Offshore shale oil slim hole high pressure completion double barrier string

Abstract

The present application relates to the technical field of oilfield completion and oil production, and provides a double safety barrier pipe string for offshore shale oil slim hole high pressure completion, which comprises: an upper pipe string, a middle pipe string and a lower pipe string which are sequentially installed on a production oil pipe from top to bottom; before oil and gas production, the lower pipe string is lowered into the oil pipe to form a first safety production barrier, then the middle pipe string is lowered above the lower pipe string to form a second safety production barrier, and finally the upper pipe string is lowered above the middle pipe string; during oil and gas production, a switch tool in the upper pipe string is activated by internal pressurization of the oil pipe, the switch tool is lowered to open the middle pipe string, and the lower pipe string is opened by continuous pressurization, so that the lower pipe string, the middle pipe string and the upper pipe string are communicated, and oil and gas production is realized. The present application adopts a one-trip pipe string structure, can realize self-flowing production in a high production capacity stage, and can also realize pump production in a low production capacity stage; meanwhile, the present application has multiple production barriers, and effectively solves the safety problem in the completion stage.

Description

Technical Field

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

[0002] As conventional oil and gas production continues to decline worldwide, exploration concepts are gradually changing and innovating, and unconventional oil and gas such as shale oil resources have become an important part of the resource ladder.

[0003] To meet the requirements of fracturing, shale oil reservoirs are typically completed using small 5.5mm casing. This results in high reservoir pressures and significant production rate fluctuations, placing high demands on production barriers and high reservoir pressure after fracturing. Currently, conventional completion technologies and tools are unable to meet the high-pressure completion requirements of offshore shale oil development. 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 double safety barrier string for high-pressure completion of offshore shale oil slim wells.

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

[0006] The upper tubing string, middle tubing string and lower tubing string are installed on the production tubing in sequence from top to bottom;

[0007] Before oil and gas production, the oil pipe is lowered into the lower pipe string to form the first safety production barrier, then the middle pipe string is lowered above the lower pipe string to form the second safety production barrier, and finally the upper pipe string is lowered above the middle pipe string;

[0008] During oil and gas production, the switch tool in the upper tubing string is activated by applying pressure inside the oil pipe. The switch tool moves downward to open the middle tubing string, and further pressure is applied to open the lower tubing string, connecting the lower tubing string, the middle tubing string and the upper tubing string to achieve oil and gas production.

[0009] According to one aspect of the present invention, the upper tubing string includes a safety valve, a cable packer, a production sleeve, an electric pump system and a mechanical intubation sleeve switching tool which are sequentially connected from top to bottom.

[0010] According to one aspect of the present invention, the safety valve is connected to a surface hydraulic control pipeline and is used to shut down the well urgently when an abnormality occurs at the bottom of the well.

[0011] According to one aspect of the present invention, the cable packer is a top-suspended packer for sealing an annulus, wherein the cable packer suspends a lower production sleeve, an electric pump system, and a mechanical intubation sleeve switching tool;

[0012] The top of the cable packer is provided with a cable passing hole, through which a cable can pass to control the start and stop of the electric pump system.

[0013] According to one aspect of the present invention, the production sleeve connects the oil pipe and the casing, and the connection and closing of the oil pipe and the casing are controlled by wireline operation.

[0014] According to one aspect of the present invention, the middle tubular string includes a first permanent packer and a mechanical insertion sleeve sequentially connected from top to bottom.

[0015] According to one aspect of the present invention, the mechanical intubation sleeve switching tool is a cannula connected to the mechanical intubation sleeve. After the upper tubing is lowered into place, the mechanical intubation sleeve switching tool is activated by pressurizing the inside of the oil pipe, so that the mechanical intubation sleeve switching tool is downwardly inserted into the inside of the mechanical intubation sleeve. The positioning step on the mechanical intubation sleeve switching tool cooperates with the core shaft positioning step inside the mechanical intubation sleeve. Under the action of pressure, the core shaft in the mechanical intubation sleeve moves downward, so that the hole on the core shaft is aligned with the hole on the mechanical intubation sleeve shell, and the communication channel is opened, thereby realizing the connection between the upper tubing and the middle tubing.

[0016] According to one aspect of the present invention, the lower tubular string includes a second permanent packer and a shear ball seat connected in sequence from top to bottom.

[0017] According to one aspect of the present invention, after the mechanical insertion sleeve switching tool is downwardly inserted into the mechanical insertion sleeve to open the mechanical insertion sleeve, the interior of the oil pipe continues to be pressurized, and the copper pin on the shear ball seat is cut off under the action of pressure to open the shear ball seat, thereby connecting the upper tubing string, the middle tubing string and the lower tubing string.

[0018] According to one solution of the present invention, a double safety barrier string for offshore shale oil small-hole high-pressure completion includes: an upper string, a middle string, and a lower string, which are sequentially installed on the production tubing from top to bottom; before oil and gas production, the tubing is lowered into the lower string to form a first safety production barrier (isolating the tubing annulus and formation high pressure), then the middle string is lowered above the lower string to form a second safety production barrier (isolating the tubing annulus and formation high pressure), and finally the upper string is lowered above the middle string; during oil and gas production, the switch tool in the upper string is activated by internal pressure in the tubing, the switch tool descends to open the middle string, and further pressure is applied to open the lower string, connecting the lower string, the middle string, and the upper string to achieve oil and gas production. This arrangement allows the present invention to have multiple safety production barriers, effectively solving the structural design problems of small-size casing high-pressure completion strings after fracturing and the safety problems of the completion stage.

[0019] According to one embodiment of the present invention, the upper tubing string includes, in descending order, a safety valve, a cable packer, a production sleeve, an electric pump system, and a mechanical sleeve opening and closing tool. This arrangement allows the mechanical sleeve opening and closing tool to be hydraulically activated after the upper tubing string is lowered into position. The tool then descends to open the sleeve, connecting the oil and sleeve to the oil and gas production system. The tool then ascends to close the sleeve, halting production.

[0020] According to one embodiment of the present invention, the middle string includes a first permanent packer and a mechanical insertion sleeve, connected sequentially from top to bottom. This arrangement allows the middle string to serve as a secondary safety barrier for oil and gas production, not only protecting the upper string during well running and completion but also connecting the upper and lower strings to enable oil and gas production.

[0021] According to one embodiment of the present invention, the lower string includes a second permanent packer and a shear ball seat connected sequentially from top to bottom. This arrangement allows the lower string to serve as the first safety barrier for oil and gas production, not only protecting the middle and upper strings during running and completion, but also ensuring connectivity between the lower and middle strings.

[0022] According to the solution of the present invention, the present invention provides a small-hole high-pressure completion double safety barrier self-flowing and pumping integrated pipe string. The present invention adopts a one-trip pipe string structure, which can realize self-flowing production in the high-production stage and pumping production in the low-production stage; at the same time, it has multiple production barriers, which effectively solves the safety problem in the completion stage.

[0023] According to the present invention, the aforementioned tubing scheme is employed to establish multiple production safety barriers, addressing safety issues associated with small-sized, high-pressure completion tubing after fracturing. By applying internal pressure to the tubing, the mechanical intubation sleeve opening tool is activated. This tool then descends to open the mechanical intubation sleeve, and further pressure is applied to open the shear ball seat, enabling oil and gas production. During high-capacity phases, production can be performed using the production sleeve, while during low-capacity phases, extraction can be performed using an electric pump system. This reduces the need for subsequent tubing string replacements, improves recovery, and reduces production costs.

[0024] According to the present invention, this invention can be used in offshore slim-bore cased wells. Due to the limited casing size, conventional offshore completion tools and processes cannot meet the high reservoir pressure and large production capacity fluctuations required for such completions. Therefore, the present invention proposes the aforementioned high-pressure completion string suitable for offshore slim-bore cased wells. This string provides multiple production barriers, enhancing the security of offshore completion operations. Using this string, high-pressure completion with self-flowing and pumping is achieved, eliminating the need for mid-process string replacement, improving recovery efficiency and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A cross-sectional view schematically shows the structural arrangement of a double safety barrier string for offshore shale oil slim-hole high-pressure completion according to one embodiment of the present invention. DETAILED DESCRIPTION

[0026] 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.

[0027] 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."

[0028] Figure 1 A schematic cross-sectional view of the structure arrangement of a double safety barrier string for offshore shale oil slim hole high pressure completion according to one embodiment of the present invention is shown. Figure 1 As shown, in this embodiment, the offshore shale oil slim hole high pressure completion double safety barrier string includes:

[0029] The upper tubing string, middle tubing string and lower tubing string are installed on the production tubing in sequence from top to bottom;

[0030] Before oil and gas production, the tubing is run into the lower string to form the first safety barrier (to isolate the tubing annulus and the formation high pressure), then the middle string is run above the lower string to form the second safety barrier (to isolate the tubing annulus and the formation high pressure), and finally the upper string is run above the middle string.

[0031] During oil and gas production, internal pressure in the tubing activates a switch tool in the upper string. The switch tool then descends to open the middle string, and further pressure is applied to open the lower string, connecting the lower, middle, and upper strings to achieve oil and gas production. This arrangement provides multiple safety barriers, effectively addressing the structural design issues of small-sized, high-pressure completion strings after fracturing and addressing safety concerns during the completion phase.

[0032] Further, according to one embodiment of the present invention, Figure 1As shown, the upper tubing string includes, connected in sequence from top to bottom, a safety valve 1, a cable packer 2, a production sleeve 3, an electric pump system 4, and a mechanical sleeve opening and closing tool 5. This arrangement allows the mechanical sleeve opening and closing tool 5 to be hydraulically activated after the upper tubing string is lowered into position. The tool then descends to open the sleeve, connecting the tubing and casing, achieving oil and gas production. The tool then ascends to close the sleeve, halting oil and gas production.

[0033] Furthermore, in this embodiment, the safety valve 1 is connected to the surface hydraulic control pipeline for emergency well shut-in when an abnormality occurs at the bottom of the well.

[0034] Furthermore, in this embodiment, the cable packer 2 is a top-suspended packer for sealing the annulus, and the cable packer 2 suspends a lower production sleeve 3, an electric pump system 4, and a mechanical intubation sleeve switching tool 5;

[0035] The top of the cable packer 2 is provided with a cable passage hole, through which a cable can pass to control the start and stop of the electric pump system 4.

[0036] Furthermore, in this embodiment, the production sleeve 3 connects the oil pipe and the casing, and the connection and closing of the oil pipe and the casing are controlled by wireline operation.

[0037] In this embodiment, during the high-productivity completion stage, self-flowing production can be performed through the production sleeve 3 ; during the low-productivity completion stage, pumping production can be performed through the electric pump system 4 .

[0038] Further, according to one embodiment of the present invention, Figure 1 As shown, the middle string includes a first permanent packer 6 and a mechanical insertion sleeve 7, connected sequentially from top to bottom. This arrangement allows the middle string to serve as a second safety barrier for oil and gas production, not only protecting the upper string during running and completion, but also connecting the upper and lower strings to enable oil and gas production.

[0039] Furthermore, in this embodiment, the mechanical intubation sleeve switching tool 5 is a cannula connected to the mechanical intubation sleeve 7. After the upper tubing is lowered into place, the mechanical intubation sleeve switching tool 5 is activated by pressurizing the inside of the oil pipe, so that the mechanical intubation sleeve switching tool 5 is downwardly inserted into the mechanical intubation sleeve 7. The positioning step on the mechanical intubation sleeve switching tool 5 cooperates with the core shaft positioning step inside the mechanical intubation sleeve 7. Under the action of pressure, the core shaft inside the mechanical intubation sleeve 7 moves downward, so that the hole on the core shaft is aligned with the hole on the outer shell of the mechanical intubation sleeve 7, and the communication channel is opened, thereby realizing the connection between the upper tubing and the middle tubing.

[0040] Further, according to one embodiment of the present invention, Figure 1As shown, the lower string includes a second permanent packer 8 and a shear ball seat 9, connected sequentially from top to bottom. This arrangement allows the lower string to serve as the first safety barrier for oil and gas production, not only protecting the middle and upper strings during running and completion, but also ensuring communication between the lower and middle strings.

[0041] Furthermore, in this embodiment, after the mechanical insertion sleeve switching tool 5 is downwardly inserted into the mechanical insertion sleeve 7 to open the mechanical insertion sleeve 7, the inside of the oil pipe continues to be pressurized, and the copper pin on the shear ball seat is cut off under the action of pressure to open the shear ball seat, so that the upper pipe string, the middle pipe string and the lower pipe string are connected.

[0042] According to the above-mentioned scheme of the present invention, the present invention provides a small-hole high-pressure completion double safety barrier self-flowing and pumping integrated pipe string. The present invention adopts a one-trip pipe string structure, which can realize self-flowing production in the high-production stage and pumping production in the low-production stage; at the same time, it has multiple production barriers, which effectively solves the safety problem in the completion stage.

[0043] According to the aforementioned solution, the present invention utilizes the aforementioned tubing string scheme, establishing multiple production safety barriers to address the safety issues associated with small-sized, high-pressure completion strings after fracturing. By applying internal pressure to the tubing, the mechanical intubation sleeve opening tool is activated. The tool then descends to open the mechanical intubation sleeve, and further pressure is applied to open the shear ball seat, enabling oil and gas production. During high-capacity phases, production can be performed using the production sleeve, while during low-capacity phases, extraction can be performed using an electric pump system. This reduces the need for subsequent tubing string replacements, improves recovery, and reduces production costs.

[0044] According to the above-mentioned solution of the present invention, the present invention can be used in offshore slim-bore cased wells. Due to the limited casing size, conventional offshore completion tools and completion processes cannot meet the requirements of such completion conditions with high reservoir pressure and large production capacity fluctuations. Therefore, the present invention proposes the above-mentioned high-pressure completion string suitable for offshore slim-bore cased wells; this string provides multiple production barriers, increasing the security of offshore completion operations; using this string, high-pressure completion self-flowing and pumping are integrated, eliminating the need for mid-process string replacement, improving recovery efficiency and reducing production costs.

[0045] 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 slim hole high pressure completion double safety barrier string, characterized by: include: The upper tubing string, middle tubing string and lower tubing string are installed on the production tubing in sequence from top to bottom; Before oil and gas production, the oil pipe is lowered into the lower pipe string to form the first safety production barrier, then the middle pipe string is lowered above the lower pipe string to form the second safety production barrier, and finally the upper pipe string is lowered above the middle pipe string; During oil and gas production, the switch tool in the upper string is activated by applying pressure inside the oil pipe. The switch tool moves downward to open the middle string, and further pressure is applied to open the lower string, connecting the lower string, the middle string, and the upper string to achieve oil and gas production. The upper tubular string includes a safety valve, a cable packer, a production sleeve, an electric pump system and a mechanical intubation sleeve switching tool connected in sequence from top to bottom; The middle pipe string includes a first permanent packer and a mechanical insertion sleeve connected in sequence from top to bottom; The mechanical insertion sleeve switching tool is a sleeve connected to the mechanical insertion sleeve. After the upper tubing string is lowered into place, the mechanical insertion sleeve switching tool is activated by applying pressure inside the oil pipe, so that the mechanical insertion sleeve switching tool is downwardly inserted into the mechanical insertion sleeve. The positioning step on the mechanical insertion sleeve switching tool cooperates with the positioning step of the core shaft inside the mechanical insertion sleeve. Under the action of pressure, the core shaft inside the mechanical insertion sleeve moves downward, so that the hole on the core shaft is aligned with the hole on the mechanical insertion sleeve housing, thereby opening a communication channel, thereby achieving communication between the upper tubing string and the middle tubing string. The lower tubular string includes a second permanent packer and a shear ball seat connected in sequence from top to bottom; After the mechanical insertion sleeve switching tool is inserted downward into the mechanical insertion sleeve and the mechanical insertion sleeve is opened, the inside of the oil pipe continues to be pressurized, and the copper pin on the shear ball seat is cut off under the action of pressure to open the shear ball seat, so that the upper pipe string, the middle pipe string and the lower pipe string are connected.

2. The offshore shale oil slim hole high pressure completion double safety barrier string according to claim 1 is characterized in that: The safety valve is connected to the surface hydraulic control pipeline and is used to shut down the well in an emergency when an abnormality occurs at the bottom of the well.

3. The offshore shale oil slim hole high pressure completion double safety barrier string according to claim 1, characterized in that: The cable packer is a top-suspended packer for sealing the annulus, and the cable packer suspends the lower production sleeve, the electric pump system and the mechanical intubation sleeve switching tool; The top of the cable packer is provided with a cable passing hole, through which a cable can pass to control the start and stop of the electric pump system.

4. The offshore shale oil slim hole high pressure completion double safety barrier string according to claim 1, characterized in that: The production sleeve connects the oil pipe and the casing, and the connection and closing of the oil pipe and the casing are controlled by wire operation.

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