GB2350382A

GB2350382A - Fail safe valve control arrangement

Info

Publication number: GB2350382A
Application number: GB0011588A
Authority: GB
Inventors: Martyn Andrew Witton
Original assignee: Kvaerner Oil and Gas Field Development
Current assignee: Kvaerner Oil and Gas Field Development
Priority date: 1999-05-14
Filing date: 2000-05-12
Publication date: 2000-11-29
Anticipated expiration: 2020-05-12
Also published as: GB0011588D0; GB2350382B; GB9911313D0

Abstract

A valve control (shutdown) arrangement for a well 21 extending into a sub-sea oil reservoir 23 comprises a tree with an actuated fail safe closed wing gate valve 26 that is actuated by the pressure of an injected liquid against a resilient element 32. The pressure of the injected liquid, through supply pipe 28, during normal operation holds the valve open but a reduction in pressure allows the resilient element to actuate the valve to a closed position and shut off the well e.g. in the event of pump failure, venting, or accidental leakage. The injected liquid may be impure sea water or a chemical. An alternative embodiment uses two valves and resilient elements of differing load/deflection ratings to allow variation in the pressure of the injected liquid. A stepped range of output pressures may be achieved by using hydraulic intensifiers. The arrangement may be located on a vertical or horizontal tree or on two trees with independent operation.

Description

2350382 -1 VALVE CONTROL ARRANGEMENT The invention relates to a valve

control arrangement for a water injection well (or a production well) extending down into a sub-sea oil reservoir.

The valve to which the control arrangement is applied may be a Down Hole Shutdown Valve (DHSV).

In order to enhance the recovery of oil from offshore oil fields, water may be injected into the reservoir below the oil. The water so injected can drive additional oil out of the reservoir.

Water injection may be effected through a well through which water can be pumped down into the reservoir, instead of oil flowing out of the reservoir and up the well.

The water to be injected into the reservoir may be produced water (which is reinjected), or seawater. In either case, the water is impure. The impure water is unsuitable for the operation of delicate valve actuating mechanisms.

During the initial phases of oil recovery, oil in the sub-sea reservoir is under high pressure. This pressure may be the cause of blow outs, and hence Emergency Shutdown Valves (ESV's) are incorporated into any oil draw off system.

(The invention is also concerned with oil production wells, in which one or more chemicals are injected into the arising crude oil to enhance the flow characteristics of the oil, or to reduce the corrosive effects of the oil.) Valves to control the well are conveniently divided into down hole valves, and wellhead valves. The latter are located on assemblies known as Christmas Trees. Wells can be completed with wellhead valves located either on the seabed, or on a deck of a fixed or floating platform, the deck being above sea level.

The present invention is concerned with wellhead control valves incorporated into Christmas trees on the seabed or above sea level.

The invention provides a valve control (shut down) arrangement for a well extending into a sub-sea oil reservoir, in which the well has a tree including an actuated fail safe closed valve, and in which that valve is actuated by the pressure of injected liquid against a resilient element, the characteristic of the resilient element being such that the pressure of the injected liquid during normal operation holds the valve open, and a reduction in that pressure allows the resilient element to actuate the valve to a closed position and so shut off the well (e.g. in the event of pump failure, venting or accidental leakage).

In one form of the invention the well is a water injection well, and the injected liquid is preponderantly water (generally impure seawater, but possibly reinjected produced water).

In this form it is preferred that the actuated fail safe closed valve is operated by an actuator characterised by its ability to tolerate impure water.

In another form of the invention the well is a production well, and the injected liquid is a chemical (e.g. to enhance flow or to reduce corrosion).

It is preferred that the actuated fail safe closed valve is a wing gate valve.

It is also preferred that there are at least two valve actuators with varying hydraulic diameters and/or resilient elements of differing load/deflection ratings such that the pressure of the injected liquid can be varied in steps to cause opening/closing of a group of valves.

Alternatively it is preferred that there are at least two valve actuators of similar hydraulic diameters and resilient element ratings which can be operated via hydraulic intensifiers creating a step range of output (actuator) pressures, thus causing a pressure (and time) sequence of opening and closing valves.

The arrangements described directly above may be combined, to operate on different trees, so allowing liquid injection and production trees to be operated independently at different actuator working pressures.

In one form there is a manually actuated valve located on the tree in a direction downstream of the actuated fail safe closed valve, and it is preferred that the manually actuated valve is a master gate valve.

Advantageously there may be a check valve upstream of the actuated fail safe closed valve.

The tree may be horizontal or vertical.

Several specific embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a diagram showing a valve control arrangement for a water injection well with a horizontal tree', Figure 2 is a diagram showing a valve control arrangement for a water injection well with a vertical tree; Figures 3 to 5 show different ways to vary valve operation forces:

Figures 6 and 7 show different ways to control multiple trees; Figure 8 is a diagram showing a valve control arrangement for a production well with chemical injection; Figure 9 shows the control of several actuators from one chemical injection pump; and Figure 10 shows the control of trees from a remote topsides.

Figure 1 illustrates a water injection well 21 extending down through mudline 22 into strata having a sub-sea oil accumulation 23. Near the bottom of the well there is a pressure operated down hole safety valve 24.

Control valves for the water injection well are mounted on a horizontal tree. These valves comprise a non return valve 25, an actuated Fail Safe Closed (FSC) wing gate valve 26, and an actuated FSC master gate valve 27. (The valve 27 may alternatively be manually controlled.) The valves 25, 26 and 27 control the flow of injected water into the well 21. Water to be injected into the well 21 is supplied through a pipe 28 from a source on a platform (not shown).

Following the invention, there is a bleed pipe 29 leading off the water supply pipe 28.

This bleed pipe 29 leads through a half inch manual isolation valve 31 to valve actuators 32 and 33, which are arranged to operate valves 26 and 27 respectively. The actuators 32 and 33 have hydraulic pistons constrained by preset springs, against which the pistons act.

In use, water under pressure is pumped from the platform down the supply pipe 28. At the initial pressure (Po), both valves 26 and 27 are closed. As the water pressure in the supply pipe 28 is raised, actuator 33 operates (at PI) to open valve 27. As the water pressure is raised further, actuator 32 operates (at P2) to open valve 26. Water can then be injected into the well 21. In this way the pressure of the water to be injected is arranged to control the operation of valves which admit water to the well. While water is being pumped down the well under pressure, the valves remain open. In the event of pump failure, venting or accidental leakage, leading to a significant reduction in pressure, the springs in actuators 32 and 33 will close the valves 26 and 27.

Figure 2 illustrates a water injection well with its control valves mounted on a vertical tree.

The components of this arrangement are similar to those described with reference to Figure 1, and in this case are designated with similar reference numerals (primed).

The actuators can have different hydraulic diameters and/or spring forces which require different pressures to open the valves. Examples of these arrangements are shown in Figures 3 to 5. - Figure 3 shows four actuators with effective hydraulic areas of Al to A4. Thus differing forces F1 to F4 can be applied from the same pressure source to operate corresponding gate valves (in a predefined sequence).

Figure 4 shows four actuators with similar hydraulic areas (A), in which there are differing presets on the actuator springs dl to d4. Thus differing forces F1 to F4 can be applied from the same pressure source to operate corresponding gate valves.

In Figure 5 a similar effect is achieved using springs with different spring rates K1 to K4.

Figures 6 and 7 show the application of these effects to two trees. In Figure 6, the hydraulic areas of the actuators are arranged to produce different operating forces F1, F2 and F3 on each of two trees. In Figure 7, the presets d are different on all of the actuators, so that different forces can be applied to operate each of the six valves.

Figure 8 illustrates a valve control arrangement for an oil production well 41 in which there is down hole chemical injection. The oil production well 41 extends down through mudline 42 into a sub-sea oil accumulation 43. Small amounts of chemical additive are dosed to the oil from a pressurised source 44. Lines 45, 46, 47 and 48 lead from the source 44 to valve actuators 51, 52, 53 and 54, on valves 55, 56, 57 and 58 respectively. Valve 55 is located at the base of the well 41, and so an hydraulic intensifier 59 is included in the line 45.

If the maximum supply pressure is 5,000 psi, the pressure may be stepped in 500psi differentials.

Figure 9 shows the arrangement of the actuators 51 to 54 with respect to a pump 60, and how an adjustment of the actuator settings can control operation of the valves in different sequences.

Figure 10 shows the control of multiple trees (in this case five) from a single chemical injection pump 60. Pressure regulating valves 61 to 65 are set on a topsides, and regulate individual pressures of chemicals to individual trees 71 to 75.

Claims

Claims

1/ A valve control (shut down) arrangement for a well extending into a sub-sea oil reservoir, in which the well has a tree including an actuated fail safe closed valve. and in which that valve is actuated by the pressure of injected liquid against a resilient element, the characteristic of the resilient element being such that the pressure of the injected liquid during normal operation holds the valve open, and a reduction in that pressure allows the resilient element to actuate the valve to a closed position and so shut off the well (e.g. in the event of pump failure, venting or accidental leakage).

21 An arrangement as claimed in claim 1 in which the well is a water injection well, and the injected liquid is preponderantly water (generally impure sea water, but possibly reinjected produced water).

31 An arrangement as claimed in claim 2, in which the actuated fail safe closed valve is operated by an actuator characterised by its ability to tolerate impure water.

41 An arrangement as claimed in claim 1, in which the well is a production well, and the injected liquid is a chemical (e.g. to enhance flow or to reduce corrosion).

5/ An arrangement as claimed in any one of the preceding claims, in which the actuated fail safe closed valve is a wing gate valve.

61 An arrangement as claimed in any one of the preceding claims, in which there are at 25 least two valve actuators with varying hydraulic diameters andlor resilient elements of differing load/deflection ratings such that the pressure of the injected liquid can be varied in steps to cause opening/closing of a group of valves.

71 An arrangement as claimed in any one of claims 1 to 5, in which there are at least two 30 valve actuators of similar hydraulic diameters and resilient element ratings which can be operated via hydraulic intensifiers creating a step range of output (actuator) pressures, thus causing a pressure (and time) sequence of opening and closing valves.

81 An arrangement as claimed in claim 6 and claim 7 in combination, to operate on different 35 trees, so allowing liquid injection and production trees to be operated independently at different actuator working pressures 9/ An arrangement as claimed in any one of the preceding claims, in which there is a manually actuated valve located on the tree in a direction downstream of the actuated fail safe closed valve. 5 101 An arrangement as claimed in claim 9 in which the manually actuated valve is a master gate valve- 111 An arrangement as claimed in any one of the preceding claims in which there is a check 10 valve upstream of the actuated fail safe closed valve.

12/ An arrangement as claimed in any one of the preceding claims in which the tree is horizontal, 131 An arrangement as claimed in any one of claims 1 to 11 in which the tree is vertical.

141 An arrangement substantially as hereinbefore described with reference to and as shown in Figures 1, 2 or 8 of the accompanying drawings.

Amendments to the claims have been filed as follows Claims 17 1/ A valve control (shut down) arrangement for a well extending into a sub-sea oil reservoir, in which the well has provision for the injection of liquid into the well at or near its lower end and the well has a tree including an actuated fail safe closed valve, and in which that valve is actuated by the pressure of the injected liquid against a resilient element, the characteristic of the resilient element being such that the pressure of the injected liquid during normal operation holds the valve open, and a reduction In that pressure allows the resilient element to actuate the valve to a closed position and so shut off the well (e.g. in the event of pump failure, venting 10 or accidental leakage).

2/ An arrangement as claimed in claim 1, in which the well is a water injection well, and the injected liquid is preponderantly water (generally Impure sea water, but possibly reinjected produced water).

3/ An arrangement as claimed in claim 2, in which the actuated fail safe closed valve is operated by an actuator characterlsed by its ability to tolerate impure water.

4/ An arrangement as claimed in claim 1, in which the well is a production well, and the 20 injected liquid is a chemical (e.g. to enhance flow or to reduce corrosion).

51 An arrangement as claimed in any one of the preceding claims, in which the actuated fail safe closed valve is a wing gate valve.

6/ An arrangement as claimed in any one of the preceding claims, in which there are at least two valve actuators with varying hydraulic diameters and/or resilient elements of differing load/deflection ratings such that the pressure of the Injected liquid can be varied in steps to cause opening/closing of individual valves In a group of valves.

7/ An arrangement as claimed in any one of claims 1 to 5, in which there are at least two valve actuators of similar hydraulic diameters and resilient element ratings which can be operated via hydraulic intensifiers creating a step range of output (actuator) pressures, thus causing a pressure (and time) sequence of opening and closing valves.

8/ An arrangement as claimed in claim 6 and claim 7 in combination, to operate on different trees, so allowing liquid injection and production trees to be operated independently at different actuator working pressures 49 91 An arrangement as claimed in any one of the preceding claims, in which there is a manually actuated valve located on the tree in a direction downstream of the actuated fail safe closed valve. 5 101 An arrangement as claimed in claim 9, in which the manually actuated valve is a master gate valve.

111 An arrangement as claimed in any one of the preceding claims, in which there is a check 10 valve upstream of the actuated fail safe closed valve, 121 An arrangement as claimed in any one of the preceding claims, in which the tree is horizontal.

131 An arrangement as claimed in any one of claims 1 to 11, in which the tree is vertical.

141 An arrangement substantially as hereinbefore described with reference to and as shown in Figures 1, 2 or 8 of the accompanying drawings.