Multi-Scale Geomechanical Modelling of Unconventional Shale Gas: The Implication on Assisting Geophysics–Geology–Engineering Integration

Abstract

In the development of unconventional shale play, simulation of the performance for wells needs to incorporate sufficient complexity in geology to take fully into account the variabilities in petrophysical and geomechanical properties. These parameters controlling the effective stimulated rock volume (eSRV) represent the heterogeneity and strong-layering nature of unconventional reservoirs: high inter-bedding anisotropy, flow behaviours and pre-existing geological disconnections (bedding planes, faults, fissuring, natural fractures). This realistic simulation model includes direct information and interpreted understanding from data sources in a wide range of resolutions and scales and is finally coupled with hydraulic fracturing and reservoir depletion modelling in terms of mechanical. The multi-scale geomechanical model incorporates processed seismic interpreted data (10 m scale), petrophysical core data (cm scale), routine scalar logs (m scale) and resistivity borehole image (0.25 cm scale). The vital role the multi-scale geomechanical model plays during the entire workflow is to underpin the disconnection among actual well logs, conventional seismic interpretation and geological complexity by calculating and predicting field scale geomechanical parameters and in situ stresses distribution. Multiple research investigations and case studies on such integration include data acquisition and processing methods, modelling upscaling methodologies and data diagnostical techniques from multidisciplinary perspectives. Although these works show great progress in improved understanding of the spatial and temporal distribution of formation reservoir and geomechanical distribution, uncertainty remains as local stress variations and mechanical-flow properties between layers are impossible to capture.