Safety barrier process pipe column for offshore shale oil high-pressure slim hole well completion

Abstract

The invention relates to the technical field of oil field well completion and oil production processes, and provides an offshore shale oil high-pressure slim hole well completion safety barrier process pipe column which comprises an outer pipe column and an inner pipe column. The outer tubular column comprises a permanent packer and an insertion tube sliding sleeve; the inner tubular column comprises a positioning back-inserting seal and a hydraulic switch tool which are connected in sequence; before oil extraction production, the pipe inserting sliding sleeve is in a closed state before an outer pipe column enters a well, and high-pressure plugging of the whole shaft is achieved; during oil extraction production, the inner tubular column is inserted back into the outer tubular column, and after the inner tubular column is positioned, inserted back, sealed and positioned to the residual top of the permanent packer, the pipe inserting sliding sleeve in a closed state is opened through a hydraulic switch tool in a ball throwing and pressing mode, and an oil liquid production channel is established. The shale oil high-pressure safety barrier plays a role of a shale oil high-pressure safety barrier, provides safety guarantee for follow-up upper well completion construction operation, facilitates later oil extraction production operation, and effectively solves the problem that the requirement for reliability of an underground safety barrier is high when a shale oil reservoir exploits a slim-hole high-pressure well.

Description

Technical Field

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

[0002] As conventional oil and gas production continues to decline worldwide, exploration concepts have gradually changed and innovated, making unconventional oil and gas such as shale oil resources an important part of the resource ladder. Shale layers can serve as source rocks and reservoir rocks for oil and gas. The reservoirs have the characteristics of continuous distribution, low porosity, ultra-low permeability, and high brittleness. Due to these characteristics of shale layers, they generally need to be released and mined through fracturing operations. However, after fracturing operations, the reservoir pressure is high and the reservoir needs to be protected. It is impossible to use high-density well pressure for high-pressure completion operations. In addition, the reservoir has a large capacity change during the entire production process and contains sand. The strength, corrosion resistance, and erosion damage resistance of the high-pressure completion tools are higher. In order to ensure the successful implementation of high-pressure completion, high-pressure completion has higher reliability requirements for downhole barriers.

[0003] Traditional downhole process tubing cannot solve the problem of high reliability requirements for downhole safety barriers in small-bore 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 object of the present invention is to solve at least one technical problem in the background technology and to provide a safety barrier process string for offshore shale oil high-pressure small-hole completion.

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

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

[0007] An 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 a pipe inserting 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 pipe string is in a closed state before entering the well. After entering the well and reaching the specified depth, the permanent packer is set and the whole wellbore is sealed. After the permanent packer is set, the outer pipe string is suspended and anchored on the casing. At this time, the permanent packer seals the casing annulus pressure, and the pipe sleeve is in a closed state, realizing high-pressure plugging of the whole wellbore;

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

[0012] After oil production, the inner pipe column is lifted up, and the inserting 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 insertion sleeve is in a closed state, the elastic sleeve locking claw of the closing sleeve is locked in a 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, thereby 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 is connected with the long hole of the middle connecting sleeve, the insert sleeve is opened, and an oil production channel is established. The oil enters the oil pipe production surface through the insert sleeve.

[0016] According to one aspect of the present invention, the outer tubular column further comprises: a foreign matter containing oil pipe, which is connected to the lower end of the inserting sleeve and is used to receive foreign debris precipitated in the oil pipe.

[0017] According to one aspect of the present invention, the outer pipe column also includes: a one-way floating shoe, which is connected to the lower end of the foreign body containing oil pipe. The one-way floating 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 insert 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 tubing string hydraulic switch tool is lowered to the specified position, a soluble ball is thrown into the inner tubing 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 tubing string. Then, 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 insertion 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 insertion sleeve.

[0027] According to the scheme of the present invention, the present invention proposes a downhole safety barrier process string for protecting the reservoir and performing high-pressure completion operations after the shale oil reservoir is fractured, in view of the high reliability requirements of the downhole barrier for high-pressure completion. The safety barrier process string is a combination of inner and outer two-layer tool strings (i.e., inner string and outer string), the outer string is a suspension isolation string, and the outer string is composed of a permanent packer, a milling extension tube, a cannulated sleeve, a foreign body containing oil pipe, and a one-way floating shoe from top to bottom. After the permanent packer carries the above tools to the designed depth, the permanent packer is sealed by the sealing tool, the tool is suspended and anchored on the casing, and the formation high pressure is sealed by the combination of the rubber tube of the permanent packer and the cannulated sleeve, which plays the role of a safety barrier. The inner string is a back-insertion sealing production string, and the inner string is composed of a positioning back-insertion seal, a lengthened short section, and a hydraulic switch tool from top to bottom. The cannulated sleeve of the outer string is opened by throwing a ball and pressurizing by the hydraulic switch tool to establish an oil production channel. This kind of process string design is simple, safe and reliable. It not only plays the role of a high-pressure safety barrier for shale oil, provides safety protection for subsequent upper completion operations, but also facilitates later oil production operations. The production channel can be established by dropping a ball to pressure. It is a safe, economical and reliable construction operation plan, which effectively solves the problem of high reliability requirements for downhole safety barriers in small-bore 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 structure arrangement according to an embodiment of the present invention;

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

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

[0031] Figure 4 A schematic diagram showing a locking claw structure arrangement diagram of a positioning back-insertion seal 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 an 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 to enable those skilled in the art to better understand and thus 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 structure arrangement according to an embodiment of the present invention; Figure 2 A cross-sectional view of the inner column structure arrangement according to an embodiment of the present invention is schematically shown. 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, which is used to hang the string and isolate the casing annulus and the formation high pressure;

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

[0038] The outer pipe string includes a permanent packer 1, a milling extension tube 2, and a cannulated sliding sleeve 3 which are connected in sequence;

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

[0040] Before oil production, the outer pipe string is placed in the well and the insert sleeve 3 is in a closed state. After the well reaches the specified depth, the permanent packer 1 is set and the whole 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 insert sleeve 3 is in a closed state, realizing high-pressure plugging of the whole wellbore;

[0041] During oil production, the inner pipe string is inserted back into the outer pipe string, and after the positioning and inserting seal 6 of the inner pipe string is positioned to the top of the permanent packer 1, the closed inserting 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 inserting 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] Further, Figure 3 A schematic cross-sectional view of the structure arrangement of the cannula sleeve according to an 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 insertion 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, isolate the pressure from the formation, and form 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 is connected with the long hole 3031 of the middle connecting sleeve 303, the insert sleeve 3 is opened, and an oil production channel is established. The oil enters the oil pipe production surface through the insert sleeve 3.

[0047] In this embodiment, the main function of the inserting sleeve 3 in the outer pipe string is to connect the formation. It is opened or closed by a special hydraulic switch tool 8, which is connected to the lower part of the positioning back-insertion seal 6. When it is necessary to open the inserting sleeve 3, a soluble ball is thrown into the ball seat inside the hydraulic switch tool 8, and the inserting pipe string is pressurized to open the inserting sleeve 3. When it is necessary to close, the inserting seal pipe string is lifted up to close it. The inserting sleeve 3 can be opened or closed repeatedly, which can realize the convenience of replacing the pipe string above this barrier.

[0048] Furthermore, if Figure 1 As shown, in this embodiment, the outer tubing 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 precipitated in the oil pipe to prevent excessive deposition from burying the switch lock claw of the closing sleeve 302 in the insertion sleeve 3, resulting in the inability to switch the insertion sleeve 3 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 body containing oil pipe 4. The one-way float shoe 5 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.

[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 of special design, 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 length matching nipple 7 is provided between the positioning and re-insertion seal 6 and the hydraulic switch tool 8. When the positioning and re-insertion seal 6 is re-inserted to the permanent packer 1 and positioned, the length of the length matching nipple 7 is adjusted so that the lower plug of the hydraulic switch tool 8 is located at the elastic sleeve locking claw 3021 of the closing sleeve 302 in the insertion sleeve 3. With such a configuration, the positioning and re-insertion seal 6 can be inserted and verified to be in place for multiple times without opening the insertion sleeve 3.

[0053] Further, Figure 5 A cross-sectional view schematically shows 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 matching length short section 7;

[0055] The sliding ball seat 802 extends into the interior of the 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 put into the inner pipe column to realize the 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 pipe string hydraulic switch tool 8 is lowered to the specified position, a soluble ball is thrown into the inner pipe string. After the soluble ball falls into the support position 8021 of the sliding ball seat 802, the shear pin 803 is sheared off by the inner pipe string pressure, and the plug 804 is pushed downward to push open the insert sleeve 3 to establish 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 realizing the closure of the intubation sleeve 3.

[0060] According to the above scheme of the present invention, the present invention proposes a downhole safety barrier process string for protecting the reservoir and performing high-pressure completion operations after the shale oil reservoir is fractured, in view of the high reliability requirements of the downhole barrier in high-pressure completion. The safety barrier process string is a combination of inner and outer two-layer tool strings (i.e., inner string and outer string), the outer string is a suspension isolation string, and the outer string is composed of a permanent packer, a milling extension tube, a cannulated sleeve, a foreign body containing oil pipe, and a one-way floating shoe from top to bottom. After the permanent packer carries the above tools to the designed depth, the permanent packer is sealed by the sealing tool, the tool is suspended and anchored on the casing, and the formation is sealed by the combination of the rubber tube of the permanent packer and the cannulated sleeve, which plays a role as a safety barrier. The inner string is a back-insertion sealing production string, and the inner string is composed of a positioning back-insertion seal, a lengthened short section, and a hydraulic switch tool from top to bottom. The cannulated sleeve of the outer string is opened by throwing a ball and pressurizing by the hydraulic switch tool to establish an oil production channel. This kind of process string design is simple, safe and reliable. It not only plays the role of a high-pressure safety barrier for shale oil, provides safety protection for subsequent upper completion operations, but also facilitates later oil production operations. The production channel can be established by dropping a ball to pressure. It is a safe, economical and reliable construction operation plan, which effectively solves the problem of high reliability requirements for downhole safety barriers in small-bore 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 rather than to limit it. 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, which is used to hang the string and isolate the casing annulus and the formation high pressure; An 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 a pipe inserting sleeve (3) which are connected in sequence; The inner pipe column comprises a positioning back-insertion seal (6) and a hydraulic switch tool (8) which are connected in sequence; Before oil production, the outer pipe string is placed in the well and the insert sleeve (3) is in a closed state. After the well reaches 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 insert sleeve (3) is in a closed state, thereby achieving high-pressure plugging of the entire wellbore. During oil production, the inner pipe string is inserted back into the outer pipe string, and after the positioning and inserting seal (6) of the inner pipe string is positioned to the top of the permanent packer (1), the plugging sleeve (3) in a closed state is opened by a hydraulic switch tool (8) by means of ball-throwing pressure, thereby establishing an oil production channel; After oil production, the inner pipe column is lifted up, and the inserting sleeve (3) is closed by the hydraulic switch tool (8), thereby closing the oil production channel.

2. The offshore shale oil high-pressure slim hole completion safety barrier process string according to claim 1, characterized in that: 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); An elastic sleeve locking claw (3021) is provided at one end of the closing sleeve (302). When the insertion 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 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.

3. The offshore shale oil high-pressure slim hole completion safety barrier process string according to claim 2 is 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) is connected with the second elongated hole (3031) of the intermediate connecting sleeve (303), the inserting sleeve (3) is opened, and an oil production channel is established. The oil enters the oil pipe production surface through the inserting sleeve (3).

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

5. The offshore shale oil high-pressure slim hole completion safety barrier process string according to claim 4, characterized in that: The outer pipe column 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.

6. 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.

7. The offshore shale oil high-pressure slim hole completion safety barrier process string according to claim 2, 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).

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

9. The offshore shale oil high-pressure slim hole completion safety barrier process string according to claim 8, characterized in that: When the insertion 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) through cooperation with the elastic sleeve locking claw (3021) at the end of the closing sleeve (302), thereby closing the insertion sleeve (3).

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