Modeling of Compositional Grading and Plus Fraction Properties Changes with Depth in Petroleum Reservoirs

Abstract

Abstract In this work we use a nonisothermal model to predict compositional variation in a petroleum fluid column; at the same time, a nonisothermal model will be used to predict change of plus fraction molecular weight (and as a result all other its properties) with depth. We will investigate the effect of several factors as mode of characterization, binary interaction coefficients, volume shifts, and near-criticality on the change of physical properties, including bubble point pressure, solution gas–oil ratio, and oil formation volume factor. A computer program will be used to predict the location of the gas–oil contact and we will show how neglecting compositional grading (CG) can lead to serious errors in the calculated initial oil in place.