RU2773834C9 - Control method of the lower column for runing - Google Patents

Abstract

FIELD: petroleum and gas industry.

SUBSTANCE: method for controlling the lower string for descent includes: closing the lower ball valve of the testing subsea Christmas tree assembly and the shutoff valving of the bypass valve, ensuring cutting of the rope/cable/flexible tubing; activating the emergency disconnection mechanism, ensuring the planned disconnection of the lower string for descent; closing the shutoff valving of the testing subsea Christmas tree assembly, ensuring emergency plugging of the borehole; closing the shutoff valving of the testing subsea Christmas tree assembly, shutoff valving of the bypass valve, followed by activating the emergency disconnection mechanism, ensuring emergency disconnection of the lower string for descent; activating the backup control of the lower string for descent using the internal hydraulic service line in case of loss of control signals supplied to the lower string for descent, ensuring activation of the emergency disconnection mechanism with disconnection thereof and disconnection of the tool for descent and ascent of the tubing suspension.

EFFECT: ensured increase in the safety in case of emergency disconnection of equipment as a result of emergency situations.

1 cl, 1 tbl, 3 dwg

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The present invention relates to the oil and gas industry. The lower string for running is designed for operation on jack-up floating drilling rigs, semi-submersible drilling rigs, drilling ships, fixed platforms as equipment for the development, testing and technological maintenance of subsea wells.

BACKGROUND OF THE INVENTION

Hydrocarbon fluids, such as oil or natural gas, are produced from a formation by drilling a wellbore into which various completion equipment is then installed to control and improve the efficiency of production of various fluids from the formation.

Running strings are used in the oil and gas industry for well completion and maintenance operations. In a subsea position, the running string extends between the surface vessel and the wellhead and is located inside the subsea BOP. The running string performs many functions, including providing barriers for well control and emergency release after sealing the well.

Well control and isolation in the event of an emergency shutdown is provided by a set of shut-off valves located in the wellbore of the running string, and the set of shut-off valves includes an assembly representing an underwater test Christmas tree. In addition, the running string is typically provided with at least one sliding joint to seal against the rams of the subsea BOP equipment. Typically, a tubing hanger tool adapter is installed at the lower end of the running string.

Typically, running strings operate in accordance with industry standard safety protocols. For example, a bypass valve may be designed to move to the closed position on loss of control signal. In some cases, this approach is not effective, for example, in the case where the loss of control signal does not necessarily represent a real risk of losing control of the well, in particular, when other well control barriers are healthy and working, or the loss of control is temporary, and the like. In addition, this can lead to spontaneous activation of one or another function of the running string, depending on pressure drops in emergency situations. At the same time, some valves may continue to function in the event of loss of control, which can lead to a genuine emergency in which it is necessary to completely close the valves.

A running string is known from the prior art (patent US 20170152723, publ. 06/01/2017), containing an upper pipe section extending from the surface of the vessel and ending with a ball-type stop valve having a cutting ability.

The disadvantages of this device are:

- the need to minimize the difference in diameter between the sealing surface of the adapter for the tubing hanger tool;

- a small range between the maximum allowable pressure in the cavity of the subsea blowout preventer and the control pressure of the backup control system;

- the need to take into account the combined load from the weight of the casing strings and the maximum control pressure in the cavity of the subsea blowout preventer;

- the need to take into account the minimum torque required to mechanically activate the emergency release mechanism;

- the possibility of involuntary operation of the system for disconnecting the tubing suspension tool, which requires means of its additional fixation.

The closest analogue of the proposed technical solution (prototype) is an underwater lower string for descent with autonomous emergency shutdown, disclosed in US 20160138355, publ. 05/19/2016, IPC E21B 33/035. The system described in said patent includes a subsea blowout preventer; a running string containing a plurality of shut-off valves, a block of valves and a measurement module, and a control system that functions in conjunction with the measurement module of the running string to provide autonomous disconnection of the running string in the valve assembly to block the flow of fluid above and below the valve assembly by closing the set valves when a predetermined condition detected by the measuring module occurs.

The proposed lower string for running during operations is installed inside the subsea blowout control equipment and forms a production shaft for accessing the well.

The running string is an integral part of the well access system. The running string functions can be controlled remotely using a control system located on the drilling platform.

The proposed invention is based on the task of improving the safety of installation of tubing suspension elements, the safety of testing connections, ensuring emergency disconnection of equipment and access of tools inside the well in case of emergency.

DISCLOSURE OF THE INVENTION

The technical result of the proposed invention is to ensure safety in the case of testing the seals between the tubing hanger and the body of the underwater Christmas tree; improving the safety of installation of a tubing hanger during well completion. In particular, this is ensured through the use of backup control, which uses the service line involved in the emergency disconnect. Also, the technical result can be attributed to the increase in the reliability of the control column for the descent; simplification of running string control with a backup control system; simplification of the design in comparison with the prototype and the release of pressure into the PVP cavity.

The technical result is achieved by the fact that in the lower string control method for running with redundancy of the safety system, including installation of a tubing hanger, carrying out a hydrocarbon production test, when cutting a cable/cable/coiled tubing, according to the invention:

- close the lower ball valve of the underwater test Christmas tree and shut-off valves of the bypass valve to ensure cutting of the cable/cable/flexible tubing;

- activating the emergency release mechanism to ensure planned release of the lower running string;

- pressurize/pressurise the closed stop valves of the underwater test X-mas tree in case of activation of the redundant safety system;

- pressurize/pressurize the closed shut-off valves of the underwater test X-mas tree, the shut-off valves of the bypass valve, followed by activation of the emergency disconnect mechanism to ensure emergency disconnection of the lower string for running;

- activate the backup control of the lower running string using the internal hydraulic service line, in case of loss of control signals to the lower running string, ensuring the activation of the emergency disconnect mechanism with its disconnection and disconnection of the tool for running and raising the tubing hanger.

The pressurization operation is a closure with the function of pressurizing to ensure the closing of the valves, which increases the safety level of operation of this equipment. Since there are no sensors in this section (there is no physical place in the system to place them), this is the most reliable way to ensure a strong closure of the valve. Such "additional pressure" is used by specialists in the world practice in the operations of lower string control for running.

At the same time, the lower string for running with redundancy of the safety system is installed in the underwater blowout prevention equipment and contains an internal hydraulic service line and installed in series with the formation of a production shaft:

bypass valve including pressure compensation system,

shear pipe,

emergency release mechanism

subsea test Christmas tree, including shut-off valves, in the form of a lower ball valve and an upper ball valve with an automatic shut-off device, and an emergency disconnect mechanism, a tool adapter for lowering and raising a tubing hanger.

The emergency release mechanism is configured to separate the running string into two parts.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, as well as its other aspects and characteristics, the description is given with reference to the accompanying drawings, where:

in FIG. 1 is a schematic diagram of the lower running string hydraulic diagram showing the functional state of the lower running string during the main mode of operation;

in FIG. 2 is a schematic representation of a running string;

in FIG. 3 is a schematic representation of a running string installed in a subsea BOP in a coupled state;

In Table 1 - symbols on the hydraulic circuit according to Fig. one.

IMPLEMENTATION OF THE INVENTION

The lower string for running is an integral part of the well access system, installed in the subsea BOP equipment and contains a bypass valve 1, a shear branch pipe 2, an underwater test Christmas tree 3, an adapter 4 of a tool for lowering and raising the tubing hanger, a production shaft the lower column for the descent 5 (Fig. 1).

The term "lower running string" is used throughout this application, which generally means that there is no upper isolation valve in the running string. An example of a top isolation valve is described in RU 2704161, publ. 24.10.2019.

Bypass valve 1 includes installed in series: an adapter 6 for connecting the running string with the riser; stop valves 7; compression fitting 8.

Underwater test tree fittings include shut-off valves in the form of an upper ball valve 9 and a lower ball valve 10, each of which is equipped with an emergency shutdown device, as well as an emergency disconnect mechanism 11.

The emergency release mechanism 11 is configured to be activated in case of closing the bypass valve 1, closing the underwater test X-mas tree and opening the pressure compensation system 12 (Fig. 2) located in the bypass valve, ensuring the separation of the running string into two parts: the first part, including bypass valve 1, shear pipe 2 and the emergency release mechanism 11 itself; and a second part including an underwater test tree 3 and a tool adapter 4 for running and retrieving a tubing hanger (FIG. 1).

In FIG. 2 is a schematic diagram of the hydraulic control system of the running string, which illustrates the control lines with hydraulic distributors installed in them (symbols of the elements of the hydraulic control system diagram are shown below).

The control lines include: a first control line 13 for controlling the operation (opening) of the bypass valve 1 and controlling the operation (closing) of the emergency release mechanism 11; a second control line 14 for controlling the operation (closing) of the bypass valve 1 and controlling the operation (opening) of the emergency release mechanism 11; control line 15 for closing the underwater test tree 3.

Wherein, the first control line 13 for controlling the operation of the bypass valve 1 and controlling the operation of the emergency release mechanism 11 controls the closing of the bypass valve 1 and the release of the emergency release mechanism 11; and the second control line 14 controls the opening of the bypass valve 1 and the attachment of the emergency release mechanism 11 .

In addition to the closing line 15 of the underwater test Christmas tree 3, there are also: a control line 16 for opening the upper ball valve 9, a control line 17 for opening the lower ball valve 10; control line 18 of the bleed valve of the upper ball valve 9; control line 19 of the bleed valve of the lower ball valve 10; line 20 to disable backup control.

Additionally, in the diagram of Fig. 2 also shows a chemical injection line 21 located between the upper ball valve 9 and the lower ball valve 10.

Additionally, in the diagram of Fig. 2 also shows the lines used in installing and retrieving a tubing hanger using a running and retrieving tool in a subsea tree 3: running and retrieving tool attachment line 22; line 23 checking the closure (attachment) of the tool for descent and ascent; line 24 disconnect tool for descent and recovery; line 25 for connecting the tubing hanger to the underwater Christmas tree 3; line 26 for checking the connection of the tubing hanger; line 27 disconnecting the tubing hanger.

These lines are used in the installation and retrieval of the tubing hanger and are shown only to assist those skilled in the art in understanding the installation and retrieval of the tubing hanger.

Further, the subsea BOP equipment includes at least the following: one annular blowout preventer, in the present embodiment, the bottom annular blowout preventer 28 (FIG. 3) at which the bypass valve 1 is installed, the upper shear rams 29 and the lower shear rams 30 , and a group of tubular ram preventers.

Additionally, in the present embodiment, the subsea blowout preventer comprises a series of tubular rams including: an upper tubular ram 31, a middle tubular ram 32, and a lower tubular ram 33 installed below the upper shear rams 29 and the lower shear rams 30.

The running string in the assembled state is made with the possibility of installation in the cavity of the underwater blowout prevention equipment in such a way that the swage pipe 8 is located opposite the lower annular preventer 28, the shear pipe 2 is located opposite the upper shear rams 29 and the lower shear rams 30, the test underwater Christmas tree 3 is located opposite the upper ram preventer 31 and the middle ram preventer 32; tool hanger adapter 4 for running and retrieving the tubing hanger is located opposite the lower ram preventer 33.

Below the adapter 4 of the tool for lowering and raising the tubing hanger is the mouth of the Christmas tree.

The lower string control method for descent with redundancy of the safety system includes the following operating modes of the lower string for descent:

1. Installation of a tubing hanger and test production of hydrocarbons (this is also the normal operation of the lower running string).

2. When the well is completed, if replacement is necessary, the tubing hanger and the tubing are removed during the well workover.

3. Cutting the rope/cable/flexible tubing using the bottom ball valve 10 in case of an emergency.

4. Scheduled disconnection of the lower running string using the emergency release mechanism 11 (this is also the regular disconnection of the lower running string).

5. Emergency well killing.

6. Quick emergency release of the lower string for descent in case of an emergency.

7. Standby control of the running string.

In more detail, these modes of operation of the lower string for the descent are presented below with reference to the drawings.

In the drawings, the lines involved in the mode of operation are shown slightly thickened.

1. Installation of a tubing hanger and test production of hydrocarbons.

When installing the tubing hanger while running the riser string, the following hydraulic lines are energized:

- line 27 to turn off the backup control;

- line 14 for opening the bypass valve and attaching the emergency release mechanism 11;

- line 16 for opening the upper ball valve 9;

- line 17 for opening the lower ball valve 10;

- line 18 of the bleed valve of the upper ball valve 9;

- line 19 of the bleed valve of the lower ball valve 10;

- line 25 for connecting the suspension of the tubing;

- line 22 for connecting the tool for descent and ascent.

The pressure in each of the listed lines is 34.5 MPa.

In the adapter 4 of the tool for lowering and raising the tubing hanger, there are four hydraulic valves: the first hydraulic valve 34, the second hydraulic valve 35, the third hydraulic valve 36 and the fourth hydraulic valve 37.

In this functional state, the lower ball valve 9 and the upper ball valve 10 of the underwater test tree valve 3 and the shut-off valve 7 of the bypass valve 2 are open.

When control pressure is applied to line 20 of shutdown of the backup control, the fifth hydraulic valve 38 in the bypass valve 1 is in the right position, due to which it is possible to close the shut-off valve 7 of the bypass valve 1 and disconnect the emergency release mechanism 11 when pressure is released to the line 13 of closing the bypass valve 1 /disconnect mechanism 11 for emergency release.

When the bypass valve 1 is open, the pressure compensation system 12 and the mechanically associated hydraulic valve 39 are in the closed position, closing the circuit of the line 14 leading to the disconnection of the emergency disconnect mechanism 11.

If there is pressure in the line 20 to turn off the backup control, the control valves 34, 36 and 37 are in the left position, and the control valve 35 is in the right position, which excludes the activation of the lower string functions for running when the pressure in the annulus rises, which can lead to the activation of the backup control system, namely, to start the activation sequence of closing all ball valves and disconnecting the emergency disconnect mechanism 11.

After installation of the tubing hanger and before starting test production, it is necessary to press out in order to check the connection between the tubing hanger and the underwater test Christmas tree 3. To do this, pressure is applied to the line 26 for checking the connection of the tubing hanger, while the control pressure in said line 26 is 69.0 MPa.

When carrying out test production of hydrocarbons from the well after installing the tubing hanger and tubing, it is necessary to maintain a pressure of 34.5 MPa in the following lines:

- lines 20 to turn off the backup control;

- line 14 for opening the bypass valve 1 and attaching the emergency release mechanism 11;

- line 16 for opening the upper ball valve 9;

- line 17 for opening the lower ball valve 10;

- lines 18 of the bleed valve of the upper ball valve 9;

- lines 19 of the bleed valve of the lower ball valve 10;

- lines 25 for connecting the suspension of the tubing;

- lines 22 for connecting the tool for descent and ascent.

2. Extraction of the tubing hanger and tubing during well workover.

When removing the tubing hanger and tubing during a well workover, the following hydraulic lines are powered:

- lines 20 to turn off the backup control;

- line 14 for opening the bypass valve 1 and attaching the emergency release mechanism 11;

- line 16 for opening the upper ball valve 9;

- line 17 for opening the lower ball valve 10;

- lines 18 of the bleed valve of the upper ball valve 9;

- lines 19 of the bleed valve of the lower ball valve 10;

- lines 25 for connecting the suspension of the tubing;

- lines 22 for connecting the tool for descent and ascent.

The pressure in each of the listed lines is 34.5 MPa.

In this functional state of the system, both ball valves 9, 10 of the underwater test fittings 3 and shutoff valves 7 of the bypass valve 1 are open.

When the bypass valve 1 is open, the pressure compensation system 12 and the associated sixth hydraulic valve 40 are in the closed state, closing the circuit of the first control line 13 to control the closing of the bypass valve 1 and the disconnection of the emergency release mechanism 11.

When the pressure in the line 20 shutdown of the backup control valves 34, 35, 36, 37, placed in the tool adapter 4 for lowering and lifting, are: the first, third and fourth valves 34, 36, 37 are in the left position, the second valve 35 is in the right position, which excludes the activation of the functions of the lower string for running in case of an increase in pressure in the annulus, which can lead to the activation of the backup control.

3. Cutting wire/cable/flexible tubing using bottom ball valve.

If it is necessary to cut the cable/cable/flexible tubing, the upper ball valve 9 of the underwater test tree valve 3 is kept open when pressure is applied to the closing line 15 of the underwater test tree valve 3 (closing the upper ball valve 12 and the lower ball valve 10) .

It should be noted that in this case, the control pressure in the opening line 16 of the upper ball valve 9 must be more than 69.0 MPa, since with equal pressures in the opening and closing lines, the springs of the emergency closing machine will slowly close the upper ball valve 9, which can lead to rope/cable/flexible tubing jamming in the production hole of the lower string for running 5.

The following hydraulic lines must be pressurized before activating the cut wire/cable/coiled tubing mode using the bottom ball valve 10:

- line 20 to turn off the backup control, while the pressure in line 20 should be 34.5 MPa;

- line 14 for opening the bypass valve / connecting the emergency disconnect mechanism, while the pressure in line 14 should be 34.5 MPa;

- line 16 for opening the upper ball valve, while the pressure in line 16 should be 34.5 MPa;

- line 17 for opening the lower ball valve, while the pressure in line 17 should be 34.5 MPa;

- line 18 of the bleed valve of the upper ball valve, while the pressure in line 18 should be 34.5 MPa;

- line 19 of the bleed valve of the lower ball valve, while the pressure in line 19 should be 34.5 MPa;

- line 15 for closing the underwater test X-mas tree, while the pressure in line 15 should be 69.0 MPa;

- line 25 for connecting the suspension of the tubing, while the pressure in line 25 should be 34.5 MPa;

- line 22 for connecting the tool for lowering and raising, while the pressure in line 22 should be 34.5 MPa.

For cutting, the following sequence of steps is performed:

Step 1. Apply a pressure of 69.0 MPa to the opening line 16 of the upper ball valve 9 and isolate the line 16 from the pressure source of the control system located on the drilling rig.

Stage 2. The pressure is maintained in the opening line 16 of the upper ball valve 9 until the cutting is completed, while in the case of the gradual closing of the upper ball valve 10 under the action of the springs of the emergency closing machine, the pressure in the line 16 of opening the upper ball valve 9 should be increased by 5-10 percent.

Step 3. Apply a pressure of 34.5 MPa to the opening line 17 of the lower ball valve 10 and isolate the line 17 from the pressure source of the control system located on the drilling rig; while Stage 1 can be performed simultaneously with Stage 2.

Step 4. Tighten the cable/cable/coiled tubing using systems located on the drilling rig.

Step 5. Release pressure from line 19 of the bleed valve of the lower ball valve 10;

Stage 6. The pressure is released from the line 17 of opening the lower ball valve 10 to 0 MPa.

Step 7. A pressure of 69.0 MPa is applied to the closing line 15 of the underwater test X-mas tree 3, as a result of which the cable/cable/flexible tubing is cut using the lower ball valve 10.

Step 8. Remove the cut cable/cable/flexible tubing.

Step 9. The pressure is released from the closing line 15 of the underwater test X-mas tree from 3 to 0 MPa.

Step 10. The pressure is released from the opening line 16 of the upper ball valve 9 to 0 MPa.

Step 11. A pressure of 69.0 MPa is applied to the closing line 15 of the underwater test X-mas tree 3 to confirm the closing of the upper and lower ball valves 9, 10, after which the pressure is released from the line 15 to 0 MPa.

4. Planned release of the lower descent string using the emergency release mechanism.

During planned, i.e. non-emergency, disconnection of the running string, the following lines are powered:

- line 13 for closing the bypass valve 1 / disconnecting the emergency release mechanism 11, while the control pressure in the line should be 34.5 MPa;

- line 15 for closing the underwater test X-mas tree 3, while the control pressure in the line should be 69.0 MPa.

Before disconnecting the upper part of the riser string from the underwater test tree valve 3, the upper and lower ball valves 9, 10 must be closed, and then the shut-off valve 7 of the bypass valve 1 must be closed.

After closing the stop valves 7 of the bypass valve 1 by applying pressure to the line 13 of closing the bypass valve 1 / disconnecting the emergency release mechanism 11 through the line of the seventh hydraulic valve 41, mechanically connected (the mechanical connection is provided by pressure applied to the elements of the pressure compensation system, such as a glass, spring) with the shutoff valve 7 drive of the bypass valve 1, the pressure compensation system is activated and the excess locked pressure in the cavity between the shutoff valve 7 of the bypass valve 1 and the closed upper ball valve 9 of the underwater test Xmas tree is vented into the annulus. 3 After equalization of pressures, the hydraulic signal from the control line goes to the emergency disconnect mechanism 11 and the upper part of the riser string is disconnected from the subsea test tree 3.

To disconnect the emergency release mechanism 11, the following sequence of steps is performed:

Stage 1. The pressure in the line 17 of the opening of the lower ball valve 10 and the line 19 of the bleed valve of the lower ball valve 10 is released to 0 MPa.

Step 2. Apply a pressure of 69.0 MPa to the closing line 15 of the subsea test tree 3 to ensure that the lower ball valve 10 is closed; after which the pressure in the line is released from 15 to 0 MPa.

Stage 3. The pressure in the line 16 of the opening of the upper ball valve 9 and the line 18 of the bleed valve of the upper ball valve 9 is released to 0 MPa.

Step 4. Apply a pressure of 69.0 MPa to the closing line 15 of the underwater test tree 3 to ensure that the top ball valve 9 is closed; after which the pressure in the line is released from 15 to 0 MPa.

Step 5. Depressurize line 20 to turn off the backup control and line 25 to connect the suspension of the tubing.

Step 6. The pressure in the line 14 of opening the bypass valve 1/attachment of the mechanism 11 of emergency disconnection is released to 0 MPa.

Step 7. Apply a pressure of 34.5 MPa to the line 13 to close the bypass valve/disconnect the emergency release mechanism 11 and isolate the line 13 from the pressure source using a shut-off valve in the control system on the drilling rig.

5. Emergency well killing.

It should be noted that during the downhole operations, all shutoff valves, namely the shutoff valve 7 of the bypass valve 1, the upper ball valve 9 and the lower ball valve 10, of the lower running string are open, including in case of activation of emergency well killing.

In case of emergency well killing, the following sequence of stages is implemented.

Step 1. Release pressure from the opening line 17 of the lower ball valve 10 through the bleed valve of the eighth valve 42 into the annulus; a pressure of 69.0 MPa is applied to the closing line 15 of the underwater test X-mas tree 3, which ensures the closing of the lower ball valve 10 of the underwater test X-mas tree 3.

Step 2. The pressure is released from the opening line 16 of the upper ball valve 9 through the bleed valve 43 into the annulus.

6. Quick emergency release of the lower string for descent.

When the quick emergency disconnect is activated, the upper and lower ball valves 9, 10 of the underwater test Christmas tree 3 are closed, after which the following sequence of steps is performed to activate the quick emergency disconnect of the lower running string:

Step 1. The pressure is released in the line 15 of closing the underwater test X-mas tree 3, in the line 20 of turning off the backup control, in the line 25, the connection of the tubing hanger.

Step 2. A pressure of 34.5 MPa is applied to the line 13 of closing the bypass valve 1/detachment of the emergency release mechanism 11 to activate the emergency release mechanism 11 and subsequently disconnect the top of the riser string.

Step 3. Remove the running string, disconnected above by the emergency release mechanism 11.

To connect the upper part of the riser column, the following sequence of steps is carried out:

Stage 1. Bleed to 0 MPa overpressure in the line 13 closing the bypass valve 1/detach mechanism 11 emergency release.

Step 2. The lower string is lowered to run down through the blowout preventer system, while the pressure in the line 14 of the opening of the bypass valve 1 / connection of the emergency disconnect mechanism 11 is 34.5 MPa, until it touches the connection interface (not shown in the drawings) on the top of the subsea test tree fitting 3, and after pressure is applied, line 14 must be isolated from the pressure source by a shut-off valve in the control system located on the drilling rig.

Step 3. Release the pressure from the opening line 14 of the bypass valve 1/connection of the emergency release mechanism 11 to 0 MPa.

Step 4. Apply a pressure of 34.5 MPa to the line 13 to close the bypass valve 1/disconnect the emergency release mechanism 11 and isolate the line 13 from the pressure source of the control system located on the drilling rig.

Step 5. Rotate the riser string until the grooves of the emergency release mechanism 11 and subsequent descent are aligned.

Step 6. The pressure is released from the line 13 of closing the bypass valve 1/disconnection of the emergency release mechanism 11 to 0 MPa.

Step 7. Apply a pressure of 34.5 MPa to the opening line 14 of the bypass valve 1 / attach the emergency disconnect mechanism 11, isolate the line 14 from the pressure source of the control system located on the drilling rig, and pull the riser string up to check the connection.

Step 8. A pressure of 34.5 MPa is applied to the running and retrieval tool connection line 22 and the tubing hanger connection line 25 .

Step 9. A pressure of 69.0 MPa is applied to the closing line 15 of the underwater test X-mas tree 3 and the line 15 is isolated from the pressure source by a shut-off valve in the control system located on the drilling rig.

Step 10. Hydrostatic testing of the riser string is carried out above the upper ball valve 9 of the subsea test Christmas tree 3.

Step 11. The pressure in the closing line 15 of the underwater test Xmas tree is bled from 3 to 0 MPa.

Step 12. Equalize the pressure above and below the top ball valve

9 underwater test tree 3 using a chemical injection line 21.

Step 13. A pressure of 34.5 MPa is applied to the opening line 16 of the upper ball valve 10 and the line 16 is isolated from the pressure source by a shut-off valve in the control system located on the drilling rig.

Step 14. Equalize the pressure above and below the lower ball valve 10 of the subsea test tree 3 by applying pressure to the production wellbore of the lower running string 5.

Step 15. A pressure of 34.5 MPa is applied to the opening line 17 of the lower ball valve 10 and the line 17 is isolated from the pressure source by a shut-off valve in the control system located on the drilling rig.

7. Redundant running lower string

Lower string back-up control is used when there is a loss of control pressure in the lower string umbilical (in all lines, including the back-up control shutdown line 20) and the following functions cannot be performed:

- disconnection of the mechanism 11 of emergency disconnection;

- disconnection of the tool for lowering and raising the tubing hanger from the tubing hanger.

These functions are provided through the use of the line 20 to disable the backup control, namely, in normal mode, the line 20 to disable the backup control is pressurized, the default backup control is disabled. When line 20 is depressurized, the back-up control is activated to provide the above functions.

The principle of operation of the backup control is that to activate the above functions, pressure is supplied to the cavities of the subsea BOP equipment through the killing lines 44 and throttling 45 (Fig. 3), and then from the cavities of the subsea BOP equipment to the production shaft 5, which leads to rupture of the diaphragms in the adapter 4 of the running and retrieval tool and switching of the hydraulic valves inside the hydraulic control system of the running string.

The lower string functions are activated by pressurizing the subsea BOP cavity through the kill and choke lines, causing the diaphragms in the running and retrieval tool adapter to burst and switching valves within the lower string hydraulic system.

In this case, by switching the hydraulic valves (related to the standby control), the isolation of the corresponding umbilical lines is ensured.

To disconnect the tool for running and retrieving, it is necessary to apply pressure to the lower cavity A (Fig. 3) under the closed lower ram preventer 33.

Activation of this function is provided by applying pressure to the cavity of the subsea BOP equipment through the kill lines 44 and throttling 45 of the subsea BOP equipment, which leads to a rupture of the membranes in the adapter 4 of the running and retrieval tool and switching the hydraulic valves inside the hydraulic system of the lower string for running (Fig. 3 ).

Thus, the control pressure will switch the fourth valve 37 and break through the first membrane 46.

Then the control hydraulic signal will go to the third valve 36 and switch it to the right position.

From the third hydraulic valve 36, control pressure will be supplied to perform the detachment of the tool for lowering and raising.

To disconnect the emergency release mechanism 11, it is necessary to apply pressure to the upper cavity B (Fig. 3) between the buried lower annular preventer 28 and the lower ram preventer 33. The control pressure will switch the first hydraulic valve 34 and break through the second membrane 47.

The second hydraulic distributor 35, due to the drive spring, in the absence of pressure in the line 20 of switching off the backup control, switches to the left position, opening the circuit to the upper part of the lower string for descent through the service line C (Fig. 2).

Service line C is the internal hydraulic line of the lower running string, used in case of activation of the backup control when pressure is applied through the upper cavity B (Fig. 3).

At the top of the lower running string, the control pressure supplied through the second valve 35 via the service line C switches the valve 38 to the left position and thereby isolates the closing line 13 of the bypass valve 1/detachment of the emergency release mechanism 11.

At the same time, the shutoff valve 7 of the bypass valve 1 is first closed, then with the help of the seventh hydraulic valve 41, the pressure compensation system 12 and the sixth hydraulic valve 40 associated with it are opened, while bleeding into the annulus of excess pressure locked between the closed shutoff valve 7 of the bypass valve valve 1 and closed top ball valve 9.

After equalization of pressures, the control hydraulic signal is supplied to the drive of the emergency disconnect mechanism 11 and the riser string and the upper part of the lower running string as part of the bypass valve 1 are disconnected from the underwater test X-mas tree 3.

The following abbreviations are used in the drawings for convenience:

KDS - column for descent;

PC - bypass valve 1;

HZ PK - hydraulic cylinder of the bypass valve 1;

SKD - pressure compensation system 12;

HZ SKD - hydraulic cylinder system 12 pressure compensation;

MEO - emergency release mechanism 11;

ГЦ МЭО - hydraulic cylinder of mechanism 11 of emergency disconnection;

VShK - top ball valve 9;

HZ VSHK - hydraulic cylinder of the upper ball valve 9;

NShK - lower ball valve 10;

HZ NShK - hydraulic cylinder of the lower ball valve 10;

PIFA - underwater test X-mas tree 3;

IDSP - tool for descent and ascent;

PPVO - underwater blowout prevention equipment;

D1-D4 - Pressure sensors.

To explain the symbols of the hydraulic scheme of the lower string for running with redundant safety system, Table 1 is given.

In the context of the present description, the numerals "first", "second", "upper", "lower", etc. are only used to indicate the difference between the nouns they refer to, not to describe specific relationships between those nouns.

It should be understood that the present description is not intended to determine the scope of protection of the proposed technical solution, the purpose of the description is to provide an understanding of the proposed technical solution. The described embodiment is not exhaustive, and it will be obvious to those skilled in the art that other embodiments of the proposed technical solution are possible.

Claims (11)

Control method for lower string for running, installed in subsea BOP equipment and containing those installed in series to form a production wellbore: bypass valve including pressure compensation system, shear tube, emergency release mechanism underwater test tree fittings, including shut-off valves, in the form of a lower ball valve and an upper ball valve, and an emergency disconnect mechanism, a tool adapter for running and retrieving a tubing hanger, the lower running string including an internal hydraulic service line; the emergency release mechanism is configured to separate the running string into two parts; wherein the method comprises the steps of: close the lower ball valve of the underwater test Christmas tree and shut-off valves of the bypass valve to ensure cutting of the cable/cable/flexible tubing; activating the emergency release mechanism to ensure planned release of the lower running string; carry out the compression of shut-off valves of the underwater test X-mas tree with the provision of emergency killing of the well; pressurizing shut-off valves of the underwater test Christmas tree, shut-off valves of the bypass valve, followed by activation of the emergency disconnect mechanism to ensure emergency disconnection of the lower string for running; activating the backup control of the lower running string using the internal hydraulic service line in case of loss of control signals to the lower running string to activate the emergency disconnect mechanism with its disconnection and disconnection of the tool for running and raising the tubing hanger.

Images