Evaluation of the Fluid Contact Estimation Using Phase Equilibrium and Irreversible Thermodynamics in The Hydrocarbon Column of Porous Media; A Case Study in Oil Fractured Saturated Reservoir in the Southwest of Iran

Determining fluid contact is one of the challenges of field development planning and reservoir management. From the thermodynamic point of view, the gas – oil contact depth there that the greatest changes in composition, so that the depth of discontinuity due to the instantaneous phase change occurs in the fluid contact. This instantaneous phase change is caused by gravitational, chemical and thermal forces. In this study, three crude oil samples from the Asmari oil fractured reservoir were evaluated in one of the fields. Samples of all three wells have datum depth, and they were obtained at above oil bubble point conditions. This study applied the combination of fluid properties and compositional gradient simulations to reduce the risk of fluid contact without the need for a new well or pilot well. In all three samples, the gas-oil contact was clearly obtained, so that in the best thermodynamic models the depth of gas-oil contact was calculated 1, 13, 75 and 73 feet respectively, is different with gas-oil contact depth by formation testing method. Finally, the results of this study will document that CGS is reliable and cost-effective for reducing fluid contact uncertainties and de-risking field development projects. Consequently, this method is recommended whenever credible PVT data are available from homogeneous and fractured saturated reservoirs.