A Unified Compositional Flow Model for Simulating Multiphase High-Enthalpy Geothermal Reservoirs

Presenter: Micheal Oguntola

Abstract:

High-enthalpy geothermal reservoir simulation presents significant challenges due to the interactions of multiphase, multicomponent geothermal fluid flow within porous media under extreme thermodynamic conditions. These conditions, characterized by high pressure and temperature gradients, induce complex phase transitions and non-ideal fluid behavior, requiring rigorous thermodynamic modeling. In addition, the dissolved minerals and high salinity of geothermal fluids often lead to mineral precipitation, which significantly impacts reservoir permeability and porosity, further complicating the simulation process. In this seminar, I will present a unified compositional model for high-enthalpy geothermal reservoir simulation, which integrates mass and energy conservation laws across predefined phases, advanced equations of state, and a comprehensive thermodynamic framework to handle phase transitions. The unified formulation maintains a persistent set of unknowns and equations, eliminating the need for manual phase switching while enhancing numerical stability and computational efficiency. The model captures essential phase behaviors and allows a general, thermodynamically consistent representation of fluid properties, crucial for the development and operation of geothermal reservoirs. Implemented within the open-source, Python-based framework PorePy, the model is validated through numerical experiments simulating various geothermal reservoir conditions. The results provide valuable insights into phase transitions, energy and component transport, and show strong agreement with key benchmark simulations from the commercial geothermal simulator CSMP++.