Safe operation tubular column of carbon dioxide injection well and operation method

Abstract

The invention discloses a safe operation tubular column for a carbon dioxide injection well and an operation method, a tubing hanger is hung at the upper end of a casing head, a load test short section is connected below the tubing hanger, and the load test short section is sequentially provided with a sliding sleeve valve, an upper centralizer, a releasing packer, a lower centralizer, a gas injection valve, a tail short section and a screwed plug towards the lower tubular column. After the pipe column enters a well, the annulus protection fluid is positively injected for fluid replacement; a constant-pressure valve ball is put in, and the sealing performance is checked through step-by-step positive pressure; a tubing hanger is seated after pressure relief; the releasing packer is set through positive pressure, then pressure is continuously increased to break the valve seat thin-wall section of the constant-pressure valve seat, and positive injection communication of the tubular column is achieved; and then water is squeezed forwards, after the sealing performance of the packer is verified, a wellhead is installed and connected with a ground process, carbon dioxide is injected forwards, and soaking is conducted after the carbon dioxide reaches the set gas injection amount. The tubular column does not overflow in the process of descending into a well, after positive replacement, a ball is thrown to press and set a packer, a shaft is protected, dirt deposition is prevented, the risk of breakage and falling of the tubular column is completely eradicated, and the operation process is safe and controllable.

Description

Technical Field

[0001] The invention relates to a carbon dioxide injection device, in particular to a safe operation pipe string for a carbon dioxide injection well, and belongs to the technical field of carbon dioxide injection. Background Art

[0002] Since the start of CO2 flooding to improve oil recovery in the oil field in the 1990s, it has gone through several stages, including technical exploration, expanded testing, and large-scale promotion, and has achieved certain results. Since CO2 can corrode the tubing, in recent years, tubing failures have occurred in injection wells in the CO2 flooding area, and sometimes the oil pipes have broken, which has become a problem affecting the on-site construction of CO2 and has seriously restricted the development of CO2 flooding to improve oil recovery.

[0003] Studies have shown that string stress changes are one of the factors that cause failure of CO2 injection well strings. The CO2 injection well safety operation string is used to continuously measure the injection string stress, pressure, temperature and other parameters in real time during the CO2 injection construction process, providing data support for in-depth research on the impact of CO2 construction site process parameters and work systems on the injection string. Through relevant research and application, technical specifications to guide on-site CO2 construction are gradually formed.

[0004] The Chinese invention patent application with publication number CN 105587306A discloses a method for monitoring the stress of the injection and production well pipe string of a gas storage reservoir, including the following steps: fixing the optical fiber sensor at the monitoring position on the injection and production pipe string, and lowering it into the injection and production well together with the injection and production pipe string; then using the optical fiber sensor to monitor the injection and production pipe string in the injection and production well in real time, and obtaining the monitoring stress parameters at the monitoring position. The application is intended to obtain the stress data of the injection and production pipe string in real time, and timely grasp the tension state of the injection and production pipe string, aiming to take timely measures when abnormalities are found, and reduce the hidden dangers and risks of failure of the injection and production pipe string. The application only gives the idea of ​​monitoring the stress state of the pipe string, but does not give specific information on how to accurately monitor the tension of the pipe string, and does not rule out how to eliminate the influence of downhole pressure changes on the tension of the pipe string.

[0005] The existing tool for testing the stress condition of downhole tubing in oil fields is to directly attach strain gauges to the outside of the test nipple. When carbon dioxide gas is injected, the internal pressure of the test nipple changes. At this time, even if the axial load of the test nipple does not change, the strain gauge attached to the outside of the test nipple will also deform due to the change in internal pressure. The measured axial load will produce errors and cannot reflect the actual situation of the downhole tubing load change.

[0006] At present, there is no direct device for real-time monitoring of CO2 injection well string stress, pressure, temperature and other parameters in domestic oil fields. The research on the impact of changes in CO2 injection well string stress on the injection string is mainly carried out through theoretical calculations and analogy analysis. There is a lack of intuitive and real-time field data to support theoretical understanding, and a lack of measured data to analyze and guide on-site CO2 injection construction.

[0007] Jiangsu Oilfield once developed a sucker rod mechanical detection device for the study of sucker rod stress when conducting research on the anti-eccentric wear technology of three-dimensional wellbore sucker rod strings. The detection device is designed in the form of a φ25mm sucker rod short section, which needs to be lowered in conjunction with the operation. The data can only be played back after the operation is pulled out and the detection device is recovered. The entire time cycle is long, the construction cost is high, and the field data cannot be obtained in a timely and real-time manner.

[0008] The detection device is connected to the set position of the sucker rod string as required by the design. It needs to be lowered into the oil well in conjunction with the pump inspection operation and has a deep lowering depth in the oil pipe string. The sucker rod string is always in a reciprocating motion state during the oil production process, and online technology is difficult or impossible to implement. The pressure and temperature in the oil pipe at the same location cannot be monitored. The sealing design only uses an "O" sealing tank ring, and there are often leakages in the detection device when it is pulled out, resulting in detection failures many times.

[0009] The Chinese invention patent with publication number CN 102536183A discloses a downhole gas injection string, which can prevent the injection gas from spitting back, can be reversely circulated, and does not require a plugging device to be thrown and salvaged. The packer is installed above the oil layer, the packer is connected to a drop-out return tube above, and the packer is connected to an injection valve below. The upper end of the oil pipe string is connected to a wellhead device, and the lower end of the oil pipe string is connected to a casing pressure valve and a sealing plug from top to bottom. The sealing plug is inserted into the drop-out return tube. The casing pressure valve and the gas injection valve are both single-flow valves. The flow direction of the casing pressure valve is from the oil casing annulus to the oil pipe, and the flow direction of the gas injection valve is from the valve inside to the valve outside.

[0010] The gas injection string in this well has the following problems: 1. The construction process is relatively complicated. It is necessary to first lower the hand-release string and the hand-release return tube. After the downhole string is pulled out, the gas injection string connected to the casing pressure valve and the sealing plug is lowered, and the sealing plug is inserted into the hand-release return tube to complete the gas injection string; 2. Due to unstable injection, alternating injection of gas and water, and changes in temperature and pressure during the injection process, the string will produce deformations such as expansion and contraction and creep. First, the sealing structure of the sealing plug is easily damaged, and second, the downward pressure generated acts on the packer, causing the packer to fail and resulting in failure of the gas injection string; 3. During operation or gas injection construction, foreign matter is easily deposited on the valve seat of the gas injection valve, affecting the closing and sealing performance of the valve ball; 4. There is leakage gas in the annulus of the oil casing. The bubbles may cause the casing pressure to be greater than the oil pressure during the rising process. The casing pressure valve opens prematurely, which may cause casing damage and increase well control and safety risks. Summary of the invention

[0011] The primary purpose of the present invention is to overcome the problems existing in the prior art and provide a safe operation pipe string for a carbon dioxide injection well, which can accurately measure the actual situation of the downhole pipe string load change and avoid the pipe string breaking accident.

[0012] In order to solve the above technical problems, a safe operation string for a carbon dioxide injection well of the present invention comprises a casing head connected to the upper end of the casing, a wellhead spool is installed above the casing head, a gas injection pipe joint is installed at a valve inlet on one side of the wellhead spool, and a gas injection pressure gauge is installed at a valve outlet on the other side of the wellhead spool, a tubing hanger is hung on the inner conical surface of the upper end of the casing head, a load test nipple is connected below the tubing hanger, and a sliding sleeve valve, an upper stabilizer, a hand-release packer, a lower stabilizer, a gas injection valve, a tail nipple and a threaded plug are sequentially arranged on the downward tubing string of the load test nipple.

[0013] As an improvement of the present invention, the load test short section includes a test upper joint and a test lower joint, a tension and compression sensor is connected between the test upper joint and the test lower joint, an inner sealing sleeve is provided in the center hole of the tension and compression sensor, an outer sealing sleeve is provided on the outer periphery of the tension and compression sensor, the upper and lower outer walls of the inner sealing sleeve are respectively sealed with the inner walls of the test upper joint and the test lower joint, and the upper and lower inner walls of the outer sealing sleeve are respectively sealed with the outer walls of the test upper joint and the test lower joint.

[0014] As a further improvement of the present invention, the load data line of the tension and compression sensor is connected to the signal conditioning circuit of the instrument cabinet, the output end of the signal conditioning circuit is electrically connected to the signal input end of the main control module, the IO port of the main control module is connected to the LCD display, the communication interface of the main control module is connected to the network communication module, and the network communication module is connected to the PC host through a network server.

[0015] As a further improvement of the present invention, a test upper joint center hole is provided along the axis of the test upper joint, a test upper joint threaded hole is provided at the lower part of the test upper joint center hole, and the upper end of the tension and compression sensor is screwed into the test upper joint threaded hole; a test lower joint center hole is provided along the axis of the test lower joint, a test lower joint threaded hole is provided at the upper part of the test lower joint center hole, and the lower end of the tension and compression sensor is screwed into the test lower joint threaded hole.

[0016] As a further improvement of the present invention, a reduced diameter test upper joint inner sealing hole is provided above the test upper joint threaded hole, and the upper end of the inner sealing sleeve is inserted into the test upper joint inner sealing hole and the two are sealed with each other; a reduced diameter test lower joint inner sealing hole is provided below the test lower joint threaded hole, and the lower end of the inner sealing sleeve is inserted into the test lower joint inner sealing hole and the two are sealed with each other.

[0017] As a further improvement of the present invention, a test upper joint outer sealing section is provided on the lower outer periphery of the test upper joint, and the upper end of the outer sealing sleeve is sleeved on the outer periphery of the test upper joint outer sealing section; a test lower joint outer sealing section is provided on the upper outer periphery of the test lower joint, and the lower end of the outer sealing sleeve is sleeved on the outer periphery of the test lower joint outer sealing section.

[0018] As a further improvement of the present invention, the sleeve valve comprises: a sleeve upper joint, the upper end of which is screwed to the lifting short section, the inner cavity accommodates a sleeve center tube, the lower end is sealed with the outer wall of the sleeve center tube and is screwed to the upper end of the sealing joint; the sleeve center tube, the upper end of which abuts against the lower part of the inner step of the sleeve upper joint, the upper circumference of which is evenly distributed with center tube bypass holes, the lower inner wall of which is provided with a sleeve center tube ball seat for a soluble ball to be sealed, and the lower end of which extends out of the sealing joint; the sleeve sealing joint, the middle section of which is evenly distributed with a plurality of sleeve bypass holes, the lower end of which is screwed to a sleeve Sleeve lower joint; the sleeve lower joint provides an accommodating space for the downward movement of the sleeve center tube, and the upper part is sealed with the outer wall of the sleeve center tube; the sleeve shear nails are evenly screwed on the circumference of the sealing joint, and the inner ends are embedded in the outer wall of the sleeve center tube; three or four elastic barbs are evenly distributed on the circumference of the lower end of the sleeve center tube, the lower end of each elastic barb is connected to the center tube body as a whole, and the other three sides are provided with inverted U-shaped slits to separate from the center tube body, and the upper end of each elastic barb protrudes outward and abuts against the limiting groove of the sleeve lower joint.

[0019] As a further improvement of the present invention, the upper end of the central tube of the sliding sleeve is provided with a salvage inner groove, the lower end inner step of the salvage inner groove is provided with a chamfer, and the upper end inner step of the salvage inner groove is a right angle.

[0020] When unclamping the valve body, the valve body is emptied and the valve body is sealed.Attorney Docket: 22222PCT of the present invention is a valve body, and a closure is attached to the valve body, and a closure is attached to the valve body, and a closure is attached to the valve body.

[0021] As a further improvement of the present invention, a large diameter valve seat section is provided on the upper part of the constant pressure valve seat, the large diameter valve seat section is embedded in the upper port of the outer sleeve and rests against the inner step of the outer sleeve, and the top of the large diameter valve seat section is located below the inner step of the gas injection upper joint.

[0022] As a further improvement of the present invention, the lower outer wall of the constant pressure valve seat is symmetrically provided with three limit bosses, a flow channel is provided between adjacent limit bosses, the outer end surface of each limit boss is provided with a limit groove, each limit groove is embedded with a limit pin, the inner end surface of each limit pin is provided with a countersunk hole and a limit spring is embedded therein, and each limit spring is supported between the bottom wall of the countersunk hole and the bottom wall of the limit groove; the outer end head of each limit pin is provided with a spherical surface, and the center of each spherical surface abuts against the inner wall of the center hole of the outer sleeve.

[0023] As a further improvement of the present invention, the lower end of the constant-pressure valve seat is symmetrically provided with valve seat support claws extending downward, and a flow channel is provided between adjacent valve seat support claws; the lower end of the central hole of the outer sleeve that accommodates the constant-pressure valve seat is successively provided with a first expansion section of the outer sleeve, a second expansion section of the outer sleeve and a third expansion section of the outer sleeve that gradually expand in diameter, the length of the first expansion section of the outer sleeve is greater than the distance between the thin-walled section of the valve seat and the limiting boss, the length of the second expansion section of the outer sleeve is greater than the diameter of the limiting pin shaft, and the length of the third expansion section of the outer sleeve is greater than the length of the valve seat support claws.

[0024] As a further improvement of the present invention, when the thin-walled section of the valve seat is pulled off and the anti-return valve seat falls, the valve seat support claw is supported on the top of the valve body, and each limit spring pushes out the limit pin so that the spherical surface of the outer end of each limit pin symmetrically rests against the inner wall of the second expanded diameter section of the outer sleeve; the radius of the third expanded diameter section of the outer sleeve is greater than or equal to the radius of the circumference of the outer edge of the axial hole of the valve body, and the outer edge radius of the valve seat support claw is smaller than the radius of the circumference of the inner edge of the axial hole of the valve body.

[0025] As a further improvement of the present invention, the outer port of the radial hole of the valve body is inclined upward; the lower end of the valve seat pressure cap is conically contracted to be closed, and a plurality of pressure cap slit channels are evenly distributed on the lower circumference of the valve seat pressure cap.

[0026] As a further improvement of the present invention, the signal conditioning circuit includes an AD7794 chip, and the main control module is a PIC18F46 chip; the tension and compression sensor is provided with signal output terminals AIN1+, AIN1-, AIN2+ and AIN2-; the signal output terminal AIN1+ is connected to the 7th pin of the AD7794 chip, the signal output terminal AIN1- is connected to the 8th pin of the AD7794 chip, the signal output terminal AIN2+ is connected to the 9th pin of the AD7794 chip, and the signal output terminal AIN2- is connected to the 10th pin of the AD7794 chip; the 24th pin of the AD7794 chip is connected to the 8th pin of the main control module, and the 23rd pin of the AD7794 chip is connected to the 9th pin of the main control module.

[0027] As a further improvement of the present invention, the network communication module is a W5500 Ethernet chip, pin 26 of the main control module is connected to pin 32 of the W5500 Ethernet chip, pin 27 of the main control module is connected to pin 33 of the W5500 Ethernet chip, pin 30 of the main control module is connected to pin 34 of the W5500 Ethernet chip, pin 31 of the main control module is connected to pin 35 of the W5500 Ethernet chip, and pin 40 of the main control module is connected to pin 36 of the W5500 Ethernet chip.

[0028] As a further improvement of the present invention, a bypass outlet on one side of the casing head is connected to a sealed tee, a main outlet of the sealed tee is installed with a casing pressure valve, an outlet of the casing pressure valve is installed with a casing pressure gauge and a casing pressure sensor, the casing pressure sensor includes an HX711 chip, the 16th pin of the HX711 chip is connected to a +5V power supply, the 9th, 10th, 14th and 15th pins of the HX711 chip are grounded, and the 12th pin of the HX711 chip is connected to the 11th pin of the AD7794 chip.

[0029] Another object of the present invention is to overcome the problems existing in the prior art and provide a safe operation method for a carbon dioxide injection well, which can meet the requirements of pressurized operation, has no overflow during the process of going down the well, can replace the wellbore annulus protection fluid, and then drop a ball to pressurize the sealing device and form an effective seal, while protecting the wellbore and preventing dirt deposition.

[0030] In order to solve the above technical problems, a safe operation method of a carbon dioxide injection well of the present invention comprises the following steps in sequence: S1. Remove the wellhead four-way and above parts, install a casing pressure valve on one side of the casing head bypass port, and install a sealing tee on the other side; S2. Assemble the pipe string as claimed in claim 1 and run it into the well section by section, and remove the soluble ball of the sleeve valve and the constant pressure valve ball of the gas injection valve before assembly; S3. The tubing string is lowered to the designed depth, and the gas injection valve reaches the gas injection layer; the anti-return valve ball is seated on the anti-return valve seat to prevent the annular well fluid from entering the inner cavity of the tubing string; S4. Inject annular protection fluid from the surface until the wellbore annulus fluid is completely replaced; S5. Throw in the constant pressure valve ball from the wellhead, and the constant pressure valve ball rolls down and is seated on the upper part of the constant pressure valve seat; lift the pipe string 0.7-1m, leaving a reserve pressure relief height; S6, positive pressure is applied step by step until the pressure reaches 8-10MPa, the shear pins of the hand-free packer are cut off, and the rubber sleeve begins to expand and seal; Increase the pressure to 16MPa and check the tightness of the pipe string; then reduce the pressure to 8MPa, slowly lower the tubing so that it hangs in the casing head, and at the same time, press down the hand-release packer to seal it; S7. Pressurize the pipe to 18-20 MPa to completely seal the packer. Then continue to increase the pressure to break the thin-walled section of the constant-pressure valve seat. The lower part of the constant-pressure valve seat falls off, and the pipe string is connected with positive injection. S8, squeezing water to verify and confirm that the seal of the drop packer is good; S9. Install the wellhead spool and connect it to the ground process. Inject carbon dioxide from the wellhead. The carbon dioxide pushes the anti-return valve ball and enters the wellbore annulus through the radial hole of the valve body and then enters the formation. After reaching the set gas injection volume, the well is shut down.

[0031] As an improvement of the present invention, lifting the pipe string includes the following steps: Step A1, inserting a soluble ball, pressurizing the wellhead to cut off the shear pins of the sliding sleeve, so that the bypass hole of the sliding sleeve is connected, positive circulation is performed to wash the well and degas, and then an annulus protection fluid is replaced; Step A2: After the soluble ball is dissolved, a throw-away ball is thrown into the tubing string, and positive pressure is applied to release the upper part of the throw-away packer, and the tubing string above the packer is lifted out of the wellhead; Step A3: lower the salvage string to salvage the drop packer and the string below it.

[0032] Compared with the existing technology, the present invention has achieved the following beneficial effects: 1. It realizes online monitoring, and the efficiency of obtaining data is greatly improved. The process parameters and working system of on-site injection construction can be adjusted through the real-time data; because the load test nipple is installed at the top of the oil pipe string, it not only saves the workload and process during the operation, but also eliminates the influence of torsional stress and bending stress on the monitoring tensile stress; it can also measure the temperature and pressure in the same part of the pipe, making the relevant research more targeted. The data can be displayed on-site or sent back to the background for analysis; there is no need to play back the data after pulling it out, which simplifies on-site operation and control.

[0033] 2. When the internal pressure of the test tool changes, or when the pressure outside the test tool changes, the strain gauge of the tension and compression sensor will not be deformed, and the measured axial load will not produce errors due to the change of downhole pressure. It can accurately reflect the actual situation of the downhole tubing load change and avoid the downhole situation of tubing breakage and packer failure.

[0034] 3. The gas injection valve can prevent the outflow of well fluid through the anti-return valve ball and anti-return valve seat, realize pressure operation, reduce the well occupation period, and reduce the operating cost, which is of great significance to safety and environmental protection.

[0035] 4. The constant pressure valve seat adopts a thin-wall pull-off opening structure. By controlling the thickness of the thin wall, the constant pressure opening pressure is more accurate compared to shearing with multiple pins. It also avoids the sharp edges of the pins after shearing to damage the inner wall of the outer sleeve, and can also reduce the downward resistance of the constant pressure valve seat opening and prevent foreign objects from falling into the well.

[0036] 5. A limit mechanism is set in three equal parts of the middle circle of the constant pressure valve seat, and the flow channel between the three equal parts of the limit mechanism can be used as a positive injection channel. The limit mechanism adopts a limit pin and a limit spring structure, which is reliable in limiting. The contact part between the limit pin and the inner wall of the jacket adopts a spherical structure, which effectively protects the inner wall of the jacket from damage, and has low friction resistance, which is convenient for the constant pressure valve seat to open and move downward.

[0037] 6. A filter screen is installed outside the liquid flow channel of the valve body to prevent foreign matter from entering the well, so as to avoid the valve ball from being sealed tightly and affecting the pressure operation. An annular groove is installed in the flow channel of the valve body to ensure the flow area.

[0038] 7. A slit channel is provided at the lower end of the seat cap to prevent foreign matter from entering the valve body during positive injection operations such as well washing or fluid replacement, thereby affecting the closing performance of the anti-return valve ball.

[0039] 8. Before lifting the tubing, you can perform positive well washing and degassing to protect the safety of the wellbore. If the casing pressure is too high after positive well washing, you can also perform positive circulation well pressure and degassing. During the process of lifting the tubing, well control safety can be guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The accompanying drawings are only provided for reference and explanation and are not intended to limit the present invention.

[0041] Figure 1 This is a front view of the safe operation string for a carbon dioxide injection well according to the present invention; Figure 2 is a cross-sectional view of a load test pup joint in the present invention; Figure 3 It is an enlarged view of the sealing tee part in the present invention; Figure 4 is a cross-sectional view of the sleeve valve in the present invention; Figure 5 It is a cross-sectional view of a sleeve center tube in a sleeve valve; Figure 6 It is a structural schematic diagram of the gas injection valve in the present invention; Figure 7It is an enlarged cross-sectional view of a constant pressure valve seat in a gas injection valve; Figure 8 for Figure 7 Bottom view of Fig. 9 is an enlarged cross-sectional view of the jacket in the gas injection valve; Fig.10 This is a state diagram after the constant pressure valve seat in the gas injection valve is pulled off; Fig.11 for Fig.10 Sectional view along AA; Fig.12 This is the principle block diagram of the control system in the instrument cabinet; Fig.13 This is the electrical schematic diagram of the signal conditioning circuit in the instrument cabinet; Fig.14 is an electrical schematic diagram of a signal conditioning circuit of another embodiment; Fig.15 It is the electrical schematic diagram of the main control module and network communication module in the instrument cabinet; In the figure: 1. Wellhead spool; 1a. Gas injection pipe joint; 1b. Gas injection pressure gauge; 2. Casing head; 2a. Casing pressure valve; 2b. Casing pressure gauge; 2c. Casing pressure sensor; 3. Sealing tee; 3a. Small steel ring; 3b. Cable sealing head; 3b1. Sealing head outer flange; 3c. Cable sealing ring; 3d. Sealing pressure cap; 3e. Sealing head sealing ring; 4. Oil pipe hanger; 5. Load test nipple; 5a. Test upper joint; 5a1. O-ring 1; 5a2. O-ring 2; 5b. Inner sealing sleeve; 5c. Tension and compression sensor; 5c1. Load data line; 5d. Outer sealing sleeve; 5e. Test lower joint; 5e1. O-ring 3; 5e2. O-ring 4; 6. Gas-sealed oil pipe; 7. Lifting nipple; 8. Sleeve valve; 8a. Sleeve upper joint; 8a1. Upper sealing gasket; 8b. Sleeve center tube; 8b1. Salvage inner groove; 8b2. Center tube bypass hole; 8b3. Sleeve center tube ball seat; 8b4. Elastic barb; 8b5. Inverted U-shaped slit; 8c. Sleeve sealing joint; 8c1. Sleeve bypass hole; 8c2. Sleeve shear nail; 8d. Sleeve lower joint; 8d1. Lower sealing gasket; 9. Upper centralizer; 10. Hand-release packer; 11. Lower centralizer; 12. Variable buckle joint; 13. Tungsten-plated oil pipe; 14. Gas injection valve; 14a. Gas injection upper joint; 14b. Gas injection upper joint sealing ring; 14c. Constant pressure valve seat; 14c1. Large diameter section of valve seat; 14c2. Thin wall section of valve seat; 14c3. Limit groove; 14c4. Valve seat support claw; 14c5. Constant pressure valve seat sealing ring; 14d. Constant pressure valve ball; 14e. Limit pin; 14f. Limit spring; 14g. Outer jacket; 14g1. Outer jacket 1. Expanded diameter section; 14g2. Second expanded diameter section of outer jacket; 14g3. Third expanded diameter section of outer jacket; 14g4. Outer jacket sealing ring; 14h. Valve body; 14h1. Axial hole of valve body; 14h2. Valve cavity; 14h3. Radial hole of valve body; 14h4. Annular groove; 14j. Filter screen; 14j1. Strip filter slit; 14k. Anti-return valve ball; 14m. Anti-return valve seat; 14n. Valve seat pressure cap; 14n1. Pressure cap strip slit channel; 14n2. Pressure cap sealing ring; 14p. Gas injection lower joint; 14p1. Gas injection lower joint sealing ring; 15. Tail nipple; 16. Thread plug; 17. Casing; 18. Instrument cabinet. Implementation

[0042] In the following description of the present invention, the directions or positional relationships indicated by terms such as "up", "down", "front", "back", "left", "right", "inside" and "outside" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and do not mean that the device must have a specific direction.

[0043] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below with reference to specific diagrams.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0045] like Figure 1 As shown, the carbon dioxide injection well safety operation string of the present invention includes a casing head 2 connected to the upper end of the casing 17, a wellhead spool 1 is installed above the casing head 2, a gas injection pipe joint 1a is installed at a valve inlet on one side of the wellhead spool 1, and is connected to the carbon dioxide injection pipe; a gas injection pressure gauge 1b is installed at a valve outlet on the other side of the wellhead spool 1 to monitor the injection pressure of the carbon dioxide.

[0046] The bypass outlet on one side of the casing head 2 is connected to a sealing tee 3. A small steel ring 3a is embedded between the bypass outlet flange of the casing head 2 and the inlet flange of the sealing tee 3. The two ends of the small steel ring 3a are respectively embedded in the annular grooves of the corresponding sealing surface, which plays both a positioning role and a sealing role. The main outlet of the sealing tee 3 is installed with a casing pressure valve 2a, and the outlet of the casing pressure valve 2a is installed with a casing pressure gauge 2b to display the pressure of the casing annulus.

[0047] The inner cone surface of the upper end of the casing head 2 is hung with a tubing hanger 4, a load test nipple 5 for monitoring the string load is connected below the tubing hanger 4, and a gas injection string is connected below the load test nipple 5. The gas injection string is provided with a sliding sleeve valve 8, an upper centralizer 9, a hand-release packer 10, a lower centralizer 11, a gas injection valve 14, a tail nipple 15 and a screw plug 16 from top to bottom. Specifically, the lower end of the load test sub 5 is connected to the gas-tight oil pipe 6 through a coupling, the lower end of the gas-tight oil pipe 6 is connected to the sliding sleeve valve 8 through a lifting sub 7, the lower end of the sliding sleeve valve 8 is connected to the upper centralizer 9, the lower end of the upper centralizer 9 is connected to the hand-release packer 10, the lower end of the hand-release packer 10 is connected to the lower centralizer 11, the lower end of the lower centralizer 11 is connected to the tungsten-plated oil pipe 13 through a variable buckle joint 12, the lower end of the tungsten-plated oil pipe 13 is connected to the gas injection valve 14, the lower end of the gas injection valve 14 is connected to the tail sub 15 through a coupling, the lower end of the tail sub 15 is screwed with a plug 16 to close the lower port, and the plug 16 is close to the bottom of the artificial well. When entering the well, screw them in order from bottom to top.

[0048] like Figure 2 As shown, the load test short section 5 includes a test upper joint 5a, an inner sealing sleeve 5b, a tension and compression sensor 5c, an outer sealing sleeve 5d and a test lower joint 5e. A test upper joint center hole is provided along the axis of the test upper joint 5a, a test upper joint threaded hole is provided at the lower part of the test upper joint center hole, a test upper joint inner sealing hole with a reduced diameter is provided above the test upper joint threaded hole, and a test upper joint outer sealing section is provided on the lower outer periphery of the test upper joint 5a.

[0049] A test lower joint center hole is provided along the axis of the test lower joint 5e, a test lower joint threaded hole is provided on the upper part of the test lower joint center hole, a test lower joint inner sealing hole with a reduced diameter is provided below the test lower joint threaded hole, and a test lower joint outer sealing section is provided on the upper outer periphery of the test lower joint 5e.

[0050] A tension and compression sensor 5c is connected between the test upper joint 5a and the test lower joint 5e. The upper end of the tension and compression sensor 5c is screwed into the threaded hole of the test upper joint, and the upper shoulder of the tension and compression sensor 5c abuts against the bottom of the test upper joint 5a, so that the upper part of the tension and compression sensor 5c is axially positioned; the lower end of the tension and compression sensor 5c is screwed into the threaded hole of the test lower joint, and the lower shoulder of the tension and compression sensor 5c abuts against the top of the test lower joint 5e, so that the lower part of the tension and compression sensor 5c is axially positioned. The threads of the test upper joint threaded hole, the test lower joint threaded hole and the two ends of the tension and compression sensor 5c are all airtight threads.

[0051] An inner sealing sleeve 5b is provided in the center hole of the tension and compression sensor 5c, the upper end of the inner sealing sleeve 5b is inserted into the inner sealing hole of the upper test joint, and the lower end of the inner sealing sleeve 5b is inserted into the inner sealing hole of the lower test joint; and the upper end of the inner sealing sleeve 5b abuts against the lower inner step above the inner sealing hole of the upper test joint, and the lower end of the inner sealing sleeve 5b abuts against the inner step below the inner sealing hole of the lower test joint, so that the inner sealing sleeve 5b is axially positioned to avoid axial movement. An O-ring 1 5a1 is embedded in the inner wall of the inner sealing hole of the upper test joint to achieve sealing with the outer periphery of the upper end of the inner sealing sleeve 5b, and an O-ring 3 5e1 is embedded in the inner wall of the inner sealing hole of the lower test joint to achieve sealing with the outer periphery of the lower end of the inner sealing sleeve 5b.

[0052] The outer periphery of the tension and compression sensor 5c is covered with an outer sealing sleeve 5d, the upper end of the outer sealing sleeve 5d is covered on the outer periphery of the outer sealing section of the upper test joint, and the lower end of the outer sealing sleeve 5d is covered on the outer periphery of the outer sealing section of the lower test joint. The upper end of the outer sealing sleeve 5d is against the lower outer step above the upper test joint outer sealing section, and the lower end of the outer sealing sleeve 5d is against the upper outer step below the lower test joint outer sealing section, so that the outer sealing sleeve 5d is axially positioned to prevent the outer sealing sleeve 5d from axial movement. The outer sealing section of the upper test joint is embedded with an O-ring 2 5a2 to achieve sealing with the inner wall of the upper end of the outer sealing sleeve 5d, and the outer sealing section of the lower test joint is embedded with an O-ring 4 5e2 to achieve sealing with the inner wall of the lower end of the outer sealing sleeve 5d.

[0053] The test upper joint 5a is threadedly connected to the tension and compression sensor 5c, and the tension and compression sensor 5c is threadedly connected to the test lower joint. The inner sealing sleeve 5b is placed in the inner hole after the tension and compression sensor 5c, the test upper joint 5a and the test lower joint 5e are connected, and forms a seal with the O-rings in the inner hole grooves of the test upper joint 5a and the test lower joint. The pressure fluctuation in the center hole of the test upper joint is borne by the inner sealing sleeve 5b, and the tension and compression sensor 5c will not be disturbed by the wellhead pressure fluctuation.

[0054] The outer sealing sleeve 5d is put on the outer circle of the tension and compression sensor 5c, the test upper joint 5a and the test lower joint 5e after they are connected, and forms a seal with the O-rings in the outer circle grooves of the test upper joint 5a and the test lower joint. The pressure fluctuations downhole are borne by the outer sealing sleeve 5d, and the tension and compression sensor 5c will not be disturbed by the pressure fluctuations downhole.

[0055] The tension and compression sensor 5c is connected to the upper part of the pipe string through the test upper joint 5a and the test lower joint 5e. The load of the pipe string can be accurately transmitted to the tension and compression sensor 5c. The load data line 5c1 of the tension and compression sensor 5c extends from the small hole on the cylindrical surface in the middle of the outer sealing sleeve 5d and is sealed by silica gel. The load data line 5c1 is connected to the test data recorder, so that the pipe string load measured by the monitoring device will be recorded on the test data recorder.

[0056] The upper part of the test upper joint 5a is provided with a tapered female thread that can be connected to the oil pipe. The upper part of the test upper joint 5a can also be provided with a tapered male thread that is directly screwed on the lower port of the oil pipe hanger 4. The lower end of the test lower joint 5e is provided with a tapered male thread connected to the oil pipe coupling.

[0057] like Figure 3 As shown, the middle outlet of the sealing tee 3 is screwed with a cable sealing head 3b, the load data line 5c1 enters the main channel of the sealing tee 3 from the bypass outlet of the casing head 2, and then turns and passes through the center hole of the cable sealing head 3b. The middle section of the center hole of the cable sealing head is an enlarged diameter light hole and is filled with multiple cable sealing rings 3c. Sealing gaskets are respectively provided on the inner and outer sides of the cable sealing ring 3c. A sealing female buckle is provided at the outer end of the center hole of the cable sealing head. A sealing pressure cap 3d is screwed in the sealing female buckle, and the inner end of the sealing pressure cap 3d presses the cable sealing ring 3c to the outer periphery of the load data line 5c1 through the sealing gasket.

[0058] The middle section of the cable sealing head 3b is a sealing head external thread section for screwing, and a sealing head sealing section is provided on the inner side of the sealing head external thread section. At least two sealing head sealing rings 3e are embedded on the outer periphery of the sealing head sealing section to achieve sealing with the inner wall of the middle outlet of the sealing tee 3.

[0059] A sealing head outer flange 3b1 is provided on the outer side of the sealing head outer thread section, and the sealing head outer flange 3b1 covers the middle outlet outer port of the sealing tee 3 .

[0060] like Figure 4 , Figure 5As shown, the sleeve valve 8 comprises a sleeve upper joint 8a, a sleeve center tube 8b, a sleeve sealing joint 8c and a sleeve lower joint 8d. The female thread at the upper end of the sleeve upper joint 8a is screwed to the lifting nipple 7, and the female thread at the lower end is screwed to the male thread at the upper end of the sleeve sealing joint 8c. The inner cavity of the sleeve upper joint 8a accommodates the sleeve center tube 8b. A sleeve upper joint sealing section is provided above the female thread at the lower end of the sleeve upper joint 8a, and an upper sealing gasket 8a1 is provided between the sleeve upper joint sealing section and the middle outer wall of the sleeve center tube 8b to seal the upper part of the sleeve bypass hole 8c1.

[0061] The upper end of the sleeve center tube 8b is against the inner step below the sleeve upper joint 8a, and a plurality of oblong center tube bypass holes 8b2 are evenly distributed on the upper circumference. The lower inner wall of the sleeve center tube 8b is provided with a sleeve center tube ball seat 8b3 for the soluble ball to be sealed, and the lower end extends out of the sealing joint.

[0062] Three or four elastic barbs 8b4 are evenly distributed on the circumference of the lower end of the central tube 8b of the sliding sleeve. The lower end of each elastic barb 8b4 is connected to the central tube body as a whole, and the other three sides are provided with an inverted U-shaped slit 8b5 separated from the central tube body. The upper end of each elastic barb 8b4 protrudes outward and abuts against the limiting groove of the lower joint 8d of the sliding sleeve, which plays an auxiliary positioning role for the central tube 8b of the sliding sleeve, and can also prevent the central tube 8b of the sliding sleeve from sliding down before the sliding sleeve shear nail 8c2 is installed.

[0063] A plurality of sleeve bypass holes 8c1 are evenly distributed in the middle section of the sleeve sealing joint 8c, and a plurality of sleeve shear pins 8c2 are evenly screwed on the circumference of the middle section of the sleeve sealing joint 8c. The inner end of each sleeve shear pin 8c2 is embedded in the outer wall of the sleeve center tube 8b to lock the sleeve center tube 8b.

[0064] The male thread at the lower end of the sleeve sealing joint 8c is screwed with the female thread at the upper end of the sleeve lower joint 8d. The lower end of the sleeve center tube 8b extends into the sleeve lower joint 8d, and the sleeve lower joint 8d provides an accommodating space for the downward movement of the sleeve center tube 8b.

[0065] A sleeve lower joint sealing section is provided below the upper female thread of the sleeve lower joint 8d, and a lower sealing gasket 8d1 is provided between the sleeve lower joint sealing section and the lower outer wall of the sleeve center tube 8b to seal the lower part of the sleeve bypass hole 8c1.

[0066] When it is necessary to wash the well, inject annular protection fluid or before lifting the pipe string, a soluble ball is put into the lower part of the central tube 8b of the sliding sleeve to seal it, and the shear nails 8c2 of the sliding sleeve are cut by pressure. The central tube 8b of the sliding sleeve slides down, and the elastic barbs 8b4 at the lower end are squeezed and contracted toward the axial direction. When the lower port of the central tube 8b of the sliding sleeve abuts against the inner step at the lower part of the lower joint 8d of the sliding sleeve, the bypass hole 8b2 of the central tube is flush with the bypass hole 8c1 of the sliding sleeve and is connected. At this time, the central channel of the pipe string is connected with the annulus, and the pressure is balanced.

[0067] The upper end of the central tube 8b of the sleeve is provided with a salvage inner groove 8b1, the lower end inner step of the salvage inner groove 8b1 is chamfered, and the upper end inner step of the salvage inner groove 8b1 is a right angle, which is convenient for inserting tools when needed to lift and reset the central tube 8b of the sleeve.

[0068] like Figures 6 to 11 As shown, the gas injection valve 14 of the present invention is used for pressure-operated wells, and includes a gas injection upper joint 14a, a constant pressure valve seat 14c, a constant pressure valve ball 14d, a jacket 14g, a valve body 14h, an anti-return valve seat 14m, an anti-return valve ball 14k, a valve seat pressure cap 14n and a gas injection lower joint 14p. The female thread at the lower end of the gas injection upper joint 14a is screwed with the male thread at the upper part of the jacket 14g, and a gas injection upper joint light hole section is provided above the female thread at the lower end of the gas injection upper joint 14a, and a gas injection upper joint sealing ring 14b is embedded in the inner wall of the gas injection upper joint light hole section to achieve sealing with the outer wall of the upper port of the jacket 14g.

[0069] A constant pressure valve seat 14c is fixed to the upper inner cavity of the outer sleeve 14g, and a valve seat large diameter section 14c1 is provided on the upper part of the constant pressure valve seat 14c. The valve seat large diameter section 14c1 is embedded in the upper port of the outer sleeve 14g and abuts against the upper inner step of the outer sleeve 14g. The top of the valve seat large diameter section 14c1 is located below the inner step of the gas injection upper joint 14a, so that the constant pressure valve seat 14c is suspended in the upper inner cavity of the outer sleeve 14g while achieving axial positioning. Two constant pressure valve seat sealing rings 14c5 are embedded in the outer wall of the valve seat large diameter section 14c1 to achieve sealing with the inner wall of the upper port of the outer sleeve 14g.

[0070] A valve seat thin-walled section 14c2 is provided below the valve seat large diameter section 14c1. If the set tensile force is exceeded, the valve seat thin-walled section 14c2 will be pulled off. A cylindrical section is provided below the valve seat thin-walled section 14c2, and a valve seat inner cone surface that is wide at the top and narrow at the bottom is provided at the lower end of the center hole. A constant pressure valve ball 14d is seated on the valve seat inner cone surface. After the constant pressure valve ball 14d is seated in the constant pressure valve seat 14c, a pressure is generated, which is used to seat the packer above the gas injection valve 14 or to pull off the valve seat thin-walled section 14c2. After the valve seat thin-walled section 14c2 is pulled off, no radial sharp edges will be generated, and the fracture will not scratch the inner wall of the outer sleeve 14g during the falling process.

[0071] The female thread at the lower end of the sleeve 14g is screwed into the male thread at the upper end of the valve body 14h. A sleeve light hole sealing section is provided above the female thread at the lower end of the sleeve 14g. A sleeve sealing ring 14g4 is embedded in the inner wall of the sleeve light hole sealing section. The sleeve sealing ring 14g4 is sealed with the upper cylindrical section of the valve body 14h.

[0072] A plurality of through valve body axial holes 14h1 are evenly arranged along the circumference of the valve body 14h for passing the liquid flow from top to bottom. A valve cavity 14h2 with a closed upper end is arranged in the center of the valve body 14h, a throat is arranged at the lower part of the valve cavity 14h2, a backflow prevention valve seat 14m is abutted below the throat, a backflow prevention valve ball 14k is seated in the upper port of the backflow prevention valve seat 14m, a valve seat pressure cap 14n is supported below the backflow prevention valve seat 14m, the middle part of the valve seat pressure cap 14n is screwed into the lower port of the valve body 14h, valve body radial holes 14h3 are symmetrically arranged on the outer peripheral wall of the valve body 14h and communicate with the middle part of the valve cavity 14h2, and a gas injection lower joint 14p is screwed into the lower end of the outer periphery of the valve body 14h. The valve body radial holes 14h3 are usually symmetrically provided with two, and each valve body axial hole 14h1 is distributed outside the valve cavity 14h2, and is staggered in phase with the valve body radial hole 14h3 and is not connected to each other.

[0073] The lower outer wall of the constant pressure valve seat 14c is symmetrically provided with three limiting bosses, and a flow passage is provided between adjacent limiting bosses. The outer end surface of each limiting boss is respectively provided with a limiting groove 14c3 extending along the radial direction of the constant pressure valve seat, and each limiting groove 14c3 is respectively inserted with a limiting pin shaft 14e, and the inner end surface of each limiting pin shaft 14e is respectively provided with a countersunk hole and a limiting spring 14f is respectively embedded, and each limiting spring 14f is respectively supported on the bottom wall of the countersunk hole and the bottom wall of the limiting groove 14c3 An outward thrust is applied to the limit pin 14e so that the outer end of the limit pin 14e can be reliably abutted against the inner wall of the outer sleeve 14g and can adapt to changes in the inner diameter of the outer sleeve, so that after the thin-walled section 14c2 of the valve seat is pulled off, the falling constant-pressure valve seat 14c is kept centered in the inner cavity of the outer sleeve 14g, thereby ensuring that the annular liquid flow channel between adjacent limit bosses is evenly distributed, and as a positive injection channel, the injection of anti-corrosion liquid or carbon dioxide or water into the well is more uniform.

[0074] The outer ends of the limit pins 14e are provided with spherical surfaces, and the centers of the spherical surfaces are respectively against the inner wall of the center hole of the outer sleeve 14g. While keeping the constant pressure valve seat 14c centered, the friction resistance of the limit pins 14e when sliding down is reduced, effectively protecting the inner wall of the outer sleeve from damage, and ensuring that after the thin wall section 14c2 of the valve seat is broken, the constant pressure valve seat 14c can fall reliably to achieve constant pressure opening.

[0075] The lower end of the constant pressure valve seat 14c is symmetrically provided with valve seat support claws 14c4 extending downward. After the valve seat thin wall section 14c2 is pulled off, the lower part of the constant pressure valve seat 14c falls down. When the valve seat support claws 14c4 fall on the top of the valve body 14h, the constant pressure valve seat 14c falls into place. There are also flow passages between adjacent valve seat support claws 14c4. When the valve seat thin wall section 14c2 is pulled off, the constant pressure valve ball 14d is in a floating state, and the valve seat center hole can also be used as an auxiliary liquid flow channel to reduce injection resistance.

[0076] The central hole of the outer sleeve that accommodates the constant pressure valve seat 14c is the section with the smallest inner diameter of the outer sleeve. The lower end of the central hole of the outer sleeve is provided with an expanded first diameter expansion section 14g1 of the outer sleeve. The length of the first diameter expansion section 14g1 of the outer sleeve is greater than the distance between the valve seat thin wall section 14c2 and the limiting boss, so that the first diameter expansion section 14g1 of the outer sleeve can accommodate the main body of the constant pressure valve seat 14c after being pulled apart.

[0077] A second expansion section 14g2 of the outer sleeve is provided below the first expansion section 14g1 of the outer sleeve, and the length of the second expansion section 14g2 of the outer sleeve is greater than the diameter of the stop pin 14e, so as to facilitate the abutment of the outer end of the stop pin 14e. When the valve seat thin wall section 14c2 is pulled off and the anti-return valve seat 14m falls, the valve seat support claw 14c4 is supported on the top of the valve body 14h, and each limit spring 14f pushes the limit pin 14e out so that the spherical surface of the outer end of each limit pin abuts symmetrically against the inner wall of the second expansion section 14g2 of the outer sleeve.

[0078] A third expansion section 14g3 of the outer sleeve is provided below the second expansion section 14g2 of the outer sleeve for further expansion. The length of the third expansion section 14g3 of the outer sleeve is greater than the length of the valve seat support claw 14c4, so that when the valve seat support claw 14c4 falls on the top of the valve body 14h, the limit pin 14e cooperates with the inner wall of the second expansion section 14g2 of the outer sleeve.

[0079] The radius of the third expanded diameter section 14g3 of the outer sleeve is greater than or equal to the radius of the circumference of the outer edge of the valve body axial hole 14h1, and the outer edge radius of the valve seat support claw 14c4 is smaller than the radius of the circumference of the inner edge of the valve body axial hole 14h1, so that both the inner and outer sides avoid obstruction to the liquid flow in and out of the valve body axial hole 14h1.

[0080] The middle outer wall of the valve body 14h is covered with a filter screen 14j, which covers the outer ports of the radial holes 14h3 of each valve body. The filter screen 14j is evenly provided with multiple strip-shaped filter slits 14j1 extending along the axial direction to prevent debris and other foreign matter in the wellbore annulus from entering the radial holes 14h3 of the valve body, so as to avoid the anti-return valve ball 14k from being loosely sealed, causing wellhead backflow pollution during pressure operation.

[0081] An annular groove 14h4 is provided on the outer periphery of the middle part of the valve body 14h, and the upper and lower ends of the annular groove 14h4 are close to the upper and lower edges of the filter screen 14j to expand the volume of the annular space inside the filter screen 14j, so that the liquid flows in and out more smoothly; the outer port of each valve body radial hole 14h3 is located on the bottom wall of the annular groove 14h4.

[0082] The outer port of the radial hole 14h3 of the valve body is inclined upward to prevent the fluid flowing out of the radial hole 14h3 of the valve body from directly scouring the inner wall of the wellbore when the anti-corrosion liquid or carbon dioxide is injected, thereby reducing damage to the wellbore.

[0083] The upper outer wall of the valve seat cap 14n is embedded with a cap seal ring 14n2 to seal with the lower inner wall of the valve body 14h. The lower end of the valve seat cap 14n is conically contracted to be closed, and multiple cap slit channels 14n1 are evenly distributed on the lower circumference of the valve seat cap 14n. Each cap slit channel 14n1 extends from the cylindrical end to the conical section to ensure sufficient flow area. When the well washing fluid is positively injected downward along the axial hole 14h1 of the valve body, each cap slit channel 14n1 can prevent foreign matter from entering the inner cavity of the valve seat cap 14n, and avoid the mating surface of the anti-return valve seat 14m and the anti-return valve ball 14k from affecting the closing performance of the anti-return valve ball 14k due to foreign matter.

[0084] A gas injection lower joint light hole sealing section is provided below the upper female thread of the gas injection lower joint 14p, and a gas injection lower joint sealing ring 14p1 is embedded in the inner wall of the gas injection lower joint light hole sealing section to achieve sealing with the lower cylindrical section of the valve body 14h.

[0085] like Figure 1 and Fig.12 As shown, the load data line 5c1 of the tension and compression sensor 5c is connected to the instrument cabinet 18, and the instrument cabinet 18 is provided with a signal conditioning circuit, a main control module and a network communication module. The output end of the signal conditioning circuit is electrically connected to the signal input end of the main control module, the IO port of the main control module is connected to the liquid crystal display screen, the communication interface of the main control module is connected to the network communication module, the network communication module is connected to the PC host through the network server, and the main control module is also connected to the memory through the address bus, the data bus and the control bus.

[0086] The address bus is used to transmit the memory address signal issued by the main control module, the data bus is used to transmit the data information between the main control module and the memory, and the control bus is used to transmit the read-write control signal and timing signal issued by the main control module. The main control module interacts with the memory through these three buses to realize the reading and writing of data and the control of the memory, so as to store or call the control program and various monitoring data for subsequent query and retrieval.

[0087] like Fig.13 , Fig.15 As shown, the signal conditioning circuit includes an AD7794 chip, and the main control module is a PIC18F46 chip; the tension and compression sensor 5c is provided with signal output terminals AIN1+, AIN1-, AIN2+ and AIN2-; the signal output terminal AIN1+ is connected to the 7th pin of the AD7794 chip, the signal output terminal AIN1- is connected to the 8th pin of the AD7794 chip, the signal output terminal AIN2+ is connected to the 9th pin of the AD7794 chip, and the signal output terminal AIN2- is connected to the 10th pin of the AD7794 chip; the 24th pin of the AD7794 chip is connected to the 8th pin of the main control module, and the 23rd pin of the AD7794 chip is connected to the 9th pin of the main control module.

[0088] The AD7794 chip converts the tension or pressure on the pipe string into a digital signal and sends it to the PIC18F46 main control module. The 9th pin of the main control module receives the digital signal of the tension and pressure sensor 5c, which can be displayed on the LCD screen and sent to the PC host through the network. The instrument cabinet 18 is also equipped with an alarm module. When the pipe string load measured by the tension and pressure sensor 5c is higher than the set value, the main control module drives the alarm module to sound an alarm, which is convenient for on-site personnel to handle emergencies.

[0089] The network communication module is the W5500 Ethernet chip, which is a high-performance Ethernet controller chip designed for embedded systems. It supports full-duplex 10 / 100Mbps Ethernet and has a hardware TCP / IP protocol stack. It uses an SPI interface to facilitate integration with a microcontroller and supports multiple network protocols such as TCP, UDP, ICMP, IPv4 and ARP. It also has a built-in 32KB buffer memory to achieve efficient data transmission, support multiple socket connections, and achieve simultaneous communication. The 26th pin of the main control module is connected to the 32nd pin of the W5500 Ethernet chip, the 27th pin of the main control module is connected to the 33rd pin of the W5500 Ethernet chip, the 30th pin of the main control module is connected to the 34th pin of the W5500 Ethernet chip, the 31st pin of the main control module is connected to the 35th pin of the W5500 Ethernet chip, and the 40th pin of the main control module is connected to the 36th pin of the W5500 Ethernet chip.

[0090] The control system also has a MAX3485 chip, which is a low-power, high-speed, RS-485 / RS-422 compatible transceiver chip. It adopts a single power supply design, with an operating voltage range of 3V to 5.5V, and can provide a maximum data transmission rate of 250kbps; it has built-in overvoltage protection, short circuit protection, ESD protection and other protection functions, which can effectively protect the transmission line and the chip itself from damage. The chip has the advantages of low power consumption, high reliability, and easy integration.

[0091] The 8th pin of the MAX3485 chip is connected to VCC-ADC, the 5th pin of the MAX3485 chip is grounded, the 6th pin of the MAX3485 chip is connected to VCC-ADC through a 10K resistor R9, the 7th pin of the MAX3485 chip is grounded through a 10K resistor R10, and the 6th and 7th pins of the MAX3485 chip are also connected through a 10K resistor R11. The 1st pin of the main control module is connected to the 1st pin of the MAX3485 chip, the 25th pin of the main control module is connected to the 2nd pin of the MAX3485 chip, the 22nd pin of the main control module is connected to the 3rd pin of the MAX3485 chip, and the 44th pin of the main control module is connected to the 4th pin of the MAX3485 chip. It provides an RS485 interface for the outside world, has good expansibility, and is convenient for communication with the outside world.

[0092] like Figure 1 and Fig.14 As shown, the outlet of the casing pressure valve 2a can also be installed with a casing pressure sensor 2c and a signal line of the casing pressure sensor 2c. The casing pressure sensor 2c includes an HX711 chip, the 16th pin of the HX711 chip is connected to a +5V power supply, the 9th, 10th, 14th and 15th pins of the HX711 chip are grounded, and the 12th pin of the HX711 chip is connected to the 11th pin of the AD7794 chip. The wellhead casing pressure measured by the casing pressure sensor 2c is converted into a digital signal by the AD7794 chip and sent to the PIC18F46 main control module.

[0093] The 8th pin of the main control module sends a control signal to the 24th pin of the AD7794 chip to select and read the digital signal of the tension and compression sensor 5c or the digital signal of the sleeve pressure sensor 2c.

[0094] A temperature sensor can also be installed in the well, and the signal line of the temperature sensor can be passed through the central hole of the cable sealing head 3b. The temperature sensor in the well can send a temperature signal to the main control module wirelessly, and the temperature sensor can also be installed at the wellhead to calculate the temperature in the well through the temperature gradient of the well depth.

[0095] The safe operation method of the carbon dioxide injection well of the present invention comprises the following steps in sequence: S1. Remove the wellhead spool 1 and the part above it, install a casing pressure valve 2a on one side of the bypass port of the casing head 2, and install a sealing tee 3 on the other side.

[0096] S2. Assemble the above-mentioned working pipe string and put it into the well section by section. Before assembly, take out the soluble ball of the sliding sleeve valve 8 and the constant pressure valve ball of the gas injection valve 14.

[0097] S3, the tubing string is lowered to the designed depth, and the gas injection valve 14 reaches the gas injection layer; the anti-return valve ball is seated on the anti-return valve seat to prevent the well fluid in the annulus from entering the inner cavity of the tubing string; during the process of going down into the well, the well fluid in the wellbore annulus passes through the filter screen 14j, and is pressed on the anti-return valve ball 14k through the radial hole 14h3 of the valve body, and the anti-return valve ball 14k is seated on the anti-return valve seat 14m, closing the downward passage, and the well fluid in the annulus cannot enter the valve seat pressure cap 14n, and will not pass through the axial hole 14h1 of the valve body into the oil pipe above, which can prevent the well fluid from flowing out of the ground and polluting the environment.

[0098] S4. Prepare 1% carbon dioxide corrosion inhibitor + 300ppm bactericide as annular protection liquid, inject annular protection liquid through the ground, the annular protection liquid passes through the center hole of the constant pressure valve seat 14c, and then goes down along the axial holes 14h1 of each valve body into the gas injection lower joint 14p, and then enters the inner cavity of the valve seat pressure cap 14n from the pressure cap slit channel 14n1, and then pushes the anti-return valve ball 14k upward to enter the valve cavity 14h2, and then enters the wellbore annulus through the radial hole 14h3 of the valve body, completely replacing the wellbore annular well fluid, delaying the corrosion of the wellbore and oil pipe. The valve cavity 14h2 is provided with a conical top to accommodate the anti-return valve ball 14k after floating.

[0099] S5. A Φ45 mm constant pressure valve ball 14d is dropped from the wellhead. The constant pressure valve ball 14d rolls down along the oil pipe and lands on the inner conical surface of the constant pressure valve seat 14c to seal the valve. The pipe string is lifted up by 0.7-1m, leaving a reserve pressure relief height.

[0100] S6, positive pressure is applied step by step and the sealing of the tubing is checked. First, the pressure is applied to 8-10MPa, and after stabilizing the pressure for 3 minutes, the pressure is continuously increased to 12MPa; after stabilizing the pressure for 3 minutes, the pressure is continuously increased to 14MPa; after stabilizing the pressure for 3 minutes, the pressure is continuously increased to 16MPa. Then the pressure is reduced to 8MPa, and the tubing hanger 4 is slowly set. The tubing hanger 4 is supported on the inner cone surface of the upper end of the casing head 2 and suspends the tubing. During the process of setting the tubing hanger 4, the shear nails of the hand-free packer 10 are cut off, and the rubber cylinder begins to expand and seal.

[0101] S7, positive pressure is applied to 18-20 MPa to completely seal the rubber tube of the drop packer 10 on the inner wall of the wellbore to protect the wellbore above; then Fig.10 , Fig.11 As shown, the pressure is continued to increase to break the thin-walled section 14c2 of the constant-pressure valve seat 14c, and the lower part of the constant-pressure valve seat 14c falls downward until the lower end of the valve seat supporting claw 14c4 abuts against the top of the valve body 14h. At this time, the limiting boss of the constant-pressure valve seat 14c reaches a position aligned with the second expanded diameter section 14g2 of the outer sleeve, and under the tension of the limiting spring 14f, each limiting pin shaft 14e extends outward, and the spherical surface of the outer end of each limiting pin shaft abuts against the inner wall of the second expanded diameter section 14g2 of the outer sleeve, so that the constant-pressure valve seat 14c is in a centered state, and the flow channels between the three limiting bosses are evenly distributed. At this time, the pipe column realizes positive injection connection.

[0102] S8, squeezing water to verify and confirm that the sealing of the drop packer 10 is good; S9. Install the wellhead spool 1 and connect it to the surface process. Inject carbon dioxide gas from the wellhead. Carbon dioxide flows downward from the annular channel between the constant pressure valve seat 14c and the inner wall of the first expanded diameter section 14g1 of the outer sleeve, and then passes through the flow passage between the three limit bosses to reach the top of the valve body 14h. Then, it flows downward from the axial holes 14h1 of each valve body to the gas injection lower joint 14p below the valve body 14h. Impurities are blocked by the slit channels 14n1 of each cap and can fall into the tail short section 15 below. The carbon dioxide gas enters the inner cavity of the valve seat cap 14n from the cap slit channels 14n1, then moves upward to push the anti-return valve ball 14k into the valve cavity 14h2, and then enters the wellbore annulus through the valve body radial hole 14h3, and then enters the formation, generating gas driving force in the liquid to improve the oil displacement effect. After reaching the set gas injection tonnage, it enters the soaking well.

[0103] When lifting the pipe column, the following steps are included: Step A1, put in a Φ55mm soluble ball, pressurize the wellhead to cut off the sleeve shear pin 8c2, make the sleeve bypass hole 8c1 penetrate, and then wash and degas the well in a positive cycle. Then replace the annulus protection fluid. The annulus protection fluid flows downward from the inner cavity of the pipe string, enters the annulus through the sleeve bypass hole 8c1, and then goes up to the wellhead to protect the wellbore.

[0104] Step A2: After the soluble ball is dissolved, a Φ50mm release ball is thrown into the tubing string, and positive pressure is applied to release the upper part of the release packer 10, and the tubing string above the packer is lifted out of the wellhead; during the process of lifting the tubing string, the rubber cylinder of the release packer 10 remains in the set state, thereby improving the safety of the operation; Step A3: lower the salvage string to salvage the drop packer 10 and the string below it.

[0105] The above is only a preferred embodiment of the present invention, which shows and describes the basic principles, main features and advantages of the present invention, but does not limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. In addition to the above embodiments, the present invention may have other implementation modes without departing from the spirit and scope of the present invention. The present invention may also have various changes and improvements, and all technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection required by the present invention. The scope of protection required by the present invention is defined by the attached claims and their equivalents. The technical features not described in the present invention can be realized by or using existing technologies, which will not be repeated here.

Claims

1. A safe operation string for a carbon dioxide injection well, comprising a casing head connected to the upper end of a casing, a wellhead spool installed above the casing head, a gas injection pipe joint installed at a valve inlet on one side of the wellhead spool, and a gas injection pressure gauge installed at a valve outlet on the other side of the wellhead spool, characterized in that: A tubing hanger is hung on the inner cone surface of the upper end of the casing head, and a load test nipple is connected below the tubing hanger. A sliding sleeve valve, an upper centralizer, a drop-out packer, a lower centralizer, an injection valve, a tail nipple and a threaded plug are arranged in sequence on the downward tubing string of the load test nipple.

2. The carbon dioxide injection well safety operation string according to claim 1, characterized in that: The load test short joint includes an upper test joint and a lower test joint, a tension and compression sensor is connected between the upper test joint and the lower test joint, an inner sealing sleeve is provided in the central hole of the tension and compression sensor, an outer sealing sleeve is provided on the outer periphery of the tension and compression sensor, the upper and lower outer walls of the inner sealing sleeve are respectively sealed with the inner walls of the upper test joint and the lower test joint, and the upper and lower inner walls of the outer sealing sleeve are respectively sealed with the outer walls of the upper test joint and the lower test joint.

3. The carbon dioxide injection well safety operation string according to claim 2, characterized in that: The load data line of the tension and compression sensor is connected to the signal conditioning circuit of the instrument cabinet, the output end of the signal conditioning circuit is electrically connected to the signal input end of the main control module, the IO port of the main control module is connected to the liquid crystal display screen, the communication interface of the main control module is connected to the network communication module, and the network communication module is connected to the PC host through a network server.

4. The carbon dioxide injection well safety operation string according to claim 1, characterized in that: A test upper joint center hole is provided along the axis of the test upper joint, a test upper joint threaded hole is provided at the lower part of the test upper joint center hole, and the upper end of the tension and compression sensor is screwed into the test upper joint threaded hole; a test lower joint center hole is provided along the axis of the test lower joint, a test lower joint threaded hole is provided at the upper part of the test lower joint center hole, and the lower end of the tension and compression sensor is screwed into the test lower joint threaded hole.

5. The carbon dioxide injection well safety operation string according to claim 4, characterized in that: A reduced diameter test upper joint inner sealing hole is provided above the test upper joint threaded hole, and the upper end of the inner sealing sleeve is inserted into the test upper joint inner sealing hole and the two are sealed with each other; a reduced diameter test lower joint inner sealing hole is provided below the test lower joint threaded hole, and the lower end of the inner sealing sleeve is inserted into the test lower joint inner sealing hole and the two are sealed with each other.

6. The carbon dioxide injection well safety operation string according to claim 4, characterized in that: The lower periphery of the test upper joint is provided with a test upper joint outer sealing section, and the upper end of the outer sealing sleeve is sleeved on the periphery of the test upper joint outer sealing section; the upper periphery of the test lower joint is provided with a test lower joint outer sealing section, and the lower end of the outer sealing sleeve is sleeved on the periphery of the test lower joint outer sealing section.

7. The carbon dioxide injection well safety operation string according to claim 1, characterized in that: The sleeve valve comprises: The upper end of the sliding sleeve joint is screwed to the lifting short section, the inner cavity contains the sliding sleeve center tube, and the lower end is sealed to the outer wall of the sliding sleeve center tube and screwed to the upper end of the sealing joint; The upper end of the central tube of the sliding sleeve abuts against the lower inner step of the upper joint of the sliding sleeve, the upper circumference is evenly distributed with central tube bypass holes, the lower inner wall is provided with a sliding sleeve central tube ball seat for a soluble ball to be set, and the lower end extends out of the sealing joint; The sliding sleeve sealing joint has a plurality of sliding sleeve bypass holes evenly distributed in the middle section and a sliding sleeve lower joint screwed on the lower end; The lower joint of the sliding sleeve provides a space for the downward movement of the central tube of the sliding sleeve, and the upper part is sealed with the outer wall of the central tube of the sliding sleeve; The shear pins of the sliding sleeve are evenly screwed on the circumference of the sealing joint, and the inner ends are embedded in the outer wall of the central tube of the sliding sleeve; Three or four elastic barbs are evenly distributed on the circumference of the lower end of the central tube of the sliding sleeve, the lower end of each elastic barb is connected to the central tube body as a whole, and the other three sides are provided with inverted U-shaped slits to separate from the central tube body, and the upper end of each elastic barb protrudes outward and rests on the limiting groove of the lower joint of the sliding sleeve.

8. The carbon dioxide injection well safety operation string according to claim 7, characterized in that: The upper end of the central tube of the sliding sleeve is provided with a salvage inner groove, the lower end inner step of the salvage inner groove is provided with a chamfer, and the upper end inner step of the salvage inner groove is a right angle.

9. The carbon dioxide injection well safety operation string according to claim 1, characterized in that: When unclamping the valve body, the valve body is emptied and the valve body is sealed.Attorney Docket: 22222PCT of the present invention is a valve body, and a closure is attached to the valve body, and a closure is attached to the valve body, and a closure is attached to the valve body.

10. The carbon dioxide injection well safety operation string according to claim 9, characterized in that: A large diameter valve seat section is provided on the upper part of the constant pressure valve seat, which is embedded in the upper port of the outer sleeve and abuts against the upper inner step of the outer sleeve, and the top of the large diameter valve seat section is located below the inner step of the gas injection upper joint.

11. The carbon dioxide injection well safety operation pipe string according to claim 9, characterized in that: The lower outer wall of the constant pressure valve seat is symmetrically provided with three limit bosses, and a flow channel is provided between adjacent limit bosses. The outer end surface of each limit boss is provided with a limit groove, and a limit pin is embedded in each limit groove. The inner end surface of each limit pin is provided with a countersunk hole and a limit spring is embedded therein, and each limit spring is supported between the bottom wall of the countersunk hole and the bottom wall of the limit groove; the outer end head of each limit pin is provided with a spherical surface, and the center of each spherical surface abuts against the inner wall of the center hole of the outer sleeve.

12. The carbon dioxide injection well safety operation string according to claim 9, characterized in that: The lower end of the constant-pressure valve seat is symmetrically provided with valve seat supporting claws extending downward, and a flow channel is provided between adjacent valve seat supporting claws; the lower end of the central hole of the outer sleeve accommodating the constant-pressure valve seat is provided with a first diameter expansion section of the outer sleeve, a second diameter expansion section of the outer sleeve and a third diameter expansion section of the outer sleeve with gradually expanding diameters in sequence, the length of the first diameter expansion section of the outer sleeve is greater than the distance between the thin-walled section of the valve seat and the limiting boss, the length of the second diameter expansion section of the outer sleeve is greater than the diameter of the limiting pin shaft, and the length of the third diameter expansion section of the outer sleeve is greater than the length of the valve seat supporting claws.

13. The carbon dioxide injection well safety operation pipe string according to claim 12, characterized in that: When the thin-walled section of the valve seat is pulled off and the anti-return valve seat falls, the valve seat support claw supports the top of the valve body, and each limit spring pushes out the limit pin shaft so that the spherical surface of the outer end of each limit pin shaft symmetrically abuts against the inner wall of the second expanded diameter section of the outer sleeve; The radius of the third expanded diameter section of the outer sleeve is greater than or equal to the radius of the circumference of the outer edge of the valve body axial hole, and the outer edge radius of the valve seat support claw is smaller than the radius of the circumference of the inner edge of the valve body axial hole.

14. The carbon dioxide injection well safety operation pipe string according to claim 9, characterized in that: The outer port of the radial hole of the valve body is inclined upward; the lower end of the valve seat pressure cap is conically contracted to be closed, and a plurality of pressure cap slit channels are evenly distributed on the lower circumference of the valve seat pressure cap.

15. The carbon dioxide injection well safety operation string according to claim 2, characterized in that: The signal conditioning circuit includes an AD7794 chip, and the main control module is a PIC18F46 chip; the tension and compression sensor is provided with signal output terminals AIN1+, AIN1-, AIN2+ and AIN2-; the signal output terminal AIN1+ is connected to the 7th pin of the AD7794 chip, the signal output terminal AIN1- is connected to the 8th pin of the AD7794 chip, the signal output terminal AIN2+ is connected to the 9th pin of the AD7794 chip, and the signal output terminal AIN2- is connected to the 10th pin of the AD7794 chip; the 24th pin of the AD7794 chip is connected to the 8th pin of the main control module, and the 23rd pin of the AD7794 chip is connected to the 9th pin of the main control module.

16. The carbon dioxide injection well safety operation pipe string according to claim 3, characterized in that: The network communication module is a W5500 Ethernet chip, pin 26 of the main control module is connected to pin 32 of the W5500 Ethernet chip, pin 27 of the main control module is connected to pin 33 of the W5500 Ethernet chip, pin 30 of the main control module is connected to pin 34 of the W5500 Ethernet chip, pin 31 of the main control module is connected to pin 35 of the W5500 Ethernet chip, and pin 40 of the main control module is connected to pin 36 of the W5500 Ethernet chip.

17. The carbon dioxide injection well safety operation pipe string according to claim 15, characterized in that: A side bypass outlet of the casing head is connected to a sealing tee, a main outlet of the sealing tee is installed with a casing pressure valve, an outlet of the casing pressure valve is installed with a casing pressure gauge and a casing pressure sensor, the casing pressure sensor includes an HX711 chip, the 16th pin of the HX711 chip is connected to a +5V power supply, the 9th, 10th, 14th and 15th pins of the HX711 chip are grounded, and the 12th pin of the HX711 chip is connected to the 11th pin of the AD7794 chip.

18. A method for safe operation of a carbon dioxide injection well, characterized in that: The steps are as follows: S1. Remove the wellhead four-way and above parts, install a casing pressure valve on one side of the casing head bypass port, and install a sealing tee on the other side; S2. Assemble the pipe string as claimed in claim 1 and run it into the well section by section, and remove the soluble ball of the sleeve valve and the constant pressure valve ball of the gas injection valve before assembly; S3. The tubing string is lowered to the designed depth, and the gas injection valve reaches the gas injection layer; the anti-return valve ball is seated on the anti-return valve seat to prevent the annular well fluid from entering the inner cavity of the tubing string; S4. Inject annular protection fluid from the surface until the wellbore annulus fluid is completely replaced; S5. Throw in the constant pressure valve ball from the wellhead, and the constant pressure valve ball rolls down and is seated on the upper part of the constant pressure valve seat; lift the pipe string 0.7-1m, leaving a reserve pressure relief height; S6, positive pressure is applied step by step until the pressure reaches 8-10MPa, the shear pins of the hand-free packer are cut off, and the rubber sleeve begins to expand and seal; Increase the pressure to 16MPa and check the tightness of the pipe string; then reduce the pressure to 8MPa, slowly lower the tubing so that it hangs in the casing head, and at the same time, press down the hand-release packer to seal it; S7. Pressurize the pipe to 18-20 MPa to completely seal the packer. Then continue to increase the pressure to break the thin-walled section of the constant-pressure valve seat. The lower part of the constant-pressure valve seat falls off, and the pipe string is connected with positive injection. S8, squeezing water to verify and confirm that the seal of the drop packer is good; S9. Install the wellhead spool and connect it to the ground process. Inject carbon dioxide from the wellhead. The carbon dioxide pushes the anti-return valve ball and enters the wellbore annulus through the radial hole of the valve body and then enters the formation. After reaching the set gas injection volume, the well is shut down.

19. The safe operation method for carbon dioxide injection wells according to claim 18, characterized in that: When lifting the pipe column, the following steps are included: Step A1, put in soluble balls, pressurize the wellhead to cut off the shear pins of the sliding sleeve, make the bypass hole of the sliding sleeve penetrate, wash the well and degas, and then replace the annulus protection fluid; Step A2: After the soluble ball is dissolved, a throw-away ball is thrown into the tubing string, and positive pressure is applied to release the upper part of the throw-away packer, and the tubing string above the packer is lifted out of the wellhead; Step A3: lower the salvage string to salvage the drop packer and the string below it.

Images