A Method of Multi-phase Compositional Modeling under Sub- and Supercritical Thermodynamic Conditions

Abstract

We propose a new compositional modeling method for sub- and supercritical flows subjected to various phase equilibria, particularly to three-phase equilibria of vapour-liquid-liquid type. The method is based on the calculation of the thermodynamic potential of reservoir fluid as a function of pressure, total enthalpy and total composition and storing its values as a spline table, which is used in hydrodynamic simulation for accelerated PVT properties prediction. This technique is utilized in our thermal simulator MUFITS (www.mufits.imec.msu.ru). We provide the description of both the spline calculation procedure and the flashing algorithm. We apply our method for the problems of hydrocarbon recovery. We evaluate the thermodynamic potential for a mixture of two pseudo-components modeling the heavy and light hydrocarbon fractions. We develop a technique for converting black oil PVT tables to the potential, which can be used for in-situ hydrocarbons multiphase equilibria prediction under sub- and supercritical conditions, particularly, in gas condensate and volatile oil reservoirs. We simulate recovery from a reservoir subject to near-critical initial conditions for hydrocarbon mixture. We consider problems of CO2 injection in shallow and deep reservoirs. We provide the simulation results for a 2D problem with a highly heterogeneous reservoir using data from the 10th SPE test. We demonstrate the simulation results for three-phase flows with both gaseous and liquid CO2-rich phases. We analyze the temperature variations in the reservoir due to the liquid CO2 evaporation under subcritical conditions. We consider parallel 3D simulations of supercritical CO2 plume evolution in Johansen formation.