Heat extraction from the geothermal reservoir is sensitive to reservoir properties, operating parameters and coupling among various processes. Due to complex reservoir structure, heat extraction performances and flow field behaviour in geothermal reservoirs are very different than the small scale laboratory model experiments. In recent past, significant progress in reservoir scale numerical modeling has been made for quantification of challenges in geothermal energy system development. In this paper, a comprehensive review of state of the art geothermal reservoir modeling for heat extraction is presented. Various numerical tools and approaches such as the finite difference method, finite element method, finite volume method, etc. to model the geothermal reservoir in the last four decades are discussed. The thrust of this paper is on a critical review of individual evaluation of coupling among all possible processes that are thermo, hydro, mechanical, and chemical processes on heat extraction performance. Future directions in developing better understanding on geothermal reservoir systems are proposed. © 2018 Elsevier B.V.