Scratch Test Utilization to Characterize Contrasting Geomechanical Properties in Enhanced Geothermal System

Enhanced geothermal systems (EGS) are reservoirs that have been stimulated to efficiently extract heat from low permeability high-temperature rocks. Hydraulic fracturing treatment is one of the most efficient stimulation techniques currently utilized in heat extraction from EGS. The subsurface reservoirs including EGS, are highly characterized by heterogeneous mechanical properties and geology, which includes pre-existing natural fracture networks that are filed with mineralization. In this paper, we present how heterogeneity in rock mechanical properties and geology will impact the extraction of heat from EGS. We utilized the Scratch test method to characterize the mechanical properties of a subsurface rock from a basin of high-temperature region. Our results show heterogeneous mineral and rock strength distributions over the rock sample length. In addition, our results show that the mechanical rock response of the stimulated geothermal system will not be the same as that of a homogenous isotropic rock volume. Further, we suggest the scratch test technique for the rapid characterization of geomechanical properties in EGS. Lastly, we recommend that modeling of fracturing for EGS should include a heterogeneous rock volume with detailed mechanical characteristics of the rock properties of individual mineralized zones or mineral zonation of the rock matrix. This work provides more insights to understand how the heterogeneity of fractomechanical behavior and geomechanical properties influence EGS.