Abstract
The estimation of the stock tank gas-oil ratio (GOR) cannot be over-emphasized because it is a vital surface parameter required in the estimation of cumulative gas-oil ratio, the stock tank production rate and bubble point solution gas-oil ratio. Ideally, this property is determined via laboratory measurement which is not done regularly due to cost and sampling time. The three popular correlations developed for predicting this property were found to be less applicable in Niger Delta region. This challenge now led to the development of a new correlation by the author of this paper using Niger Delta data which is more applicable than the existing ones but still associated with appreciable error in its prediction. In this study, an improved stock tank GOR correlation for Niger Delta crudes is presented so as to reduce error of prediction. Unlike the former correlation, it is a non-linear four parameter mathematical model that depends on stock tank oil API gravity, separator pressure, separator temperature and separator gas gravity. A total of 222 PVT reports were obtained and validated using material balance, Campbell and Hoffman's Plots. Microsoft excel solver was used to generate the improved model for stock tank gas-oil ratio. The model was then validated with existing correlations including the one from Niger Delta region using statistical analysis and performance plots. The results of the validation showed an improvement in the accuracy of the prediction.
