CN119062258A

CN119062258A - Construction method of coiled tubing wellhead suspension and well bottom plugging completion string

Info

Publication number: CN119062258A
Application number: CN202310643960.9A
Authority: CN
Inventors: 吕维平; 张炎; 付悦; 刘家炜; 任彬; 周士杰; 张正; 祝叶; 辛永安; 贾夏; 陈智
Original assignee: China National Petroleum Corp; CNPC Engineering Technology R&D Co Ltd; CNPC Jianghan Machinery Research Institute Co Ltd
Current assignee: China National Petroleum Corp; CNPC Engineering Technology R&D Co Ltd; CNPC Jianghan Machinery Research Institute Co Ltd
Priority date: 2023-06-01
Filing date: 2023-06-01
Publication date: 2024-12-03
Also published as: WO2024244359A1

Abstract

The invention relates to the field of natural gas well completion, and discloses a construction method for hanging a coiled tubing wellhead and plugging a well completion string at the bottom, which comprises the steps of placing coiled tubing (1) operation equipment, installing wellhead equipment and testing pressure, enabling the coiled tubing (1) to pass through an injection head (8), installing a well logging tool string for well flushing operation, replacing the well logging tool string for the well completion string, arranging an oil pipe hanger (3) on the coiled tubing (1), lowering the coiled tubing (1) to a designed depth, opening an operation window (13), installing hanging slips (2) on the coiled tubing (1), lowering the coiled tubing (1) to enable the hanging slips (2) to fall into the oil pipe hanger (3), cutting off the coiled tubing (1), removing wellhead equipment, recovering a gas production tree (18), and enabling a plug (7) to be put into production. Through above-mentioned technical scheme, through prefabricated suspension slips before cutting the pipe, avoided the temporary potential safety hazard that causes of hanging of well head equipment.

Description

Construction method for coiled tubing wellhead suspension and well completion string for bottom plugging

Technical Field

The invention relates to the technical field of natural gas well completion, in particular to a construction method for a coiled tubing wellhead suspension and a well completion string for bottom plugging.

Background

With the development of dense gas/shale gas, the problems of decreasing yield, increasing water content and the like caused by adopting a well completion and gas production of a tubing string seriously affect the gradual development of gas production, the traditional tubing operation under pressure has the disadvantages of complex construction and low efficiency, the traditional equipment has the advantages of low operation level under pressure and high price, liquid accumulation in a later-stage pit shaft, poor liquid carrying of a conventional tubing, the need of carrying out an auxiliary process for liquid discharge and gas production and development cost increase. The continuous pipe has the advantages of no need of connecting a single pipe, small internal drift diameter, high completion speed and the like, and the corresponding characteristics are also reflected in the speed pipe column process. The method applies the congenital advantages of the coiled tubing to the development of dense gas/shale gas to form a coiled tubing well completion and gas production integrated technology, leads to the promotion of cost reduction and quality improvement of resource development, is safe and efficient in construction operation, and has important significance in low-oil-price and large-environment.

Regarding the presently disclosed coiled tubing completion string process, patent CN105064940B discloses a built-in coiled tubing completion string and a construction method, the string comprises a built-in hanger, a coiled tubing, a plug and a plug rod, the process sequence adopts the built-in hanger to be installed in a tubing head, a primary pipe is cut down to a design position, a temporary hanging coiled tubing is cut off, a locking type sitting-hanging joint is installed, a secondary pipe is cut down, the joint and the coiled tubing are hung in the hanger body in a sitting manner, then a wellhead gas production tree is restored, and the production of the coiled tubing completion string is completed. Patent CN115162999a discloses a construction method for throwing large-diameter continuous gas production pipe column, the technological sequence adopts once pipe-dropping to the design position, temporarily suspending pipe-cutting, connecting continuous pipe with oil pipe hanger, secondarily pipe-dropping to seat oil pipe hanger to wellhead, then recovering wellhead gas production tree, completing continuous pipe completion pipe column to produce. The mode is also the most widely applied continuous pipe completion string technology in the oil field and the market at present, and the following two problems exist for the two completion technologies:

(1) After cutting the pipe, the continuous pipe is in a temporary suspension state, and is suspended only by wellhead blowout prevention equipment, so that the requirement on the safety performance of the wellhead blowout prevention equipment is high, if the equipment suspension function is invalid, the continuous pipe directly falls into a well to cause accidents, and therefore, the process flow has great potential safety hazards;

(2) The annular channel between the coiled tubing and the shaft is sealed only by the hanger of the well head, and in the process of the well head disassembly and assembly operation, the hanger of the well head is in a long-term pressure state, and if the setting operation is improper, air leakage and top-up risk exist, so that the well head operator is threatened. In addition, the annulus is exposed in the production environment for a long time, and the casing and the production pipe column are easy to corrode and perforate, so that the follow-up production operation is affected.

Aiming at the problems of the existing coiled tubing completion process and combining the requirements of the coiled tubing completion and gas production integrated process, the existing technology lacks to meet the requirement that the coiled tubing is hung at a wellhead, and simultaneously realizes a safe, efficient and economical completion string process for plugging at the bottom of a well.

Disclosure of Invention

The invention aims to overcome the problem of the risk caused by temporary suspension of a continuous pipe in the prior art.

In order to achieve the above purpose, the invention provides a construction method for hanging a coiled tubing wellhead and plugging a well completion string at the bottom, wherein the construction method comprises the following steps:

S1, placing continuous pipe operation equipment, installing wellhead equipment and testing pressure, wherein the wellhead equipment comprises an injection head, a blowout preventer, a four-ram blowout preventer, a pressure relief tee joint and an operation window from top to bottom;

S2, penetrating a continuous pipe through the injection head, installing a well logging tool string for well flushing, and descending the continuous pipe to a designed position to perform well flushing operation;

S3, lifting the continuous pipe to the operation window, replacing a well entering tool string for a well completion string, arranging an oil pipe hanger on the continuous pipe, and descending the continuous pipe to enable the oil pipe hanger to fall into a wellhead four-way joint and be seated, and continuing to descend the continuous pipe to the designed depth;

S4, opening the operation window, installing a hanging slip on the continuous pipe, and lowering the continuous pipe to enable the hanging slip to fall into the oil pipe hanger, and cutting off the continuous pipe after the hanging slip is continuously lowered to zero in hanging weight;

S5, removing wellhead equipment, recovering the gas production tree, and opening the blanking plug for production.

In some embodiments, slip teeth are provided on an inner peripheral surface of the hanging slips, an outer peripheral surface of the hanging slips is formed as a tapered surface from top to bottom, and an inner peripheral surface of an upper end of the tubing hanger is formed as a tapered surface from top to bottom to receive and hang the hanging slips.

In some embodiments, the hanging slip includes two half-pipe portions and a connector for detachably connecting the two half-pipe portions.

In some embodiments, the tubing hanger is in sealing engagement with the wellhead four-way joint, the tubing hanger being secured by a jackscrew of the wellhead four-way joint.

In some embodiments, in S3, the replacing the string of well tools for the completion string includes opening the operating window, removing the string of well tools for flushing, installing a release, a packer at a lower end of the coiled tubing, and hanging the tubing hanger on the packer.

In some embodiments, in S3, after the continuing to run the coiled tubing to a design depth, the casing is pressurized such that the packer sets in a design position, continuing to run the coiled tubing to release a portion of the sling weight of the injector head.

In some embodiments, the step S3 further comprises opening the pressure relief tee and controlling the blowout through a surface choke manifold, releasing the pressure above the packer, and filling the annular area with packing fluid so that the wellhead is pressureless.

In some embodiments, in S3, the continuing to lower the coiled tubing to the design depth comprises lowering the coiled tubing at a speed of no more than 5m/min, running the observation device when the lowering depth reaches 50m, continuing to lower the coiled tubing at a speed of 25-30m/min, performing an upward suspension weight test every 500m in the lowering process, lowering the speed to 10-15m/min when the lowering speed is 300m from the design depth, lowering the speed to 5m/min when the lowering speed is 100m from the design depth, and lifting the coiled tubing to the design depth after the lowering speed is 15m from the design depth.

In some embodiments, in S1, each ram switching function of the four ram blowout preventer is tested to be in a fully open position, and then the injector head, the blowout preventer, the four ram blowout preventer, the pressure relief tee, the lubricator, the operating window are installed, and the connection to the surface high pressure pump stack pipeline is subjected to surface pipeline and wellhead equipment pressure testing, respectively.

In some embodiments, the pressure test requires that the pump pressure is increased to 35MPa step by step according to 10%, 50% and 100%, and the pressure test is qualified by stabilizing the pressure for 10min and reducing the pressure by less than 0.7MPa, and if leakage is found, the pump is stopped immediately for pressure relief correction.

In some embodiments, in S2, the coiled tubing passes through the injection head and is lowered to the position of the operation window, the operation window is opened, the lower end of the coiled tubing is chamfered, a connector is installed, a tensile test is performed, a motor head and a well dredging and cleaning tool are installed at the lower end of the connector, the operation window is closed, wellhead equipment is tested for pressure through a ground high-pressure pump set pipeline, a flat valve is opened, the coiled tubing is lowered to a design depth, the ground high-pressure pump set pipeline is opened, and well dredging and cleaning operation of a design area is completed.

In some embodiments, the lower end of the coiled tubing is subjected to 45 DEG chamfering during installation of the connector, and 15 tons of tensile testing is performed on the connector, wherein displacement of less than 3-5mm is acceptable.

In some embodiments, in S4, the operation window is opened, the hanging slips are installed on the outer wall of the continuous pipe and close to the upper part of the tubing hanger, the continuous pipe is continuously lowered, the hanging slips fall into the tubing hanger, the continuous pipe is continuously lowered until the hanging weight of the injection head is zero, the continuous pipe has no sliding and no abnormal load, the continuous pipe is sheared by using the shearing flashboard of the four-flashboard blowout preventer, the continuous pipe is lifted, the load and the pressure change of the injection head are observed, and whether the shearing pipe is successful or not is verified.

In some embodiments, in S5, all equipment above the wellhead four-way joint is removed, the coiled tubing above the hanging slips is cut by a manual cutter, and the mouth of the upper end of the coiled tubing is chamfered to remove cut tubing necking and burrs.

In some embodiments, a liner tube No.1 and a liner tube No. 2 are installed in the gas production tree, the gas production tree is assembled, a main valve of the gas production tree is closed, and after a plug of a plug is knocked off through a pipeline of a ground high-pressure pump group, a well is shut in.

Through above-mentioned technical scheme, through prefabricated suspension slips before cutting the pipe, avoided the temporary potential safety hazard that causes of hanging of well head equipment.

Drawings

FIG. 1-schematic diagram of a coiled tubing completion string

FIG. 2-schematic diagram of wellhead assembly of coiled tubing completion string process

FIG. 3-schematic diagram of a wellhead flow of a coiled tubing completion string process

FIG. 4-schematic of a coiled tubing string of well cleanout tools

FIG. 5-schematic of a coiled tubing completion tool string

FIG. 6-schematic diagram of a process for installing a hanging slip

FIG. 7-schematic diagram of a coiled tubing wellhead hanging process

FIG. 8-construction of a continuous pipe hanging slip

FIG. 9-tubing hanger block diagram

FIG. 10-continuous pipe connector block diagram

FIG. 11-continuous pipe releasing structure

FIG. 12-Structure of coiled tubing packer

FIG. 13-construction of a continuous tube blanking plug

FIG. 14-wellhead gas production tree Structure

Description of the reference numerals

The well-logging tool comprises a continuous pipe, 2 parts of hanging slips, 2 parts of slip teeth, 2 parts of outer walls, 3 parts of oil pipe hanging devices, 3 parts of hanging device bodies, 3 parts of sealing assemblies, 4 parts of connectors, 4 parts of slip connections, 4 parts of rubber sleeve sealing devices, 5 parts of releasing devices, 5 parts of upper parts of pins, 5 parts of 3 parts of lower parts of pins, 6 parts of packers, 6 parts of rivets, 6 parts of annular sealing rubber sleeves, 7 parts of plugs, 7 parts of 1 parts of double-flap back pressure valves, 7 parts of plugs, 7 parts of 3 parts of screens, 7 parts of guide heads, 8 parts of injection heads, 9 parts of blowout preventer, 10 parts of four-blowout preventer, 11 parts of blowout preventer, 12 parts of pressure relief tee joints, 13 parts of operation windows, 14 parts of flat valves, 15 parts of well heads, 16 parts of motor heads, 17 parts of well logging tools, 18 parts of gas production trees, 18 parts of 1 number of liner tubes, and 18 parts of 2 parts of liner.

Detailed Description

The following describes specific embodiments of the present invention in detail with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.

Example 1

The scheme provides a construction method for coiled tubing wellhead suspension and well completion string plugging at bottom, wherein the construction method comprises the following steps:

s1, placing continuous pipe 1 operation equipment, installing wellhead equipment and testing pressure, wherein the wellhead equipment comprises an injection head 8, a blowout preventer 9, a four-ram blowout preventer 10, a blowout preventer 11, a pressure relief tee joint 12 and an operation window 13 from top to bottom, and the pressure relief tee joint is shown by referring to FIG. 2;

S2, penetrating the continuous pipe 1 through the injection head 8, installing a well logging tool string for well flushing, and descending the continuous pipe to a designed position to perform well flushing operation;

s3, lifting the continuous pipe 1 to the operation window 13, replacing a well entering tool string for a well completion string, arranging an oil pipe hanger 3 on the continuous pipe 1, and lowering the continuous pipe 1, so that the oil pipe hanger 3 falls into a wellhead four-way 15 and is set, and continuing to lower the continuous pipe 1 to the designed depth;

s4, opening the operation window 13, installing a hanging slip 2 on the continuous pipe 1, and lowering the hanging slip 2 into the continuous pipe 1 to enable the hanging slip 2 to fall into the oil pipe hanger 3, and cutting off the continuous pipe 1 after the hanging weight is continuously lowered to zero;

S5, removing wellhead equipment, and recovering the production tree 18, destroy and the blanking plug 7 to put into production.

Wherein the tubing hanger 3 is movably arranged on the coiled tubing 1, so that the tubing hanger 3 can be dropped onto the wellhead four-way joint 15 to be set when the coiled tubing 1 is lowered, and the hanging slips 2 are fixed on the coiled tubing 1, can be held in the tubing hanger 3 along with the downward movement of the coiled tubing 1, thereby hanging the coiled tubing 1 on the tubing hanger 3, and solving the risk brought by temporary hanging.

In this scheme, through prefabricated suspension slips before cutting the pipe, avoided the temporary potential safety hazard that causes of hanging of well head equipment.

Wherein, referring to fig. 8 and 9, slip teeth 2-1 are provided on the inner circumferential surface of the hanging slip 2, the outer circumferential surface of the hanging slip 2 is formed as a tapered surface from top to bottom, and the inner circumferential surface of the upper end of the tubing hanger 3 is formed as a tapered surface from top to bottom to accommodate and hang the hanging slip 2. As shown in fig. 8, the hanging slips 2 are engaged with the outer wall of the coiled tubing 1 through slip teeth 2-1, the outer peripheral surface is matched with the inner peripheral surface of the tubing hanger 3 so as to support the hanging slips 2 axially upwards through the tubing hanger 3, and after the coiled tubing 1 is connected with the hanging slips 2 through dead weight, the hanging slips 2 hang the coiled tubing 1 at a wellhead through the tubing hanger 3.

As shown in fig. 9, the tubing hanger 3 comprises a hanger main body 3-1 and a sealing assembly 3-2, and a sealing groove on the inner circumferential surface is matched with the outer circumferential surface of the hanging slips 2.

Wherein the hanging slip 2 comprises two half-pipe sections and a connector for detachably connecting the two half-pipe sections. As shown in fig. 8, the hanging slip 2 is mainly composed of two half-pipe parts and detachably connected by a connecting member, and by such a structure, the hanging slip 2 is easily installed on the continuous pipe 1.

Wherein, tubing hanger 3 with well head cross 15 sealing engagement, tubing hanger 3 passes through the jackscrew of well head cross 15 is fixed. Referring to fig. 14, tubing hanger 3 is disposed in wellhead four-way 15 with its outer periphery in sealing engagement with the inner periphery of wellhead four-way 15 to effect a seal. The wellhead four-way joint 15 is propped against the oil pipe hanger 3 through a radial jackscrew to realize relative fixation.

Wherein in S3, the replacing the logging tool string for the completion string includes opening the operation window 13, removing the logging tool string for well cleanout, installing a release 5, a packer 6, a packer 7 at the lower end of the coiled tubing 1, and hanging the tubing hanger 3 on the packer 6, as shown with reference to fig. 5. The release 5, the packer 6 and the plug 7 are completion tool strings, and after the well logging tool strings are disassembled through the operation window 13, the completion tool strings are installed at the lower end of the coiled tubing 1.

As shown in FIG. 11, the releasing device 5 adopts a mechanical releasing structure, and comprises an upper joint 5-1, a pin 5-2 and a lower joint 5-3 from top to bottom, and is arranged between a connector 4 and a packer 6, and when a tool string at the bottom end of the continuous pipe 1 encounters a card, the pin 5-2 is sheared by an upward lifting pipe column, so that the releasing operation of the continuous pipe 1 is realized.

As shown in fig. 12, the packer 6 is installed between the release 5 and the packer 7, and the continuous pipe 1 and the casing annular passage at the position of the packer 6 can be plugged by pressing in the pipe.

As shown in fig. 13, the blanking plug 7 adopts a function integration design, and comprises a double-flap back pressure valve 7-1, a plug 7-2, a screen 7-3 and a guide head 7-4 from top to bottom. The double-flap back pressure valve 7-1 is positioned at the front end of the plug 7-2, is restrained to be in an open state by the control sliding sleeve, and is thrown out by throwing a ball to start the double-flap back pressure valve 7-1, so that the pipe with pressure is lifted. The plug 7-2 is arranged at the tail end of the blanking plug 7, so that the blocking in the pipe is realized, and the blanking plug 7-2 is dropped by a pressing and shearing fixed pin pump to put into production. The screen 7-3 is positioned at the lower end of the functional area of the blanking plug 7, and the grid-shaped design is adopted, and the grid spacing can be adjusted according to the production requirement. The guide head 7-4 is positioned at the tail end of the blanking plug 7, is connected with the screen 7-3 and is fixed by the rivet.

In addition, in S3, after the continuing run-in of the coiled tubing 1 to the design depth, the tubing is pressurized so that the packer 6 sets in the design position, continuing to run-in the coiled tubing 1 to release a portion of the sling weight of the injector head 8. When the lower end of the coiled tubing 1 reaches the designed depth, the packer 6 is set on the casing by pressing into the coiled tubing 1, further lowering the coiled tubing 1, thereby releasing a portion of the sling weight of the injector head 8. The packer 6 can realize the plugging of a coiled tubing as a completion string to a downhole annulus, and can develop a specific production interval.

Further, the step S3 further comprises the steps of opening the pressure relief tee joint 12, controlling blowout through a surface throttling manifold, releasing pressure on the upper part of the packer 6, and filling packing fluid in an annular area so that a wellhead is pressureless. And injecting packing fluid into the annulus to protect the casing, the production pipe column and the wellhead from pressure safety operation.

In S3, the continuous pipe 1 is continuously lowered to the design depth, wherein the continuous pipe 1 is lowered at a speed of not more than 5m/min, observation equipment is operated when the lowering depth reaches 50m, the continuous pipe 1 is continuously lowered at a speed of 25m/min, an upward suspension weight test is carried out once every 500m in the lowering process, the speed is lowered to 10m/min when the lowering distance is 300m from the design depth, the speed is lowered to 5m/min when the lowering distance is 100m from the design depth, and the continuous pipe is lifted to the design depth after the lowering distance is 15m from the design depth. When the continuous pipe 1 is lowered, the pipe is lowered at a lower speed, then is lowered at a higher speed, and is subjected to a sling weight test, and finally is lowered at a lower speed, and the pipe is lowered to a depth exceeding the design depth and then is lifted up.

In S1, each ram opening and closing function of the four ram blowout preventer 10 is tested to be in a fully opened position, and then the injection head 8, the blowout preventer 9, the four ram blowout preventer 10, the pressure release tee 12, the lubricator 11, and the operation window 13 are installed and connected to a ground high pressure pump group pipeline to perform pressure test on the ground pipeline and wellhead equipment, respectively. Pressure testing is performed through the ground high pressure pump stack line (shown with reference to fig. 3) to detect the presence of a leak.

Furthermore, the pressure test is required to gradually increase the pumping pressure to 35MPa according to 10%, 50% and 100%, the pressure is stabilized for 10min, and the pressure drop is smaller than 0.7MPa, and if leakage is found, the pump is stopped immediately for pressure relief correction. When pressure test is carried out, the pressure is increased step by step, when the maximum pressure is reached, the corresponding pressure needs to be kept for a certain period of time, and if leakage exists, the pressure needs to be modified and maintained.

In S2, the coiled tubing 1 is passed through the injection head 8 and lowered to the position of the operation window 13, the operation window 13 is opened, the lower end of the coiled tubing 1 is chamfered, the connector 4 is installed, a tensile test is performed, a motor head 16 and a well-flushing tool 17 are installed at the lower end of the connector 4, the operation window 13 is closed, wellhead equipment is tested by a ground high-pressure pump group pipeline, the flat valve 14 is opened, the coiled tubing 1 is lowered to a designed depth, the ground high-pressure pump group pipeline is opened, and well-flushing operation on a designed area is completed, as shown in fig. 4. As shown in fig. 4, a motor head 16 and a through-well tool 17 are attached to the lower end of the connector 4. As shown in fig. 10, the connector 4 is designed in a packing element sealing manner, and comprises a slip connection 4-1 and a packing element sealing 4-2 from top to bottom, and is arranged at the bottom of the continuous pipe 1, so that the continuous pipe 1 can be combined and connected with a downhole tool.

Further, in the process of installing the connector 4, the lower end part of the continuous pipe 1 is subjected to 45-degree chamfering treatment, and the connector 4 is subjected to 15t tensile force test, wherein the displacement is smaller than 3-5mm, and the connector is qualified. The continuous tube 1 is chamfered to be connected with the connector 4, and the connector 4 is subjected to a tensile test to confirm the connection strength thereof.

In S4, the operation window 13 is opened, the hanging slips 2 are installed on the outer wall of the continuous pipe 1 and close to the upper portion of the oil pipe hanger 3, the continuous pipe 1 is continuously lowered, the hanging slips 2 fall into the oil pipe hanger 3, the continuous pipe 1 is continuously lowered until the hanging weight of the injection head 8 is zero, after the continuous pipe 1 has no sliding and no abnormal load, the continuous pipe 1 is sheared by using the shearing flashboard of the four-flashboard blowout preventer 10, the continuous pipe 1 is lifted, the load and the pressure change of the injection head 8 are observed, and whether the pipe shearing is successful or not is verified. After the hanging slips 2 are installed on the continuous pipe 1, the continuous pipe 1 is put down, so that the hanging slips 2 are hung on the oil pipe hanger 3, the continuous pipe 1 is continuously put down, the downward pulling force of the continuous pipe 1 on the injection head 8 is zero, the continuous pipe 1 is sheared, and the continuous pipe 1 above the shearing position is lifted to judge whether the continuous pipe 1 is sheared or not.

In S5, all the devices above the wellhead four-way joint 15 are removed, the continuous pipe 1 above the hanging slips 2 is cut off by using a manual cutter, and the pipe orifice at the upper end of the continuous pipe 1 is chamfered, so that pipe cutting necking and burrs are removed.

The method comprises the steps of installing a liner tube No. 1 and a liner tube No. 2 in a gas production tree 18, assembling the gas production tree 18, closing a main valve of the gas production tree 18, and closing a well by pressing and removing a plug 7-2 of a blanking plug 7 through a pipeline of a ground high-pressure pump group. Referring to fig. 14, the gas production tree 18 includes a multi-stage structure, in which liner pipes 18-1 and 18-2 are installed before the multi-stage structure is connected, such that liner pipes 18-1 and 18-2 are butted with coiled tubing 1, and then the multi-stage structure is connected, a main valve of the gas production tree 18 is closed, and a ground high-pressure pump group pipeline is pressed to open plug 7-2 of blanking plug 7, communicate reservoir with coiled tubing 1, and shut in.

Example two

In S3, the continuous pipe 1 is continuously lowered to the design depth, wherein the continuous pipe 1 is lowered at a speed of not more than 5m/min, observation equipment is operated when the lowering depth reaches 50m, the continuous pipe 1 is continuously lowered at a speed of 30m/min, an upward suspension weight test is carried out once every 500m in the lowering process, the speed is lowered to 15m/min when the lowering distance is 300m from the design depth, the speed is lowered to 5m/min when the lowering distance is 100m from the design depth, and the continuous pipe is lifted to the design depth after the lowering distance is 15m from the design depth. When the continuous pipe 1 is lowered, the pipe is lowered at a lower speed, then is lowered at a higher speed, and is subjected to a sling weight test, and finally is lowered at a lower speed, and the pipe is lowered to a depth exceeding the design depth and then is lifted up.

In S1, each ram opening and closing function of the four ram blowout preventer 10 is tested to be in a fully opened position, and then the injection head 8, the blowout preventer 9, the four ram blowout preventer 10, the pressure release tee 12, the lubricator 11, and the operation window 13 are installed and connected to a ground high pressure pump group pipeline to perform pressure test on the ground pipeline and wellhead equipment, respectively. Pressure testing is performed through the ground high-pressure pump set pipeline to detect whether leakage exists.

The following describes a construction method for hanging a coiled tubing wellhead and plugging a completion string under the bottom, which comprises the following steps:

In the first step, coiled tubing equipment is placed according to the recommended coiled tubing operation method for oil and gas wells, the original wellhead device is disassembled, and only the flat valve 14 is reserved. Each ram opening and closing function of the four ram blowout preventer 10 is tested to be in the fully open position. As shown in fig. 2, the injector head 8, blowout preventer 9, four-ram blowout preventer 10, pressure release tee 12, lubricator 11, and operation window 13 are mounted on the plate valve 14. As shown in figure 3, ground pipeline connection is carried out, and the pressure of the ground high-pressure pump group pipeline and the wellhead are respectively tested, the pressure test requirement is that the pump pressure is gradually increased to 35MPa according to 10%, 50% and 100%, the pressure is stabilized for 10min, the pressure drop is smaller than 0.7MPa, and the pressure relief and correction of the pump is immediately stopped when the leakage is found.

In a second step, the continuous tube 1 is passed through the injection head 8 down to the position of the operating window 13. The operation window 13 is opened, the lower end of the continuous tube 1 is chamfered, the connector 4 is installed, the lower end of the continuous tube 1 is chamfered at 45 degrees in the process of installing the connector 4, the continuous tube 1 is ensured to be vertical as much as possible, and the sealing ring is prevented from being damaged by installation. After the installation is finished, a tensile test is carried out, the tensile test is carried out for 15t, and the displacement is smaller than 3-5mm and is qualified. As shown in fig. 4, a motor head 16 and a flushing tool 17 are mounted at the lower end of the connector 4, the operation window 13 is closed, and pressure is tested on wellhead equipment through a surface high-pressure pump group pipeline. And (3) opening the flat valve 14, discharging the pipe to the designed depth, opening the ground pump set, completing the well flushing operation on the designed area, and ensuring the cleaning of the inner wall of the shaft.

And thirdly, lifting the continuous pipe 1 to the position of the operation window 13, and closing the flat valve 14. The operation window 13 is opened, the motor head 16 and the well-flushing tool 17 are disassembled, the releasing device 5, the packer 6 and the plug 7 are arranged at the lower end of the connector 4, the oil pipe hanger 3 is hung on the packer 6, and the well-flushing tool string is contained in the lubricator 11 as shown in fig. 5. And closing the operation window 13, and testing the pressure of the logging tool string through the high-pressure pump assembly pipeline on the ground. The flat valve 14 is opened, the tubing hanger 3 is slowly lowered into the wellhead four-way 15, and the jackscrews are fixed and sealed. The continuous pipe 1 passes through the oil pipe hanger 3 to continue to slowly drop the pipe, the speed of dropping the pipe is not more than 5m/min, the operation of the equipment is observed when the dropping depth is 50m, after the operation of the equipment is normal, the constant dropping speed is controlled to be normal, the speed is controlled to be 25m/min, the upward suspension weight test is carried out once every 500m in the dropping process, the pressure change of the continuous pipe 1 is noted in the dropping process, the speed is reduced to 10m/min when the pressure is 300m away from the design depth, the speed is reduced to 5m/min when the pressure is reduced to 100m away from the design depth, and the upward lifting is carried out after the pressure is 15m away from the design depth. The packer 6 is set at the designed position by pressing in the pipe, the continuous pipe 1 is continuously lowered to release 1/3 of the maximum suspension weight of the injection head 8, the packer 6 is confirmed to be in a normal working state, and sealing and packing at the annular position are realized. And opening the pressure relief tee joint 12 to control blowout through a ground choke manifold, releasing the pressure at the upper part of the packer 6, and injecting packing fluid after the pressure is released until the annular area is fully filled, wherein the wellhead is pressureless.

Fourth, as shown in fig. 6, the operating window 13 is opened, and the hanging slips 2 are installed on the outer wall of the coiled tubing 1 near the upper part of the tubing hanger 3. As shown in fig. 7, the coiled tubing 1 is run in, the hanging slips 2 fall into the inner groove of the tubing hanger 3, the hanging weight of the coiled tubing 1 is zero after the coiled tubing is continuously run in, the coiled tubing 1 has no slip, after the load has no abnormality, the four-ram blowout preventer 10 is used for shearing ram pipe, the pipe lifting is used for observing the load and pressure change of the injection head 8, and whether the pipe shearing is successful or not is verified.

And fifthly, removing all equipment above the wellhead four-way joint 15, cutting off the continuous pipe 1 above the hanging slips 2 by using a manual cutter, chamfering the pipe orifice at the upper end of the continuous pipe 1, and removing the necking and burrs of the cut pipe. A first liner tube 18-1 and a second liner tube 18-2 are arranged in the gas production tree 18, as shown in fig. 14, a gas production wellhead is restored, and a main valve of the gas production tree 18 is closed. And (3) pressing the pipeline of the ground high-pressure pump set until the wellhead pressure has sudden drop display, determining to break off the plug 7-2 of the blanking plug 7, and closing the well.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of individual specific technical features in any suitable way. The various possible combinations of the invention are not described in detail in order to avoid unnecessary repetition. Such simple variations and combinations are likewise to be regarded as being within the scope of the present disclosure.

Claims

1. A method of constructing a coiled tubing wellhead suspension and lower plugging completion string, the method comprising:

s1, placing continuous pipe (1) operation equipment, installing wellhead equipment and testing pressure, wherein the wellhead equipment comprises an injection head (8), a blowout preventer (9), a four-ram blowout preventer (10), a blowout preventer (11), a pressure relief tee joint (12) and an operation window (13) from top to bottom;

S2, penetrating the continuous pipe (1) through the injection head (8), installing a well logging tool string for well flushing, and discharging the continuous pipe to a designed position to perform well flushing operation;

S3, lifting the continuous pipe (1) to the operation window (13), replacing a well entering tool string for a well completion pipe string, arranging an oil pipe hanger (3) on the continuous pipe (1), and lowering the continuous pipe (1) so that the oil pipe hanger (3) falls into a wellhead four-way joint (15) and is seated, and continuing to lower the continuous pipe (1) to the designed depth;

S4, opening the operation window (13), installing a hanging slip (2) on the continuous pipe (1), and lowering the continuous pipe (1) to enable the hanging slip (2) to fall into the oil pipe hanger (3), and cutting off the continuous pipe (1) after the hanging slip continuously falls into the hanging weight to be zero;

s5, removing wellhead equipment, recovering the gas production tree (18), and turning on the blanking plug (7) for production.

2. The construction method of coiled tubing wellhead hanging, bottom-hole plugging completion string according to claim 1, wherein slip teeth (2-1) are provided on an inner peripheral surface of the hanging slips (2), an outer peripheral surface of the hanging slips (2) is formed as a tapered surface from top to bottom, and an inner peripheral surface of an upper end of the tubing hanger (3) is formed as a tapered surface from top to bottom to accommodate and hang the hanging slips (2).

3. A method of construction of a coiled tubing wellhead suspended, lower plugged completion string according to claim 2, characterised in that the hanging slips (2) comprise two half-tubular portions and a connector for detachably connecting the two half-tubular portions.

4. The method of construction of a coiled tubing wellhead suspended, bottom-hole plugging completion string according to claim 2, wherein the tubing hanger (3) is in sealing engagement with the wellhead four-way (15), the tubing hanger (3) being secured by a jackscrew of the wellhead four-way (15).

5. The construction method for hanging and plugging a completion string at the wellhead of a continuous pipe according to claim 2, wherein in S3, the replacement of the logging tool string for a completion string comprises opening the operation window (13), disassembling the logging tool string for flushing a well, installing a release (5), a packer (6), a packer (7) at the lower end of the continuous pipe (1), and hanging the tubing hanger (3) on the packer (6).

6. The method of construction of a coiled tubing wellhead suspended, bottomhole completion string according to claim 5, characterized in that in S3, after the running down of the coiled tubing (1) to design depth, the inside of the tubing is pressurized so that the packer (6) sets in design position, running down of the coiled tubing (1) to release a portion of the sling weight of the injector head (8).

7. The method of constructing a coiled tubing wellhead suspended, bottomhole completion string of claim 6, wherein S3 further comprises opening the pressure relief tee (12) and controlling blow-out via a surface choke manifold, releasing the packer (6) upper pressure, and filling the annulus with packing fluid so that the wellhead is pressureless.

8. The method for constructing a coiled tubing wellhead suspended, bottom-hole plugging completion string according to claim 2, wherein in S3, the continuing to run the coiled tubing (1) to the designed depth comprises running the coiled tubing (1) at a speed of not more than 5m/min, running observation equipment when the running depth reaches 50m, continuing to run the coiled tubing (1) at a speed of 25-30m/min, performing an upward lifting weight test every 500m in the running process, and reducing the speed to 10-15m/min when the running speed is 300m from the designed depth, reducing the running speed to 5m/min when the running speed is 100m from the designed depth, and lifting the running speed to the designed depth after the running speed is 15 m.

9. The method for constructing a coiled tubing wellhead suspended and bottom-hole plugging completion string according to claim 2, wherein in S1, each ram switching function of the four ram blowout preventer (10) is tested to be in a fully opened position, and then the injection head (8), the blowout preventer (9), the four ram blowout preventer (10), the pressure relief tee (12), the lubricator (11) and the operation window (13) are installed, and the pressure test of the surface pipeline and wellhead equipment is performed by connecting the four ram blowout preventer (10) to the surface high pressure pump group pipeline, respectively.

10. The construction method of the coiled tubing wellhead hanging and bottom hole plugging completion string according to claim 9, wherein the pressure test requirement is that the pump pressure is increased to 35MPa step by step according to 10%, 50% and 100%, the pressure is stabilized for 10min, the pressure drop is less than 0.7MPa, and if leakage is found, the pump is stopped immediately, and the pressure is relieved and corrected.

11. The construction method of the coiled tubing wellhead hanging and bottom-hole plugging completion string according to claim 1, wherein in the step S2, the coiled tubing (1) is passed through the injection head (8) and is lowered to the position of the operation window (13), the operation window (13) is opened, the lower end of the coiled tubing (1) is chamfered, a connector (4) is installed, tension test is carried out, a motor head (16) and a well flushing tool (17) are installed at the lower end of the connector (4), the operation window (13) is closed, wellhead equipment is tested by a ground high-pressure pump group pipeline, a flat valve (14) is opened, the coiled tubing (1) is lowered to a designed depth, the ground high-pressure pump group pipeline is opened, and well flushing operation on a designed area is completed.

12. The construction method of a coiled tubing wellhead suspension and bottom-hole plugging completion string according to claim 11, wherein in the process of installing the connector (4), the lower end part of the coiled tubing (1) is subjected to 45-degree chamfering treatment, and the connector (4) is subjected to 15 tons of tensile force test, wherein the displacement is less than 3-5 mm.

13. The construction method of a coiled tubing wellhead hanging and bottom-hole plugging completion string according to claim 1, wherein in the step S4, the operation window (13) is opened, the hanging slips (2) are installed on the outer wall of the coiled tubing (1) and close to the upper portion of the tubing hanger (3), the hanging slips (2) are continuously lowered into the coiled tubing (1) until the hanging weight of the injection head (8) is zero, after the coiled tubing (1) has no slip and no abnormal load, the cutting rams of the four-ram blowout preventer (10) are used for cutting the coiled tubing (1), the coiled tubing (1) is lifted, the load and the pressure change of the injection head (8) are observed, and whether the cutting is successful or not is verified.

14. The construction method of a coiled tubing wellhead suspension and bottom-hole plugging completion string according to claim 1, wherein in S5, all equipment above the wellhead four-way joint (15) is disassembled, the coiled tubing (1) above the suspension slips (2) is cut by a manual cutter, and a pipe orifice at the upper end of the coiled tubing (1) is chamfered to remove pipe cutting necking and burrs.

15. The construction method of the coiled tubing wellhead hanging and bottom hole plugging completion string according to claim 14, wherein a liner tube No. 1 (18-1) and a liner tube No. 2 (18-2) are installed in the gas production tree (18), the gas production tree (18) is assembled, a main valve of the gas production tree (18) is closed, and after a plug (7-2) of a plug (7) is knocked out through a ground high-pressure pump assembly pipeline, the well is closed.