GB2297568A

GB2297568A - Hydraulic power source

Info

Publication number: GB2297568A
Application number: GB9501808A
Authority: GB
Inventors: John L Schneider; Leslie Eric Jordan
Original assignee: Phoenix Petroleum Services Ltd
Current assignee: Phoenix Petroleum Services Ltd
Priority date: 1995-01-31
Filing date: 1995-01-31
Publication date: 1996-08-07
Also published as: GB9501808D0

Abstract

A down hole hydraulic system for use with an electrical submergible pump or ESP in an oil or water well comprises a hydraulic circuit communicating with an inlet and a discharge of said pump. The pressure difference which exists across the inlet and the discharge of said pump in use is utilised to drive at least one hydraulic actuator 430. A separate closed hydraulic circuit operates the actuator 430 preventing damage due to contaminated well fluid. Solenoid operated valves 400, 410 control flow of fluid from the pump to high and low pressure reservoirs 401 and 411 which have movable barriers 402, 412 to separate contaminated fluid in chambers 403, 414 from clean fluid in chambers 404, 413. Solenoid operated valves 431, 432 control the flow of clean fluid to either end of actuator 430.

Description

HYDRAULIC POWER SOURCE The present invention relates to a hydraulic power source for use with an electrical submergible pump.

The use of hydraulic power for the manipulation of equipment deployed in oil or water producing wells is common practice. Typically hydraulic supply lines are connected to an hydraulic pressure system and the operation of the deployed equipment controlled by valving positioned at, or close to, the wellhead. The use of equipment so described often requires the installation and connection of many thousands of feet of hydraulic supply line which would typically comprise long lengths of seamless stainless steel tubing which may, or may not, be joined by suitable splicing arrangements. Further equipment designed to support and protect such hydraulic supply lines is commonly deployed in such completions.

In wells where an electrical submergible pump (ESP) is used to provide artificial lift of the produced fluid to surface it is common practice to install a packer above the ESP for reasons of safety. Such packers provide a pressure seal within the well casing above the ESP which must be penetrated by hydraulic supply lines from the surface installed for the manipulation of equipment deployed below the packer.

It is an aim of the present invention to provide selectively controllable hydraulic power in oil and water wells using an ESP for artificial lift purposes.

According to a first aspect of the invention there is provided a method of operating at least one down hole actuator using an electrical submergible pump, comprising the step of utilising the pressure difference across an inlet and a discharge of the pump to drive the at least one actuator.

According to a second aspect of the invention there is provided a down hole hydraulic system powered by an electrical submergible pump comprising, a hydraulic circuit communicating with an inlet and a discharge of said pump such that, in use, the pressure difference existing across the inlet and the discharge of said pump is utilised to drive at least one hydraulic actuator, whose operation is controllable by remotely operable control means.

Preferably, said hydraulic system further includes a separate closed hydraulic circuit responsive to said pressure difference, which circuit contains clean hydraulic fluid for driving said at least one actuator.

Still preferably, the control means includes a number of electrically operated valves. Conveniently, the valves may be selectably operable in response to electrical signals received from the surface.

Preferably the manipulation of deployed equipment will be by clean hydraulic pressure means which in the present invention is provided by a closed hydraulic system which displaces clean hydraulic fluid from a high pressure reservoir to a reservoir at lower pressure during the manipulation of equipment and is controllable so as to enable the displaced clean fluid to be returned to the high pressure reservoir to maintain an adequate supply of high pressure clean fluid for continuing hydraulic manipulations.

It would further be preferable for the selective electrical control system at surface to be connected to the electro-hydraulic control circuit located in the well bore by way of the electric power cable used to supply power to the ESP motor.

Figure 1 describes an hydraulic circuit wherein contaminated fluid from the ESP discharge is directed by a controllable hydraulic valve (400) to a high pressure reservoir (401) divided by a moveable barrier (402) such that the contaminated high pressure fluid in chamber (403) is separated by the moveable barrier (402) from clean hydraulic fluid in chamber (404) maintained at the same high pressure as the contaminated fluid in chamber (403) by the movement of the moveable barrier (402).Contaminated fluid from the ESP inlet and hence at a lower pressure than the fluid from the ESP discharge is similarly connected via a controllable valve (410) to a low pressure reservoir (411) wherein a moveable barrier (412) separates contaminated fluid in chamber (414) from clean hydraulic fluid in chamber (413) whilst maintaining an equal pressure in clean and contaminated fluids by the movement of the moveable barrier (412).

An hydraulic oilway (420) connects the H.P. clean fluid chamber (404) to the L.P. clean fluid chamber (413), such oilway containing a check valve (421) configured so as to permit flow from the low pressure reservoir (411) to the high pressure reservoir (401) and to prevent flow in the opposite manner. An actuator (430) connects via controllable valves (431) and (432) to the oilway (420), such connection being selectively made to either side of the check valve (421).

From the diagram it may be determined that the actuator (430) is connected via ports (433) and (434) and controllable valves (431) and (432) to the L.P. clean fluid chamber (413) in the reservoir (411). It may further be determined that by operation of the controllable valve (431) H.P. clean fluid from chamber (404) will be directed to port (433) of the actuator (430) which will thus move to the right expelling fluid via port (434) and controllable valve (432) to the L.P. clean fluid chamber (413) in reservoir (411). Simultaneous switching of controllable valves (431) and (432) will then serve to reconnect port (433) of the actuator (430), to the L.P. clean fluid chamber (413) in reservoir (411) and connect H.P. clean fluid chamber (404) from the reservoir (401) to the port (434) of the actuator (430) moving the actuator to the left.Therefore, full manipulation of the actuator wil transfer H.P. clean fluid from the reservoir (401) to the L.P. fluid chamber (413) of the reservoir (411), thus ultimately exhausting the supply of fluid available to effect manipulation of the actuator.

In order to ensure a continuing supply of H.P. clean fluid to the actuator it is necessary to return fluid from chamber (413) of reservoir (411) to chamber (404) of reservoir (401). It may be determined from the diagram that simultaneous operation of the controllable valves (400) and (410) will connect the low pressure contaminated fluid supply from the ESP inlet to chamber (403) of the reservoir (401) and similarly connect the high pressure contaminated fluid supply from the ESP discharge to the chamber (414) of the reservoir (411) thus creating a pressure imbalance between chambers (404) and (413) in the respective reservoirs (401) and (411) which will effectively transfer clean hydraulic fluid through oilway (420) and check valve (421) to replenish chamber (404) with clean hydraulic fluid expelled from chamber (413).Return of controllable valves (400) and (410) to their original condition will then permit continued operation of the actuator.

Electrical solenoid controlled valves may be used to control the hydraulic circuit from the surface. The method has particular application where an electrically submergible pump (ESP) is in use, and the control signals are sent over the power cable. The method has further application whereby the control of downhole valves may be achieved, via the ESP power cable, at the same time as a down hole instrumentation package sends data to the surface, over the same power cable.

For the control of downhole valves, the surface system may vary the surface voltage, and the downhole system may monitor the DC voltage that it receives. Note that the absolute value of the downhole voltage will depend on cable, motor and choke resistance, as well as the current drawn by the downhole tool. However, changes in downhole voltage caused by changes in surface voltage, may be detected by the downhole controller. To facilitate this detection, the downhole controller may hold a constant current at the end of the normal measurement cycle, so that the signals from the uphole system may more readily be detected.

The surface system may send digital data to the downhole system by varying the voltage, with the voltage transitions indicating digital "high" or "low" values.

Standard error correction techniques, such as check-sums and parity bits may be used, as is very well known in the field of digital data transmission.

The digital data may then be used by the downhole controller to switch on and off solenoid valves as required.

The valves may require a surge of energy for a relatively short time. However, high current may be difficult to send from the surface, due to the need to isolate the DC current path from the high voltage AC current used by the main motor system. Large downhole capacitors may be used to overcome this problem, storing up energy over a period of several seconds, ready for a rapid discharge to achieve effective valve switching.

Claims

CLAIMS:

1. A down hole hydraulic system for use with an electrical submergible pump comprising, a hydraulic circuit communicating with an inlet and a discharge of said pump such that, in use, the pressure difference existing across the inlet and the discharge of said pump is utilised to drive at least one hydraulic actuator, whose operation is controllable by remote control means.

2. A system as claimed in Claim 1, in which said hydraulic circuit communicating with said inlet and discharge of said pump contains contaminated well fluid and further includes a separate closed circuit responsive to said pressure difference, which circuit contains clean hydraulic fluid for driving said at least one actuator.

3. A system as claimed in Claim 1 or Claim 2, in which the control means includes a number of electrically operated valves.

4. A system as claimed in Claim 3, in which said valves are selectably operable in response to electrical signals received from the surface.

5. A system as claimed in Claim 3 or Claim 4, in which said closed circuit incorporates a pair of reservoirs pressurisable by said contaminated fluid, said valves being operable by said control means to cause said clean hydraulic fluid to be displaced from a high pressure reservoir to a reservoir at lower pressure during the manipulation of said at least one actuator, said valve means being operable so at to enable said displaced clean fluid to be returned to said high pressure reservoir to maintain an adequate supply of high pressure clean fluid for continuing hydraulic manipulations.

6. A system as claimed in Claim 5, in which said reservoirs are each divided by movable seal means separating said clean hydraulic fluid from said contaminated well fluid, equal pressure being maintained in said fluids by movement of the movable seal.

7. A system as claimed in any preceding Claim, in which said control means utilises the electrical submergible pump power cable.

8. A system as claimed in any one of Claims 1 to 6, in which said control means utilises a separate power supply.

9. A down hole hydraulic system for use with an electrical submergible pump substantially as described herein with reference to the sole Figure of the accompanying drawing.

10. The features herein described or illustrated, or their equivalents, in any patentably novel selection.