Do anybody experience in oil and gas production wells with artificial gas lift that operate without any choke valve installation at upstream the well flowlines?
I have seen many oil and gas natural flow wells that all of them have choke valve after x-tree to control the flow and/or pressure of well fluids.
But last week for the first time I visited one oil field with artificial gas lift that had not any choke valve. The information about the gas lift process are as follow: the source of producing high-pressure gas is high pressure compressor (40 mmscfd @140 barg outlet pressure) for 10 wells (each well 4 mmscfd). Each well produce 4,000 barrel oil and 3,000 barrel water per day and the first stage separator pressure is 10 barg and feed of the compressors supply from separated gas at separators. (my concern is not about gas lift line choke valve because in the gas lift line choke valve has been installed before the x-tree)
My question is that all of artificial gas lift wells dosen’t need choke valve?
appreciate your guidance and experience sharing. A bit odd for sure, but if the field needs gas lift it tells you that the shut in tubing head pressure is low and the flowing tubing head pressure without the gas lift very low.

Choke valves are simply high pressure, three phase control valves. If the filed pressures are that low then maybe you don't need them and you can control everything on the separator control valves.

What happens if / when you get a well bore full of gas I'm not really sure, but presumably this is below the pressure rating of the downstream system.

So the devil is in the detail and especially what the maximum shut in tubing head pressure can be so that on start up you don't overpressure your downstream system or strip out a wing valve which you are using to start up a well.

So no you can't extrapolate one field to any other.

Whilst the operating pressure of the separator might be 10 bar what is its design pressure / MAWP??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

So the devil is in the detail and especially what the maximum shut in tubing head pressure can be so that on start up you don't overpressure your downstream system or strip out a wing valve which you are using to start up a well.

1. there isn't any fluid flow without gas lift operation.
2. gas lift operation is continuous and after stopping the gas lift, production will stop.
3. wellhead flowing pressure is a bit greater than 10 bar and wellhead shut in pressure without gas lift is about atmospheric pressure. 3 wells have a little positive pressure maximum up to 2 barg.

So no you can't extrapolate one field to any other.

have you seen an oil field with gas lift operation with choke valve?

Whilst the operating pressure of the separator might be 10 bar what is its design pressure / MAWP??

the separator PSV set point is 14 barg. No you don't need a choke valve when the well will not overpressure your separator. A normally full open ball valve will do nicely. A choke would simply put more backpressure on your lift and reduce flow. Surely you want to avoid that.

You may need a pressure control valve to vary the amount of gas being injected into the well by the compressor.

You need choke valves when the wells could overpressure downstream equipment, functioning as a downstream pressure control valve, or if a valve is needed to block well flow and study well pressure recovery times verses pressure, i.e. when running well testing procedures, normally to determine the most productive flow and best liquid and gas production ratios which can vary considerably at different back pressures. As you can probably control those variables through injection pressure, no need to do that by using a choke valve.

No I have not personally seen no chokes with lifting ops, since it is common to find the wells still with chokes, as per the originally dssigned configuration, even though they have become redundant and actually operate at full open, unless manually closed. There may be a lot of wells that do not have them, maybe not. All of my production field experience was with 100% gas-high VP, very light condensate wells, where gas lifting was never intended. We would usually not replace a choke with a new control valve when the wells reached the low pressure stage of life, but we would sometimes change a choke for a common block valve as opportunity allowed. I have not actually seen a lot of gas lifting operations, but I expect that there could be some old gas lifting operations without chokes out there somewhere.

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