Geomechanical Restoration as a Means for Fault and Fracture Likelihood Prediction in Frontier, Tectonically Complex Basins

Continental rift basins result from lithospheric extension and thinning and can geometrically be characterized by graben, half-graben, horst blocks and tilted blocks separated mainly by normal faults. Formation of these structures, as well as smaller scale features such as fracture zones, is controlled by the interplay of stress, strain, strain rate, rock properties and pre-existing fabric and weakness zones during continental extension, leading to a great variety of basin geometries and architectures. Understanding the distribution and extent of subsurface faults and fractures is of paramount importance for various energy exploration and development activities, including hydrocarbon exploration and production, geothermal energy extraction, and subsurface fluid storage (e.g., carbon sequestration, wastewater disposal), as they can profoundly influence the distribution and flow of fluids (Salomon et al., 2020). Fractures in rift basins, mostly un-imaged using seismic data, are linked to the formation and growth of large seismically-imaged faults. Knowledge of the initiation and growth of the large faults can, therefore, provide insights into the distribution, orientation and extent of smaller fracture zones. Several models have been put forward in the literature to explain the initiation and growth of normal faults, with two major end members: constant length model (faults accumulating displacement after establishing their near-full lengths) and isolated fault model (faults growing by incrementally increasing their lengths and displacements) (e.g., see review in Childs et al., 2017). As the faults grow and interact, relay zones form in between individual faults. These zones transfer the strain between the discrete normal fault segments and, in doing so, become themselves deformed by form of fracturing, monoclinal folding and bed rotation (Fossen and Rotevatn, 2016). The strain transfer through these relay zones means that individual fault segments comprise a kinematically-linked fault. With continued extension, the relay zones become breached, hard-linking the fault segments to form a larger geometrically connected fault. Along the new fault surfaces, the locations of the breached relay zones are manifested as fault splays and bends along both the strike and dip.