| Abstract |
The mechanical properties variation, the fracture characteristic and the inclination of the well might perturb the development of wellbore failures. A comprehensive analysis of wellbore failures in the reservoir which related to various factors is performed based on detailed 1221 and 827 compressional and tensional wellbore failures, respectively, observed in a 3.5 km crystalline rock section of the GPK4 well in Soultz-sous-Forêts. Based on the different characteristics of the geometry of wellbore failures, two types of failures are observed: type I and type II. Type I failures show systematic deviation of wellbore failures orientation in the surrounding of major fracture zones, which might represent the large-scale stress heterogeneities. While type II has a characteristic of asymmetric failures shape and localized in the fracture zones. It is found that only type I failures can be used to estimate the in-situ stress field and its heterogeneity. As the development of type II failures is highly affected by the fracture characteristics, a careful analysis of type II failures can be used to qualitatively estimate the mechanical properties of the fracture zone. As most of the EGS target the crystalline rock, the understanding of the stress heterogeneity and fracture characteristics in granitic rock is crucial for the future development of the EGS. |