Offshore shale oil high pressure slim hole completion safety barrier tubing string

Abstract

The present application relates to oilfield completion and oil production technical field, provide a kind of offshore shale oil high pressure small hole completion safety barrier process pipe column, comprising: outer pipe column, inner pipe column;Outer pipe column includes permanent packer, bushing sliding sleeve;Inner pipe column includes sequentially connected positioning back insertion seal, hydraulic switch tool;Before oil production, bushing sliding sleeve is closed state before outer pipe column is inserted into well, realize the high pressure plugging to entire wellbore;When oil production, inner pipe column is back inserted into outer pipe column, and the positioning back insertion seal of inner pipe column is positioned to the rear of permanent packer, and the bushing sliding sleeve in closed state is opened by the way of ball pressure through hydraulic switch tool, establishes oil production passage.The present application not only plays the role of shale oil high pressure safety barrier, provides security guarantee for subsequent upper completion construction operation, but also facilitates later oil production operation, effectively solve the problem that shale oil reservoir exploitation small hole high pressure well requires high reliability to downhole safety barrier.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield completion and oil production technology, and in particular to a safety barrier process string for offshore shale oil high-pressure slim-hole completion. Background Art

[0002] As conventional oil and gas production continues to decline worldwide, exploration concepts are gradually shifting and innovating, making unconventional oil and gas resources such as shale oil an important part of the resource ladder. Shale layers can serve as both source and reservoir rocks for oil and gas. Reservoirs have characteristics such as continuous distribution, low porosity, ultra-low permeability, and high brittleness. Due to these characteristics of shale layers, they generally need to be released and produced through fracturing operations. However, after fracturing, the reservoir pressure is high and the reservoir needs to be protected, making it impossible to use high-density wellbore pressure for high-pressure completion operations. In addition, the reservoir's production capacity varies greatly throughout the production process and contains sand. This places higher demands on the strength, corrosion resistance, and erosion damage resistance of high-pressure completion tools. To ensure the successful implementation of high-pressure completion, high-pressure completion requires a higher reliability of the downhole barrier.

[0003] Traditional downhole process tubing cannot solve the problem of high reliability requirements for downhole safety barriers in small-hole, high-pressure wells for shale oil reservoir exploitation, resulting in an inability to provide safety guarantees for well completion operations, affecting oil production operations. Summary of the Invention

[0004] The purpose of the present invention is to solve at least one technical problem in the background technology and provide a high-pressure slim-hole completion safety barrier process string for offshore shale oil.

[0005] To achieve the above-mentioned object, the present invention provides a high-pressure slim-hole completion safety barrier process string for offshore shale oil, comprising:

[0006] The outer string is a hanging isolation string used to hang the string and isolate the casing annulus and formation high pressure;

[0007] Inner tubing string, which is a back-inserted sealed production tubing string;

[0008] The outer pipe string includes a permanent packer, a milling extension tube, and an intubation sleeve connected in sequence;

[0009] The inner pipe string includes a positioning back-insertion seal and a hydraulic switch tool connected in sequence;

[0010] Before oil production, the outer string is placed in the well before the insertion sleeve is in a closed state. After the well reaches the specified depth, the permanent packer is set and the entire wellbore is sealed. After the permanent packer is set, the outer string is suspended and anchored on the casing. At this time, the permanent packer seals the casing annulus pressure, and the insertion sleeve is in a closed state, achieving high-pressure plugging of the entire wellbore.

[0011] During oil production, the inner pipe string is inserted back into the outer pipe string. After the inner pipe string is positioned and sealed to the top of the permanent packer, the closed insert sleeve is opened by a hydraulic switch tool through a ball-throwing method to establish an oil production channel.

[0012] After oil production, the inner pipe string is lifted up, and the intubation sleeve is closed by the hydraulic switch tool to close the oil production channel.

[0013] According to one aspect of the present invention, the cannula sliding sleeve is composed of an upper joint, a closing sleeve, an intermediate connecting sleeve, a combined seal, and a lower joint;

[0014] An elastic sleeve locking claw is provided at one end of the closing sleeve. When the intubation sleeve is in the closed state, the elastic sleeve locking claw of the closing sleeve is locked in the groove provided on the upper joint. At this time, the combined seal is located at both ends of the middle connecting sleeve, and cooperates with the sealing surface of the closing sleeve to form a seal, isolating the pressure from the formation and forming a safety barrier.

[0015] According to one aspect of the present invention, a long hole is provided in the middle of the closing sleeve. When the closing sleeve moves axially downward, the long hole of the closing sleeve and the long hole of the intermediate connecting sleeve are connected, the inserting sleeve is opened, and an oil production channel is established. The oil enters the oil pipeline through the inserting sleeve to the ground.

[0016] According to one aspect of the present invention, the outer tubing string further comprises: a foreign matter receiving oil pipe connected to the lower end of the inserting sleeve for receiving foreign matter debris deposited in the oil pipe.

[0017] According to one aspect of the present invention, the outer tubing string further comprises: a one-way float shoe, which is connected to the lower end of the foreign body containing oil pipe. The one-way float shoe is conductive when pressurized in the forward direction but blocked in the reverse direction, and is used to shield the high pressure from the formation.

[0018] According to one aspect of the present invention, when the inner tubing string is inserted back into the outer tubing string, the maximum diameter of the upper joint of the positioning back-insertion seal is positioned to the remaining top of the permanent packer, the locking claw of the positioning back-insertion seal cooperates with the locking groove of the permanent packer to form an anchor, and the vulcanized ring of the positioning back-insertion seal cooperates with the central pipe of the permanent packer to form a seal.

[0019] According to one aspect of the present invention, a matching short section is provided between the positioning and re-insertion seal and the hydraulic switch tool. When the positioning and re-insertion seal is re-inserted to the permanent packer and positioned, the length of the matching short section is adjusted so that the lower plug of the hydraulic switch tool is located at the locking claw of the closing sleeve elastic sleeve in the inserting sleeve.

[0020] According to one aspect of the present invention, the hydraulic switch tool is composed of an upper joint, a sliding ball seat, a shear pin, and a plug;

[0021] The upper joint is connected to the lower end of the matching short section;

[0022] The sliding ball seat extends into the interior of the upper joint, and the upper end of the sliding ball seat is provided with a support position for supporting a soluble ball inserted into the inner pipe column to realize pressure holding in the inner pipe column;

[0023] The outer wall of the lower end of the sliding ball seat is connected to the lower end of the upper joint through the shear pin;

[0024] The plug is connected to the lower end of the sliding ball seat;

[0025] After the inner string hydraulic switch tool is lowered to the specified position, a soluble ball is thrown into the inner string. After the soluble ball falls into the support position of the sliding ball seat, the shear pin is cut off by the pressure of the inner string. The plug is pushed downward to push open the insert sleeve to establish an oil production channel.

[0026] According to one aspect of the present invention, when the cannula sleeve needs to be closed, the inner pipe column is lifted, and the plug in the hydraulic switch tool lifts the closing sleeve through cooperation with the elastic sleeve locking claw at the end of the closing sleeve, thereby closing the cannula sleeve.

[0027] According to the present invention, addressing the high reliability requirements of downhole barriers during high-pressure well completion, a downhole safety barrier process string is proposed for protecting shale oil reservoirs and performing high-pressure well completion operations after fracturing. This safety barrier process string comprises an inner and outer tool string (i.e., an inner string and an outer string). The outer string is a suspended isolation string. From top to bottom, the outer string comprises a permanent packer, a milling extension tube, a cannulated sleeve, a foreign body containment tubing, and a one-way float shoe. After the permanent packer, carrying these tools, reaches the designed depth, it is set using a sealing tool. The tool is suspended and anchored on the casing. The combination of the permanent packer's rubber sleeve and the cannulated sleeve seals the formation's high pressure, acting as a safety barrier. The inner string is a re-insertion sealing production string. From top to bottom, the inner string comprises a positioning re-insertion seal, a lengthened short joint, and a hydraulic opening tool. The hydraulic opening tool applies pressure by dropping a ball to open the cannulated sleeve of the outer string, establishing an oil production channel. This process string design is simple, safe and reliable. It not only serves as a high-pressure safety barrier for shale oil, provides safety for subsequent upper completion operations, but also facilitates later oil production operations. The production channel can be established by simply dropping balls and pressure. It is a safe, economical and reliable construction operation solution, which effectively solves the problem of high reliability requirements for downhole safety barriers in small-hole high-pressure wells for shale oil reservoir exploitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A cross-sectional view schematically showing an outer string structural arrangement according to an embodiment of the present invention;

[0029] Figure 2 A cross-sectional view schematically showing an inner string structural arrangement according to one embodiment of the present invention;

[0030] Figure 3 A cross-sectional view schematically showing the structural arrangement of a cannula sleeve according to one embodiment of the present invention;

[0031] Figure 4 A schematic diagram showing the structural arrangement of a locking claw for positioning and re-insertion sealing according to an embodiment of the present invention;

[0032] Figure 5 A cross-sectional view schematically shows the structural arrangement of a hydraulic switch tool according to one embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only for enabling those skilled in the art to better understand and implement the present invention, rather than implying any limitation on the scope of the present invention.

[0034] As used herein, the term "including" and variations thereof are to be interpreted as open-ended terms meaning "including, but not limited to." The term "based on" is to be interpreted as "based, at least in part, on." The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment."

[0035] Figure 1 A cross-sectional view schematically showing an outer string structural arrangement according to an embodiment of the present invention; Figure 2 Schematically shows a cross-sectional view of the inner column structure arrangement according to one embodiment of the present invention. Figure 1 and Figure 2 As shown, in this embodiment, the offshore shale oil high-pressure slim-hole completion safety barrier process string includes:

[0036] The outer string is a hanging isolation string used to hang the string and isolate the casing annulus and formation high pressure;

[0037] Inner tubing string, which is a back-inserted sealed production tubing string;

[0038] The outer string includes a permanent packer 1, a milling extension tube 2, and an intubation sleeve 3 connected in sequence;

[0039] The inner pipe string includes a positioning back-insertion seal 6 and a hydraulic switch tool 8 connected in sequence;

[0040] Before oil production, the outer string is placed in the well before the insertion sleeve 3 is in a closed state. After the well reaches the specified depth, the permanent packer 1 is set and the entire wellbore is sealed. After the permanent packer 1 is set, the outer string is suspended and anchored on the casing. At this time, the permanent packer 1 seals the casing annulus pressure, and the insertion sleeve 3 is in a closed state, achieving high-pressure plugging of the entire wellbore;

[0041] During oil production, the inner string is inserted back into the outer string. After the positioning and re-insertion seal 6 of the inner string is positioned to the top of the permanent packer 1, the closed insertion sleeve 3 is opened by the hydraulic switch tool 8 by ball-throwing pressure to establish an oil production channel.

[0042] After oil production, the inner pipe string is lifted up, and the intubation sleeve 3 is closed by the hydraulic switch tool 8 to close the oil production channel.

[0043] In this embodiment, the permanent packer 1 in the outer string is composed of an anchoring unit and a rubber cartridge unit, and its main function is to provide anchoring and sealing effects.

[0044] Furthermore, Figure 3 A schematic cross-sectional view of the structure arrangement of the cannula sleeve according to one embodiment of the present invention is shown. Figure 3 As shown, in this embodiment, the cannula sliding sleeve 3 is composed of an upper joint 301, a closing sleeve 302, an intermediate connecting sleeve 303, a combined seal 304, and a lower joint 305;

[0045] An elastic sleeve locking claw 3021 is provided at one end of the closing sleeve 302. When the intubation sleeve 3 is in the closed state, the elastic sleeve locking claw 3021 of the closing sleeve 302 is locked in the groove 3011 provided on the upper joint 301. At this time, the combined seal 304 is located at both ends of the middle connecting sleeve 303, and cooperates with the sealing surface of the closing sleeve 302 to form a seal, isolating the pressure from the formation and forming a safety barrier.

[0046] Furthermore, if Figure 3 As shown, in this embodiment, a long hole 3022 is provided in the middle of the closing sleeve 302. When the closing sleeve 302 moves axially downward, the long hole 3022 of the closing sleeve 302 and the long hole 3031 of the intermediate connecting sleeve 303 are connected, the inserting sleeve 3 is opened, and an oil production channel is established. The oil enters the oil pipe production ground through the inserting sleeve 3.

[0047] In this embodiment, the main function of the cannulated sleeve 3 in the outer string is to connect to the formation. It is opened and closed by a dedicated hydraulic opening and closing tool 8, which is connected to the lower portion of the positioning and re-insertion seal 6. To open the cannulated sleeve 3, a soluble ball is dropped into the ball seat inside the hydraulic opening and closing tool 8. Pressurizing the re-inserted string opens the cannulated sleeve 3. To close it, the re-inserted seal string is lifted to close it. The cannulated sleeve 3 can be opened and closed repeatedly, making it easy to replace the string above the barrier.

[0048] Furthermore, if Figure 1 As shown, in this embodiment, the outer tubing string also includes: a foreign matter containing oil pipe 4, which is connected to the lower end of the insertion sleeve 3 and is used to receive foreign debris deposited in the oil pipe to prevent excessive deposition from burying the switch lock claw of the closing sleeve 302 in the insertion sleeve 3, causing the insertion sleeve 3 to fail to open and close normally.

[0049] Furthermore, if Figure 1 As shown, in this embodiment, the outer pipe string also includes: a one-way float shoe 5, which is connected to the lower end of the foreign matter containing oil pipe 4. The one-way float shoe 5 is conductive when pressurized in the forward direction and blocked in the reverse direction, and is used to shield the high pressure from the formation.

[0050] Furthermore, in this embodiment, when the inner tubing string is inserted back into the outer tubing string, the maximum diameter of the upper joint of the positioning back-insertion seal 6 is positioned to the remaining top of the permanent packer 1, the locking claw of the positioning back-insertion seal 6 cooperates with the locking groove of the permanent packer 1 to form an anchor, and the vulcanized ring of the positioning back-insertion seal 6 cooperates with the central tube of the permanent packer 1 to form a seal.

[0051] like Figure 4 As shown, in this embodiment, the locking claw buckle type of the positioning back-insertion seal 6 is specially designed, the locking claw introduction angle is small, which is convenient for trial insertion, and the locking claw locking angle is large, which is firmly locked.

[0052] Furthermore, if Figure 2 As shown, in this embodiment, a lengthening nipple 7 is provided between the positioning and re-insertion seal 6 and the hydraulic opening and closing tool 8. When the positioning and re-insertion seal 6 is re-inserted into the permanent packer 1 and positioned, the length of the lengthening nipple 7 is adjusted so that the lower plug of the hydraulic opening and closing tool 8 is positioned at the locking claw 3021 of the elastic sleeve of the closing sleeve 302 in the cannulation sleeve 3. This arrangement allows the positioning and re-insertion seal 6 to be inserted multiple times to verify its position without opening the cannulation sleeve 3.

[0053] Furthermore, Figure 5 Schematically shows a cross-sectional view of the structural arrangement of a hydraulic switch tool according to an embodiment of the present invention. Figure 5 As shown, in this embodiment, the hydraulic switch tool 8 is composed of an upper joint 801, a sliding ball seat 802, a shear pin 803, and a plug 804;

[0054] The upper joint 801 is connected to the lower end of the lengthening short section 7;

[0055] The sliding ball seat 802 extends into the interior of the upper joint 801. The upper end of the sliding ball seat 802 is provided with a support position 8021 for supporting a soluble ball inserted into the inner pipe column to achieve pressure holding in the inner pipe column.

[0056] The outer wall of the lower end of the sliding ball seat 802 is connected to the lower end of the upper joint 801 through the shear pin 803;

[0057] The plug 804 is connected to the lower end of the sliding ball seat 802;

[0058] After the inner string hydraulic switch tool 8 is lowered to the specified position, a soluble ball is thrown into the inner string. After the soluble ball falls into the support position 8021 of the sliding ball seat 802, the shear pin 803 is cut off by the pressure of the inner string. Then, the plug 804 is pushed downward to push open the insert sleeve 3, thereby establishing an oil production channel.

[0059] Furthermore, in this embodiment, when the intubation sleeve 3 needs to be closed, the inner pipe column is lifted, and the plug 804 in the hydraulic switch tool 8 lifts the closing sleeve 302 by cooperating with the elastic sleeve locking claw 3021 at the end of the closing sleeve 302, so that the above-mentioned first long hole 3022 and the second long hole 3031 are staggered and separated, and the combined seal 304 cooperates with the sealing surface of the closing sleeve 302 to form a seal, thereby achieving the closure of the intubation sleeve 3.

[0060] According to the above-mentioned solution of the present invention, in response to the high reliability requirements of downhole barriers during high-pressure well completion, a downhole safety barrier process string is proposed for protecting shale oil reservoirs and performing high-pressure well completion operations after fracturing. This safety barrier process string is a combination of inner and outer tool strings (i.e., inner and outer strings). The outer string is a suspension isolation string. From top to bottom, the outer string consists of a permanent packer, a milling extension tube, a cannulated sleeve, a foreign body containment tubing, and a one-way float shoe. After the permanent packer, carrying these tools, reaches the designed depth, it is set using a sealing tool. The tool is suspended and anchored on the casing. The combination of the permanent packer's rubber sleeve and the cannulated sleeve seals the formation's high pressure, thus acting as a safety barrier. The inner string is a re-insertion sealing production string. From top to bottom, the inner string consists of a positioning re-insertion seal, a lengthened short joint, and a hydraulic opening tool. The hydraulic opening tool is used to pressurize the cannulated sleeve of the outer string by dropping a ball, thereby opening the oil production channel. This process string design is simple, safe and reliable. It not only serves as a high-pressure safety barrier for shale oil, provides safety for subsequent upper completion operations, but also facilitates later oil production operations. The production channel can be established by simply dropping balls and pressure. It is a safe, economical and reliable construction operation solution, which effectively solves the problem of high reliability requirements for downhole safety barriers in small-hole high-pressure wells for shale oil reservoir exploitation.

[0061] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. Offshore shale oil high-pressure slim hole completion safety barrier process string, characterized by: include: The outer string is a hanging isolation string used to hang the string and isolate the casing annulus and formation high pressure; Inner tubing string, which is a back-inserted sealed production tubing string; The outer pipe string comprises a permanent packer (1), a milling extension tube (2), and an intubation sleeve (3) connected in sequence; The inner pipe string includes a positioning back-insertion seal (6) and a hydraulic switch tool (8) connected in sequence; Before oil production, the outer pipe string is inserted into the well and the sleeve (3) is in a closed state. After entering the well and reaching a specified depth, the permanent packer (1) is set and the entire wellbore is sealed. After the permanent packer (1) is set, the outer pipe string is suspended and anchored on the casing. At this time, the permanent packer (1) seals the casing annulus pressure, and the sleeve (3) is in a closed state, achieving high-pressure sealing of the entire wellbore; During oil production, the inner pipe string is inserted back into the outer pipe string, and after the positioning and re-insertion seal (6) of the inner pipe string is positioned to the top of the permanent packer (1), the closed insert sleeve (3) is opened by a hydraulic switch tool (8) by means of a ball-throwing pressure, thereby establishing an oil production channel; After oil production, the inner pipe string is lifted up, and the inserting sleeve (3) is closed by the hydraulic switch tool (8), thereby closing the oil production channel; The cannula sliding sleeve (3) is composed of a first upper joint (301), a closing sleeve (302), an intermediate connecting sleeve (303), a combined seal (304), and a lower joint (305); An elastic sleeve locking claw (3021) is provided at one end of the closing sleeve (302). When the cannula sliding sleeve (3) is in a closed state, the elastic sleeve locking claw (3021) of the closing sleeve (302) is locked in a groove (3011) provided on the first upper joint (301). At this time, the combined seal (304) is located at both ends of the middle connecting sleeve (303) and cooperates with the sealing surface of the closing sleeve (302) to form a seal, thereby isolating the pressure from the formation and forming a safety barrier.

2. The offshore shale oil high-pressure slim-hole completion safety barrier process string according to claim 1, characterized in that: A first elongated hole (3022) is provided in the middle of the closing sleeve (302). When the closing sleeve (302) moves axially downward, the first elongated hole (3022) of the closing sleeve (302) and the second elongated hole (3031) of the intermediate connecting sleeve (303) are connected, the inserting sleeve (3) is opened, and an oil production channel is established. The oil enters the oil pipe production ground through the inserting sleeve (3).

3. The offshore shale oil high-pressure slim-hole completion safety barrier process string according to claim 1, characterized in that: The outer tubing string further comprises: a foreign matter containing oil pipe (4), the foreign matter containing oil pipe (4) being connected to the lower end of the inserting sleeve (3) and being used for receiving foreign matter debris deposited in the oil pipe.

4. The offshore shale oil high-pressure slim-hole completion safety barrier process string according to claim 3, characterized in that: The outer pipe string further comprises a one-way floating shoe (5), the one-way floating shoe (5) being connected to the lower end of the foreign matter containing oil pipe (4), the one-way floating shoe (5) being conductive when pressurized in the forward direction but blocked in the reverse direction, and being used to shield the high pressure from the formation.

5. The offshore shale oil high-pressure slim-hole completion safety barrier process string according to claim 1, characterized in that: When the inner pipe string is inserted back into the outer pipe string, the maximum diameter of the upper joint of the positioning and inserting seal (6) is positioned to the top of the permanent packer (1), the locking claw of the positioning and inserting seal (6) cooperates with the locking groove of the permanent packer (1) to form an anchor, and the vulcanized ring of the positioning and inserting seal (6) cooperates with the central pipe of the permanent packer (1) to form a seal.

6. The offshore shale oil high-pressure slim-hole completion safety barrier process string according to claim 1, characterized in that: A matching short section (7) is provided between the positioning re-insertion seal (6) and the hydraulic switch tool (8). When the positioning re-insertion seal (6) is re-inserted to the permanent packer (1) and positioned, the lower plug of the hydraulic switch tool (8) is positioned at the elastic sleeve locking claw of the closing sleeve (302) in the inserting sleeve (3) by adjusting the length of the matching short section (7).

7. The offshore shale oil high-pressure slim-hole completion safety barrier process string according to claim 6, characterized in that: The hydraulic switch tool (8) is composed of a second upper joint (801), a sliding ball seat (802), a shear pin (803), and a plug (804); The second upper joint (801) is connected to the lower end of the matching short section (7); The sliding ball seat (802) extends into the interior of the second upper joint (801), and the upper end of the sliding ball seat (802) is provided with a support position (8021) for supporting a soluble ball inserted into the inner pipe column to achieve pressure holding in the inner pipe column; The outer wall of the lower end of the sliding ball seat (802) is connected to the lower end of the second upper joint (801) via the shear pin (803); The plug (804) is connected to the lower end of the sliding ball seat (802); After the inner string hydraulic switch tool (8) is lowered to the designated position, a soluble ball is thrown into the inner string. After the soluble ball falls into the support position (8021) of the sliding ball seat (802), the shear pin (803) is cut off by the pressure of the inner string. Then, the plug (804) is pushed downward to push open the insert sleeve (3), thereby establishing an oil production channel.

8. The offshore shale oil high-pressure slim-hole completion safety barrier process string according to claim 7, characterized in that: When the cannula sliding sleeve (3) needs to be closed, the inner pipe column is lifted, and the plug (804) in the hydraulic switch tool (8) lifts the closing sleeve (302) by cooperating with the elastic sleeve locking claw (3021) at the end of the closing sleeve (302), thereby closing the cannula sliding sleeve (3).

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