A Streamline-Based 3-Phase Equilibrium Compositional Model with Adaptive Implicit Method
選択的陰解法によるストリームライン法3相平衡多成分系モデル

Koya Akamine, Shusei Tanaka, Norio Arihara
2009 Journal of the Japanese Association for Petroleum Technology  
Oil and gas recovery processes in which transfer of fluid components between phases is a crucial factor require compositional simulation to appropriately evaluate production behavior. As compositional simulation computes phase compositions in equilibrium in addition to pressure and saturation, fast computation performance is highly desired. The streamline method, which excels the conventional finite-difference method in computational efficiency, was first developed for incompressible two-phase
more » ... low, and then has been proved later to be applicable to black-oil models and compositional models with compressibility effects. This paper presents development of a 3-dimensional, 3-phase compositional reservoir simulator based on the streamline method and its applications. The streamline method is an IMPES approach, in which a pressure equation derived from the component mole-balance equations is first solved implicitly for grid-block pressures, followed by explicitly solving 1-dimensional mole-conservation equations for compositions and saturation along streamlines. In the developed model, we implemented two essential functions, i.e. to effectively model fluid compressibility in the flow equation and to equally treat three phases in equilibrium calculations. The concept of effective density was utilized in the 1-dimensional equations to formulate the fluid compressibility that causes changes in fluid volumes on streamlines. Also in this model, the adaptive implicit formulation was employed in order to improve simulation accuracy in the neighborhood of well blocks where pressure, saturation and component mole fractions of each phase undergo rapid changes. The model validation was conducted by comparing the results from this model with those from a commercial finitedifference compositional model, and good agreements were confirmed. Use of the model was demonstrated for CO 2 injection into a depleted oil reservoir, which illustrates reliability of 3-phase equilibrium calculations. Further work includes improvement of water-saturation calculations.
doi:10.3720/japt.74.211 fatcat:h556toqrjvatpo6qimiytezxra