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Reservoir Management

Reservoir Management

(OP)
hey guys, Well my question is simple,What type of reservoir is one containing an 'initial GOR' of 11,000 scf/bbl.

RE: Reservoir Management

In Texas or Pennsylvania it would be an Oil Reservoir (less than 100 MSCF/bbl). Other jurisdictions have other definitions.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

RE: Reservoir Management

Given that someone is quoting it to you in GOR, this implies that they believe it is a rather gassy oil field.

The point at which it become instead a wet gas field and is quoted in CGR (Condensate to Gas Ratio) - GOR of 11,000 = CGR of 90 - is a matter of interpretation and to a certain extent what the liquid actually is that is coming out - is it "Crude Oil" or is it "condensate" or sometimes "natural gasoline"?

My motto: Learn something new every day

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

RE: Reservoir Management

(OP)
thanks, so possibly an overpressured reservoir

RE: Reservoir Management

Not necessarily "over pressured", just an indication of the fluids in the rock.

Whether you call this an oil field or a gas field is to a certain extent irrelevant, but it does colour peoples perceptions. whether the GOR goes up or down over time is also important in dealing with what comes out of the ground in the best manner.

My motto: Learn something new every day

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

RE: Reservoir Management

LittleInch,
You are tossing those numbers around like they are physical laws. 90 bbl Condensate/MMSCF is an oil well in Texas, Pennsylvania, and New Mexico (and probably other places, that is as far as I looked). The classification of an Oil Reservoir or Gas Reservoir is a regulatory construct, not a physical cone. States have different rules for gas wells than oil wells (e.g., several states have proration rules that limit production from gas wells to "ensure correlative rights", I worked on a project to eliminate such a program in New Mexico in the early 1990's). Getting outside capital has generally been easier for oil reservoirs since gas prices tanked in 2008.

Other than administrative things, the designation is meaningless--just because you call it an oil reservoir doesn't mean that the reservoir will ever give you a drop of oil in the next well you drill.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

RE: Reservoir Management

zdas04,

I probably responded a little fast, but it's always been interesting to me to see where different people and jurisdictions separate a gas field from a gas condensate field from an oil field. As you say it can affect finance, how it is regulated, how it is taxed etc and GOR / CGR is not as precise as it might be, but is the best we have. If there is one thing about HC fields it is that everything keeps changing and as the GOR changes over time it can affect the physical aspect as well as the regulatory one.

For me a GOR of 100,000 as the upper limit for an oil system is rather high, but I can easily accept that this is a definition now set in stone.

IMHO, a GOR of something less than 5,000 is an oil field, 5 - 20,000 is a gas condensate field and > 20,000 is a gas well, but if in whatever jurisdiction the OP resides there are different set definitions then that's what you go with.

My motto: Learn something new every day

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

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