Numerical Investigation of Hydraulically-Driven and Chemically-Driven Fractures in Geological Subsurface

Abstract:

Geological subsurface systems have shown promises in terms of both storage as well as energy units. Newly-formed and pre-existing fractures as well as the existence of faults introduce highly heterogeneous systems that pose many challenges in predicting the long-term performance of these geological systems. Most subsurface fracture networks are hydraulically-driven, which is dependent on the hydrological and geomechanical properties of the host formation. However, geochemical effects at the crack tip can also impact the fracture behaviors. This presentation highlights the role of couple processes in long-term assessment of geological systems by looking at (i) hydro-mechanical coupling at reservoir scale and (ii) chemo-mechanical processes at mesoscale. At the reservoir scale, equally-spaced fracture networks will be modeled throughout the caprock formation and their interaction with fault systems will be investigated. The non-linearity associated with stress field and the fracture aperture lead to anisotropic permeability tensor, which defines the leakage pathway. At the mesoscale, the state-of-the-art phase-field fracture technique will be used to study chemically-driven fractures in different rock formations. The reservoir models show the integrity of the system depends on the interaction of pre-existing fractures and fault, which itself is highly dictated by its hydrological properties. The mesoscale simulations reveal the importance of chemical damage in addition to mechanical damage and how crack behavior is influenced by dissolution rate leading to a non-linearity in the overall performance of fractured rock.