Coupled Reservoir, Wellbore and Surface Plant Simulations for Enhanced Geothermal Systems

摘要

To enable the complete optimization of a geothermal system requires fully-coupled models that include the reservoir, the wellbore, and the surface plant. In order to find a true global optimum for the operation of a geothermal system over its lifetime requires that one should be able to integrate the subsurface and the surface, including operating parameters and the subsequent capital cost as well as operating costs. Integrating these simulations together could allow for a reduction in the levelized cost of electricity (LCOE) or direct-use heat (LCOH) as well as decreased simulation time due to the implicit coupling of the three major components of a geothermal system. This paper presents a combined model to simulate flow in reservoir as well as in the wellbore and evaluates the LCOE and LCOH from Enhanced Geothermal Systems. The components of this combined model includes two dimensional unsteady state single phase wellbore simulator coupled with the reservoir simulator TOUGH2-EGS (Xiong et al., 2013) plus a surface plant model. The wellbore and surface plant models are incorporated implicitly as subroutines in the TOUGH2-EGS main program. A single input file is read in to the combined model and the flow in reservoir and wellbore is solved in fully-coupled manner. The output parameters at the production well head are then taken as an input in to surface model which provides an estimate of the LCOE or LCOH. The coupling procedure is explained in detail in this paper. Two example problems are shown to demonstrate use of the model.