Well Fluid Optimization

[asade]

Good day All,

I am a Process Engineer with task to provide optimization scenarios for well fluids from different wells which are proposed to be re-opened for production activities. The data available to me shows the respective choke sizes, gross well flow, GOR, THP and FLP for each of the individual wells. The distance between each of these wells to the flow stations varies.

So far, I understand that the higher the choke size, the higher the possibility of increase GOR.

How can I achieve production optimization from each of the wells?
Are there equations that relate the choke size with the flow rate.

Kindly revert back if further information is required.

I am what I am by His grace

 

[zdas04]

What I tell people who take my class is "Every well has a personality (and most of them are unpleasant)". "Optimizing" production for a "field" is truly a pointless, non-productive exercise that is almost always counter to the needs of the reservoir. There is no such thing as an homogeneous reservoir. There are many discontinuities, many variations in fluid composition, and a wide spread in pressures and temperatures. Increasing choke size beyond a certain point often increases GOR, but not nearly always, and finding that "certain point" cannot be done for a field, it must be done for each specific well.

You've been set on a fools errand that will only be successful by the rankest of coincidence.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[asade]

zdas04

Thank you. Your comments are noted.

I am what I am by His grace

 

[LittleInch]

The choke size has nothing really to do with GOR, which is gas at standard conditions per standard barrel. if you have a large choke, you could get greater flow, but possibly lower pressure, you will probably then get more Actual volume flow rate of gas at the wellhead, but the GOR is a reservoir / well function and is not affected by the surface facilities. It will change over time as the reservoir changes and any injection of gas or water has an impact so any GOR figure is just a snapshot at that time (normally only accurately judged by a test separator or multi phase meter.

What are you trying to optimise? Gas or Oil flow? As zdas04 says, this is a reservoir engineers function much more than surface proceesing. if you over flow a well you can reduce the overall recovery from the reservoir, cone up water from below or create too much gas flow if you fall below the reservoir bubble point. This is not a process engineers role to do downhole and reservoir modelling / maximise recovery.

To enhance liquid recovery, you want o minimise gas in the well bore and hence although it seems strange, a higher pressure is needed to get more liquids. However this could be an illusion if the "liquid" then flashes off to become gas at some other point in the processing train.

you can get some pretty crude flow rate estimated from percent open versus valve CV and then calculate flow, but it has a very low accuracy, especially if you've got two phase flow through it.

Even if by some miracle you "optimise" the field one day, at the end of the week something will change in the reservoir and you need to do it all over again.....

My motto: Learn something new every day

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

 

[asade]

Thank you BigInch.



I am what I am by His grace

 

[zdas04]

LittleInch
I didn't say that it was a Reservoir Engineer function, I said it was a well-by-well function (I've done a lot of it as a surface function). Opening a choke can indeed increase coning and increase GOR which is both a reservoir function and a production function and the reservoir GOR does not necessarily have anything to do with the production GOR.

I do absolutely agree with your last statement. I keep seeing Process Engineers try to "get it right" and if they should happen to get close, they tend to run to the next project and can say "it was right when I left, what did you guys do wrong?"

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[LittleInch]

ZDAS04 - true - putting words into your mouth, sorry. I still can't see how increasing choke size and hence presumably flow will directly change the GOR. Over time yes as it will strip out the gas a bit faster, but maybe that's what we both mean by saying it is not something you can learn or fix by a forum like this and ultimately figuring out what is going to come out of the ground now or in the future is more art than science (though I'm sure the rock doctors might disagree...).

aside - Its the little inch brother not the big one(!)

My motto: Learn something new every day

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

 

[zdas04]

Flow in a reservoir is amazingly complex. Channels are normal, and can change paths from second to second. If the lowest pressure drop is between a gas cap and a wellbore, gas cut can increase dramatically over a very short period. Often closing the choke some can cause liquid to flood that channel.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[BigInch]

Reservoir flow rate can't be just a function of pressure at the choke alone, but must also be highly formation dependent. I'm thinking, too high a flow of anything just might kick up dust, dirt causing it to migrate and wind up plugging or otherwise damaging the formation. Least that's what I was always told. It can be very fine wire tight rope walk.

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