation unit is located in the upper new layer.

[0016] S2. During fracturing, apply pressure to the tubing. The hydraulic-setting and upward-unsetting packer and the hydraulic-setting packer are set. Continue to apply pressure to disengage the plug core in the setting matching tool. The reverse-pressure differential sliding sleeve is in the closed state.

[0017] S3. The fracturing fluid passes through the circulating well-washing sliding sleeve, safety joint, old-layer isolation unit, new-layer isolation unit, open-hole drift and setting matching tool to fracture the lower new layer.

[0018] S4. Drop a soluble ball into the ball-injection sliding sleeve. The hydraulic-setting packer is set repeatedly to fracture the upper new layer from bottom to top in sequence.

[0019] S5. When entering the combined-layer production after fracturing, when the formation pressure of the old layer corresponding to the reverse-pressure differential sliding sleeve is greater than the target value of the production pressure in the tubing, the sliding sleeve moves downward under the action of the pressure difference between the tubing and the casing after shearing the first shear pin, exposing the port, and the casing and the tubing are connected. When the production pressure in the tubing is greater than the target value of the old-layer pressure, the sliding sleeve moves upward under the action of the throttling pressure difference to close the port until the production is completed.

[0020] Advantages of the present invention:

[0021] 1. The old-layer-preserving, new-layer-exploiting, layer-checking and hole-filling string and operation method provided by the present invention include a circulating well-washing sliding sleeve, a safety joint, an old-layer isolation unit, a new-layer isolation unit, an open-hole drift and a setting matching tool. The circulating well-washing sliding sleeve, the safety joint, the old-layer isolation unit, the new-layer isolation unit, the open-hole drift and the setting matching tool are connected by tubing. The old layer is isolated by the old-layer isolation unit, and the new layer is isolated by the new-layer isolation unit, avoiding the interference of the drained old layer on the new-layer liquid drainage after fracturing, being beneficial to the new-layer productivity, and solving the problem that the interference between the new and old layers affects the gas-well productivity in the current layer-checking and hole-filling process.

[0022] 2. The old-layer-preserving, new-layer-exploiting, layer-checking and hole-filling string and operation method provided by the present invention adopt a string with a hydraulic-setting and upward-unsetting packer and a hydraulic-setting packer to replace the existing process string that is all based on hydraulic setting and releasing of packers. During the construction process, the hydraulic-setting and upward-unsetting packer for isolating the old layer is in the set state, isolating the old layer from the new layer, avoiding the interference of the drained old layer on the new-layer liquid drainage, and being beneficial to the new-layer productivity.

[0023] 3. The tubing string and operation method for preserving old layers, extracting new layers, inspecting layers, and filling holes provided by the present invention are provided with a reverse pressure differential sliding sleeve for the old layers. It is self-opened under the action of the positive pressure difference between the annulus and the tubing. During the operation, the reverse pressure differential sliding sleeve is in a closed state, isolating the old layers from the tubing, avoiding the interference of the depleted old layers on the liquid drainage of the new layers after pressure application, and facilitating the production capacity of the new layers. During the later combined production, when the pressure of the old layers is higher than the combined production pressure in the tubing or the combined production pressure in the tubing is controlled to be lower than the pressure of the old layers, the reverse pressure differential sliding sleeve is self-opened under the action of the pressure difference between the annulus and the tubing, and vice versa, to automatically control the timing of the old layer gas entering the tubing, avoiding the "backflow" between the high and low pressure layers, ensuring the effective production capacity of the new layers while improving the production capacity contribution of the old layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described in detail below with reference to the drawings.

[0025] Figure 1 It is a schematic structural diagram of the tubing string for preserving old layers, extracting new layers, inspecting layers, and filling holes (when the old layer is above the upper new layer and the lower new layer);

[0026] Figure 2 It is a schematic structural diagram of the tubing string for preserving old layers, extracting new layers, inspecting layers, and filling holes (when the old layer is between the upper new layer and the lower new layer);

[0027] Figure 3 It is a schematic structural diagram of the reverse pressure differential sliding sleeve;

[0028] Figure 4 It is a schematic structural diagram of the setting tool.

[0029] Description of the reference numerals in the drawings: 1, casing; 2, tubing; 3, circulating and washing well sliding sleeve; 4, safety joint; 5, old layer sealing unit; 6, new layer sealing unit; 7, hole opener; 8, setting tool;

[0030] 51, hydraulic setting and upward releasing packer; 52, reverse pressure differential sliding sleeve;

[0031] 521, body one; 522, sliding sleeve; 523, shear pin one; 524, sealing ring one; 525, sealing ring three; 526, sliding sleeve seat; 527, sealing ring two; 528, shear pin two; 529, limit seat;

[0032] 5211, port; 5212, liquid passing hole; 5213, thread;

[0033] 61, hydraulic setting packer; 621, ball dropping sliding sleeve; 622, sliding sleeve seating joint; 63, hydraulic anchor;

[0034] 81, body two; 82, plugging core; 83, shear pin three; 84, sealing ring four; A, old layer; B1, upper new layer; B2, lower new layer;

[0035] 811, reduced diameter section; 812, expanded diameter section; 813, transition section; 814, plug core section; 815, flared section. Detailed implementation mode

[0036] Example 1:

[0037] As Figure 1 and Figure 2 shown, a tubing string for protecting old layers, exploring new layers, checking layers and filling holes, a tubing 2 is sleeved inside a casing 1, and the tubing string for protecting old layers, exploring new layers, checking layers and filling holes is connected between the tubings 2. The tubing string for protecting old layers, exploring new layers, checking layers and filling holes includes a circulating well flushing sleeve 3, a safety joint 4, an old layer sealing unit 5, a new layer sealing unit 6, a hole opener 7 and a setting matching tool 8. The circulating well flushing sleeve 3, the safety joint 4, the old layer sealing unit 5, the new layer sealing unit 6, the hole opener 7 and the setting matching tool 8 are connected through the tubing 2.

[0038] By sealing the old layers with the old layer sealing unit 5 and sealing the new layers with the new layer sealing unit 6, the interference of the depleted old layers after fracturing on the liquid drainage of the new layers is avoided, which is beneficial to the productivity of the new layers and solves the problem that the interference between the new and old layers affects the productivity of the gas well during the current layer checking and hole filling process and measures.

[0039] Example 2:

[0040] On the basis of Example 1, the number of the old layer sealing units 5 is more than 1. Each old layer sealing unit 5 includes 2 hydraulic setting and pulling-up releasing packers 51 and 1 reverse pressure difference sleeve 52. The two hydraulic setting and pulling-up releasing packers 51 are spaced up and down and connected through the tubing 2. The reverse pressure difference sleeve 52 is connected to the tubing 2 between two adjacent hydraulic setting and pulling-up releasing packers 51.

[0041] Specifically, it is selected according to the number of old layers to meet the actual requirements. The hydraulic setting and pulling-up releasing packer 51 is used to replace the existing process tubing string based on hydraulic setting and releasing packers. During the construction process, the hydraulic setting and pulling-up releasing packer 51 for sealing the old layers is in the set state, isolating the old layers from the new layers, avoiding the interference of the depleted old layers after fracturing on the liquid drainage of the new layers, and being beneficial to the productivity of the new layers. The hydraulic setting and pulling-up releasing packer 51 is preferably a Y441 packer.

[0042] Preferably, as Figure 3 shown, the reverse pressure difference sleeve 52 includes a body one 521, a sleeve 522, a sleeve seat 526 and a limit seat 529. The upper and lower ends of the body one 521 are connected to the tubing 2. The outside of the upper part of the body one 521 is sleeved with the sleeve 522. A sleeve seat 526 is sleeved between the lower part of the sleeve 522 and the body one 521. The outside of the lower part of the sleeve 522 is sleeved with the upper part of the limit seat 529. The lower part of the limit seat 529 is sleeved outside the body one 521, and the lower part of the sleeve seat 526 is located inside the limit seat 529 and the body one 521.

[0043] Specifically, a reverse pressure differential sliding sleeve 52 is provided for the old formation, which is self-opened under the action of the positive pressure difference between the casing annulus and the tubing. During the operation, the reverse pressure differential sliding sleeve 52 is in a closed state (i.e., the sliding sleeve 522 blocks the opening), isolating the old formation from the tubing, avoiding the interference of the old formation with fluid drainage of the new formation after fracturing, and facilitating the productivity of the new formation. During the later commingled production, when the pressure of the old formation is higher than the commingled production pressure in the tubing or the commingled production pressure in the tubing is controlled to be lower than the pressure of the old formation, the reverse pressure differential sliding sleeve 52 is self-opened under the action of the pressure difference between the casing annulus and the tubing (i.e., the sliding sleeve 522 slides to expose the opening), and vice versa for closing, automatically controlling the timing of the old formation gas entering the tubing, avoiding "backflow" between high- and low-pressure formations, ensuring the effective productivity of the new formation while increasing the productivity contribution of the old formation.

[0044] Preferably, threads 5213 are provided both inside and outside the main body one 521. The upper part of the main body one 521 is successively provided with a port 5211 and a liquid passing hole 5212 from top to bottom.

[0045] The threads facilitate connection and disassembly. Specifically, the threads provided inside and outside the main body one 521 are tubing taper threads. The upper female thread and the lower male thread of the main body one 521 are both sealed pipe thread joints, and the thread 5213 is a common thread joint; the port 5211 and the liquid passing hole 5212 facilitate the flow of liquid or gas.

[0046] Preferably, the lower part of the sliding sleeve 522 has an expanded diameter. A first cavity is formed between the sliding sleeve 522, the sliding sleeve seat 526 and the main body one 521, and a second cavity is formed among the limit seat 529, the sliding sleeve 522 and the sliding sleeve seat 526.

[0047] The expanded diameter of the lower part of the sliding sleeve 522 is conducive to connecting with the sliding sleeve seat 526 inside. The formed first cavity and second cavity are conducive to the up and down movement of the sliding sleeve 522, and then closing or opening the port 5211.

[0048] Preferably, the sliding sleeve 522 and the main body one 521 are connected by a first shear pin 523 and a first sealing ring 524, and both the first shear pin 523 and the first sealing ring 524 are located above the port 5211; the sliding sleeve seat 526 and the main body one 521 are connected by a second sealing ring 527 and a second shear pin 528, and a third sealing ring 525 is connected between the sliding sleeve seat 526 and the sliding sleeve 522.

[0049] The first shear pin 523 and the second shear pin 528 are convenient for fixing and shearing, meeting the requirements of fixing and moving, and the first sealing ring 524, the second sealing ring 527 and the third sealing ring 525 meet the sealing requirements.

[0050] Preferably, the first shear pin 523 is made of a soluble material.

[0051] Specifically, the first shear pin 523 is made of a soluble material. After being lowered into the well, after the fracturing and flowback operations of the new formation are completed and production starts, the first shear pin 523 self-dissolves, the fixing between the sliding sleeve 522 and the first body 521 is released, the sliding sleeve 522 opens, the pressure difference between the annulus and the tubing decreases accordingly, the self-opening condition is reduced, and it is easier to open.

[0052] Preferably, the length of the second cavity is not less than the length of the first cavity, and the length of the first cavity is greater than the length of the upper sealing surface of the port 5211.

[0053] The length of the second cavity not being less than the length of the first cavity ensures the sufficient downward movement of the sliding sleeve 522, and the length of the first cavity being greater than the length of the upper sealing surface of the port 5211 ensures the full opening and closing of the port 5211.

[0054] Preferably, when the sliding sleeve 522 is not moved, the fluid passing hole 5212 is located inside the first cavity.

[0055] Embodiment 3:

[0056] Based on Embodiment 2, the number of the new formation isolation units 6 is more than 1. Each new formation isolation unit 6 includes a hydraulic setting packer 61, a ball injection sliding sleeve 621, a sliding sleeve seating joint 622, and a hydraulic anchor 63. The hydraulic anchor 63 and the hydraulic setting packer 61 are sleeved on the outside of the ball injection sliding sleeve 621 in sequence from top to bottom; when the old formation is above the new formation, the lower end of the hydraulic setting packer 61 is connected to the sliding sleeve seating joint 622; when the old formation is below the new formation, the lower end of the ball injection sliding sleeve 621 is connected to the sliding sleeve seating joint 622; a port is provided on the ball injection sliding sleeve 621.

[0057] Specifically, the number of the new formation isolation units 6 is determined according to the number of new formations. During use, a soluble ball is injected into the ball injection sliding sleeve 621, the sliding sleeve core moves down into the sliding sleeve seating joint 622, and the port on the ball injection sliding sleeve 621 is exposed to form a fracturing channel for this layer.

[0058] Specifically, the hydraulic setting packer 61 adopts a K344 packer or a hydraulic setting and pulling-to-release packer. During the operation, the hydraulic setting and pulling-to-release packer 51 for isolating the old formation is in the set state, isolating the annulus between the old formation and the new formation casing, avoiding the interference of the drained old formation on the new formation's liquid drainage after fracturing, and being beneficial to the productivity of the new formation.

[0059] Embodiment 4:

[0060] Based on Embodiment 3, as Figure 4 shown, the setting matching tool 8 includes a second body 81 and a plug core 82, and the plug core 82 is connected inside the second body 81.

[0061] The main body II 81 is connected to the tubing 2 through a male buckle. Through the cooperation of the main body II 81 and the plug core 82, it is convenient to block the tubing to ensure the safety of the tubing string being lowered under pressure and to establish a new fracturing channel at the bottom layer or block the fracturing channel of this layer in the later stage.

[0062] Preferably, inside the main body II 81, from top to bottom, there are a transition section 813, a reduced-diameter section 811, a plug core section 814, an expanded-diameter section 812, and a flared section 815 in sequence. The shape of the transition section 813 is an inverted cone. The outer diameter of the reduced-diameter section 811 is the same as the outer diameter at the lower end of the transition section 813. The outer diameter of the plug core section 814 is larger than the outer diameter of the reduced-diameter section 811. The outer diameter of the expanded-diameter section 812 is the same as the outer diameter of the plug core section 814. The diameter of the flared section 815 increases from top to bottom.

[0063] Specifically, when a soluble ball is dropped into the wellhead to the transition section 813 of the setting tool 8, 813 is used for seating the ball, and the plug core section 814 is used for limiting the plug core 82. If the shear pin III 83 fails, due to the end-face limitation of the plug core section 814, when lowering under pressure and there is pressure in the well, it can still ensure that the tubing is blocked. And this structure is convenient for extruding the plug core 82 out of the main body II 81 to establish a channel during pressure application.

[0064] Preferably, the outer side of the plug core 82 is hermetically connected to the main body II 81 through a shear pin III 83 and a seal ring IV 84. During use, after the drill pipe is lowered to the position, apply pressure to cut the shear pin III 83, so that the plug core 82 is disengaged from the plug core section 814. Drop a soluble ball into the wellhead to the transition section 813 of the setting tool 8, and apply pressure to set the hydraulic setting and upward releasing packer 51 and the hydraulic setting packer 61 to isolate the annulus between the old layer and the new layer casing. After the soluble ball dissolves, the setting tool 8 restores the through-hole diameter to provide a channel for fracturing the new layer at the bottom. The structure is simple.

[0065] Example 5:

[0066] Based on Example 4, an operation method for a tubing string for protecting the old layer, extracting the new layer, inspecting the layer, and filling the hole includes the following steps:

[0067] S1. Lower the tubing string for protecting the old layer, extracting the new layer, inspecting the layer, and filling the hole to the target position. Among them, the upper hydraulic setting and upward releasing packer 51 is located above the old layer, the lower hydraulic setting and upward releasing packer 51 is located between the old layer and the new upper layer B1, and the hydraulic setting packer 61 of the new layer sealing unit 6 is located in the new upper layer.

[0068] Specifically, before lowering the tubing string for protecting the old layer, extracting the new layer, inspecting the layer, and filling the hole to the target position, first kill the well, remove the wellhead, install the blowout preventer, pull out the original well tubing string, ream the well, scrape, wash the well, and conduct a wellbore pressure test; then perforate the new layer (under pressure) by cable transmission; after the perforation operation is completed, (using the underpressure operation device, under pressure) lower the tubing string for protecting the old layer, extracting the new layer, inspecting the layer, and filling the hole to the designed position.

[0069] S2. During fracturing, pressure is applied to the tubing 2 to set the hydraulic setting and retrieving packer 51 and the hydraulic setting packer 61, and further pressure is applied to disengage the plug core 82 in the setting accessory tool 8; the reverse differential pressure sliding sleeve 52 is in the closed state;

[0070] Specifically, before fracturing, the wellhead is modified into a fracturing and gas testing wellhead device (from bottom to top): wellhead large cross joint + KQ65 - 70 fracturing and gas testing wellhead, and then pressure is applied to disengage the plug core 82 in the setting accessory tool 8.

[0071] S3. The fracturing fluid fractures the lower new layer B2 through the circulating well washing sliding sleeve 3, safety joint 4, old layer sealing unit 5, new layer sealing unit 6, well flushing gauge 7 and setting accessory tool 8;

[0072] Specifically, a soluble ball is dropped into the wellhead to the transition section 813 of the setting accessory tool 8, and pressure is built up to set the hydraulic setting and retrieving packer 51 and the hydraulic setting packer 61, isolating the annulus between the old layer and the new layer casing; after the soluble ball dissolves, the setting accessory tool 8 resumes its through - hole diameter, providing a channel for fracturing the bottom new layer, with a simple structure.

[0073] S4. Soluble balls are dropped to the ball - dropping sliding sleeve 621, and the hydraulic setting packer 61 is set multiple times to fracture the upper new layers from bottom to top in sequence;

[0074] Specifically, soluble balls of gradually increasing size are dropped to the ball - dropping sliding sleeve 621 in sequence. The sleeve core moves down into the sleeve seating joint 622, exposing the port on the ball - dropping sliding sleeve 621 to form a fracturing channel for this layer. The hydraulic setting packer 61 is set multiple times to fracture the upper new layers from bottom to top in sequence; after the new layer transformation measures are completed by dropping soluble balls from bottom to top, the well is opened after 20 - 40 minutes, and the well is flowed back, drained, and the new layers are combined for production testing.

[0075] S5. When entering combined production after fracturing, when the formation pressure of the old layer corresponding to the reverse differential pressure sliding sleeve 52 is greater than the production pressure target value in the tubing 2, the sliding sleeve 522 moves down after shearing the shear pin 523 under the action of the oil - casing pressure difference, exposing the port 5211, and the casing 1 and the tubing 2 are connected; when the production pressure in the tubing 2 is greater than the old layer pressure target value, the sliding sleeve 522 moves up under the action of the throttling pressure difference to close the port 5211; until the production is completed.

[0076] The present invention solves the problems existing in the current main process of gas field layer inspection and hole compensation by mechanical - sealed stratified fracturing. When the depleted old layer is not the bottommost layer, there is interference between layers during the liquid drainage process after fracturing, which affects the productivity of the new layer. When multiple layers are produced simultaneously in the later stage, there are differences in inter - layer pressures, and there is a phenomenon of "back - flow" from the high - pressure layer to the low - pressure layer during combined production, restricting the productivity of gas wells. The pipe string timely controls the timing of the old layer gas entering the tubing, ensuring the effective productivity of the new layer while improving the productivity utilization of the old layer, thereby increasing the gas well production and the degree of reserve utilization, and generating economic benefits.

[0077] In the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "inner", etc., indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings, 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. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation of the present invention.

[0078] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. Any design identical or similar to the present invention falls within the scope of protection of the present invention.

Claims

1. A tubing string for maintaining old production, exploring new layers, checking layers and filling holes. A tubing (2) is sleeved inside a casing (1), and the tubing string for maintaining old production, exploring new layers, checking layers and filling holes is connected between the tubings (2). It is characterized in that: The old layer preserving, new layer exploring, layer checking and hole compensating string includes a circulating well flushing sleeve (3), a safety joint (4), an old layer sealing unit (5), a new layer sealing unit (6), a well flushing gauge (7) and a setting matching tool (8). The circulating well flushing sleeve (3), the safety joint (4), the old layer sealing unit (5), the new layer sealing unit (6), the well flushing gauge (7) and the setting matching tool (8) are connected through a tubing string (2).

2. The old-preserving, new-exploring, layer-checking and hole-filling string according to claim 1, characterized in that: The number of the old layer sealing units (5) is more than 1. Each old layer sealing unit (5) includes two hydraulic setting and lifting releasing packers (51) and one reverse pressure difference sleeve (52). The two hydraulic setting and lifting releasing packers (51) are spaced up and down and connected through the tubing string (2). The reverse pressure difference sleeve (52) is connected to the tubing string (2) between two adjacent hydraulic setting and lifting releasing packers (51).

3. The old-preserving and new-exploring logging and hole-filling string according to claim 1, characterized in that: The number of the new layer sealing units (6) is more than 1. Each new layer sealing unit (6) includes a hydraulic setting packer (61), a ball dropping sleeve (621), a sleeve seating joint (622) and a hydraulic anchor (63). The hydraulic anchor (63) and the hydraulic setting packer (61) are sleeved on the outer side of the ball dropping sleeve (621) in sequence from top to bottom. When the old layer is above the new layer, the lower end of the hydraulic setting packer (61) is connected to the sleeve seating joint (622). When the old layer is below the new layer, the lower end of the ball dropping sleeve (621) is connected to the sleeve seating joint (622). The ball dropping sleeve (621) is provided with a port.

4. The old-preserving, new-exploring, layer-checking and hole-filling string according to claim 2, characterized in that: The reverse pressure difference sleeve (52) includes a body one (521), a sleeve (522), a sleeve seat (526) and a limit seat (529). The upper and lower ends of the body one (521) are connected to the tubing string (2). The sleeve (522) is sleeved on the outer side of the upper part of the body one (521). The sleeve seat (526) is sleeved between the lower part of the sleeve (522) and the body one (521). The upper part of the limit seat (529) is sleeved on the outer side of the lower part of the sleeve (522). The lower part of the limit seat (529) is sleeved on the outer side of the body one (521), and the lower part of the sleeve seat (526) is located inside the limit seat (529) and the body one (521).

5. The old-preserving and new-exploring hole-checking and hole-filling string according to claim 4, wherein: Threads (5213) are arranged both inside and outside the body one (521). A port (5211) and a liquid passing hole (5212) are arranged on the upper part of the body one (521) in sequence from top to bottom.

6. The old-preserving, new-exploring, layer-checking and hole-filling string according to claim 5, wherein: The lower part of the sleeve (522) has an expanded diameter. A first cavity is formed among the sleeve (522), the sleeve seat (526) and the body one (521). A second cavity is formed among the limit seat (529), the sleeve (522) and the sleeve seat (526).

7. The old-preserving and new-exploring layer-checking and hole-filling string according to claim 6, wherein: The sleeve (522) and the body one (521) are connected through a first shear pin (523) and a first sealing ring (524), and both the first shear pin (523) and the first sealing ring (524) are located above the port (5211). The sleeve seat (526) and the body one (521) are connected through a second sealing ring (527) and a second shear pin (528). A third sealing ring (525) is arranged between the sleeve seat (526) and the sleeve (522).

8. The old-preserving, new-exploring, layer-checking and hole-filling string according to claim 6, wherein: The length of the second cavity is not less than that of the first cavity, and the length of the first cavity is greater than the length of the upper sealing surface of the port (5211).

9. The old-preserving, new-exploring, layer-checking and hole-filling string according to claim 1, characterized in that: The setting tool (8) includes a second body (81) and a plug core (82), and the plug core (82) is connected inside the second body (81).

10. An operating method for a tubing string for preserving old layers, extracting new layers, inspecting layers and filling holes, characterized in that: It includes the following steps: S1. Lower the old-layer-preserving, new-layer-exploiting, layer-checking, and hole-filling string to the target position. Among them, the hydraulic setting and upward-releasing packer (51) above is located above the old layer, the hydraulic setting and upward-releasing packer (51) below is located below the old layer, and the hydraulic setting packer (61) of the new-layer isolation unit (6) is located in the upper new layer; S2. During fracturing, pressurize the tubing (2). The hydraulic setting and upward-releasing packer (51) and the hydraulic setting packer (61) are set. Continue to pressurize to disengage the plug core (82) in the setting tool (8); the reverse differential pressure sliding sleeve (52) is in the closed state; S3. The fracturing fluid passes through the circulating well-washing sliding sleeve (3), safety joint (4), old-layer isolation unit (5), new-layer isolation unit (6), open hole wiper (7) and setting tool (8) to fracture the lower new layer; S4. Drop a soluble ball into the ball-seating sliding sleeve (621). The hydraulic setting packer (61) is set repeatedly for multiple times to fracture the upper new layer from bottom to top in sequence; S5. When entering the combined-layer production after fracturing is completed, when the formation pressure of the old layer corresponding to the reverse differential pressure sliding sleeve (52) is greater than the target value of the production pressure in the tubing (2), the sliding sleeve (522) moves downward after shearing the first shear pin (523) under the action of the differential pressure between the tubing and the casing, exposing the port (5211), and the casing (1) and the tubing (2) are connected; when the production pressure in the tubing (2) is greater than the target value of the old-layer pressure, the sliding sleeve (522) moves upward under the action of the throttling differential pressure to close the port (5211); until the production is completed.

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