PVT Publications

Adjustment of Differential Liberation Data to Separator Conditions

 M.A. Al-Marhoun, SPE, King Fahd U. of Petroleum & Minerals

SPE Reservoir Evaluation & Engineering - June 2003

Abstract:

The actual reservoir process is neither flash nor differential.  Thus, regardless of the testing procedure, some adjustment needs to be made to the resultant data to approximate the fluid behavior in the oil production process.  The conventional method of adjustment extrapolates to negative values of solution gas-oil ratio and formation volume factor leads to values less than one at low pressure. Both extrapolations do not conform to the physical behavior. This is due to the fact that the conventional approach does not observe that the oil relative density at reservoir conditions is the same regardless of the process.

This paper presents a new approach to the adjustment of differential liberation data to separator conditions.   This approach is based on the fact that both flash and differential data should give the same value for the oil relative density at the reservoir conditions. This is achieved by correcting all the properties, i.e. solution gas-oil ratio, formation volume factor, gas relative density and oil relative density. The new method overcomes the disadvantages and limitation of the conventional approach. This method is tested on 400 PVT files from all over the world and the result is consistent with physical behavior. A sample calculation is presented to outline the new method.

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