Real-time micro-fracture development and petrophysical evolution in shale during progressive loading using in-situ X-ray Micro-CT techniques
摘要
Understanding the evolution of shale microstructures under mechanical stress is critical for predicting reservoir behaviour in unconventional energy development. This study investigates the poromechanical response of Krishna-Godavari Basin shales using a multi-technique approach that combines in-situ X-ray micro-computed tomography, mercury intrusion porosimetry, and low-pressure gas adsorption (N2 and CO2). Cylindrical core plugs were subjected to progressive stress conditions (0–22 MPa) while being imaged in real time to capture microfracture initiation, propagation, and pore network reorganisation. Results show a clear transition from isolated micropores to larger, interconnected pore systems as stress increased. Micro-CT data reveal that void volume fraction increases from 0 to 22 MPa, with coordination numbers and permeability rising in tandem. Progressive loading increases the pore connectivity. Permeability increases from 0.05596 millidarcy to 2.2496 millidarcy as the applied stress increases from 0 MPa conditions to a stress of 22 MPa. Elastic behaviour continued up to 11 MPa, followed by crack nucleation at 11 MPa, stable crack propagation up to 19 MPa, and eventual coalescence and failure at 22 MPa. Pore network modelling confirmed that mechanical loading enhanced connectivity by merging smaller pores into larger, transport-efficient pathways. These changes reflect stress-induced systematic microstructural reorganisation, demonstrating the stress-sensitive nature of shale pore systems. The novelty of this work lies in its real-time, multiscale characterisation of poromechanical evolution, directly linking microstructural alterations to permeability gains. The findings have broad implications for optimising hydraulic fracturing design, forecasting hydrocarbon recovery, and improving geomechanical models of shale reservoirs.