Akademik Veri Yönetim Sistemi
Rock Mechanics and Rock Engineering, 2026 (SCI-Expanded, Scopus)
Abstract: The pre-Neogene Menderes metamorphic basement rocks of the Gediz Graben host Türkiye’s second-largest installed geothermal capacity, highlighting the region’s pivotal role in advancing renewable energy initiatives. In this study, we present a comprehensive geomechanical model of the geothermal reservoir from Alaşehir field, located in the eastern part of the Gediz Graben. The “C-quality” breakouts in the overburden sedimentary interval indicate an E-W to ESE-WNW SHmax orientation in the study area. The studied pre-Neogene metamorphic basement rocks exhibit a predominantly normal faulting tectonic regime, with a breakout-constrained mean SHmax:Shmin ratio of 1.26. Caprock integrity assessment indicates that tensile failure within the Alaşehir shales may commence at an injection-induced pressure build-up of 22 MPa, which can be considered the practical injection threshold. The region’s structural framework is dominated by steeply dipping normal faults trending E-W or NW–SE, combined with low-angle detachment faults dissecting the metamorphic basement and Miocene sediments. Through detailed geomechanical modeling, we have simulated the shear slip potential of these discontinuities under various pressure build-up scenarios with varying geomechanical considerations. Critically stressed SHmax-parallel or subparallel steeply dipping fractures and normal faults exhibit shear slippage as pore pressure increases, enhancing hydraulic connectivity between injection and production wells. Under a pore pressure–horizontal stress coupling scenario, assuming a reduced frictional strength of these discontinuities, the model forecasts that approximately 33% of natural fractures with dips > 45° may undergo slip, which can contribute to the permeability enhancement of the fluid conduits, facilitating improved heat extraction. In contrast, low-angle graben-bounding detachment faults (dip < 15°) appear stable within the practical injection window. The study offers critical insights into the complex interactions between natural fractures and in situ stress redistribution during fluid injection, which contribute to improved hydraulic connectivity and induced seismicity risks, thereby impacting geothermal resource management. Highlights : The in-situ stress distribution indicates a normal faulting stress regime in the Alaşehir geothermal field. Maximum horizontal stress is constrained based on the breakout occurrences. Rock-mechanical properties of the geothermal reservoir are established by core tests. Caprock integrity assessment provided the practical injection threshold. Injection-induced shear slippage on optimally oriented discontinuities is simulated at various pressure build-up scenarios with varying geomechanical considerations.