GB2275069A

GB2275069A - Down hole installations

Info

Publication number: GB2275069A
Application number: GB9401847A
Authority: GB
Inventors: Edward Roderick Bryan Moore
Original assignee: Baker Hughes Ltd
Current assignee: Baker Hughes Ltd
Priority date: 1993-02-03
Filing date: 1994-02-01
Publication date: 1994-08-17
Anticipated expiration: 2014-02-01
Also published as: GB2275069B; GB9302091D0; GB9401847D0

Abstract

In use a motor 9 drives a pump 11 to force oil and gas up the tube 7. The motor and pump can be raised partially within the liner 2 or removed from the liner 2. A packer 8 remains in the liner when the motor and pump are raised and kill fluid may be added to isolate the region below the packer from the region above. The packer 8 may incorporate a valve to isolate the producing zone when the pump is removed. <IMAGE>

Description

DOWN HOLE INSTALLATIONS The present invention relates to a down hole installation, a method of operating a down hole installation and a kit of parts arranged to be used in a down hole installation.

In wells which are used to produce water or gas and oil it is required, from time to time, to prevent the fluid from leaving the rock formation and moving up the string or mixing with other fluid in the string. To achieve the control on the gas and oil a "kill" fluid is dumped on top of the gas and oil. If the pressure exerted by the kill fluid on the fluid being extracted is not balanced carefully then the kill fluid can contact the rock formation and potentially damage the formation.

In a known arrangement incorporating a pump and motor down the hole for powering the gas and oil upwards, the pump and motor are located towards the bottom of the well and a packer is located above the assembly to isolate the pump and motor and the production area from the remainder of the bore and to restrict the gas and oil to that lower area. A conduit is provided which extends from the top of the well, through the packer, to the pump and motor in order to transport gas and oil to the surface.

Accordingly flow rate is restricted to the internal diameter of the conduit. When required, kill fluid is passed down that conduit into the region of the pump and water and the rock formation.

As any kill fluid that has to be located is supplied through the pump to the area beneath the packer adjacent to the rock formation, in order to suppress the pressure and achieve the required balance, the kill fluid must have a considerable density making that fluid expensive, and difficult and time consuming to remove. Furthermore, the kill fluid sinks to the bottom of the well and contacts the rock formation. Such contact can have a damaging effect on subsequent flow of oil and gas out of the formation into the well.

In addition, during a workover, for instance to replace a faulty pump or motor, the pump and motor and also the packer must all be removed from the well. When the packer is removed from its location in the well it is necessary to insert a new plug. Accordingly if there is a cable problem 10 feet below the top of the well then kill fluid has to be dumped and the complete length of cable as well as the motor, pump and packer must be withdrawn. It is then necessary to install a new pumping system complete with packer. Thus production is interrupted for a long time and thousands of feet of equipment is withdrawn despite the fact that the fault is only 10 feet deep.

According to one aspect of the present invention, a down hole installation includes a passage leading from a fluid source, a pump located in the passage and obstruction means located in the passage, the obstruction means being arranged to remain in the passage when the pump is raised.

With such an installation, when it is required to raise the pump, either partially or completely out of the passage, it is not necessary to have kill fluid at a location where contact with the rock formation is risked.

This is because either the obstruction means which remains can prevent fluid from the source from rising up within the passage or because kill fluid can be added which will remain on the other side of the obstruction means to the fluid source.

The obstruction means may be located closer to the fluid source than the pump.

The pump may be arranged to be in fluid communication through the obstruction means with the fluid source.

The pump may be arranged to move axially along the passage to a limited extent whilst the pump is in communication with the fluid source.

When the pump is raised, the obstruction means may be arranged to be sealed with respect to fluid flow in at least one direction, and preferably two directions.

The pump may be arranged to be placed in fluid communication with the fluid source as the pump is moved towards the fluid source. The pump may include a portion which is arranged to pierce the obstruction means in order to place the pump in fluid communication with the fluid source.

The fluid source may be arranged to be sealed from the space on the other side of the obstruction means from the fluid source when the pump is raised.

The obstruction means may include a valve and may comprise a one-way valve. The valve may be hydraulically operable and may be remotely operable. The valve may be arranged to require a greater force to open than it does to close.

The installation may include a motor located within the passage arranged to power the pump. The motor may be arranged adjacent to the pump and the motor may comprise part of a common assembly with the pump.

The arrangement may include a valve operable to seal the inlet of the pump.

The arrangement may include a valve operable to vent excess fluid pressure from beneath the obstruction means.

The pump may be arranged to be moved into position by an elongate portion. The elongate portion may comprise a conduit. Fluid may be arranged to flow from the pump within the conduit. Fluid may be arranged to flow from the pump around the elongate portion.

The pump may be arranged to be suspended by the elongate portion.

The elongate portion may be of substantial length and may be of a length equal at least to the depth of the passage.

The elongate portion may comprise a single member.

The elongate portion may be flexible. The elongate portion may be arranged to be unwound when moving the pump downwardly along the passage.

According to a further aspect of the present invention a method of operating a down hole installation comprises raising a pump located in a passage of the installation leading from the fluid source and leaving obstruction means in the passage, beneath the pump.

The method may comprise adding kill fluid to the passage before the pump is raised. The method may comprise arranging for the kill fluid to be located above the obstruction means.

The method may comprise locating the obstruction means in the passage before the pump is located in the passage.

The method may comprise actuating a valve in the obstruction means to prevent fluid flow through the obstruction means towards the fluid source.

According to another aspect of the present invention, a kit of parts arranged to be used in a down hole installation includes obstruction means arranged to be located in a passage leading from a fluid source and a pump arranged to be raised from a fluid source whilst the obstruction means remains in place.

The present invention includes any combination of the herein referred to features or limitations.

The present invention may be carried into practice in various ways but two embodiments will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a schematic side section of a completion string showing a first embodiment of the invention; Figure 2 is a view similar to Figure 1 of a second embodiment, and Figure 3 is a similar view of a third embodiment.

As shown in Figure 1, a well casing 1 surrounds a production liner 2. (The down hole dompletion illustrated in Figure 2 can be installed in a well casing without a liner if required). A hanger assembly 3 suspends a tubing 4 within the liner, and a pump and motor assembly 5 hang from the bottom of the tubing 4. An axially movable joint 6 connects the bottom of the assembly 3 with a tube 7 which extends through a packer 8. The region below the packer 8 is in fluid communication with the rock formation out of which the oil or gas is flowing.

In use, the motor 9 of the assembly is powered from a cable 10 to drive the pump 11. Oil and gas beneath the packer is then allowed or forced up the tube 7 into the pump. The oil or gas can then either flow to the surface within the tubing 4 or within the very much larger cross sectional area afforded by the interior of the production liner 2. When the oil or gas flows upwardly within the liner 2 then that fluid can enter the liner at the top of the pump 11, beneath the motor 9. The tubing may permit a flow rate of 6000 barrels per day whereas the increased cross-sectional area of the liner 2 may allow up to 65000 barrels per day to flow.

When it is required to raise the pump and motor assembly, or even to remove that assembly from the well, kill fluid can be poured down the well from outside of the tubing 4 within the liner. That kill fluid can rest on the oil above the packer to restrict its upwards movement and yet the kill fluid is away from the rock formation and indeed spaced from the packer. The packer can then be left in place whilst the pump and motor assembly is raised. The pump and motor assembly can then be lowered to cooperate with the same packer again.

The packer 8 can be provided with a valve assembly which can isolate the regions above and below the packer when the pump and motor assembly are raised from the position shown. In this instance kill fluid need not necessarily be provided.

A safety valve 12 may be provided at the lower region of the pump and motor assembly. The valve 12 can be actuated from the well head to isolate the assembly 5 from the well bore fluid, when the valve is closed. When the safety valve 12 is actuated the space between the larger assembly and the packer 8 containing well bore fluid can be isolated both when the pumped motor assembly cooperates with the packer and when that assembly is being raised or lowered within the well.

In order to locate the parts in the position shown the packer is first lowered and secured in place. (In an alternative embodiment (not shown) the packer can be moved down the well with the pump and motor assembly). The pump and motor assembly are then lowered down the well on the tubing 4 which is unwound from a continuous coil thereby negating the need for a large rig to be used to connect small lengths of tubing as the assembly is being lowered.

Conventional tubing that carries a pump and motor is provided by lengths of approximately 30 feet which have to connect in series. It can take up to two weeks to perform a workover with that system and up to 30 men can be working on the operation. With the coiled tubing men can complete the changeover in up to 6 days.

As the assembly nears the packer the tube 7 is then stabbed through the packer to place the pump in fluid communication with the oil and gas beneath the packer.

The axially movable joint 6 permits a small difference between the estimated distance to the packer and the actual distance to be accommodated and allows the assembly to hang free.

The operation of the apparatus shown in Figures 2 and 3 is similar to that shown and described in Figure 1 and it will be appreciated that any of the previously described features or methods may be applied to Figures 2 and 3.

In the embodiment shown in Figure 2 a point of communication 13 is provided between the safety valve 12 and the pump 11. The point of communication 13 allows communication of well fluid from beneath the packer 8 to the space above, when the valve is open.

In Figure 3, the packer 8 is separate from the motor and pump assembly 5 and does not require to be physically connected to the assembly 5 as in the previously described embodiments. Accordingly any problems associated with the precise relative axial positioning of the assembly 5 and the packer 8 are avoided.

The packer 8 includes a valve that permits fluid to flow upwardly but not downwardly. The valve may be pressure actuated and may include a latching operation whereby a greater pressure differential is required to open the valve than is needed to close the valve. The pressure differential may be enhanced by a pump located at the drill head which can be operated to open or close the valve.

In the embodiment of Figure 3 an additional packer 14 is located above the assembly 5. This packer 14 causes oil to flow within the coiled tubing 4 and isolates the space between the tubing and the casing. That isolated space is then able to be filled with salt water, for instance, to protect the internal parts of the well.

The packer 14 may be hydraulically set or released by a control provided at the well head. The hydraulic release is important as the tubing is not strong enough to allow a conventional mechanically released assembly packer to unseat.

The system can be installed with a logging by pass tool which allows access through the production tubing to the well bore below the pump and water assembly. The bypass system allows there to be change out of a valve located in the packer 8 by using a wire line tool that is run through the coiled tubing and logging by pass tubing that latches on to the component set in the fluid loss device.

Although the embodiments have been described in relation to the production of gas or oil it will be appreciated that they are equally applicable to the production of water.

Claims

1. A down hole installation including a passage leading from a fluid source, a pump located in the passage and an obstruction means located in the passage, the obstruction means being arranged to remain in the passage when the pump is raised.

2. An installation as claimed in Claim 1 in which the obstruction means is arranged to remain in the passage when the pump is removed from the passage.

3. An installation as claimed in Claim 1 or 2 in which the obstruction means is located closer to the fluid source than the pump.

4. An installation as claimed in any preceding claim in which the pump is arranged to be in fluid communication with the fluid source.

5. An arrangement as claimed in any preceding claim in which the pump is arranged to move axially along the passage to a limited extent whilst the pump is in communication with the fluid source.

6. An installation as claimed in any preceding claim in which, when the pump is raised, the obstruction means is arranged to be sealed with respect to fluid flow in at least one direction.

7. An installation as claimed in Claim 6 in which the pump is arranged to be placed in fluid communication with the fluid source as the pump is moved towards the fluid source.

8. An installation as claimed in Claim 7 in which the pump includes a portion which is arranged to pierce the obstruction means in order to place the pump in fluid communication with the fluid source.

9. An installation as claimed in any preceding claim in which the fluid source is arranged to be sealed from the space on the other side of the obstruction means from the fluid source when the pump is raised.

10. An installation as claimed in any preceding claim in which the obstruction means includes a valve.

11. An installation as claimed in Claim 10 in which the valve comprises a one-way valve.

12. An installation as claimed in Claim 10 or 11 in which the valve is arranged to be operable by the application of fluid pressure.

13. A valve as claimed in Claim 12 in which the pressure can be applied from a location remote from the obstruction.

14. An installation as claimed in any of Claims 10 to 13 in which the valve is arranged to require a greater force to open than the force that is arranged to close the valve.

15. An installation as claimed in any preceding claim including a motor located within the passage arranged to power the pump.

16. An installation as claimed in Claim 15 in which the motor is arranged adjacent to the pump.

17. An installation as claimed in Claim 16 in which the motor comprises part of a common assembly for the pump.

18. An arrangement as claimed in any preceding claim including a valve operable to seal the inlet to the pump.

19. An arrangement as claimed in any preceding claim including a valve operable to vent excess fluid pressure from beneath the obstruction means.

20. An installation as claimed in any preceding claim in which the pump is arranged to be moved into position by an elongate portion.

21. An installation as claimed in Claim 20 in which the elongate portion comprises a conduit.

22. An installation as claimed in Claim 21 in which fluid is arranged to flow from the pump within the conduit.

23. An installation as claimed in any of Claims 20 to 22 in which fluid is arranged to flow from the pump around the elongate portion.

24. An installation as claimed in any of Claims 20 to 23 in which the pump is arranged to be suspended by the elongate portion.

25. An installation as claimed in any of Claims 20 to 24 in which the elongate portion is of a substantial length.

26. An installation as claimed in Claim 25 in which the elongate portion is of a length at least equal to the depth of the passage.

27. An installation as claimed in any of Claims 20 to 26 in which the elongate portion comprises a single member.

28. An installation as claimed in any of Claims 20 to 27 in which the elongate portion is flexible.

29. An installation as claimed in Claim 28 in which the elongate portion is arranged to be unwound when moving the pump downwardly along the passage.

30. An installation substantially as herein described with reference to, and as shown in any of Figures 1, 2 or 3 of the accompanying drawings.

31. A method of operating a down hole installation comprising raising a pump located in a passage of the installation leading from the fluid source and leaving obstruction means in the passage, beneath the pump.

32. A method as claimed in Claim 31 comprising adding kill fluid to the passage before the pump is raised.

33. A method as claimed in Claim 32 comprising locating kill fluid above the obstruction means.

34. A method as claimed in any of Claims 31 to 33 comprising locating the obstruction in the passage before the pump is located in the passage.

35. A method as claimed in any of Claims 31 to 34 comprising actuating a valve in the obstruction to prevent fluid flow through the obstruction means towards the fluid source.

36. A method of operating a down hole installation substantially as herein referred to with reference to, and as shown in the accompanying drawings.

37. A method as claimed in any of Claims 31 to 36 in which the down hole installation is according to any of Claims 1 to 30.

38. A kit of parts arranged to be used in a down hole installation and including obstruction means arranged to be located in a passage leading from a fluid source and a pump arranged to be raised from a fluid source whilst the obstruction means remains in place.

39. A kit of parts as claimed in Claim 38 arranged to be used in a down hole installation as claimed in any of Claims 1 to 30 or in a method of operating a down hole installation as claimed in any of Claims 31 to 36.