A kind of suitable for CO2 drive coiled tubing separate injection process

Abstract

The application belongs to the technical field of CCUS injection, and discloses a CO2 drive continuous tubing separate injection process. A double-suspension device design integrated separate layer gas injection wellhead, double-channel continuous tubing combination and downhole insertion sealing type separate layer gas injection tool with two sets of different size slips and combined seals are provided. A CO2 vortex flowmeter and an automatic adjusting device are simultaneously provided, which can automatically identify the injection medium and switch the database, realize automatic metering of water-gas alternation, and have an online regulation function.

Description

Technical Field

[0001] This invention belongs to the field of CCUS injection technology, specifically relating to a CO2-driven continuous tubing injection process. Background Technology

[0002] CCUS technology, after years of research and development, is gradually moving towards localization, intelligentization, and low cost. The coiled tubing gas injection completion process has been widely applied in major oilfields, effectively solving the problems of numerous weak points in the gas seal of CO2-driven gas injection tubing, high completion costs, and long completion cycles, providing technical support for the safe, low-cost, and large-scale application of CCUS technology. However, general gas injection cannot solve the problems of multiple development layers and prominent inter-layer contradictions. The injected CO2 will rapidly advance along high-permeability zones, leading to severe gas channeling in the production well. The injected CO2 forms an ineffective circulation, significantly reducing the swept volume of injected CO2 and the extent to which it improves recovery.

[0003] Patent CN110965950B discloses a non-circular continuous tubing surface injection process string. This string is composed of multiple layered water injection structures. These structures are sequentially connected from top to bottom in a single-stage, double-stage, triple-stage, and quadruple-stage water injection configuration to form a non-circular continuous tubing injection process string. These sections are then sealed with drillable bridge plugs to create multiple independent layered water injection channels, each communicating with a different oil layer without interfering with the others. Water is injected through a dedicated surface injection wellhead and distributed to various oil layers via water outlets on the inner casing of the injection well, thus meeting the multi-layered water injection requirements of the reservoir design. However, this multi-stage, layered process incurs significant costs and increases maintenance costs, posing a higher risk of major overhauls. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a CO2-driven coiled tubing injection process. This process can achieve multiple goals, including improving wellbore integrity, significantly reducing completion costs, extending pipe inspection cycles, reducing workover risks, simplifying operational procedures, shortening operation cycles, and enabling pressurized operations throughout the entire lifecycle. It provides technical support for the safe, low-cost, and large-scale application of CCUS technology. This technology is the first of its kind in the industry both domestically and internationally.

[0005] The above-mentioned objective of this invention is achieved through the following technical solution: a CO2-driven continuous tubing injection process, comprising the following steps:

[0006] 1. Install the integrated multi-functional gas injection wellhead under depressurized conditions and close the main control valve;

[0007] 2. Install a coiled tubing live-line device;

[0008] 3. After the lower sealing tool is connected to the interlayer coiled tubing, it is lowered into the well. The upper end of the interlayer coiled tubing is lowered to the wellhead. It is then connected to the upper sealing tool via the dual-channel coiled tubing. The upper sealing tool is then connected to the interlayer coiled tubing at the wellhead and lowered into the well.

[0009] 4. After reaching the predetermined depth of the oil layer, insert slips to suspend the coiled tubing outside the wellhead;

[0010] 5. Cut off the coiled tubing outside the wellhead and install an external tubing sealing device;

[0011] 6. Disconnect the coiled tubing inside the wellhead and install an internal tubing sealing device;

[0012] 7. Pressure test and expand the upper and lower sealing tools from the inner and outer coiled tubing and the annulus of the inner and outer coiled tubing at the wellhead, and verify the seals in sequence;

[0013] 8. Install the wellhead tree and safety valve control system; then pressurize the coiled tubing to open the channels in the small tubing and the annulus channel between the small and large tubing to achieve gas injection.

[0014] Furthermore, the coiled tubing includes a large-diameter coiled tubing and a small-diameter coiled tubing, with the large-diameter coiled tubing sleeved over the small-diameter coiled tubing.

[0015] Furthermore, the integrated multi-functional gas injection wellhead includes: a four-way casing with a main control valve, the main control valve and the four-way casing being integrated.

[0016] In a further preferred embodiment of the present invention, each of the four-way sleeves is provided with a control valve.

[0017] Furthermore, the continuous tubing pressurization device is mounted on the four-way sleeve.

[0018] Furthermore, the upper sealing tool includes a sealing tube and a drillable bridge plug, and the lower sealing tool includes a sealing tube, a drillable bridge plug, and a pressure-regulating plug.

[0019] Furthermore, a double suspension device is installed at the wellhead.

[0020] Furthermore, the dual suspension device includes a pre-installed hanger connected to the wellhead and a rear hanger above the pre-installed hanger.

[0021] Furthermore, a slip is provided between the pre-installed hanger and the continuous tubing, and a sealing device is provided on the rear hanger.

[0022] Furthermore, the sealing device includes an external oil pipe sealing device and an internal oil pipe sealing device.

[0023] The beneficial effects of this invention compared to the prior art are:

[0024] 1. Improve the efficiency and effectiveness of CO2 enhanced oil recovery. By injecting CO2 in different layers and with different fluids, the injected CO2 can be more evenly distributed in the reservoir, expanding the swept volume and thus more effectively displacing crude oil and improving oil recovery.

[0025] 2. Addressing problems caused by reservoir heterogeneity. Differentiated injection methods are implemented for areas with varying permeability and porosity, improving the targeting and adaptability of injections and reducing residual oil saturation within the reservoir;

[0026] 3. Reduce production costs. By combining the coiled tubing injection process with the stratified injection process, the high completion costs and long completion cycles can be addressed, thereby reducing material and operating costs and improving economic efficiency. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0028] Figure 1 This is a schematic diagram of the structure of the present invention after assembly in the CO2-driven continuous tubing injection process;

[0029] Figure 2 This is a schematic diagram of the downhole structure after assembly for the CO2-driven continuous tubing injection process, according to the present invention.

[0030] Figure 3 This is a schematic diagram of the wellhead structure after the CO2-driven continuous tubing injection process is assembled according to the present invention;

[0031] Figure 4 This is a schematic diagram of the double suspension device after assembly of the CO2-driven continuous tubing injection process.

[0032] The diagram shows: 1. Integrated multi-functional gas injection wellhead; 2. Dual suspension device; 3. Coiled tubing; 4. Oil layer; 5. Four-way casing; 6. Main control valve; 7. Control valve; 8. Large-diameter coiled tubing; 9. Small-diameter coiled tubing; 10. Upper section sealing tool; 11. Lower section sealing tool; 12. Drillable bridge plug; 13. Sealing insert; 14. Pressure-regulating plug; 15. Pre-installed hanger; 16. Post-installed hanger; 17. Slips; 18. Sealing device; 19. Interlayer coiled tubing. Detailed Implementation

[0033] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0034] Example 1

[0035] (1) A dual-channel, layered injection string. The outer string includes a 27 / 8” coiled tubing upper section sealing tool, interlayer coiled tubing, and a lower section sealing tool; the inner string includes a 1.5” coiled tubing and a sealing insert. The inner insert and the lower sealing device of the upper section sealing tool form an insertion seal, thereby separating the inner and outer coiled tubing to form two independent injection channels: one for injecting the lower layer inside the inner coiled tubing, and the other for injecting the upper layer through an annulus in the outer coiled tubing.

[0036] (2) A downhole layered gas injection tool: Utilizing high-temperature and corrosion-resistant sealing materials to meet long-term gas sealing requirements, it is easy to operate, has good stability, and a wide range of applications. It can withstand gas pressures of 47 MPa, temperatures of 120℃, and CO2 corrosion. The upper sealing tool has connecting devices at both ends to connect and seal with the outer continuous tubing and interlayer tubing respectively. Simultaneously, the lower part of the upper sealing tool has a sealing cylinder that forms a seal with the inner insert, isolating internal and external communication. A constant pressure switch is installed on the sealing cylinder to prevent blowout during well completion. After the tool is set, it opens at the set pressure, becoming the upper injection channel. The lower sealing tool has a connecting device at the upper end to connect and seal with the outer continuous tubing. Simultaneously, a constant pressure plug for blowout prevention is designed at the end of the lower sealing tool to achieve internal blowout prevention during well completion, meeting the requirements for pressurized operations in conjunction with the operating equipment. To further improve the reliability of the insertion sealing process, an innovative integrated insertion sealing structure is developed. The sealing tool and insertion seal are pre-connected before the tool is lowered into the well for completion, further improving process reliability and reducing the difficulty of subsequent tubing string pulling operations.

[0037] (3) An integrated multi-functional layered gas injection wellhead. The coiled tubing double hanger mounting flange, casing four-way valve, and shut-in valve are designed as an integrated unit, equipped with two sets of slips of different sizes and combined seals, further reducing the wellhead height. The mounting valve can be mounted on conventional tubing or coiled tubing for completion according to different process completion requirements; the shut-in valve can shut off the well when the well is empty, and can be used to switch between different wellhead operating equipment; the wellhead production tree is designed with a double valve structure, and a safety valve and a matching control system are designed as the main production valve, which can realize automatic shut-in and remote control in abnormal conditions, further improving safety;

[0038] (4) A layered gas injection coiled tubing double suspension device. It is divided into two key parts: a pre-installed suspension device and a post-installed suspension device, which meets the two requirements of large-diameter tools passing through the wellhead mounting flange and being taken out through the coiled tubing live operation device, and further meets the full life cycle of live operation.

[0039] ①Large tubing suspension device: The inner diameter of the mounting flange of the coiled tubing suspension device is 130mm. It is designed with a double top screw structure. During the well completion process, the top screw compresses the sealing sleeve of the suspension device to achieve high-pressure sealing at the wellhead. The inner diameter of the pre-installed suspension device is 80mm or more. It is lowered after the large-diameter tool (insertion sealing device) passes through the mounting flange. The outer diameter of the rear-installed suspension device is within 130mm. It is lowered after the coiled tubing is cut during well completion. It can be retrieved with the coiled tubing in the pressurized operation equipment during the later well completion.

[0040] ② Small tubing suspension device: The inner diameter of the mounting flange of the coiled tubing suspension device is 130mm. It is designed with a double top screw structure. During the well completion process, the top screw compresses the sealing sleeve of the suspension device to achieve high-pressure sealing at the wellhead. The inner diameter of the pre-installed suspension device is 45mm or more. It is lowered after the large-diameter tool (insertion sealing device) passes through the mounting flange. The outer diameter of the rear-installed suspension device is within 130mm. It is lowered after the coiled tubing is cut during well completion. It can be retrieved with the coiled tubing in the pressurized operation equipment during the later well completion.

[0041] Example 2

[0042] A device structure suitable for CO2-driven coiled tubing injection process is shown in Example 1, and the steps are as follows:

[0043] 1. Install the integrated multi-functional gas injection wellhead under depressurized conditions and close the main control valve;

[0044] 2. Install a coiled tubing live-line device;

[0045] 3. After the lower sealing tool is connected to the interlayer tubing, it is lowered into the well. The upper end of the interlayer tubing is lowered to the wellhead. It is then connected to the upper sealing tool via the dual-channel coiled tubing. The upper sealing tool is then connected to the interlayer tubing at the wellhead and lowered into the well.

[0046] 4. After reaching the predetermined depth of the oil layer, insert slips to suspend the external tubing.

[0047] 5. Disconnect the external coiled tubing and install an external tubing sealing device;

[0048] 6. Cut off the inner oil pipe and install the inner oil pipe sealing device;

[0049] 7. Pressure test the expansion plugs from the inner and outer oil pipes and the annulus of the inner oil pipe; and verify the seals in sequence.

[0050] 8. Install the wellhead tree and safety valve control system; then pressurize separately to open the two channels: the channel inside the small tubing and the annulus channel between the small tubing and the large tubing, to achieve gas injection.

[0051] The dual-channel connecting pipe is larger in size and weight, and has higher requirements for wellhead suspension and downhole tool connection. Experiments have confirmed that the wellhead slip suspension capacity is 30t, the mechanical load of the downhole connecting tool is 20t, and the overall gas sealing capacity is 47MPa.

[0052] This invention fully considers the maximum transport capacity of the outer tubing, takes into account the principle of similar flow areas in different channels, and optimizes the tubing size by combining the minimum diameter of downhole tools. Through calculation of annular flow area and mechanical parameters, the 27 / 8”+1.5” continuous tubing combination is finally selected.

[0053] This invention belongs to the field of CCUS injection technology and discloses a CO2-driven coiled tubing injection process. It provides an integrated stratified gas injection wellhead with two sets of slips of different sizes and combined seals, a dual-suspension device design, a dual-channel coiled tubing assembly, and a downhole insertion sealing stratified gas injection tool. It is also equipped with a CO2 vortex flow meter and an automatic adjustment device, which can automatically identify the injection medium and switch databases to achieve automatic water-gas alternation metering, and also has online control functionality.

[0054] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for continuous tubing injection in CO2 flooding, characterized in that, The steps are as follows: S1. Install the integrated multi-functional gas injection wellhead (1) under the condition of no pressure at the wellhead and close the main control valve (6); S2. Install a coiled tubing live-line device; S3. After the lower sealing tool (11) is connected to the interlayer coiled tubing (19), it is lowered into the well. The upper end of the interlayer coiled tubing (19) is lowered to the wellhead. It is connected to the dual-channel coiled tubing and the upper sealing tool (10). The upper sealing tool (10) is connected to the interlayer coiled tubing at the wellhead and continues to be lowered into the well. S4. After descending to the predetermined depth of the oil layer, insert slips (17) to suspend the coiled tubing (3) outside the wellhead; S5. Cut off the continuous tubing outside the wellhead (3) and install the external tubing sealing device (18); S6. Insert slips (17) to suspend the coiled tubing (3) inside the wellhead, cut off the coiled tubing (3) inside the wellhead, and install the inner tubing sealing device (18). S7. Pressurize and expand the upper sealing tool (10) and lower sealing tool (11) from the annulus of the coiled tubing (3) inside the wellhead and the coiled tubing (3) inside and outside the wellhead, and verify the seal in sequence; S8. Install the wellhead tree and safety valve control system; then pressurize the two channels of continuous tubing (3) to open the channel in the small tubing and the annular channel between the small tubing and the large tubing to achieve gas injection.

2. The CO2-driven continuous tubing injection process according to claim 1, characterized in that, The coiled tubing (3) includes a large-diameter coiled tubing (8) and a small-diameter coiled tubing (9), with the large-diameter coiled tubing (8) fitted over the small-diameter coiled tubing (9).

3. The CO2-driven continuous tubing injection process according to claim 1, characterized in that, The integrated multi-functional gas injection wellhead (1) includes: a four-way casing (5) with a main control valve (6) installed on it. The main control valve (6) and the four-way casing (5) are integrated.

4. The CO2-driven coiled tubing injection process according to claim 3, characterized in that, Each of the four-way sleeves (5) is equipped with a control valve (7).

5. The CO2-driven coiled tubing injection process according to claim 3, characterized in that, The continuous tubing pressurization device is installed on the four-way sleeve (5).

6. The CO2-driven coiled tubing injection process according to claim 1, characterized in that, The upper sealing tool (10) includes a sealing tube (13) and a drillable bridge plug (12), and the lower sealing tool (11) includes a sealing tube (13), a drillable bridge plug (12), and a pressure-regulating plug (14).

7. The CO2-driven continuous tubing injection process according to claim 1, characterized in that, The wellhead is equipped with a double suspension device (2).

8. The CO2-driven continuous tubing injection process according to claim 7, characterized in that, The dual suspension device (2) includes a pre-installed hanger (15) connected to the wellhead and a rear hanger (16) above the pre-installed hanger (15).

9. The CO2-driven coiled tubing injection process according to claim 8, characterized in that, A slip (17) is provided between the pre-installed hanger (15) and the continuous oil pipe (3), and a sealing device (18) is provided on the rear hanger (16).

10. The CO2-driven continuous tubing injection process according to claim 9, characterized in that, The sealing device (18) includes an external oil pipe sealing device and an internal oil pipe sealing device.

Images