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

Mohammad Hossain Nikpoor, Riyaz Kharrat, and Zhangxing Chen


In this work we use a non-isothermal model to predict compositional variation in a petroleum fluid column; at the same time, a non-isothermal 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 effect of several factors as mode of characterization, binary interaction coefficients, volume shifts and near-criticality on the change of physical properties like bubble point pressure, solution gas-oil ratio and oil formation volume factor. A computer program will be used to predict location of gas-oil contact and finally we will show how neglecting compositional grading (CG) can lead to serious errors in the calculated initial oil in place.