Open thermodynamic model for compressible multicomponent two-phase flow in porous media

The compressible compositional two-phase flow in porous media was considered. This system was characterized by two essential parameters: the perturbation parameter and the relative mobility parameter. The perturbation parameter represents the stabilization time of the pressure field after perturbation. The relative mobility parameter represents the interior characteristic of the system by the ratio between liquid mobility and gas mobility. For the contrast phase mobility and fast pressure relaxation process an open thermodynamic model was obtained by HT-splitting. This model includes several differential thermodynamic equations for characterization of the transport phenomena (Delta Law), i.e. describes the equilibrium in an open system. A new open thermodynamic simulator (OTS) was developed. The OTS simulations are validated by the full compositional flow simulations using Eclipse. However, compared to the full compositional simulator an evident advantage of the new OTS simulator is the fact that due to the independence from space and time, data construction demands an extremely short time of calculation. Moreover this new approach does not limit the number of chemical components in the system. The closed thermodynamic system was shown as behaving similarly to the open system for several test cases. In order to characterize the difference between the closed and the open thermodynamics we proposed to use Delta Law for one chemical component and a variation function for the combination of all components. This behavior depends on mass conservation in an individual volume. The closed description can be realistic if the incoming gas in an individual volume is not different from the leaving gas: otherwise the use of the open approach (new or classical) is suggested. (C) 2011 Elsevier B.V. All rights reserved.