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Integrating Geomechanical Modeling with Conceptual Fracture Network Models

Stephen J. Dee1, Serena Jones2, Brett Freeman1, and Graham Yielding1
1 Badley Geoscience Limited, Hundleby, Lincolnshire, United Kingdom
2 Midland Valley Exploration Limited, Glasgow, United Kingdom

Predicting the effects of the small-scale fault and fracture network on reservoir behaviour requires a definition of the total fracture network. Advances in the application of Elastic Dislocation theory predict the 3D strain and stress tensors in the rock volume surrounding seismically-resolved faults using their fault geometry and cumulative slip. Displacement and strains may be computed at the surface or subsurface for any fault geometry slip distribution or source mechanism, for multiple and intersecting faults and for complex faulting histories. Key to the development of a robust model of small-scale faulting and fracturing are (1) a geometrically consistent framework model, (2) choice of mechanical properties, and (3) the applied regional background strain. Elastic dislocation modelling provides a robust basis for the development of conceptual models of fracture orientations, density and mode that are used to feed stochastic modelling.

The conceptual fracture model is built from the geomechanical modelling results and integrated with a geological understanding of the reservoir. In order to test its validity, the conceptual model needs to be calibrated against ground truth data, including observed densities of fractures from cores and borehole image logs, seismic data, models of the sedimentology and production data sets. Discrete fracture network models based on a geomechanical, geometrical and conceptual understanding of the fracture network can be calibrated to, and tested against, the observed production characteristics at well locations. Key to effective dynamic simulation of the fractured reservoir is the development of appropriate model parameters.