A CCS project CO2 geological storage monitoring well and completion technology

Abstract

The present invention discloses a monitoring well and completion technology for CO₂ geological storage in CCS projects, including a downhole string. The downhole string includes a vertical section and a horizontal section. On the tubing inside the string, there are a traversable packer and a pressure gauge carrier seated in the horizontal section. The monitoring well further includes three monitoring systems for synchronous downhole sampling of liquid samples, pressure / temperature, and gas samples. The downhole part thereof includes steel pipes / transmission cables extending from the wellhead to the seated position in the horizontal section, and the steel pipes / transmission cables are respectively connected to an optical fiber pressure gauge, an electronic pressure gauge, a three-way valve block, a liquid sample screen pipe or a gas sample screen pipe according to the sequence and depth, and the optical fiber pressure gauge and the electronic pressure gauge are installed in the pressure gauge carrier. The monitoring well monitors the storage pressure and temperature in the horizontal section using a dual system, and directly samples from the formation using capillary steel pipes to achieve permanent monitoring and sampling of the storage.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon dioxide capture and storage (CCS), and relates to a monitoring well, specifically to a monitoring well for permanent monitoring and sampling of CO2 geological storage in CCS projects and its well completion technology. Background Art

[0002] To address future climate change, countries have signed the Copenhagen Accord on carbon dioxide emissions, and China joined the accord in 2009. As time goes by, the three visions and specific goals of carbon emission reduction, carbon peak, and carbon neutrality have become clearer, the measures have been gradually refined, and the intensity has been gradually increased. To achieve the "dual carbon" goal, the main ways are to reduce carbon emissions and increase removals. "Carbon reduction" means to strengthen energy conservation and consumption reduction, and the substitution of clean energy, especially to significantly improve the electrification level and the proportion of green electricity, so as to reduce the consumption of fossil energy from the source and achieve carbon dioxide reduction. "Carbon removal" means carbon dioxide capture and storage (Carbon Capture and Storage) and the layout of forestry carbon sink projects, and to strengthen the chemical utilization or burial of carbon dioxide to achieve carbon removal.

[0003] At present, CCS technology is an optional measure to address the severe challenges posed by energy and the environment, and is also a major strategic measure to address climate change. CCS technology consists of two parts: carbon capture (CC) and carbon storage (CS). Among them, CO2 geological storage is to inject the captured CO2 into the pores of the underground trap formation, and seal the CO2 underground through the sealing of the caprock and the surrounding barriers. The driving forces for promoting the migration of CO2 during the CO2 enhanced oil recovery / geological storage process are overpressure and gas column buoyancy. However, there is also a risk of leakage, and the main leakage paths (without considering engineering factors) are: migration / leakage through the parts with weak sealing ability of the upper and lower barriers and the lateral barriers. During the storage process, the density of the CO2 groundwater solution is an important parameter affecting the migration of CO2, which determines the safety of geological storage. During the operation of CO2 enhanced oil recovery storage projects, there are still many human and natural uncertainties that may lead to the escape and leakage of CO2. Activities such as CO2 injection and fracturing, as well as potential natural geological movements, will damage the structural trap and wellbore integrity of the storage body, generate CO2 escape channels, and cause large-scale CO2 leakage safety incidents. Therefore, for the carbon dioxide sealed in the formation, how to obtain parameters such as pressure, temperature, and composition that reflect the carbon dioxide storage state in a long-term, continuous, and real-time manner to judge the storage state is the key technical problem restricting CS projects.

[0004] At present, the vertical monitoring well sampling adopted in the CO2 geological storage detection of CCS projects cannot meet the multiple spatial and temporal scales that need to be considered when monitoring carbon dioxide storage during the implementation process of CCS projects and during long-term storage, and thus cannot master the short-term and long-term risks of carbon dioxide from the reservoir to the regional scale, nor understand the injection and storage effects and safety of carbon dioxide on the geological time scale. Therefore, in order to ensure the safety of CO2 geological storage construction and subsequent processes, there is an urgent need for a monitoring technology that can monitor the entire life cycle process of CO2 geological storage in terms of time and space. Summary of the Invention

[0005] In view of the above problems, the present invention proposes a monitoring well and its completion technology for permanent monitoring and sampling of CO2 geological storage in CCS projects. Starting from aspects such as the completion string, pressure, temperature monitoring, and formation fluid sampling, it overcomes the problems of small detection range and inability to ensure spatial and temporal detection scales in storage monitoring and sampling, providing strong technical support for the safe and efficient development of CCS projects.

[0006] The object of the present invention is achieved by adopting the following technical solutions:

[0007] A monitoring well for CO2 geological storage in a CCS project includes a wellhead device and a downhole string. The downhole string includes a casing and a tubing inside the casing. It is characterized in that the downhole string is in an L shape, including a vertical section and a horizontal section. The monitoring well also includes a liquid sample collection system, a pressure / temperature collection system, and a gas sample collection system. The liquid sample collection system in the downhole string includes a liquid sample capillary steel pipe and an injection gas capillary steel pipe extending from the wellhead to the horizontal section, as well as a three-way valve block and a liquid sample screen pipe. The liquid sample capillary steel pipe and the injection gas capillary steel pipe are respectively connected to two ports of the three-way valve block, and the third port of the three-way valve block is connected to the liquid sample screen pipe. A check valve is included in the three-way valve block, and the check valve is connected to the third port, with the direction being that the fluid flows from the outside of the valve block into the inside. The pressure / temperature collection system in the downhole string includes an optical fiber and a cable extending from the wellhead to the horizontal section, as well as an optical fiber pressure gauge and an electronic pressure gauge. The optical fiber is connected to the optical fiber pressure gauge, and the cable is connected to the electronic pressure gauge. The gas sample collection system in the downhole string includes a gas sample capillary steel pipe extending from the wellhead to the horizontal section and a gas sample screen pipe connected to its end. A retrievable packer and a pressure gauge carrier are included on the tubing. The retrievable packer is set in the horizontal section, and the liquid sample, injection gas, and gas sample capillary steel pipes, optical fiber, and cable extend through the retrievable packer to the rear of the setting position. The optical fiber pressure gauge and the electronic pressure gauge are installed in the pressure gauge carrier.

[0008] Preferably, the liquid sample screen pipe is located in the perforated section on the horizontal section, and the gas sample screen pipe is located at one end of the retrievable packer on the horizontal section.

[0009] Further, the tubing includes a circulating sliding sleeve, a retrievable packer, a blind plug nipple, and a round head blind plug connected in sequence.

[0010] Further, the liquid sample, the gas injection, and the capillary steel pipes for gas samples, optical fibers, and cables are fixed to the tubing by fixing clips.

[0011] Further,

[0012] The liquid sample collection system further includes a liquid sample collection device and a liquid sample gas injection device on the wellhead. The liquid sample collection device is connected to the capillary steel pipe for liquid samples, and the liquid sample gas injection device is connected to the capillary steel pipe for gas injection;

[0013] The pressure / temperature collection system further includes an optical fiber pressure gauge collection device and an electronic pressure gauge collection device on the wellhead. The optical fiber pressure gauge collection device is optically connected to the optical fiber, and the electronic pressure gauge collection device is electrically connected to the cable;

[0014] The gas sample collection system further includes a gas sample collection device on the wellhead. The gas sample collection device is connected to the capillary steel pipe for gas samples.

[0015] The liquid sample collection device, the liquid sample gas injection device, the gas sample collection device, the optical fiber pressure gauge collection device, and the electronic pressure gauge collection device are installed on the well site ground to analyze and process the fluid, pressure, and temperature parameters collected from the wellbore.

[0016] Further, the retrievable packer can be an expansion packer, including five through channels. The general structure of the retrievable packer is that there are several axial channels inside, which can connect the upper and lower parts through the internal channels when the packer is in the set condition.

[0017] Further, the tubing is a CO2 corrosion-resistant tubing.

[0018] Further, the monitoring well further includes a tubing hanger between the wellhead device and the downhole string.

[0019] Further,

[0020] The circulating sliding sleeve is a device on the vertical section of the downhole string, designed with an outer cylinder and an inner sleeve. The outer cylinder is designed with radial holes, and a wire tool can be used to open or block the radial holes of the outer cylinder by the inner sleeve, thereby opening or closing the sliding sleeve;

[0021] The blind plug nipple is a middle solid tubing nipple;

[0022] The round head blind plug is at the end of the tubing, installed at the bottom of the string to block the string.

[0023] Further, the liquid sample and gas sample sieve tubes are hollow cylinders with fine pores from the outside to the inside. External fluid enters the inside through the fine pores and filters the fluid.

[0024] The present invention also provides a well completion technology for the CCS project CO2 geological sequestration monitoring well, characterized in that the well completion string and the monitoring system enter the well synchronously. The downhole string is L-shaped, including a vertical section and a horizontal section, and includes a casing and a tubing. The tubing includes a traversable packer and a pressure gauge carrier. The monitoring system includes a liquid sample collection system, a gas sample collection system, and a pressure / temperature collection system;

[0025] It includes the following steps:

[0026] (1) Well completion string entering the well: Drill and set the casing and cement it. According to the depths and connection sequences of the components of the well completion string, connect the tubing in sequence and lower it into the casing well section by section to realize the well completion string entering the well;

[0027] (2) Monitoring system entering the well: The downhole part of the monitoring system, including the steel pipe / transmission cable composed of liquid sample capillary steel pipes, gas injection capillary steel pipes, gas sample capillary steel pipes, optical fibers and cables, connects the steel pipe / transmission cable with the fiber optic pressure gauge, electronic pressure gauge, three-way valve block, liquid sample sieve tube and gas sample sieve tube respectively according to the connection sequence and depth, and installs the fiber optic pressure gauge and the electronic pressure gauge in the pressure gauge carrier, and lowers them into the casing well synchronously with the well completion string, keeping the steel pipe / transmission cable in a straight state;

[0028] (3) Steel pipe / transmission cable passing through the packer: When the well completion string and the monitoring system are synchronously lowered to the well entry position of the traversable packer, first connect the traversable packer to the well completion string, cut off the steel pipe / transmission cable, pass it through the reserved passing channel of the traversable packer, and then connect it with a sealing nipple or a cable connector;

[0029] (4) Steel pipe / transmission cable passing through the wellhead: After the traversable packer is lowered to the predetermined position in the horizontal well section, start the steel pipe / transmission cable passing through the wellhead. Cut off the steel pipe / transmission cable, pass it through the reserved passing channel at the wellhead, and then connect it with a sealing nipple or a cable connector;

[0030] (5) Wellhead pressure test: Conduct a wellhead pressure test through the pressure test channel;

[0031] (6) Downhole packer setting: After the pressure test is qualified, pump liquid into the tubing to increase the pressure until the traversable packer is set; pump an anti-corrosion and anti-freezing protection liquid into the annular space between the oil pipe and the casing.

[0032] Further, the well completion technology also includes the steps:

[0033] (7) Connection of the monitoring system: Connect the steel pipe / transmission cable passing through the wellhead to the ground part of the monitoring system respectively, that is, connect them to the liquid sample collection device, liquid sample gas injection device, fiber optic pressure gauge collection device, electronic pressure gauge collection device and gas sample collection device respectively.

[0034] Furthermore, the oil pipe includes a circulating sliding sleeve, a traversable packer, a blind plug short section and a round head blind plug connected in sequence. The steel pipe / transmission cable is fixed to the oil pipe through fixing clips.

[0035] Furthermore, in the completion process, to reduce the self-weight of the completion string in the horizontal well section and increase the buoyancy of the completion string in the horizontal well section itself, the connection of the oil pipe is a gas-tight threaded connection to prevent leakage, and no fluid is added during the completion string entering the well, and the medium is air.

[0036] Beneficial effects: The CCS project CO2 geological storage monitoring well of the present invention adopts an L-shaped downhole string, and the monitoring system composed of a liquid sample collection system, a pressure / temperature collection system and a gas sample collection system enters the well synchronously. For the carbon dioxide stored in the formation in the CCS project, it can continuously and real-timely obtain its pressure, temperature, composition and other parameters for a long time to judge the storage state, so as to realize the permanent monitoring and sampling of the storage. The monitoring well specifically has the following advantages:

[0037] 1) In the CCS project CO2 geological storage monitoring well of the present invention, the downhole string is L-shaped and includes a horizontal section located in the storage area of the CCS project. The horizontal section detection can accurately track and detect the sealed area, making up for the defect of insufficient spatial detection range of the longitudinal monitoring well.

[0038] 2) The pressure and temperature data are collected using two channels, and the devices used for data collection are different, with different principles, information transmission media, and different conditions for failure, ensuring the safety and accuracy of the collected data under complex downhole conditions.

[0039] 3) The sampling point of the liquid sample collection system is set at the formation perforation section. The formation fluid reaches the sampling capillary steel pipe after filtration, and high-pressure nitrogen is used to directly sample from the formation to the ground, which is simple and convenient.

[0040] 4) The gas sample collection operation directly samples by the capillary steel pipe in the gas accumulation area below the packer, and the process is simple and convenient.

[0041] 5) A traversable packer is designed in the completion string, and the capillary steel pipe, optical fiber and cable of the collection system can all reach the bottom of the well to collect real samples and data in real time.

[0042] The CCS project CO2 geological storage monitoring well and completion technology of the present invention can achieve the purpose of obtaining downhole gas and liquid samples in real time while completing long-term monitoring of the storage pressure and temperature. The completion string structure of the present invention is simple, and the acquisition system is safe and efficient, and can operate for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Structure schematic diagram of the CCS project CO2 geological storage monitoring well of the present invention;

[0044] Figure 2 Structure schematic diagram of the three-way valve block in the monitoring well of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0045] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments are only used to illustrate the present invention, and the protection scope of the present invention is not limited by the specific embodiments, but is defined by the claims.

[0046] The structure schematic diagram of the CCS project CO2 geological storage monitoring well of the present invention is as Figure 1 shown, and the structure schematic diagram of the three-way valve block is as Figure 2 . It mainly includes a liquid sample collection device 1; a liquid sample gas injection device 2; an optical fiber pressure gauge collection device 3; an electronic pressure gauge collection device 4; a gas sample collection device 5; a wellhead device 6; a fixed clamp 7; a casing 8; a tubing 9; a circulating sliding sleeve 10; a penetrable packer 11; a blind plug short section 12; a pressure gauge support cylinder 13; a three-way valve block 14; a round head blind plug 15; a liquid sample capillary steel pipe 101; a liquid sample screen pipe 102; an injection capillary steel pipe 201; an optical fiber 301; an optical fiber pressure gauge 302; a cable 401; an electronic pressure gauge 402; a gas sample capillary steel pipe 501; a gas sample screen pipe 502; a perforation section 801; a one-way valve 1401; a liquid sample extraction capillary steel pipe 1402.

[0047] As Figure 1A CCS project storage monitoring well includes a wellhead device and a downhole tubing string. The downhole tubing string is suspended / supported by a tubing hanger located at the wellhead. The downhole tubing string includes a casing 8 and a tubing 9 in the casing 8, including the tubing 9, a circulating sleeve 10, a traversable packer 11, a blind plugging nipple 12, a pressure gauge holder 13, and a round-head blind plug 15 connected in sequence. According to the monitoring well described by the present invention, the downhole tubing string is L-shaped, including a vertical section and a horizontal section, and also includes three monitoring systems that are synchronously entered into the well, namely, a liquid sample collection system, a pressure / temperature collection system, and a gas sample collection system; the liquid sample collection system includes a tubing 9 in the casing 8, a circulating sleeve 10, a traversable packer 11, a blind plugging nipple 12, a pressure gauge holder 13, and a round-head blind plug 15. A liquid sample capillary steel tube 101 and a gas injection capillary steel tube 201, as well as a three-way valve block 14 and a liquid sample sieve tube 102, wherein the liquid sample capillary steel tube 101 and the gas injection capillary steel tube 201 extend from the wellhead to the horizontal section respectively, and connect the two ports of the three-way valve block 14, the three-way valve block 14 contains a one-way valve 1401, and the third port of the three-way valve block 14 is connected to the one-way valve 1401, in the direction that the fluid flows from the outside of the valve block to the inside, and the third port is connected to the external liquid sample sieve tube 102; the pressure / temperature acquisition system includes an optical fiber 301 and a cable 401 extending from the wellhead to the horizontal section in the casing 8, and The optical fiber pressure gauge 302 and the electronic pressure gauge 402, the optical fiber 301 is connected to the downhole optical fiber pressure gauge 302; the cable 401 is connected to the downhole electronic pressure gauge 402; the optical fiber pressure gauge 302 and the electronic pressure gauge 402 are installed in the pressure gauge holder 13; the gas sample collection system includes a gas sample capillary steel pipe 501 and a gas sample sieve pipe 502 extending from the wellhead to the horizontal section in the casing 8, and the end of the gas sample capillary steel pipe 501 is connected to the gas sample sieve pipe 502; the liquid sample, gas injection and gas sample capillary steel pipes 101, 201, 501, optical fiber 301, cable 401 are all connected It is fixed to the oil pipe 9 through the fixing clip 7. The penetrable packer 11 is sealed in the horizontal section of the downhole tubing. The penetrable packer 11 has five penetrating channels. The liquid sample, gas injection and gas sample capillary steel pipes 101, 201, 501, optical fiber 301, and cable 401 extend to the rear of the setting position through the penetrable packer 11. The liquid sample screen tube 102 and the gas sample screen tube 502 are both located on the horizontal section behind the penetrating packer 11, wherein the liquid sample screen tube 102 is located in the perforation section 801 on the horizontal section, and the gas sample screen tube 502 is located at one end of the penetrable packer 11 on the horizontal section.

[0048] The oil pipe 9 is a main component of the downhole pipe string and is a CO2 corrosion-resistant oil pipe.

[0049] The liquid sample and gas sample sieve tubes 102 and 502 are hollow cylinders with small pores from the outside to the inside. External fluid enters the inside through the small pores and filters the fluid.

[0050] The tubing hanger, circulating sliding sleeve 10, through - type packer 11, pressure gauge carrier 13, blind plug nipple 12, round - head blind plug 15, etc. can adopt well - completion equipment or devices in the prior art in combination with the present invention. Taking this embodiment as an example, it specifically includes:

[0051] The tubing hanger is a device located at the wellhead to suspend or support the downhole string and seal the annular space between the tubing and the casing. It is seated into the large - four - way cone by the gravity of the tubing for sealing, which is convenient for operation, has a fast wellhead replacement speed and is safe;

[0052] The circulating sliding sleeve 10 is a device in the vertical section of the downhole string, designed with an outer cylinder and an inner sleeve. The outer cylinder is designed with radial holes, and a wire tool can be used to open or block the radial holes of the outer cylinder by the inner sleeve, thus opening or closing the sliding sleeve;

[0053] The through - type packer 11 adopts an expandable packer, which has several axial channels inside. When the packer is in the setting condition, it can be connected up and down through the internal channels;

[0054] The blind plug nipple 12 is a short section of solid - middle tubing;

[0055] The pressure gauge carrier 13 is a short section for installing an electronic pressure gauge 402 and an optical - fiber pressure gauge 302;

[0056] The round - head blind plug 15 is installed at the end of the tubing 9 at the bottom of the string to block the string.

[0057] The monitoring well of the present invention includes 3 monitoring systems that enter the well synchronously, namely a liquid - sample collection system, a pressure / temperature collection system, and a gas - sample collection system; in addition to downhole devices or equipment, the liquid - sample collection system, gas - sample collection system, and pressure / temperature collection system also include parts installed on the well - site ground to process the fluid, pressure, and temperature parameters collected downhole.

[0058] The liquid - sample collection system further includes an on - well liquid - sample collection device 1 and a liquid - sample gas - injection device 2. The liquid - sample collection device 1 is connected to a liquid - sample capillary steel pipe 101, usually including a liquid - sample container and accessories such as valves, pipe fittings, filters, control instruments, etc., and an off - line or on - line analyzer set as required; the liquid - sample gas - injection device 2 is connected to an injection capillary steel pipe 201, including a high - pressure gas source (nitrogen) and accessories such as valves, pipe fittings, control instruments, etc.

[0059] The pressure / temperature collection system further includes an on - well optical - fiber pressure - gauge collection device 3 and an electronic pressure - gauge collection device 4. The optical - fiber pressure - gauge collection device 3 is optically signal - connected to an optical fiber 301, and the electronic pressure - gauge collection device 4 is electrically connected to a cable 401.

[0060] The gas sample collection system further includes a gas sample collection device 5 on the wellhead. The gas sample collection device 5 is connected to a gas sample capillary steel pipe 501 and includes accessories such as a gas sample container, a high-pressure gas source (nitrogen), valves, pipe fittings, control instruments, etc., and an off-line or on-line analyzer set as required.

[0061] The well completion technology of the CCS project CO2 geological storage monitoring well of the present invention involves the downhole well completion string carrying three monitoring systems into the well synchronously. The well completion string is an L-shaped string including a vertical section and a horizontal section, and includes a wellhead device 6, a tubing hanger, a tubing 9, a circulating sleeve 10, a traversable packer 11, a blind plug nipple 12, a pressure gauge carrier 13, and a round head blind plug 15 connected in sequence; the monitoring systems include a liquid sample collection system, a gas sample collection system, and a pressure / temperature collection system; the three monitoring systems enter the well synchronously along with the well completion string, and each component of the well completion string is connected by screw threads.

[0062] The well completion technology of the monitoring well includes the following steps:

[0063] (1) Lowering the well completion string into the well: Connect the round head blind plug 15 to the front end of the tubing 9 and tighten the screw threads. Place the first elevator on the tubing 9 at the lower end face of the tubing collar. The workover rig hoists the tubing 9 with the round head blind plug 15 and lowers the tubing 9 into the casing well, and seats the lower end face of the elevator on the wellhead end face; Repeat the operation of hoisting the tubing 9. Place the second elevator on the tubing 9 at the lower end of the second tubing collar, hoist the second tubing 9 and connect and tighten the connection screw threads of the two tubings 9. Lift the second elevator and release the first elevator. Lower the lifting system to lower the well completion string and seat the lower end face of the elevator on the upper end face of the wellhead; The two elevators alternate in hoisting and lowering to achieve the connection and lowering of the well completion string. According to the tool design depth and connection sequence of each component of the well completion string, connect the pressure gauge carrier 13, the blind plug nipple 12, the traversable packer 11, the circulating sleeve 10, the tubing 9, and add a centralizer every 3 tubings 9.

[0064] (2) Lowering the monitoring systems into the well: The components of the three monitoring systems, including the fiber optic pressure gauge 302 and the electronic pressure gauge 402, the liquid sample screen pipe 102 and the gas sample screen pipe 502, the three-way valve block 14, and the capillary steel pipes 101, 201, 501, the optical fiber 301, the cable 401, etc., are lowered into the casing well synchronously with the well completion string according to the connection sequence and the designed lowering depth requirements; The steel pipes / transmission cables (capillary steel pipes, optical cables for optical fiber transmission, cables for electronic pressure gauges) of the monitoring systems are fixed to the outer side of the well completion string at each tubing connection collar by special fixing clips 7 with five slots, and keep the steel pipes / transmission cables in a straight state to avoid the risk of wear and extrusion of the steel pipes / transmission cables during the lowering of the horizontal well section string.

[0065] (3) Wear protection for the downhole horizontal well section monitoring system: In the completion string, the tubing 9, pressure gauge carrier 13, and centralizer between the round head blind plug 15 and the blind plug nipple 12 are connected by gas-tight threads to prevent leakage. No fluid is added during the lowering of the completion string, and the medium is air. The purpose is to reduce the self-weight of the completion string in the horizontal well section and increase the buoyancy of the completion string in the horizontal well section.

[0066] (4) Steel pipe / transmission cable passing through the packer: When the completion string and the three sets of monitoring systems are simultaneously lowered to the well entry position of the penetrable packer 11, first connect the penetrable packer 11 to the completion string, leave an operation margin for the steel pipe / transmission cable, and perform the penetration operation of the steel pipe / transmission cable according to the designed sequence of penetration. Select one of the steel pipes / transmission cables and cut it off. Then, put a special sealing nipple on the steel pipe / transmission cable from bottom to top, pass the steel pipe / transmission cable through the reserved penetration channel at the lower end of the penetrable packer 11, put on the second sealing nipple, tighten the threads of the sealing nipples at both ends of the penetrable packer 11, or connect the cables of the cut-off steel pipe / transmission cable with the cable connectors configured for their respective monitoring systems, and repeatedly detect the integrity of the medium or signal transmission with a special instrument. After passing the inspection, complete the penetration of the first steel pipe / transmission cable through the packer. Repeat the steps for the first steel pipe / transmission cable for the 2nd, 3rd, 4th, and 5th steel pipes / transmission cables. After each steel pipe / transmission cable passes the inspection, the operation of passing the steel pipe / transmission cable through the packer is completed.

[0067] (5) Steel pipe / transmission cable passing through the wellhead: After the penetrable packer 11 is lowered to the designed predetermined position in the horizontal well section, start the operation of passing the steel pipe / transmission cable through the wellhead. The operation lifting system hoists the tubing hanger of the completion string to a position 1.5 meters above the wellhead end face. Select one of the 5 steel pipes / transmission cables, cut it off after leaving an operation margin, put on a sealing nipple, pass the steel pipe / transmission cable from bottom to top through the reserved penetration channel of the tubing hanger, and tighten the threads of the sealing nipple, or connect the cables with a cable connector, and repeatedly test the integrity of the medium or signal transmission with a special instrument. After passing the inspection, complete the penetration of the first steel pipe / transmission cable. Repeat the steps for the first steel pipe / transmission cable for the 2nd, 3rd, 4th, and 5th steel pipes / transmission cables. After each steel pipe / transmission cable passes the inspection, the operation of passing the steel pipe / transmission cable through the wellhead is completed. Lower the tubing hanger to the "concave" position at the wellhead, tighten the top screws around the wellhead, and position the tubing hanger.

[0068] (6) Steel pipe / transmission cable passing through the lower flange of the Christmas tree: Select one of them, put the steel pipe / transmission cable through the sealing joint, lead the steel pipe / transmission cable out from the reserved passing channel of the Christmas tree, connect the sealing nipple to the thread of the reserved channel, and tighten it to complete the passing of the first steel pipe / transmission cable through the Christmas tree at the wellhead; Repeat the steps of the first steel pipe / transmission cable for the 2nd, 3rd, 4th, and 5th steel pipes / transmission cables. Use a special instrument to repeatedly test the integrity of the transmission signal or channel. After passing the inspection, the operation of the steel pipe / transmission cable passing through the lower flange of the Christmas tree is completed. Clean the wellhead end face, install the sealing steel ring, install the Christmas tree on the wellhead flange, put on the flange fixing screws, and gradually tighten the screws symmetrically.

[0069] (7) Wellhead pressure test: Conduct a wellhead pressure test through the pressure test channel. The pressure rises to 30 MPa and remains stable for 30 minutes without dropping, which is qualified.

[0070] (8) Setting operation of the downhole packer: Open the gate valve of the casing 8, pump liquid through the single oil pump to increase the pressure, and the pressure in the tubing 9 rises slowly. When the pressure rises to 22 MPa, the downhole retrievable packer 11 is set.

[0071] (9) Open the circulating sleeve and pump the anti-corrosion and anti-freezing protection liquid into the annulus between the tubing and the casing: Use a wire transmission tool to open the circulating sleeve 10 on the completion string from the paraffin removal channel, connect the high-pressure pipe manifold of the pump truck to the front end of the gate valve of the casing 8, open the casing gate valve and the tubing gate valve on the Christmas tree, and connect a drainage pipe manifold to the front end of the tubing valve to the sewage treatment tank. The injection pump pumps the anti-corrosion and anti-freezing liquid from the casing position, close the oil and casing valves of the Christmas tree, and the completion process of the monitoring well ends.

[0072] (10) Connection of the surface monitoring system: Connect the five steel pipes / transmission cables to the liquid sample collection device 1, liquid sample gas injection device 2, fiber optic pressure gauge collection device 3, electronic pressure gauge collection device 4, and gas sample collection device 5 on the ground respectively, and detect that the fiber optic and electronic signal transmissions are normal, and the gas injection, liquid output, and gas output of the deep well sampling system are normal. The installation of the monitoring system is completed.

[0073] The completion process for a CO2 geological storage monitoring well in a CCS project described herein involves adjusting the length of the tubing 9 according to the wellbore conditions, ensuring that the rounded blind plug 15 in the tubing string is located above the bottom of the artificial wellbore; ensuring that the liquid sample screen 102 and the lower perforated section 801 of the casing 8 are in the same position; ensuring that the gas sample screen 502 is located near the bottom of the traversable packer 11; and positioning the pressure gauge holder 13 above the perforated section 801. The traversable tubing packer 11 is set away from the casing coupling. During drilling, care must be taken to secure the liquid sample, gas injection, and gas sample capillary steel pipes 101, 201, and 501, as well as the optical fiber 301 and cable 401, to the tubing 9. Fixing clips 7 are installed on the tubing coupling to securely secure the capillary steel pipes 101, 201, and 501, the optical fiber 301, and the cable 401. A rigid centralizer should be connected to the middle of the oil pipe 9 to ensure that the capillary steel pipes 101, 201, 501, optical fiber 301, and cable 401 do not rub against the inner wall of the casing 8 during the wellbore. When the penetrable packer 11 is lowered into the well, the connection between the capillary steel pipes 101, 201, 501, optical fiber 301, and cable 401 should be checked to ensure that the upper and lower connections of the penetrable packer 11 are unobstructed and sealed. When lowering the tubing string, pay attention to a steady and uniform speed during the drilling process. Do not lift, brake, or release suddenly. The tonnage should not exceed 20KN when encountering resistance. Be careful to prevent falling objects from the wellbore to prevent the tubing string from getting stuck. Do not force it through when encountering resistance, as this may damage the packer rubber sleeve or downhole tools. After the tubing is lowered into place, the tubing is adjusted to ensure that the penetrable packer 11 is set in a position that avoids the casing joint; each capillary steel pipe 101, 201, 501, optical fiber 301 and cable 401 pass through the tubing hanger, the tubing is lowered and set and the top screw is tightened; the blowout preventer group is removed, and each capillary steel pipe 101, 201, 501, optical fiber 301 and cable 401 pass through the oil production spool, and it is verified whether each pipeline is unobstructed; each pipeline is connected to the uphole part of each acquisition system (a control box is set); after the wellhead device 6 is installed, the penetrable packer 11 is set by staged positive pressure in the tubing 9, and then the penetrable packer 11 is tested by annulus pressure; after the test is qualified, the circulating sleeve 10 is opened with a wire tool, and the annulus protection fluid is injected in a positive circulation, and the circulating sleeve 10 is closed with a wire tool, and the tubing lowering operation is completed.

[0074] According to the present invention, the permanent monitoring of the pressure and temperature of CO2 geological storage in CCS projects is completed by a pressure / temperature acquisition system, specifically an electronic pressure gauge 402 and an optical fiber pressure gauge 302. The electronic pressure gauge 402 has been widely used underground. Its core is a pressure sensor and a temperature sensor. Under the combined influence of the underground formation pressure and temperature, the oscillation circuit of the electronic pressure gauge converts the pressure value and temperature value of the measured formation into resistance values and voltage values recognizable by the circuit system, and then converts them into current frequency signals recognizable by a computer through frequency conversion by the oscillation circuit. After being recognized and converted by software, they are converted into underground pressure and temperature data required for testing. The electrical signal of the electronic pressure gauge 402 is transmitted to the electronic pressure gauge acquisition device 4 through the cable 401. After being processed, underground pressure and temperature data are formed, which can be stored in the electronic pressure gauge acquisition device 4 or remotely transmitted to the monitoring center. The optical fiber pressure gauge 302 is a technology that has developed rapidly with the development of optical fibers and optical fiber communication technologies. It has been gradually adopted in the fields of oil and gas exploration, exploitation, and monitoring. Its basic principle is to utilize the conduction of light in optical fibers. When affected by changes in measured parameters, parameters such as the intensity, wavelength, and phase of light will change. Compared with traditional sensing technologies, it has the advantages of small size, good electrical insulation, immunity to formation electromagnetic interference, and can be used in some harsh measurement environments. The optical signal of the optical fiber pressure gauge 302 is transmitted to the optical fiber pressure gauge acquisition device 3 through the optical fiber 301. After being processed, underground pressure and temperature data are formed, which can be stored in the optical fiber pressure gauge acquisition device 3 or remotely transmitted to the monitoring center. For CCS projects, the changes in the sealed pressure and temperature reflect the changes in the volume and state of the sealed carbon dioxide. The long-term or permanent monitoring of the sealed pressure and temperature is very important for CCS projects. In terms of pressure and temperature monitoring, the acquisition principles and data transmission methods of the electronic pressure gauge and the optical fiber pressure gauge are different. The dual monitoring system design can ensure the normal acquisition of monitoring parameters to the greatest extent.

[0075] The liquid sample collection is completed by a liquid sample collection system, which mainly includes a liquid sample collection device 1, a liquid sample gas injection device 2, a liquid sample capillary steel pipe 101, a gas injection capillary steel pipe 201, a three-way valve block 14, a liquid sample extraction capillary steel pipe 1402, and a liquid sample sieve tube 102. A check valve 1401 is installed inside the three-way valve block 14, and its fluid can only flow from the outside to the inside of the three-way valve block 14, that is, the liquid flowing out of the perforation section 801 enters the liquid sample sieve tube 102, passes through the liquid sample extraction capillary steel pipe 1402 into the three-way valve block 14, and enters the liquid sample and gas injection capillary steel pipes 101 and 201 through the check valve 1401. The height of the liquid entering the capillary steel pipe is determined by the sealing pressure and the fluid density. When the fluid density and the sealing pressure are known, the height and volume of the fluid entering the liquid sample and gas injection capillary steel pipes 101 and 201 can be calculated, and further the pressure of the high-pressure nitrogen required during sampling can be determined. During sampling, high-pressure nitrogen is injected from the liquid sample gas injection device 2. Under the action of the check valve 1401 in the three-way valve block 14, the high-pressure nitrogen drives the liquid in the gas injection capillary steel pipe 201 to flow through the three-way valve block 14 to the liquid sample capillary steel pipe 101 until it returns to the liquid sample collection device 1 on the ground, completing the liquid sampling. In order to obtain a fresh liquid sample in the seal, the fluid in the seal is allowed to enter the capillary steel pipes 101 and 201 only when sampling is about to be carried out. When sampling is not carried out daily, the capillary steel pipes 101 and 201 should be filled with nitrogen and maintained at a certain pressure, forcing the check valve 1401 in the three-way valve block 14 to close, so that the liquid sample in the seal will not enter the liquid sample and gas injection capillary steel pipes 101 and 201. During sampling, the evacuation rate of nitrogen in the gas injection capillary steel pipe 201 is controlled to accurately control the sample entry speed and avoid the local pressure reduction caused by too fast sample injection, which may damage the quality of the sample. In addition, when collecting samples on the ground, in order to avoid the contamination of the current sampling by the fluid remaining in the liquid sample and gas injection capillary steel pipes 101 and 102 during the previous sampling, the sampling should start after the fluid has been stable for a certain period of time. The stable time can be determined by the height of the fluid in the capillary steel pipe determined as described above. The best sampling time is one-third of the middle of the entire liquid column of the liquid sample and gas injection capillary steel pipes 101 and 201.

[0076] Gas sample collection is completed by the gas sample collection system, which mainly includes a gas sample collection device 5, a gas sample capillary steel pipe 501, and a gas sample screen pipe 502. The gas sample screen pipe 502 is located at one end of the traversable packer 11 and is the underground gas accumulation area. Generally, under the sealing pressure, when the gas sample collection system is opened, the underground gas will enter the gas sample capillary steel pipe 501 from the gas sample screen pipe 502 and reach the ground gas sample collection device 5. When the underground sealing pressure is insufficient, high-pressure high-purity nitrogen is injected into the well through the gas sample collection device 5, the gas sample capillary steel pipe 501, and the gas sample screen pipe 502. As the nitrogen is injected, the underground pressure increases, and the nitrogen squeezes the well fluid into the formation. This process causes the gas in the seal and the casing to quickly converge towards the traversable packer 11. After the pressure reaches the preset value and stabilizes for a period of time, the gas sample collection device 5 is opened, and the injected nitrogen carries the underground gas back to the ground through the original path. It should be noted that all the nitrogen injected returns to the ground first after the gas sample collection device 5 is opened, and it does not carry the target gas. When the exhaust is almost over and the pressure is already very small, the gas returning at this time carries a large amount of the target gas, and this is the time to collect and preserve the gas.

Claims

1. A CCS project CO2 geological storage monitoring well, comprising a wellhead device and a downhole string. The downhole string includes a casing and a tubing, and is characterized in that, The downhole string is in an L shape, including a vertical section and a horizontal section. The monitoring well further includes a liquid sample collection system, a pressure / temperature collection system, and a gas sample collection system. In the downhole string, the liquid sample collection system includes a liquid sample capillary steel pipe and an air injection capillary steel pipe extending from the wellhead to the horizontal section, as well as a three-way valve block and a liquid sample screen pipe. The liquid sample capillary steel pipe and the air injection capillary steel pipe are respectively connected to two ports of the three-way valve block, and the third port of the three-way valve block is connected to the liquid sample screen pipe. A one-way valve connected to the third port is included in the three-way valve block, and the direction is that the fluid flows from the outside of the valve block into the inside. In the downhole string, the pressure / temperature collection system includes an optical fiber and a cable extending from the wellhead to the horizontal section, as well as an optical fiber pressure gauge and an electronic pressure gauge. The optical fiber is connected to the optical fiber pressure gauge, and the cable is connected to the electronic pressure gauge. In the downhole string, the gas sample collection system includes a gas sample capillary steel pipe extending from the wellhead to the horizontal section and a gas sample screen pipe connected to the end thereof. The tubing includes a retrievable packer and a pressure gauge carrier. The retrievable packer is set in the horizontal section, and the liquid sample, air injection, and gas sample capillary steel pipes, optical fiber, and cable extend through the retrievable packer to the rear of the set position. The optical fiber pressure gauge and the electronic pressure gauge are installed in the pressure gauge carrier.

2. The CCS project CO2 geological sequestration monitoring well according to claim 1, characterized in that, The liquid sample screen pipe is located in the perforated section on the horizontal section, and the gas sample screen pipe is located at one end of the retrievable packer on the horizontal section.

3. The CCS project CO2 geological sequestration monitoring well according to claim 1, characterized in that, The tubing includes a circulating sliding sleeve, a retrievable packer, a blind plug nipple, and a round head blind plug connected in sequence.

4. The CCS project CO2 geological storage monitoring well according to claim 1, characterized in that, The liquid sample, air injection, and gas sample capillary steel pipes, optical fiber, and cable are fixed to the tubing by fixing clips.

5. The CCS project CO2 geological sequestration monitoring well according to claim 1, characterized in that, The liquid sample collection system further includes a liquid sample collection device and a liquid sample air injection device on the wellhead. The liquid sample collection device is connected to the liquid sample capillary steel pipe, and the liquid sample air injection device is connected to the air injection capillary steel pipe. The pressure / temperature collection system further includes an optical fiber pressure gauge collection device and an electronic pressure gauge collection device on the wellhead. The optical fiber pressure gauge collection device is optically signal-connected to the optical fiber, and the electronic pressure gauge collection device is connected to the cable. The gas sample collection system further includes a gas sample collection device on the wellhead. The gas sample collection device is connected to the gas sample capillary steel pipe.

6. The CCS project CO2 geological storage monitoring well according to claim 1, characterized in that, The retrievable packer uses an expansion type packer and includes five through channels.

7. The CCS project CO2 geological storage monitoring well according to claim 1, characterized in that, The tubing is an anti-CO2 corrosion tubing.

8. The CCS project CO2 geological storage monitoring well according to claim 1, characterized in that, The liquid sample and gas sample screen pipes are hollow cylinders with fine pores from the outside to the inside, and the external fluid enters the inside through the fine pores.

9. The well completion process of the CCS project CO2 geological storage monitoring well according to claim 1, characterized in that, The completion string and the monitoring system are run into the well synchronously. The monitoring system includes a liquid sample collection system, a gas sample collection system, and a pressure / temperature collection system. It includes the following steps: (1) Running the completion string into the well: Drilling and casing and cementing. According to the depths and connection sequences of the components of the completion string, the tubing is connected in sequence and run into the casing well section by section to realize running the completion string into the well. (2)Monitoring system runs into the well: The downhole part of the monitoring system, including the steel pipe / transmission cable composed of liquid sample capillary steel pipe, gas injection capillary steel pipe, gas sample capillary steel pipe, optical fiber and cable, connects the steel pipe / transmission cable with the fiber optic pressure gauge, electronic pressure gauge, three-way valve block, liquid sample screen pipe and gas sample screen pipe respectively according to the connection sequence and depth, installs the fiber optic pressure gauge and electronic pressure gauge in the pressure gauge carrier barrel, runs into the casing well synchronously with the completion string, and keeps the steel pipe / transmission cable in a straight state; (3)Steel pipe / transmission cable passes through the packer: When the completion string and the monitoring system are run down to the well entry position of the retrievable packer synchronously, first connect the retrievable packer to the completion string, cut off the steel pipe / transmission cable, pass it through the reserved passage of the retrievable packer, and then connect it with a seal nipple or cable connector; (4)Steel pipe / transmission cable passes through the wellhead: After the retrievable packer is run into the predetermined position of the horizontal well section, start the wellhead passing of the steel pipe / transmission cable, cut off the steel pipe / transmission cable, pass it through the reserved passage at the wellhead, and then connect it with a seal nipple or cable connector; (5)Wellhead pressure test: Conduct the wellhead pressure test through the pressure test channel; (6)Downhole separator setting: After the pressure test is qualified, pump liquid into the tubing to increase the pressure until the retrievable packer is set; pump the anti-corrosion and anti-freezing protection liquid into the annulus between the tubing and the casing.

10. The completion process of the monitoring well for CO2 geological storage in the CCS project according to claim 9, characterized in that, It also includes the steps: (7)Connection of the monitoring system: Connect the steel pipe / transmission cable passing through the wellhead with the ground part of the monitoring system respectively.

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