Gas injection wellhead valve open/close sequence 1

[stk123]

The gas injection wellhead consists of hydraulically actuated wing valve (WV) followed by surface safety valve (SSV) and sub-surface safety valve (SSSV). We have to define the closing and opening sequence of these wellhead valves. The following sequence was proposed in the design manual: First close the SSSV, followed by SSV and then WV. The opening sequence was reverse that of the closing sequence i.e., first open the WV, followed by SSV and then SSSV. But there is difference of opinion to follow exactly the opposite of that proposed above which is normally followed for a oil producer wellhead.

Please advise the correct operating sequence of a gas injection wellhead valves.

 

[LittleInch]

The SSSV is normally the last thing to be closed and first thing to be opened in either production or injection systems as they don't really like opening or closing under differential pressure. There is a real risk that the valve will not open unless there is no flow and minimal pressure difference. An injection system is a little different to a production well as you are preventing flow in two directions as opposed to one, but the SSSV is there primarily to be a lst line of defence to stop the gas coming out and needs to be treated with care and preferably not closed at all unless you really need to.

Personally I would close WV, SSV then SSSV (only closed if you have a fire or level 1 ESD) and opened in reverse sequence. If the WV is closing on flow, then it is the most likely to gradually wear and leak, but the easist to replace / repair. Flow direction doesn't realy matter.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[stk123]

LittleInch,

Thanks for your valuable insight into my query.

 

[LittleInch]

Ok. You might like to put this in the petrolueum engineers section and link to this question to get other views as chemical engineering isn't probably the right forum...

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way