CCUS injection well completion device and method for preventing gas channeling outside pipe

Abstract

The invention discloses a well completion device and method for preventing external gas channeling of a CCUS injection well, and provides an innovative scheme for forming an epoxy resin sealing layer in a shaft at the upper section of a target layer in order to solve the problems of low gas driving efficiency and resource waste caused by external gas channeling in the prior art. MS-1086T epoxy resin sealant (the volume ratio of epoxy resin to a curing agent is 3: 1) is adopted as a sealing material, and a stable sealing barrier is formed in a low-temperature and high-pressure environment through the high viscosity, shear thinning characteristic and underwater curing capacity of the sealing material, so that a gas upward flowing path is effectively blocked. The scheme has the characteristics of simplicity and convenience in construction, controllable cost and excellent sealing performance, and is suitable for ocean and land CCUS engineering.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field completion engineering technology, specifically relating to a CCUS injection well anti-gas channeling completion device and method based on epoxy resin sealant, which is suitable for improving CO2 oil displacement efficiency and reducing resource waste. Background Technology

[0002] During the high-pressure CO2 displacement and storage process in CCUS injection wells, the large temperature gradient in the wellbore, the complex multi-layer interface of the casing, and the long-term immersion in acidic fluids often lead to microcracks and interface peeling in the cement sheath, forming gas seepage channels and causing gas channeling outside the casing. Existing anti-gas channeling technologies mainly rely on cement cementing or mechanical packer schemes, but they have obvious limitations. The cement sheath is prone to shrinkage microcracks under temperature fluctuations and CO2 corrosion, forming gas escape channels. Mechanical packers have poor adaptability to wellbore structures, are difficult to install in multi-layer casing or highly deviated wells, and are costly. Some chemical grouting materials (such as polyurethane) have insufficient oil resistance and CO2 corrosion resistance, making it difficult to guarantee long-term sealing stability.

[0003] Therefore, there is an urgent need for a well completion scheme that combines good adaptability and long-term sealing to prevent gas leakage. Summary of the Invention

[0004] A CCUS injection well anti-gas channeling completion device includes a casing assembly, a wellbore sealing layer, and an annular sealing mechanism. The sealing layer is disposed between the casing and the well wall in the upper section of the target layer of the wellbore, and the annular sealing mechanism is fixedly installed on the casing wall to block the annular gas channel in the wellbore.

[0005] The annular sealing mechanism includes a sealing shell, a support ring, an injection channel, and a double-layer anti-channeling sealing plug; the sealing shell is fixedly connected to the sleeve wall, the support ring is located inside the sealing shell, and an annular sealing cavity is provided on the inner side of the support ring, which is filled with epoxy resin sealant.

[0006] The double-layer anti-seepage sealing plug is arranged along the wellbore axis and includes an upper sealing plug and a lower sealing plug. The upper sealing plug is connected to the support ring, and the lower sealing plug is bonded and fixed to the cured epoxy layer. Together, they form a sealing structure that integrates pressure resistance and seepage prevention.

[0007] The injection channel is connected to the surface injection pipeline and is used to inject epoxy resin sealant into the sealing cavity. The sealant and curing agent are mixed in proportion and then enter the sealing cavity and are cured under downhole temperature conditions to form a solid sealing layer.

[0008] Preferably, the epoxy resin sealant is composed of modified elastic epoxy resin, underwater curing agent and CO2-resistant composite filler, and has a viscosity greater than 200 Pa·s and a compressive strength of not less than 150 kPa after curing.

[0009] Preferably, the outer wall of the sealing housing is provided with an anti-slip textured structure to prevent the device from sliding axially along the sleeve wall.

[0010] Preferably, a one-way valve is provided in the injection channel to prevent the sealant from flowing back after injection is completed.

[0011] Preferably, the sealed housing is provided with an elastic compensation pad to absorb micro-deformation caused by downhole pressure fluctuations.

[0012] Preferably, the annular sealing mechanism is covered with a corrosion-resistant protective layer to prevent CO2 and downhole brine from corroding the main body of the sealing device.

[0013] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantage: (1) It adopts a dual sealing structure of "mechanical support + epoxy chemical sealing", which has a significant anti-channeling effect; (2) Epoxy resin materials have shear thinning and high viscosity curing properties, which can achieve self-flowing plugging under complex well conditions; (3) The device has a modular structure, is easy to install, and can be installed in one go with the well completion string; (4) It can withstand CO2, high salt and temperature fluctuations for a long time and has a long sealing life. Attached Figure Description

[0014] Figure 1 Schematic diagram of the CCUS injection well anti-gas leakage completion device.

[0015] Figure 2 : Schematic diagram of the WD-L050G dispensing machine.

[0016] Figure 3 : Viscosity of sealant with different curing times.

[0017] Figure 4 : Real-time pressure change characteristics of sealed pipe fittings during pressurization.

[0018] In the diagram: 1. Upper sealing plug and support ring; 2. Check valve; 3. Lower sealing plug; 4. Epoxy resin sealant; 5. Target layer; 6. Material handle stirring motor; 7. Inlet valve; 8. Material handle stirring blades; 9. Heating device; 10. Stepper motor; 11. Precision gear pump; 12. Vacuum extraction valve; 13. Cleaning tank; 14. Mixing system. Detailed Implementation

[0019] The CCUS injection well anti-gas channeling completion device and method provided by this invention, through the matching completion device such as Figure 1 As shown, specialized dispensing equipment, such as Figure 2The standardized operating procedures shown demonstrate how to achieve efficient sealing of the annular space in the upper section of the wellbore at the target layer. The specific implementation process is as follows.

[0020] Material Preparation: MS-1086T epoxy resin sealant is selected. This sealant consists of modified elastic epoxy resin (component A), modified fully underwater epoxy curing agent (component B), and 8% silica powder composite filler. Before use, components A and B should be mixed at a volume ratio of 3:1, ensuring uniform mixing and absence of particulate impurities. Check all performance parameters of the material to ensure its specific gravity is within the range of 1.2 to 1.3, and the viscosity after curing can reach greater than 200 Pa·s. Figure 3 As shown, the pressure bearing capacity is not less than 150 kPa. Figure 4 As shown.

[0021] Equipment Debugging: Using a WD-L050G dispensing machine, load the prepared components A and B into the dual-material tanks of the dispensing machine. Connect the dual-gear pump and the mixing head, and adjust the speed ratio of the stepper motor corresponding to the dual-gear pump to ensure that components A and B are delivered according to the preset ratio. Start the vacuum pump to maintain stable internal pressure of the dispensing machine, and debug the dispensing rate adjustment function to ensure precise control within the range of 5-20 L / min. Set the shear rate parameter through the equipment's built-in control system to ensure that a shear rate of 50-200 seconds is generated during the dispensing process. -1 The shear rate; check the gas-liquid combination automatic cleaning function of the mixing head to ensure that the mixing tube can be cleaned without disassembly, avoiding residual sealant from affecting the subsequent injection effect; install downhole temperature sensors and feedback control systems, calibrate the temperature monitoring accuracy, and ensure that downhole temperature changes can be captured in real time and fed back to the surface control terminal.

[0022] Well completion assembly: Assemble the well completion device, which includes the wellbore, casing, epoxy resin sealing layer, and annular sealing mechanism. The outer wall of the sealing shell in the annular sealing mechanism is machined with anti-slip texture to prevent axial slippage of the device along the casing wall. A support ring is installed inside the sealing shell to form an annular sealing cavity, and an elastic compensation pad is laid inside the sealing cavity to absorb micro-deformation caused by subsequent downhole pressure fluctuations. Double-layer anti-channeling sealing plugs (upper and lower sealing plugs) are fixed axially along the wellbore. The upper sealing plug is tightly connected to the support ring, and the lower sealing plug has a pre-reserved bonding interface with the cured epoxy layer. A one-way valve is installed in the injection channel to prevent backflow of the sealing compound after injection. Finally, a corrosion-resistant protective layer is applied to the outside of the annular sealing mechanism to resist corrosion from CO2 and downhole brine. After assembly, check the sealing of each component connection to ensure there are no loosening or leakage risks.

[0023] Pre-treatment of the annular space in the wellbore: The annular space in the upper section of the target layer is treated using specialized cleaning equipment. A combination of high-pressure flushing and negative pressure suction is used to remove residual mud, rock cuttings, and other impurities from the annular space, ensuring that there are no attachments on the well wall and the outer wall of the casing. After cleaning, the annular space is inspected using downhole imaging equipment to confirm that there are no obvious cracks or holes inside, and that the space dimensions meet the injection requirements of the epoxy resin sealing layer (thickness 10-30 cm), ensuring that the subsequent sealant can fully fill the annular space.

[0024] Adhesive Injection Connection and Parameter Setting: Seal the adhesive injection pipeline of the WD-L050G adhesive injection machine to the adhesive injection channel of the completion unit. Set the adhesive injection parameters through the ground control system, setting the initial value of the adhesive injection rate to an adaptive value within the range of 5-20 L / min, and the corresponding shear rate to 50-200 s. -1 By utilizing the shear-thinning rheological properties of the sealant, the viscosity of the sealant is reduced from about 200 Pa·s to 10-50 Pa·s during the injection process, thereby improving its fluidity in the annular space and ensuring that it can be evenly filled to all corners.

[0025] Injection process control: The injection machine is started, and the dual gear pump synchronously delivers components A and B to the mixing head. After being fully mixed by the mixing head, the sealant is injected into the annular sealing cavity and the annular space of the upper section of the wellbore in the target layer through the injection channel. During the injection process, the injection rate, shear rate and internal pressure are monitored in real time by the injection machine's control system. If the parameters deviate from the preset values, the stepper motor speed or vacuum pump working status is automatically adjusted to maintain the stability of the injection process. At the same time, the downhole ambient temperature is monitored in real time by the downhole temperature sensor. If the temperature exceeds the suitable curing range of 4-20℃, the surface injection rhythm is adjusted through the feedback control system to avoid temperature fluctuations affecting the fluidity of the sealant.

[0026] Curing Condition Control: After the epoxy resin sealant is injected, maintain the downhole ambient temperature at 4–20°C and allow it to cure for 24–72 hours. During the curing process, the downhole temperature sensor continuously collects temperature data and transmits it to the feedback control system. If the temperature is below 4°C, the local temperature of the wellbore is appropriately increased by the surface auxiliary heating equipment. If the temperature is above 20°C, cooling measures are initiated to ensure that the sealant cures slowly within the appropriate temperature range, forming a structurally stable epoxy resin sealing layer. The feedback control system monitors the volume change of the sealant during the curing process, and the deformation adjustment of the elastic compensation pad is used to offset the micro-cracks that may be generated by curing shrinkage.

[0027] Post-curing quality inspection: After the sealant has cured, the pressure-bearing capacity of the epoxy resin sealing layer is tested using a downhole pressure sensor. The pressure is gradually increased to 150 kPa using a staged pressurization method, and the stability of the pressure is observed to confirm that there is no leakage in the sealing layer. Sonic logging is performed on the sealing layer using surface acoustic wave detection equipment to analyze the sound wave propagation speed and reflection signal, and to determine whether the thickness of the sealing layer meets the design requirement of 10-30 cm and whether there are any defects such as voids or cracks inside. The double sealing effect of the annular sealing mechanism is checked to confirm the connection stability between the upper sealing plug and the support ring, the bonding strength between the lower sealing plug and the cured epoxy layer, and the integrity of the anti-corrosion protective layer of the sealing shell, to ensure that the sealing performance of the entire well completion device meets the design standards.

[0028] This patented integrated CCUS injection well completion solution, combining mechanical support and epoxy chemical sealing, successfully addresses the problems of complex structure, poor corrosion resistance, and long-term unstable sealing in existing technologies. By using MS-1086T epoxy resin sealant (containing 8% silica powder) in conjunction with a WD-L050G injection machine, a stable sealing layer with a thickness of 10-30 cm and a pressure resistance of no less than 150 kPa is formed in the upper section of the target layer, effectively preventing gas leakage from outside the casing. The solution boasts advantages such as modular design for easy installation, materials resistant to CO2 and high salinity, adaptability to a temperature range of 4-20℃, and low construction costs. Practical application verification has shown that it can significantly improve CO2 flooding efficiency and is suitable for both onshore and offshore CCUS projects, providing a replicable technological paradigm for controlling gas leakage in similar wells.

[0029] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A completion device and method for preventing external gas leakage in CCUS injection wells, characterized in that: It includes a wellbore, casing, target layer, and epoxy resin sealing layer; the epoxy resin sealing layer is located in the annular space of the upper section of the wellbore of the target layer, and is formed by injection and curing of MS-1086T epoxy resin sealant (developed and produced by Changsha Puzhao Biochemical Technology Co., Ltd., with a specific gravity of 1.2 to 1.

3. This type of sealant is composed of modified elastic epoxy resin, modified fully underwater epoxy curing agent and selected composite filler, and has the characteristics of oil resistance, solvent resistance, durability, environmental protection and non-toxicity, and the volume ratio of epoxy resin to curing agent is 3:1).

2. A completion method for preventing external gas leakage in CCUS injection wells, characterized in that: Includes the following steps: Step 1: Pre-treat the annular space of the upper section of the target layer to remove mud and debris, ensuring the annular space is clean. Step 2: Inject MS-1086T epoxy resin sealant into the annular space using a rotary injection device at a rate of 5–20 L / min, utilizing the shear-thinning rheological properties of the MS-1086T epoxy resin sealant to achieve uniform distribution. Step 3: Allow the sealant to cure at 4–20℃ for 24–72 hours, monitoring and controlling the curing process using a downhole temperature sensor to form an epoxy resin sealing layer in the upper section of the target layer with a thickness of 10–30 cm, a cured viscosity greater than 200 Pa·s, and a pressure-bearing capacity of not less than 150 kPa.

3. A WD-L050G dispensing machine, characterized in that: The dispensing machine includes two material tanks, a dual-gear pump, a mixing head, and a control system. The two material tanks are used to hold component A and component B of MS-1086T epoxy resin sealant, respectively. The dual-gear pump is connected to the two material tanks and driven by two stepper motors. The mixing ratio of components A and B is adjusted by regulating the speed ratio of the two stepper motors. The dual-gear pump synchronously delivers components A and B to the mixing head. The mixing head uses an automatic cleaning method combining gas and liquid to fully mix components A and B. The dispensing machine also includes a temperature sensor and a vacuum pump to monitor the dispensing process and maintain stable internal pressure.

4. The well completion method according to claim 2, characterized in that: The injection rate in step two is controlled at 5–20 L / min, during which 50–200 seconds of fluid is generated in the wellbore annulus. -1 The shear rate reduces the viscosity of the epoxy resin sealant from about 200 Pa·s to about 10 to 50 Pa·s.

5. The well completion device according to claim 1, characterized in that: The well completion device also includes a downhole temperature sensor and a feedback control system, which are used to monitor the downhole temperature in real time during the curing process and automatically adjust the curing conditions of the epoxy resin sealing layer according to the monitoring results.

6. The well completion method according to claim 2, characterized in that: In step two, silica powder is added to the injected MS-1086T epoxy resin sealant at a ratio of 8% to improve the compressive strength of the epoxy resin sealing layer formed after injection.

7. The WD-L050G dispensing machine according to claim 3, characterized in that: The mixing head adopts an automatic cleaning method combining gas and liquid, which enables automatic cleaning of the mixing tube without disassembly.

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