A velocity string for oil and gas production and its under pressure running-in method and under pressure running-out method

Abstract

The application relates to the field of oil and gas exploitation, and particularly discloses a velocity string for oil and gas exploitation, which is formed by cutting off the lower end of a coiled tubing after connecting a plug to the lower end of the coiled tubing; the plug is in a column type, and the upper part and the lower part of the plug are respectively a connecting head and a screen pipe; when the plug is not pressed, gas and liquid in a well block the lower end of the connecting head; when the plug is pressed, the upper end of the plug is blocked by a ball; a method for lowering the velocity string under pressure and a method for lifting the velocity string under pressure are also disclosed. The application has the advantages that: when the velocity string is lowered, annular pressure relief and well killing are not needed, the steps of lowering the velocity string are changed, and thus the operation time of about 9 hours is shortened; when the velocity string is lifted, wellhead pressure relief and well killing are not needed, the steps of lifting the velocity string are changed, and thus the operation time of about 37 hours is shortened.

Description

Technical Field

[0001] This invention relates to the field of petroleum extraction technology, and in particular to a speed string for oil and gas extraction and its pressurized running-in and pressurized tripping-out methods. Background Technology

[0002] A velocity string is a production string formed by running coiled tubing of a designed length into the well using coiled tubing equipment (coiled tubing system) and suspending it in the well using specialized equipment. This is done because in low-pressure, low-production gas wells, or wells that have been in production for a period of time, the gas / oil production is low and the fluid-carrying capacity is limited. Therefore, the gas velocity within the tubing is a crucial factor affecting fluid drainage in gas wells. By running a velocity string with a small diameter, the cross-sectional area is effectively reduced, thereby increasing the gas / fluid velocity at the bottom of the well tubing, achieving the purpose of gas / oil production and fluid drainage.

[0003] However, conventional velocity string operations (running / pulling out the string) require prior well control or depressurization until the wellhead is depressurized before any action can be taken, which takes a significant amount of time. For example, when running a velocity string, it is necessary to depressurize the annulus, control the well, and open the well for observation to ensure there is no pressure buildup before installing the hanger slips and cutting the tubing for suspension and fixation. Similarly, when pulling out a velocity string, it is necessary to depressurize the wellhead, control the well, and open the well for observation to ensure there is no pressure at the wellhead before proceeding with the velocity string pulling operation.

[0004] Based on this, our company has designed a velocity string for oil and gas extraction, along with its pressurized running-in and pressurized tripping-out methods, which enable the velocity string to operate under pressure, saving time spent running down and tripping the velocity string. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a velocity string for oil and gas extraction, as well as a method for running the string down and running it out under pressure, which solves the problems of long running time and low efficiency of traditional conventional velocity string running and running out methods.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] (First aspect)

[0008] A velocity string for oil and gas extraction is formed by connecting a plug to the lower end of a coiled tubing and then cutting it off. The plug is cylindrical, with a connector and a screen tube at the top and bottom, respectively.

[0009] The connector and the screen tube each have an inner cavity A and an inner cavity B. The inner cavity A passes through the connector from top to bottom, the upper end of the inner cavity B is connected to the inner cavity A, and the lower end of the inner cavity B is closed.

[0010] The inner cavity A has tapered flares at both its upper and lower openings;

[0011] The inner cavity B has a larger diameter than the inner cavity A;

[0012] The inner cavity B has a sieve hole on its lower wall and a spherical plug is placed near its upper end; the spherical plug is abutted against the lower conical flare of the inner cavity A by a pin on the inner cavity B.

[0013] The above scheme mainly focuses on the design of the plug at the bottom of the velocity string. The objectives are: ① When the velocity string is run into the well, there is no need for annular depressurization or well control, thus changing the process and saving time; ② When the velocity string is pulled out of the well, there is no need for wellhead depressurization or well control (avoiding open wellhead connection and subsequent gas lift drainage, thus avoiding the safety risks of open well operations, effectively protecting the producing formation, and facilitating rapid post-operation recovery). The principle employed in this scheme is: ① When the plug is not pressurized, the gas and fluid in the well enter the inner cavity B through the screen holes, and the spherical plug blocks the lower conical flare of the inner cavity A; ② When the plug is pressurized, the pressure acts on the spherical plug, causing it to shear the pin, and the spherical plug falls to the bottom of the inner cavity. The gas and fluid in the well then enter the inner cavity B through the screen holes and flow upwards through the inner cavity A.

[0014] In one advantageous extension, the installation of the velocity string is designed. The upper end of the velocity string is connected to the internal slips of the hanger; the internal slips of the hanger are seated inside the external hanger, together forming the hanger; the hanger is installed inside a large crossover and secured by a set screw; the large crossover is installed at the wellhead and has a No. 1 wellhead valve at its top.

[0015] In a favorable extension scheme, the formation of the velocity string was further designed. The lower end of the coiled tubing is connected to a plug and then seated inside the blowout preventer (BOP); the lower end of the BOP is connected to the No. 1 wellhead valve of the large four-way connector; after the coiled tubing and plug are lowered to the designated depth, they are cut off by setting a clamp at the upper end of the BOP.

[0016] (Second aspect)

[0017] A pressurized downhole method for velocity tubing in oil and gas extraction, based on the first aspect, includes the following steps:

[0018] S1. Installation;

[0019] First, install the oil connection equipment; loosen the blowout preventer union, raise the injection head, connect the lower end of the coiled tubing to the retrieval tool via the tool string, and connect the retrieval tool to the external hanger; lower the injection head, mount the external hanger into the blowout preventer, and then tighten the blowout preventer union to connect the injection head to the blowout preventer; connect the blowout preventer to the No. 1 wellhead valve at the top of the large cross-joint at the wellhead;

[0020] S2, Deploy the external suspension device;

[0021] Open the valve at wellhead #1, lower the continuous tubing through the roller, and then lower the external hanger. After the external hanger encounters resistance at the large cross-connector, repeat the lowering attempt. Then tighten the set screw on the large cross-connector and test to confirm whether the external hanger is properly seated.

[0022] If the test confirms that the setting is in place, open the top screw and restore the normal suspension weight; then pressurize the coiled tubing to release the retrieval tool, allowing the external hanger to sit in the tubing hanger, and tighten the top screw.

[0023] The coiled tubing is lifted using a roller to retrieve the fishing tool from the wellhead; then the No. 1 wellhead valve is closed.

[0024] S3, Cut the coiled tubing to form a velocity string;

[0025] Loosen the blowout preventer union to disconnect the injection head from the blowout preventer. Lift the injection head and replace the plug at the lower end of the continuous tubing. Lower the injection head, put the plug into the blowout preventer, and then tighten the blowout preventer union to connect the injection head to the blowout preventer.

[0026] Open the valve at wellhead #1, and lower the coiled tubing through the roller to lower the plug into the well to the designated depth;

[0027] Then close the blowout preventer suspension gate and the semi-sealed gate, and perform a pressure relief test to confirm that there is no pressure on the upper part of the blowout preventer semi-sealed gate.

[0028] After the test is completed, loosen the blowout preventer by connecting the injector head to the blowout preventer, then reduce the roller back pressure, loosen the chain clamping pressure, and then slowly lift the injector head to the appropriate height using a crane.

[0029] Install tubing clamps on the blowout preventer to hold and fix the coiled tubing in place. After checking and confirming that the clamps are effective, cut the coiled tubing at an appropriate height. After the coiled tubing is cut, it is divided into two parts. The coiled tubing left in the well after cutting forms a velocity string. The part that can still be rolled by the drum after cutting is called the drum tubing.

[0030] S4, Deployment speed column;

[0031] Raise the injection head, connect the retrieval tool to the lower end of the drum tubing via a tool string, and connect the internal slips of the hanger to the top of the velocity tubing; use a crane to lower the injection head, allowing the retrieval tool to align with the internal slips of the hanger, and test lift to confirm the connection is secure;

[0032] If it is confirmed that the retrieval tool is securely connected to the internal clamps of the hanger, the speed string is lifted 20cm by the roller, and then the tubing clamp is removed; the blowout preventer union is tightened and sealed well, and the blowout preventer half-sealing gate is opened;

[0033] Raise the injection head to the free tonnage of the tubing, then open the blowout preventer (BOP) slip gate. Slowly lower the tubing through the drum until it encounters resistance. At this point, the internal slip of the hanger is set inside the external hanger. Pressurize the tubing in the drum to separate the retrieval tool from the internal slip of the hanger, thus releasing the internal slip. After the release is complete, release the pressure inside the BOP and observe the pressure. No pressure fluctuation indicates successful setting.

[0034] The roller lifts the oil pipe and the fishing tool to the No. 1 wellhead valve; the No. 1 wellhead valve is connected to an external pressure-pressurizing device, which pressurizes the velocity string through the blowout preventer, and the blowout preventer is repressurized; when pressurizing into the velocity string, the spherical plug in the plugger shears off the pin in the plugger under pressure, and the spherical plug falls to the bottom of the plugger.

[0035] Close the valve at wellhead #1, depressurize the velocity tubing via the blowout preventer, and disassemble the equipment.

[0036] In one advantageous extension, a toolchain is designed. The toolchain includes, in sequence, a tubing connector and a check valve. The tubing connector facilitates connection, and the check valve prevents fluid backflow.

[0037] Preferably, when cutting the tubing to form a velocity string: after lowering the entire coiled tubing to the specified depth, raise it 10m, close the blowout preventer slips and partially seal it; then attach the clamps and cut the coiled tubing 30cm above the blowout preventer.

[0038] (Third aspect)

[0039] A method for pulling out a well under pressure using a velocity string for oil and gas extraction, implemented based on the first and second aspects, includes the following steps:

[0040] S1. Installation;

[0041] Install the oil-connecting equipment. The lower end of the drum oil pipe is connected to the centralizer and the auxiliary alignment tool in sequence through the oil pipe joint. The lower end of the auxiliary alignment tool has a tapered cavity that is larger at the top and smaller at the bottom.

[0042] Install the auxiliary alignment tool into the blowout preventer, tighten the blowout preventer hose union, and connect the injection head to the blowout preventer; then connect the blowout preventer to the No. 1 wellhead valve at the top of the four-way valve.

[0043] S2, Throwing;

[0044] Open the valve at wellhead #1 and lower the auxiliary alignment tool until it encounters resistance. At this point, the conical cavity of the auxiliary alignment tool is aligned with the upper end of the velocity string.

[0045] The ball is dropped through the roller tubing and pumped to the auxiliary alignment tool. The auxiliary alignment tool aligns the ball with the upper end of the velocity string through the tapered cavity at its lower end, thus accurately inserting the ball into the velocity string. Finally, the ball falls to the spherical plug at the upper end of the plug.

[0046] Observe the wellhead pressure, release the wellhead pressure, and ensure that the wellhead is pressure-free;

[0047] S3, initial velocity tubing;

[0048] After the ball is thrown, lift the drum hose; disconnect the blowout preventer union, remove the auxiliary alignment tool at the lower end of the drum hose, and connect the lower end of the drum hose to the centering device and the throwing tool in sequence via the hose connector;

[0049] The fishing tool was lowered into the well until it encountered resistance of 1 ton (i.e., pressure was generated when it encountered resistance, and the pressure reached 1 ton). The fish was then pulled out to confirm that the fish had entered the slips inside the hanger.

[0050] Lift the retrieval tool, which will cause the internal slips and speed tube of the suspension device to rise together; when the upper end of the speed tube leaks out from the blowout preventer's blowout preventer's blowout preventer union, close the blowout preventer suspension and slip gate.

[0051] S4, restart velocity column;

[0052] Pressurize the internal locking lugs of the release suspension device to confirm there is no pressure;

[0053] Open the wellhead, remove the internal slips of the hanger, and use a double roll-on connector to connect the upper end of the velocity string to the lower end of the drum tubing; after confirming that the connection is secure, connect the blowout preventer and restore the wellhead;

[0054] Open the blowout preventer slips and partially seal the gate valve; then start the velocity string to the wellhead; then close the wellhead gate valve.

[0055] S5. Remove the external suspension unit;

[0056] Replace the plug at the lower end of the removed velocity string with a retrieval tool suitable for external suspension devices;

[0057] The fishing tool was lowered through the drum tubing and speed string tubing. After encountering resistance during lowering, it was checked and confirmed that the external suspension device had entered the fish.

[0058] Loosen the external suspension top screw and lift the tubing out of the wellhead;

[0059] Then disassemble the equipment.

[0060] In one advantageous extension, the auxiliary alignment tool used during the throw is designed to be cylindrical with a through-cavity running vertically, and its lower end is tapered. The lower end of the auxiliary alignment tool is fitted to the tapered flare at the upper end of the stopper. The purpose is to ensure that the ball falls accurately into the tapered flare at the upper end of the stopper for sealing.

[0061] Preferably, when starting the initial velocity column: lift the upper end of the velocity column to 30cm from the blowout preventer, close the blowout preventer slips and partially seal it, then pressurize and release.

[0062] To facilitate understanding, some core design aspects of this scheme will be explained below:

[0063] I. The blocker was designed;

[0064] In the conventional process of running a velocity string, it is necessary to release annular pressure, kill the well, and then open the well for observation (which takes twice as long as the annular pressure release and well kill operation) to ensure that there is no pressure rise before running the velocity string. The entire process of annular pressure release, well kill, and well open observation takes 8 hours. If well kill is unsuccessful, multiple well kills and observations are required, which is very time-consuming.

[0065] In the conventional process of raising the velocity string, it is necessary to release pressure at the wellhead, kill the well, and observe the well (twice the working time of annular pressure release and well killing) to ensure that the pressure does not rise before raising the velocity string. The entire process of releasing pressure, killing the well, and observing the well takes 36 hours. If the well killing is unsuccessful, multiple well killing observations are required, and based on experience, it may even take up to 4 days to kill the well.

[0066] In this scheme, when running the velocity string, there is no need to release pressure in the annulus or kill the well. Even if there is pressure in the well, the pressurized gas and fluid enter the inner cavity B through the screen holes, which pushes the spherical plug up and seals the lower conical flare of the inner cavity A, thus preventing gas and fluid from gushing out of the inner cavity A. Therefore, the entire velocity string can be suspended and fixed without confirming that there is no pressure at the wellhead, which takes less time.

[0067] In this scheme, when raising the velocity string, a ball is dropped while maintaining the pressure inside the plug; even without wellhead pressure release or well kill, the velocity string can still be raised normally.

[0068] II. Methods for lowering the velocity column;

[0069] The standard procedure for velocity tubing string operation is as follows: ① Close valve #1, disassemble all components above valve #1, and connect the external components of the hanger to valve #1 using screws (requires 3 hours); ② Connect the coiled tubing equipment and run the velocity tubing string to the target depth (install a plug at the lower end of the tubing) (requires 10 hours); ③ Deflate the annulus, kill the well, and observe the well for twice the operating time. After ensuring there is no pressure rise, install the hanger slips and cut the tubing for suspension and fixation (estimated 8 hours; if well killing is unsuccessful, multiple well killing observations are required); In short, the estimated operation time under normal circumstances is approximately 20 hours.

[0070] The speed tubing operation steps under this scheme are as follows: ① Connect the coiled tubing equipment, connect the tubing connector and centralizer, and lower the speed tubing to the position to drop a ball, blocking the tubing production channel (this process is estimated to take 5 hours); ② Connect the tubing connector and retrieval tool, connect them to the speed tubing, and lift the speed tubing to 30cm above the blowout preventer (BOP), close the BOP slips, partially seal it, and pressurize and release it (this process is estimated to take 2 hours); ③ Connect the drum tubing to the speed tubing and lift the tubing (this process is estimated to take 5 hours); In short, under normal circumstances, the operation is expected to take about 12 hours.

[0071] III. Methods for starting the velocity-increasing tubing;

[0072] The standard procedure for starting a speed tubing string is as follows: ① Pressure release at the wellhead, well control, and observation of the open well for twice the operating time to ensure no pressure rise (requires 36 hours; if well control is unsuccessful, multiple well control observations are required, and based on past experience, the longest well control time is 4 days); ② Connect the coiled tubing equipment, and after the roller tubing is connected to the speed tubing string, pull up the tubing (requires 13 hours); In short, under normal circumstances, the expected operation time is approximately 49 hours.

[0073] The following are the steps for setting the velocity tubing in this plan: ① Connect the coiled tubing equipment (coiled tubing + tubing connector + check valve + drop and retrieve tool + hanger), run it down to the wellhead four-way hanger position, confirm setting, and then pressurize and release (this step is estimated to take 5 hours); ② Run the velocity tubing to the target depth and lift it 10m, close the blowout preventer slips and partially seal it, cut the tubing 30cm above the blowout preventer. (Install a ball-type plug at the lower end of the tubing) (this step is estimated to take 4 hours); ③ Connect the coiled tubing equipment (coiled tubing + tubing connector + drop and retrieve tool + hanger internal slips) to the velocity tubing 30cm above the blowout preventer, run the tubing down to the hanger position, confirm setting, and then pressurize and release (this step is estimated to take 2 hours); In short, the estimated operation time under normal conditions is about 11 hours.

[0074] IV. Location of the external suspension unit;

[0075] Traditional external hangers are installed above the valve at wellhead #1 (e.g.) Figure 1 (Point C in the middle);

[0076] The external hanger in this design is located below the valve at wellhead #1, specifically inside the large four-way valve (e.g., Figure 1 Point D in the diagram); The advantages of this setup are: 1. Firstly, valve #1 can be opened and closed normally, avoiding valve malfunction; 2. It avoids the need for later cutting, welding, and modification work on the wellhead gas production pipeline and operating platform; 3. It avoids the need for launching the velocity string without well control measures; 4. It ensures well control safety during velocity string launch, eliminating the need for well control and avoiding the gas lift and fluid removal operation steps required after well control (the estimated cost of a single well operation for gas lift and fluid removal is 1 million RMB).

[0077] The present invention has the following advantages:

[0078] (1) When running the velocity string, there is no need for annular depressurization or well control, which changes the entire process of running the velocity string and shortens the operation time by about 9 hours.

[0079] (2) When starting the speed string, there is no need to release pressure at the wellhead or kill the well, which changes the entire speed string starting procedure and shortens the operation time by about 37 hours.

[0080] (3) When running tubing, the plug is designed with a pressure-bearing plug according to the height of the liquid column to prevent the pressure in the well from rising back into the coiled tubing, thereby ensuring that there is no pressure inside the coiled tubing and the tubing can be cut at the wellhead.

[0081] (4) Because the internal pressure of the conventional velocity tubing cannot be sealed, there is always pressure at the wellhead of the velocity tubing, making it impossible to complete the connection of the continuous tubing and thus lift it up. Therefore, it is necessary to inject kill fluid into the continuous tubing and observe it after killing the well to ensure that the kill is successful, so that the connection of the continuous tubing can be completed without pressure at the wellhead. Attached Figure Description

[0082] Figure 1 This is a schematic diagram of the structure of the present invention;

[0083] Figure 2 This is a schematic diagram of the unpressurized salvage tool.

[0084] Figure 3 A schematic diagram of the sealing structure of the retrieval tool;

[0085] Figure 4 for Figure 3 Enlarged view of the lower end;

[0086] Figure 5 This is a schematic diagram of the internal locking plate of the suspension unit being mounted inside the external suspension unit.

[0087] Figure 6 This is a schematic diagram of the blocker's structure;

[0088] Figure 7 A schematic diagram of the structure of the alignment tool;

[0089] In the diagram: 100-retrieval tool, 1-mandrel, 2-claw cylinder, 3-upper connector, 4-spring, 5-oil cavity, 6-annular protrusion A, 601-transition section, 602-equal diameter section, 603-limiting protrusion section, 7-annular protrusion B, 8-inner annular protrusion C, 9-sealing ring A, 10-sealing ring B, 11-sealing ring C, 12-outer cylinder, 13-through hole;

[0090] 200-Plug, 22-Connector, 2201-Inner cavity A, 2202-Conical flare, 23-Sieve tube, 2301-Inner cavity B, 24-Sieve hole, 25-Spherical plug, 26-Pin;

[0091] 300 - External suspension, 400 - Internal slip of suspension;

[0092] 51-Drum, 52-Injection head, 53-Blowout preventer, 54-Large four-way valve, 55-Gooseneck tube. Detailed Implementation

[0093] The present invention will be further described below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0094] (Example 1)

[0095] Conventional velocity string lowering operations require annular depressurization, well control, and well opening for observation, which are time-consuming. Similarly, conventional velocity string raising operations require wellhead depressurization, well control, and well opening for observation, also time-consuming. Therefore, this solution addresses this by lowering and raising the velocity string under pressure, eliminating the need for annular depressurization, well control, and well opening for observation. This solution achieves the above objectives through structural improvements to the velocity string.

[0096] like Figure 6 As shown, a velocity string for oil and gas extraction is formed by connecting a plug 200 to the lower end of a coiled tubing and then cutting it off; the plug 200 is cylindrical, with a connector 22 at the top and a screen 23 at the bottom; the connector 22 and the screen 23 have inner cavities A2201 and B2301, respectively.

[0097] The inner cavity A2201 passes through the connector 22 from top to bottom, and both its upper and lower openings are tapered flared openings 2202; while the upper end of the inner cavity B2301 is connected to the inner cavity A2201, the lower end of the inner cavity B2301 is closed, and the diameter of the inner cavity B2301 is larger than the diameter of the inner cavity A2201.

[0098] Furthermore, the inner cavity B2301 has a sieve hole 24 on the lower part of its wall, and a spherical plug 25 is placed near the upper end; the spherical plug 25 is abutted against the lower conical flared opening 2202 of the inner cavity A2201 by a pin 26 on the inner cavity B2301.

[0099] ① When the velocity string is lowered into the well, there is no need to release the well pressure. At this time, the plugger 200 is not pressurized. The gas and liquid in the well enter the inner cavity B2301 through the screen hole 24 and the spherical plug 25 blocks the lower conical flared opening 2202 of the inner cavity A2201, thus achieving automatic sealing of the plugger 200 and enabling the velocity string to be lowered into the well under pressure. ② When oil production is required through the velocity string, pressure is applied to the plugger 200. The pressure force acts on the spherical plug 25, causing the spherical plug 25 to shear the pin 26. The spherical plug 25 falls to the bottom of the inner cavity B2301. Then the pressure of the velocity string is removed, and the gas and liquid in the well enter the inner cavity B2301 through the screen hole 24 and flow upward through the inner cavity A2201. ③ When it is necessary to extract the velocity string, a ball is dropped and placed at the conical flare 2202 at the upper end of the plug 200. Then, pressure is applied to the coiled tubing, and the plug 200 is sealed by the ball. As long as the pressure applied is greater than the pressure inside the well, the velocity string can be extracted under pressure even without releasing the pressure inside the well.

[0100] In this embodiment, when the coiled tubing is sheared to form a velocity string: the lower end of the coiled tubing is connected to the plug 200 and then placed inside the blowout preventer 53; the lower end of the blowout preventer 53 is connected to the No. 1 wellhead valve of the large four-way valve 54; after the coiled tubing and the plug 200 are lowered to the specified depth, they are cut off by setting a clamp at the upper end of the blowout preventer 53.

[0101] In this embodiment, when the velocity column is installed: the upper end of the velocity column is connected to the internal slip 400 of the hanger; the internal slip 400 of the hanger is mounted inside the external hanger 300, and the two together form the hanger (e.g., Figure 5 (As shown); the hanger is installed inside the large four-way connector 54 and fixed by a top screw; the large four-way connector 54 is installed at the wellhead and has a No. 1 wellhead valve on its top.

[0102] (Example 2)

[0103] Because conventional velocity string lowering takes a long time, Example 1 improves the plug 200 in the velocity string. This solution, based on the improvement of the plunger 100, forms a new method for lowering velocity strings into the well.

[0104] For ease of understanding, it should be noted that during the process of running the velocity tubing into / out of the well, the following components are required: roller 51, crane, injection head 52, and blowout preventer 53. The crane is equipped with roller 51 and boom, and injection head 52 is suspended on the boom. Below injection head 52, it is connected to blowout preventer 53 via a union in the blowout preventer pipe. Blowout preventer 53 is installed and connected to wellhead valve #1 at the top of the large cross-connector 54 at the wellhead. One end of the coiled tubing is wound around roller 51, and the other end extends into large cross-connector 54 via gooseneck tube 55 on injection head, injection head 52, and blowout preventer 53.

[0105] (refer to Figure 1 )

[0106] A method for running a velocity string under pressure in an oil and gas extraction well includes the following steps:

[0107] S1. Installation;

[0108] First, install the oil connection equipment; loosen the blowout preventer union, raise the injection head 52, connect the lower end of the coiled tubing to the retrieval tool via the tool string, and connect the retrieval tool to the external hanger 300; lower the injection head 52, mount the external hanger 300 into the blowout preventer 53, and then tighten the blowout preventer union to connect the injection head 52 to the blowout preventer; connect the blowout preventer 53 to the No. 1 wellhead valve at the top of the large cross-joint 54 at the wellhead;

[0109] S2, Deploy the external suspension device 300;

[0110] Open the valve at wellhead #1, and lower the continuous tubing through roller 51, thereby lowering the external hanger 300. After the external hanger 300 encounters resistance at the large cross-connector 54, repeat the lowering attempt. Then tighten the set screw on the large cross-connector 54 and test to confirm whether the external hanger 300 is properly seated.

[0111] If the test confirms that the setting is in place, open the top screw and restore the normal suspension weight; then pressurize the coiled tubing to release the retrieval tool, so that the external hanger is seated into the tubing at 300°, and tighten the top screw.

[0112] The coiled tubing is lifted using roller 51, and the retrieval tool is pulled out from the wellhead; then the No. 1 wellhead valve is closed.

[0113] S3, Cut the coiled tubing to form a velocity string;

[0114] Loosen the blowout preventer union to separate the injection head 52 from the blowout preventer 53, lift the injection head 52, and replace the lower end of the continuous tubing with the plug 200; lower the injection head 52, put the plug 200 into the blowout preventer 53, and then tighten the blowout preventer union to connect the injection head 52 to the blowout preventer 53.

[0115] Open the valve at wellhead #1, and lower the continuous tubing through roller 51 to lower the plug 200 into the well to the designated depth;

[0116] Then close the blowout preventer suspension gate and the semi-sealing gate, and perform a pressure relief test to confirm that there is no pressure on the upper part of the blowout preventer semi-sealing gate.

[0117] After the test is completed, loosen the blowout preventer and disconnect the injection head 52 from the blowout preventer 53. Then reduce the roller back pressure, loosen the chain clamping pressure, and slowly lift the injection head 52 with a crane to a suitable height.

[0118] Install tubing clamps on the blowout preventer 53, and then clamp and fix the coiled tubing. After checking and confirming that the clamps are effective, cut the coiled tubing at an appropriate height. After the coiled tubing is cut, it is divided into two parts. The coiled tubing left in the well after cutting forms a velocity tubing string. The part that can still be rolled by the drum 51 after cutting is called the drum tubing.

[0119] S4, Deployment speed column;

[0120] Raise the injection head 52, connect the retrieval tool to the lower end of the drum tubing via a tool string, and connect the internal slip 400 of the hanger to the top of the speed tubing; use a crane to lower the injection head 52, allowing the retrieval tool to align with the internal slip 400 of the hanger, and test lift to confirm whether the connection is secure.

[0121] If it is confirmed that the retrieval tool is securely connected to the internal clamp 400 of the hanger, the speed string is lifted 20cm via the roller 51, and then the oil pipe clamp is removed; the blowout preventer union is tightened and sealed well, and the blowout preventer half-sealing gate is opened;

[0122] The injection head 52 is raised to the free tonnage of the tubing, and then the blowout preventer (BOP) slip gate is opened; the tubing is slowly lowered through the drum 51 until it encounters resistance, at which point the internal slip 400 of the hanger is set inside the outer hanger 300; pressure is applied to the tubing of the drum to separate the retrieval tool from the internal slip 400 of the hanger, thus releasing the internal slip 400 of the hanger; after the release is completed, the pressure inside the BOP 53 is released and the pressure is observed. If there is no pressure fluctuation, the setting is considered successful.

[0123] The drum tubing and the fishing tool are lifted out of the No. 1 wellhead valve via the drum 51; the No. 1 wellhead valve is connected to an external pressure testing device, which pressurizes the velocity tubing through the blowout preventer 53, and the blowout preventer 53 is repressurized; when pressurizing into the velocity tubing, the spherical plug 25 in the plugger 200 shears the pin 26 inside the plugger 200 under pressure, and the spherical plug 25 falls to the bottom of the plugger 200;

[0124] Close the valve at wellhead #1, depressurize the velocity tubing via blowout preventer 53, and disassemble the equipment.

[0125] In this embodiment, the tool string includes a tubing connector and a check valve connected in sequence. The tubing connector facilitates quick connection, and the check valve prevents fluid backflow in the well.

[0126] In this embodiment, preferably, when cutting the tubing to form a velocity string: after the entire coiled tubing is lowered to a specified depth, it is then raised 10m, the blowout preventer slips are closed and partially sealed; then the clamps are installed, and the coiled tubing is cut at a point 30cm above the blowout preventer.

[0127] (Example 3)

[0128] Since conventional speed-starting tubing requires a long time, this embodiment, based on Embodiments 1 and 2, forms a new speed-starting tubing method.

[0129] A method for pulling out a well under pressure using a velocity string for oil and gas extraction includes the following steps:

[0130] S1. Installation;

[0131] Install the oil-connecting equipment. The lower end of the drum oil pipe is connected to the centralizer and the auxiliary alignment tool in sequence through the oil pipe joint. The lower end of the auxiliary alignment tool has a tapered cavity that is larger at the top and smaller at the bottom.

[0132] Install the auxiliary alignment tool into the blowout preventer 53, tighten the blowout preventer union, and connect the injection head 52 to the blowout preventer 53; then connect the blowout preventer 53 to the No. 1 wellhead valve at the top of the four-way connector 54.

[0133] S2, Throwing;

[0134] Open the valve at wellhead #1 and lower the auxiliary alignment tool until it encounters resistance. At this point, the conical cavity of the auxiliary alignment tool is aligned with the upper end of the velocity string.

[0135] The ball is dropped through the roller tubing and pumped to the auxiliary alignment tool. The auxiliary alignment tool aligns the ball with the upper end of the velocity string through the tapered cavity at its lower end, thus accurately inserting the ball into the velocity string. Finally, the ball falls to the spherical plug at the upper end of the plugger 200.

[0136] Observe the wellhead pressure, release the wellhead pressure, and ensure that the wellhead is pressure-free;

[0137] S3, initial velocity tubing;

[0138] After the ball is thrown, lift the drum hose; disconnect the blowout preventer union, remove the auxiliary alignment tool at the lower end of the drum hose, and connect the lower end of the drum hose to the centering device and the throwing tool in sequence via the hose connector;

[0139] The fishing tool was lowered into the well until it encountered resistance of 1 ton (i.e., pressure was generated when it encountered resistance, and the pressure reached 1 ton). The fish was then pulled out to confirm that the internal slips of the hanger were 400mm.

[0140] Raise the retrieval tool, which will cause the internal slip 400 and speed tube to rise together; when the upper end of the speed tube leaks out from the blowout preventer's blowout preventer union, close the blowout preventer suspension and slip gate.

[0141] S4, restart velocity column;

[0142] Pressurize the internal locking lugs of the release suspension device by 400 mm, and confirm that there is no pressure after depressurization.

[0143] Open the wellhead, remove the 400 slips inside the hanger, and use a double roll-on connector to connect the upper end of the velocity string to the lower end of the drum tubing; after confirming the connection is secure by test lifting, connect the blowout preventer and restore the wellhead;

[0144] Open the blowout preventer slips and partially seal the gate valve; then start the velocity string to the wellhead; then close the wellhead gate valve.

[0145] S5. Remove the external suspension unit 300;

[0146] Replace the plug 200 at the lower end of the removed velocity string with a retrieval tool suitable for the external hanger 300;

[0147] The fishing tool was lowered through the drum tubing and speed string tubing. After encountering resistance during lowering, it was checked and confirmed that the external suspension device was 300mm in place.

[0148] Loosen the external suspension top screw and lift the tubing out of the wellhead;

[0149] Then disassemble the equipment.

[0150] In this embodiment, as Figure 7 As shown, the auxiliary alignment tool used when throwing the ball is cylindrical and has a through cavity running vertically, with a tapered opening at its lower end; the lower end of the auxiliary alignment tool is adapted to the tapered flare at the upper end of the blocker 200.

[0151] In this embodiment, preferably, when starting the initial velocity column: the upper end of the velocity column is raised to 30cm from the blowout preventer, the blowout preventer slips are closed and partially sealed, and then pressure is applied and released.

[0152] (Example 4)

[0153] The retrieval and casting tools in Examples 2 and 3 were designed.

[0154] Specifically, such as Figures 2-4 As shown, the tool for retrieving and deploying coiled tubing includes a mandrel 1, a claw sleeve 2, and an upper connector 3. During installation, the claw sleeve 2 is slidably fitted onto the mandrel 1, and then the upper end of the mandrel 1 is connected to the upper connector 3. The upper end of the claw sleeve 2 is connected to the lower end of the upper connector 3 via a spring 4.

[0155] Furthermore, the upper part of the chuck cylinder 2 is a cylinder part and the lower part is a chuck part; wherein, the cylinder part and the outer wall of the mandrel 1 form a closed oil cavity 5, and the oil cavity 5 is connected to the central cavity of the mandrel through the through hole 13; wherein, the chuck part can be opened by the annular protrusion A6 at the lower end of the mandrel 1.

[0156] When using this method to hoist the hanger: the oil pipe connector is threaded into the upper connector 3, and the hanger is adapted and connected by the buckle on the outer side of the claw part (at this time, no pressurized oil is introduced into the oil chamber 5; the adaptation buckle is achieved under the action of the spring 4); after the hanger is in place, pressurized oil is injected into the oil chamber 5 through the through hole 12 in the central cavity. At this time, the claw cylinder 2 moves upward, the claw part disengages from the annular protrusion A6, and the claw part retracts radially; due to the retraction of the claw part, the buckle separates from the hanger; then the entire oil pipe connector and the tool of this method are removed upward. (The corresponding operating steps are very mature in this field; this is only an explanation of the operating steps in conjunction with this method to facilitate understanding by those who are not skilled in the art.)

[0157] When removing the hanger using this method: First, inject oil into the oil chamber 5 to allow the latches of the claw part to retract radially. Then, after the entire delivery tool is in place, when the pressurized oil in the oil chamber 5 is withdrawn, the claw cylinder 2 moves downward, and the claw part engages with the annular protrusion A6, thus being radially expanded. When the entire delivery tool is lifted upward, the latches engage with the hanger, thereby removing the hanger. (The above are the conventional operating steps; this explanation is only based on this method.)

[0158] In this embodiment, the mandrel 1 has an annular protrusion B7 in its middle portion, and the upper end of the cylindrical portion of the chuck cylinder 2 has an annular inner protrusion C8. The oil cavity 5 is formed by the chuck cylinder 2, the mandrel 1, the annular inner protrusion C8, and the annular protrusion B7. Furthermore, the through hole 13 is formed on the wall of the mandrel 1. Figure 3 As shown, to ensure a seal, the annular protrusion B7 is sealed to the inner wall of the claw cylinder 2 by a sealing ring A9; the annular inner protrusion C8 is sealed to the outer wall of the mandrel 1 by a sealing ring B10.

[0159] In this embodiment, a design was implemented to ensure smooth axial sliding of the claw cylinder 2. The upper connector 3 also has a corresponding central cavity, with an internal threaded cavity at its upper end and a stepped cavity at its lower end. The stepped cavity includes a small-diameter stepped cavity and a large-diameter stepped cavity. The small-diameter stepped cavity is fitted into the mandrel 1 and locked together with screws and sealed with a sealing ring C11. An annular groove is formed between the large-diameter stepped cavity and the wall of the mandrel 1, and the spring 4 is placed in this annular groove. The upper end of the claw cylinder 2 is always inserted into the annular groove.

[0160] When the chuck cylinder 2 slides axially, its upper end forms a force-bearing point with the annular groove, and the annular protrusion B9 forms another force-bearing point; this ensures the accuracy of the axial movement of the chuck copper part 2 (if there is only one force-bearing point, it is easy to move or tilt axially). Furthermore, the annular groove also allows for spring storage. The upper outer column of the cylinder part 2 is stepped, with its smaller diameter portion inserted into the annular groove, and the stepped portion abutting against the end face of the upper connector 3.

[0161] In this embodiment, a design was implemented to prevent the jaw cylinder 2 from being excessively stretched. This includes an outer cylinder 12, which is threadedly fitted onto the middle of the jaw cylinder 2. Its function is to limit the degree of stretching when the jaw portion of the jaw cylinder 2 is stretched open by the annular protrusion A6.

[0162] In this embodiment, an annular protrusion 6 is also designed. The annular protrusion A6 consists of a tapered transition section 601, a constant diameter section 602, and a limiting protrusion section 603, from top to bottom. When the jaw portion of the jaw cylinder 2 is gradually opened by the annular protrusion A6 (which gradually and gently opens it), the jaw portion slides through the transition section 601 to the constant diameter section 602, and finally abuts against the limiting protrusion section 603 (to prevent the jaw cylinder 2 from falling off).

[0163] The above embodiments only illustrate preferred implementation methods, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this invention, and these all fall within the protection scope of this invention.

Claims

1. A method for running a velocity string under pressure in an oil and gas extraction well, characterized in that: Includes the following steps: S1. Installation; First, install the oil connection equipment; loosen the blowout preventer union, raise the injection head, connect the lower end of the coiled tubing to the retrieval tool via the tool string, and connect the retrieval tool to the external hanger; lower the injection head, mount the external hanger into the blowout preventer, and then tighten the blowout preventer union to connect the injection head to the blowout preventer; connect the blowout preventer to the No. 1 wellhead valve at the top of the large cross-joint at the wellhead; S2, Deploy the external suspension device; Open the valve at wellhead #1, lower the continuous tubing through the roller, and then lower the external hanger. After the external hanger encounters resistance at the large cross-connector, repeat the lowering attempt. Then tighten the set screw on the large cross-connector and test to confirm whether the external hanger is properly seated. If the test confirms that the setting is in place, open the top screw and restore the normal suspension weight; then pressurize the coiled tubing to release the retrieval tool, allowing the external hanger to sit in the tubing hanger, and tighten the top screw. The coiled tubing is lifted using a roller to retrieve the fishing tool from the wellhead; then the No. 1 wellhead valve is closed. S3, Cut the coiled tubing to form a velocity string; Loosen the blowout preventer union to disconnect the injection head from the blowout preventer. Lift the injection head and replace the plug at the lower end of the continuous tubing. Lower the injection head, put the plug into the blowout preventer, and then tighten the blowout preventer union to connect the injection head to the blowout preventer. Open the valve at wellhead #1, and lower the coiled tubing through the roller to lower the plug into the well to the designated depth; Then close the blowout preventer suspension gate and the semi-sealed gate, and perform a pressure relief test to confirm that there is no pressure on the upper part of the blowout preventer semi-sealed gate. After the test is completed, loosen the blowout preventer by connecting the injector head to the blowout preventer, then reduce the roller back pressure, loosen the chain clamping pressure, and then slowly lift the injector head to the appropriate height using a crane. Install tubing clamps on the blowout preventer to hold and fix the coiled tubing in place. After checking and confirming that the clamps are effective, cut the coiled tubing at an appropriate height. After the coiled tubing is cut, it is divided into two parts. The coiled tubing left in the well after cutting forms a velocity string. The part that can still be rolled by the drum after cutting is called the drum tubing. The velocity string is formed by connecting a plug to the lower end of a continuous tubing and then cutting it off. The plug is cylindrical, with a connector and a screen tube at the top and bottom, respectively. The connector and the screen tube each have an inner cavity A and an inner cavity B. The inner cavity A passes through the connector from top to bottom, the upper end of the inner cavity B is connected to the inner cavity A, and the lower end of the inner cavity B is closed. The inner cavity A has tapered flared openings at both its upper and lower ends; the inner cavity B has a larger diameter than the inner cavity A. The lower part of the inner cavity B has a sieve hole on its wall, and a spherical plug is placed near the upper end of the inner cavity B; the spherical plug is abutted against the lower conical flare of the inner cavity A by a pin on the inner cavity B. When the plug is not pressurized, the gas and liquid in the well enter the inner cavity B through the screen holes and the spherical plug blocks the lower conical flare of the inner cavity A; when the plug is pressurized, the pressurizing force acts on the spherical plug, causing the spherical plug to shear the pin, and the spherical plug falls to the bottom of the inner cavity. The gas and liquid in the well enter the inner cavity B through the screen holes and flow upward through the inner cavity A. The velocity string is connected at its upper end to the internal slip of the hanger; the internal slip of the hanger is mounted inside the outer hanger, and the two together form the hanger; the hanger is installed in the large cross and fixed by the set screw; the large cross is installed at the wellhead and has a No. 1 wellhead valve at its top. The lower end of the coiled tubing is connected to the plug and then mounted inside the blowout preventer (BOP); the lower end of the BOP is connected to the No. 1 wellhead valve of the large four-way valve; after the coiled tubing and the plug are lowered to the designated depth, they are cut off by setting a clamp at the upper end of the BOP. S4, Deployment speed column; Raise the injection head, connect the retrieval tool to the lower end of the drum tubing via a tool string, and connect the internal slips of the hanger to the top of the velocity tubing; use a crane to lower the injection head, allowing the retrieval tool to align with the internal slips of the hanger, and test lift to confirm the connection is secure; If it is confirmed that the retrieval tool is securely connected to the internal clamps of the hanger, the speed string is lifted 20cm by the roller, and then the tubing clamp is removed; the blowout preventer union is tightened and sealed well, and the blowout preventer half-sealing gate is opened; Raise the injection head to the free tonnage of the tubing, then open the blowout preventer (BOP) slip gate. Slowly lower the tubing through the drum until it encounters resistance. At this point, the internal slip of the hanger is set inside the external hanger. Pressurize the tubing in the drum to separate the retrieval tool from the internal slip of the hanger, thus releasing the internal slip. After the release is complete, release the pressure inside the BOP and observe the pressure. No pressure fluctuation indicates successful setting. The roller lifts the oil pipe and the fishing tool to the No. 1 wellhead valve; the No. 1 wellhead valve is connected to an external pressure-pressurizing device, which pressurizes the velocity string through the blowout preventer, and the blowout preventer is repressurized; when pressurizing into the velocity string, the spherical plug in the plugger shears off the pin in the plugger under pressure, and the spherical plug falls to the bottom of the plugger. Close the valve at wellhead #1, depressurize the velocity tubing via the blowout preventer, and disassemble the equipment.

2. The method for running a velocity string under pressure for oil and gas extraction according to claim 1, characterized in that: The tool string includes a tubing connector and a check valve connected in sequence.

3. The method for running a velocity string under pressure for oil and gas extraction according to claim 1, characterized in that: When cutting the coiled tubing to form a velocity string: after lowering the entire coiled tubing to the specified depth, raise it 10m, and close the blowout preventer slips and partially seal it; Then, attach the clamps and cut the coiled tubing 30cm above the blowout preventer.

4. A method for pulling out a well under pressure using a velocity string for oil and gas extraction, characterized in that: Includes the following steps: S1. Installation; Install the oil-connecting equipment. The lower end of the drum oil pipe is connected to the centralizer and the auxiliary alignment tool in sequence through the oil pipe joint. The lower end of the auxiliary alignment tool has a tapered cavity that is larger at the top and smaller at the bottom. Install the auxiliary alignment tool into the blowout preventer, tighten the blowout preventer union and connect the injection head to the blowout preventer; then connect the blowout preventer to the No. 1 wellhead valve at the top of the four-way valve. S2, Throwing; Open the valve at wellhead #1 and lower the auxiliary alignment tool until it encounters resistance. At this point, the conical cavity of the auxiliary alignment tool is aligned with the upper end of the velocity string. The ball is dropped through the roller tubing and pumped to the auxiliary alignment tool. The auxiliary alignment tool aligns the ball with the upper end of the velocity string through the tapered cavity at its lower end, thus accurately inserting the ball into the velocity string. Finally, the ball falls to the spherical plug at the upper end of the plug. Observe the wellhead pressure, release the wellhead pressure, and ensure that the wellhead is pressure-free; The velocity string is formed by connecting a plug to the lower end of a continuous tubing and then cutting it off. The plug is cylindrical, with a connector and a screen tube at the top and bottom, respectively. The connector and the screen tube each have an inner cavity A and an inner cavity B. The inner cavity A passes through the connector from top to bottom, the upper end of the inner cavity B is connected to the inner cavity A, and the lower end of the inner cavity B is closed. The inner cavity A has tapered flared openings at both its upper and lower ends; the inner cavity B has a larger diameter than the inner cavity A. The inner cavity B has a sieve hole on its lower wall and a spherical plug is placed near its upper end; the spherical plug is abutted against the lower conical flare of the inner cavity A by a pin on the inner cavity B. When the plug is not pressurized, the gas and liquid in the well enter the inner cavity B through the screen holes and the spherical plug blocks the lower conical flare of the inner cavity A; when the plug is pressurized, the pressurizing force acts on the spherical plug, causing the spherical plug to shear the pin, and the spherical plug falls to the bottom of the inner cavity. The gas and liquid in the well enter the inner cavity B through the screen holes and flow upward through the inner cavity A. The velocity string is connected at its upper end to the internal slip of the hanger; the internal slip of the hanger is mounted inside the outer hanger, and the two together form the hanger; the hanger is installed in the large cross and fixed by a set screw; the large cross is installed at the wellhead and has a No. 1 wellhead valve at its top. After the lower end of the coiled tubing is connected to the plug, it is installed inside the blowout preventer; the lower end of the blowout preventer is connected to the No. 1 wellhead valve of the large four-way valve; after the coiled tubing and the plug are lowered to the designated depth, they are cut off by setting a clamp at the upper end of the blowout preventer. S3, initial velocity tubing; After the ball is thrown, lift the drum hose; disconnect the blowout preventer union, remove the auxiliary alignment tool at the lower end of the drum hose, and connect the lower end of the drum hose to the centering device and the throwing tool in sequence via the hose connector; The fishing tool was lowered into the well. When it encountered resistance during lowering, pressure was generated. The pressure reached 1 ton. A test lift confirmed that the fish had entered the fish by the slips inside the hanger. Lift the retrieval tool, which will cause the internal slips and speed tube of the suspension device to rise together; when the upper end of the speed tube leaks out from the blowout preventer's blowout preventer's blowout preventer union, close the blowout preventer suspension and slip gate. S4, restart velocity column; Pressurize the internal locking lugs of the release suspension device to confirm there is no pressure; Open the wellhead, remove the internal slips of the hanger, and use a double roll-on connector to connect the upper end of the velocity string to the lower end of the drum tubing; after confirming that the connection is secure, connect the blowout preventer and restore the wellhead; Open the blowout preventer slips and partially seal the gate valve; then start the velocity string to the wellhead; then close the wellhead gate valve. S5. Remove the external suspension unit; Replace the plug at the lower end of the removed velocity string with a retrieval tool suitable for external suspension devices; The fishing tool was lowered through the drum tubing and speed string tubing. After encountering resistance during lowering, it was checked and confirmed that the external suspension device had entered the fish. Loosen the external suspension top screw and lift the tubing out of the wellhead; Then disassemble the equipment.

5. A method for pulling out a well under pressure using a velocity string for oil and gas extraction according to claim 4, characterized in that: The auxiliary alignment tool used when throwing the ball is cylindrical, with a through cavity running vertically through it, and a tapered opening at its lower end. The lower end of the auxiliary alignment tool is adapted to the tapered flare at the upper end of the plug.

6. A method for pulling a speed string into a well under pressure for oil and gas extraction according to claim 4, characterized in that: When the initial velocity string is used: Raise the speed column to 30cm from the blowout preventer, close the blowout preventer slips and partially seal it, then pressurize and release.

Images