QA/QC on physical, mechanical, and mineralogical properties of geothermal rocks relevant for increasing the efficiency in EGS Wells

ABSTRACT: Geothermal energy provides clean, low-carbon, renewable energy, reducing dependence on fossil fuels. However, it is underutilized due to technical and economic challenges, particularly in Enhanced Geothermal Systems (EGS). Reports from NREL, CATF, and DOE-GTO highlight the main challenge: the geomechanical properties of crystalline rocks. Drilling efficiency in geothermal wells is lower compared to oil and gas (O&G) wells. While O&G technology can be applied to geothermal wells, the unique geomechanical properties of igneous rocks present a challenge. Collaborative efforts should infer these properties from parameters like gamma, mineralogy, density, porosity, and sonic measurements. However, geothermal resources for budget, hardware, software, and trained manpower are limited, and fit-for-purpose empirical models are lacking. This paper describes a method for qualifying and integrating rock properties for geomechanical models using eight mechanical, microstructural, and physical properties. Appropriate data quality assurance and control (QA/QC) procedures are performed. Pairs of property values are cross-plotted and compared for consistent correlation from literature. Outliers are flagged as questionable. In-depth investigation may highlight sources of inconsistency and establish more reliable values. Where this is not possible, the user has a rationale for rejecting the property value.