GB2465168A

GB2465168A - Disposing of hydraulic well fluid by pumping it into a production flowline.

Info

Publication number: GB2465168A
Application number: GB0820326A
Authority: GB
Inventors: Peter J Davey
Original assignee: Vetco Gray Controls Ltd
Current assignee: Baker Hughes International Treasury Services Ltd
Priority date: 2008-11-07
Filing date: 2008-11-07
Publication date: 2010-05-12
Anticipated expiration: 2028-11-07
Also published as: GB0820326D0; AU2009312547A1; AU2009312547B2; US20110203808A1; BRPI0916054A2; WO2010052490A1; EP2347089A1; GB2465168B; CN102209833A

Abstract

A method of disposing of hydraulic well fluid vented from a hydraulically controlled actuating device 1 involves pumping the fluid via a pump 6 and a valve 8 into a production flowline (7) of the well. A well control system, controlling said method is also claimed. The well may be a subsea production well.

Description

DISPOSAL OF WELL CONTROL FLUIDS

Fie'd of the invention: The present invention re'ates to the disposa' of we contro' fluids.

Background of the invention:

During the operation of a subsea weU, hydrauUc fluid is expeUed from hydrauUc control actuating devices, such as va've and choke actuators. Typicafly. in the past. this fluid has been exhausted to the sea. The fluid is, typica'ly, ethy'ene glyco based and is now considered to be a poutant.

Environmenta' egisIation now prompts we'l operators to stop exhausting such fluids into the sea, particuary on new instaations, which presents weI equipment supp'iers with the prob'em of finding a so'ution to the new requirements. This invention reso'ves the prob'em, removing the need to exhaust such fluids into the sea.

Summary of the invention:

According to the present invention from one aspect, there is provided a method of disposing of hydrau'ic weU contro' fluid, comprising pumping the fluid into a production flowline of the weU.

The fluid typicay comprises hydrau'ic fluid vented from a hydrauicay controed actuating device of a contro' system of the weU.

Preferab'y, the fluid is pumped into the production fiowine via a va've, which preferab'y opens at a pressure greater than the pressure of fluid in the fiowine.

The weU cou'd be a subsea hydrocarbon production weU.

According to the present invention from another aspect, there is provided a weU contro' system, which inc'udes means for disposing of hydraulic weU contro' fluid by pumping the fluid into a production flowine of the weL

Brief Description of the Drawings:

Fig. 1 is a schematic diagram of a system according to an embodiment of the present invention.

Detailed description of the Invention:

Referring to Fig. 1, for simplicity a single hydraulic actuator I of a subsea hydrocarbon well, is shown. The hydraulic actuator 1 is operated by hydraulic fluid, under pressure, fed to it through feed pipes 2 and 3 via an electricay operated directional control valve (DCV) 4. The actuator 1 typicay operates a valve as part of the control of the production fluid from the well. The actuator I is released, by de-energising the DCV 4, which then shuts off the hydraulic I1uid feed from the hydraulic fluid source via the feed pipe 2 and connects the actuator I to a vent pipe 5.

The hydraulic fluid exhausted from the actuator is fed via the vent pipe 5 into a pump 6, which could be electrically or hydraulically powered.

The production fluid pressure from the well in a production fluid flowline 7 (shown in section view) is at a much higher pressure than the hydraulic control fluid pressure and is typicaUy as high as 3000 psi. The pump 6 has, therefore, to raise the pressure of the vented hydraulic control fluid to a pressure that is greater than the production fluid fiowline pressure in order to be able to inject it into the flowline. The high pressure vented hydraulic fluid from the pump 6 is fed via a relief valve 8 to a feed pipe 9, and injected into the flowline 7, through a nozzle 10. A typical r&ief valve 8 is illustrated in the inset sectioned diagrammatic view in Fig. 1 and primarily consists of a steel ball 11, held against a valve seat 12 by a spring 13. The compression of the spring is arranged to allow the valve to open only when the inputted hydraulic fluid pressure is significantly greater than the pressure in the flowline 7, that is the "cracking pressure" of the relief valve 8 is significantly greater than the pressure in the flowline 7.

Although the principle of the nvention as shown in Fig I is applied to a single actuator, in practice, well hydraulic control systems employ several hydraulic actuators and the vented fluids from all the actuators would all be fed to the single pump 6.

Thus vented hydraulic control fluid, at a relatively low pressure, is pressurised by a pump, allowing it to be injected into the production fluid flowline, thus avoiding the pollution which results from such fluid being injected into the sea in existing systems.

The above embodiment of the invention injects the exhausted hydraulic fluid from hydraulic operated devices into a production fluid pipeline, using a pump to achieve this function.

Compared to the production fluid flow rate, the quantity of exhausted hydraulic fluid injected is negligible in terms of contamination of the production fluid and is, anyway, likely to be extracted by the water extraction process, typical of most installations, remote from the subsea well.

Advantages of using the invention: The invention avoids disposal of vented hydraulic fluids from the control systems of wells into the environment, thus enabling well operators to meet new environmental requirements.

In alternative systems that employ containers to store vented hydraulic fluid, the containers can be dispensed with and the costly process of emptying them avoided.