An EGS Site Evaluation Method for Geothermal Resources Based on Geology, Engineering and Economic Considerations

Abstract

Site screening is one of the most crucial factors in the ultimate success of EGS (Enhanced Geothermal System) resource exploration. It should cover key project factors such as the geothermal gradient, reservoir temperature, water-storage capacity, and water-bearing condition in the reservoir rocks. During the technical and economic evaluation of geothermal resources, middle-to-deep geothermal resources can be classified as either hydrothermal or HDR (Hot Dry Rock). The former involves fluid-bearing reservoirs with excellent or poor storage capacity, while the latter consists of the following reservoir types: HDR with excellent storage capacity, HDR with poor storage capacity, and HDR with no storage capacity. Of these reservoir types, inferior fluid-bearing reservoirs, HDR reservoirs with excellent storage capacity, and HDR reservoirs with poor storage capacity are the most suitable for EGS exploration and development. The quantities of these five natural geothermal resources can be arranged into a pyramid-like structure, wherein the technical difficulty of resource exploration increases from top to bottom. Based on geological resources, engineering technology, and economic considerations, an evaluation method has been proposed for EGS site screening and the identification of key indexes by combining tri-factor analysis and multi-tiered index calculations.