Correlation of Oil Formation Volume Factor and Solution Gas-Oil Ratio

Abstract

Abstract Thermally-reduced oil formation volume factor is correlated with solution gas-oil ratio from 0 to 3,500 cu ft/bbl. This correlation was made from the differential liberation curves of 159 analyses of saturated Eastern Venezuelan crudes. Average error, determined by comparing correlation and calculated with the laboratory-determined oil formation volume factor, was found to be 2.00 per cent. Average error of 104 separator flash tests was 1.97 per cent. Introduction Based on the original method of Katz, a correlation of thermally-reduced oil formation volume factor and solution gas-oil ratio has been made from saturated Eastern Venezuelan crudes. The accuracy of this correlation, which requires a minimum amount of data and is easy to use, is sufficient for most reserves estimates. The average correlation error of 2.00 per cent for reservoir differential data compares closely with the 1.97 per cent error for separator flash data. While the accuracy of this correlation for other oil-producing areas is not known, there is close agreement with the general correlation of Katz. Also, there is a wide crude-oil gravity range represented, 15 degrees to 47.5 degrees API, with reservoir temperatures that range from 142 degrees to 307 degrees F. It is thought, therefore, that this correlation can be universally applied with reasonable accuracy. Wherever sufficient data exist, a cross plot can quite easily be made so that an area-oriented correlation is obtained. Construction and Error Fig. 1 is a correlation obtained from 159 differential liberation curves of saturated Eastern Venezuelan crudes. This correlation closely parallels the Katz general correlation previously made to a maximum solution ratio of 1,300 cu ft/bbl. Data obtained from volatile Venezuelan crudes shows that this correlation can be extended to 3,500 cu ft/bbl with good data conformance. The extension of the correlation is almost linear. Data used in Fig. 1 represent crude oils which range from 15 degrees to 47.5 degrees API. Reservoir temperatures of these crudes range from 142 degrees to 307 degrees F.