How to Address Subsidence Evaluation for a Fractured Carbonate Gas Reservoir Through a Multi-disciplinary Approach

This paper presents and discusses the outcome of a multi-disciplinary study aimed at evaluating ground surface movements which could be potentially induced by the future gas production of a carbonate reservoir located in central Italy. Thanks to both good quality and quantity of data (i.e. seismic surveys, well logs, petrophysical data, PVT-PressureVolumeTemperature- fluid data, geotechnical lab data) the issue was addressed via the set-up of a coupled 3D fluid flow and mechanical model based on the preliminary definition of a 3D structural and geological model. Because it is a forecast study, no model calibration was possible, consequently a set of sensitivity analyses were performed so as to assess the effect of the most critical parameters on subsidence evolution. The 3D FEM (Finite Element Method) mechanical model was set up by adopting an elastoplastic constitutive law. The model was populated via the integration of data from different sources at different scales (i.e. lab tests, in situ acquisition, literature) and data interpretation adopting a traditional rock mechanics approach, in other words Bieniawski classification and the Barton classification. The obtained strength and deformation parameters depend on the Hoek and Brown criterion and the GSI classification application