Development of geothermal reservoir simulator for predicting water-steam flow behavior considering non-equilibrium state and MINC/EDFM model

Although the reservoir simulation is widely utilized to predict geothermal reservoir performances, the results of the simulation are sometimes different from those actually observed in field operations due to non-equilibrium conditions and poor modeling of fracture system. Therefore, in this research, we attempted to develop a numerical simulator that can deal with the phase change of non-equilibrium state and the fractured system to predict geothermal reservoir performances more accurately. Also, we aimed to construct an optimization simulator which can estimate the appropriate parameters associated with the non-equilibrium state and the fracture model for history matching. First, we developed a three-dimensional simulator that can predict the flow behavior of geothermal fluids in the non-equilibrium state. Non-equilibrium vaporization and condensation of water molecules are expressed by adjusting the kinetic rate of transportation of water molecules across phases. Next, we expanded the functions of the above simulator, incorporating two types of double porosity models of Kazemi and MINC (Multiple Interacting Continua), and EDFM (Embedded Discrete Fracture Model), to reproduce the fluid flow preferentially through fractures and faults. Then, we added the function to tune the parameters defining fracture and non-equilibrium properties in order to assist us to optimize these parameters. After verifying the simulator functions, we conducted case studies. Case studies suggests that the optimization simulator could give us the appropriate parameters of non-equilibrium state and fractured reservoir model, which enable us to get more accurate prediction even in coarse grids model and improve the fracture model. Finally, we concluded that this simulator could successfully handle the fluid flow through faults/fractures in non-equilibrium state which improved the reliability of prediction.