Gentlemen
We are dealing with an exploratory target zone where the fluid type is known. DST was conducted in this well and in short production period, we produced both oil & gas from this zone. Detailed PVT analysis was not possible on these samples due to business concerns. I am trying to construct well evaluation model for this zone and have trouble classifying this reservoir as retrograde condensate or volatile oil.
Is there a technique to classify the reservoir?
Awaiting response.
Regards
Dear Mr Patel,
Thank you for writing at ProPetra. We are glad that the industry has started connecting with colleagues to learn and share their knowledge.
Your question is excellent, as it refers to a long industry wide debate. Ideally, we would always want to have PVT analysis on reservoir fluid samples, unfortunately managers dont allow this luxury for engineers due to the cost. In such scenarios, we can either guess and make a calibrated (but not unique) model and use it for further analysis, or we can classify the reservoir using Gas Oil Ratio or GOR.
Classifying reservoir based on GOR has its history in petroleum/reservoir engineering. The accuracy of such assumption is always questionable, however in my personal experience, for modelling purposes classifying the reservoir based on producing GOR gives results within reasonable uncertainty.
As a rule of thumb, i would say refer the following:
Type: GOR (sm3/sm3)
Oil: <500 sm3/sm3
Volatile Oil: 500 - 800 sm3/sm3
Retrograde Condensate: 800-10000 sm3/sm3
Wet Gas: >10000 sm3/sm3
Dry Gas: Almost negligible condensate in production or a GOR greater than 100000 sm3/sm3
Hope this helps. We are in the process of writing an article on Fluid type and characterization will be an element on that blog. Stay tuned.
Regards
Farooq