Brittle and Semibrittle Deformation of Limestones - Experiments and Model
A. Nicolas, J. Fortin, J.B. Regnet and Y. Guéguen
Event name: 79th EAGE Conference and Exhibition 2017
Session: Fractured Reservoirs
Publication date: 12 June 2017
Info: Extended abstract, PDF ( 767.46Kb )
Price: € 20
Deformation of carbonate rocks can either occur with dilatancy or compaction, having implications for porosity changes, failure and petrophysical properties. Hence, understanding the micro-mechanisms responsible for deformation is of great interest. In this study, the brittle-ductile transition of a low-porosity limestone is observed during constant strain rate deformation experiments performed at various confining pressures and T=70°C. A constitutive model for the stress-strain relation during deformation of low-porosity carbonate rocks is derived from the micro-mechanisms identified. The micro-mechanical model is based on (1) brittle crack propagation, (2) a plasticity law for porous media with hardening and (3) crack nucleation due to dislocation pile-ups. The model adequately predicts a brittle behaviour at low confining pressures, which switches to a semibrittle behaviour characterized by inelastic compaction followed by dilatancy at higher confining pressures. Model predictions are in close agreement with experimental results. The porosity range of applicability of the model is found to be 0-20%.