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Power-User

Join Date: Mar 2008
Location: Mumbai
Posts: 256
Good Answers: 2

Choke Valve

09/01/2016 11:53 PM

Dear All,

Why Choke Valve are used after oill wells,

Can a Globe type Flow control valve meet the the requirement of Choke valve

interview question

regards

jose

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Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 17403
Good Answers: 997
#1

Re: Choke Valve

09/02/2016 2:06 AM

"The choke is the only device used to limit the production of flowing fluids. Using a valve, such as the wing valve or master valve, to limit fluid flow would allow fluid flow (possibly with solids) to cross the sealing surface of the valve. This could lead to erosion and a leaking master valve and would require killing the well to replace the valve."

Read all...

http://gekengineering.com/Downloads/Free_Downloads/Well_Heads_Chokes_SSSV_Chapter_5.pdf

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Power-User

Join Date: Feb 2007
Location: Aberdeen, Scotland
Posts: 322
Good Answers: 14
#2

Re: Choke Valve

09/02/2016 4:56 AM

Almost always I hear it referred to as a choke rather than a choke valve. The choke is designed to be used in a position other than fully open or fully closed whereas the Production Master Valve (PMV) and Production Wing Valve (PWV) are designed to only be open or shut for the reason already given.

The choke can either be fixed in one position or can vary depending on design but will have replaceable parts like the choke bean which can be changed out when the Cv value wanted cannot be achieved. These parts are often made from tungsten carbide for the erosion properties. Incidentally, whatever anyone says, a choke cannot be used to shut in a well. Some may market ones which can but in reality they will wear and you can never guarantee a full seal. I've seen surface chokes where the body had cracked by people overtightening to try and get a seal.

Chokes are a whole subject in themselves and there is plenty of material to read on the web. Try google for more info.

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Guru

Join Date: Oct 2009
Location: sometimes Wales,UK.. was Libya, now Oman!
Posts: 1613
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#3

Re: Choke Valve

09/03/2016 8:43 AM

Good for being honest regarding the question.

choke or choke valve, found at the top of the Xmas tree, and as previously stated to control the flow of well fluid to the surface.
The choke is usually used with Artificial Lift, namely an ESP (Electrical Submersible Pump) to control the following

1. Flow rate to surface
2. Well head Pressure
3. Dynamic Fluid Level
4. Prevent gas breakout down hole

1. Flow rate.. an ESP has an operating range (OR) and a Best Efficiency Point (BEP), the idea is to keep the ESP operating within the OR and close to it's BEP. To do this you can open or close the choke. Then measure the RC and flow rate. Modern day down hole gauges can now tell you the flow rate, so you just adjust the choke to suit.
In an ESP you also have to be careful of upthrust in the pump caused by not keep the pump in the OR close to the BEP, where the lower pump stages rub on the pump stage above, shortening the life of the ESP. Same for downthrust.

2. Well head pressure, as you close the choke the WHP increase, flow rate goes down and so does the running current. The RC is also important to watch as you do not want to overload the motor.

3. The dynamic level, the level of fluid in the well when the ESP is running changes as you open or close the choke. Open and the DL drops and visa versa. You also need to maintain a level of fluid above the intake of the ESP, the rule of thumb is over 500ft.

4 Gas breakout or gas lock in the pump will mean you will get no fluid to surface, the ESP will trip on underload if the U/L is set correctly or you will burn the motor as there is no motor cooling. By choking back, you change the TDH thereby increasing the fluid pressure in the pump, preventing gas breaking out of solution inside the pump stages.

hope this helps...
ps.. do not over think this... it is very simple

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Participant

Join Date: Oct 2016
Posts: 3
#4

Re: Choke Valve

10/18/2016 8:04 AM

Choke valves can also be seen at the oil manifolds. where the flow lines from oil wells are collected in Production Header.

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