Influence of Complex Internal Structures of Reservoir-scale Fault Zones on Shear Reactivation Induced by C02 Injection

摘要

Even though reservoirs targeted for C02 storage are expected to be located in low-deformed tectonic settings, they can still present reservoir-scale faulted structures. Such faulting at the medium sub-seismic scale can play a significant role regarding several risk issues related to the injection-induced fluid pressure increase (fluid compartmentalization, loss of integrity in reservoir-caprock systems potentially associated with triggered seismicity and generation of leakage pathways). Yet, the characterization of the hydro- mechanical behaviour of such reservoir-scale fault structures is still lacking mainly due to the necessary seismic resolution ranging from 1 to 10 m at the reservoir scale (i.e. the "sub-seismic region"). The objective of the present study is to gain a deeper understanding of the shear reactivation of such structures subjected to pore pressure increase induced outside the C02 injection zone. The present study relies on the combination of geological outcrop surveys in a carbonate analogue for C02 storage reservoir (southern France) and fully coupled hydro-mechanical finite-element two-dimensional simulations. A special attention was paid to the influence of the characteristics of two specific fault components: 1. damage zone geometry and 2. fault core architecture (curvature and number of curved branches).