Geomechanical Characterization of Storage Reservoirs by Assimilation of Surface Displacements

Gas injection into the subsurface is becoming increasingly popular worldwide in connection with Underground Gas Storage (UGS) and CO2 sequestration (CCS) projects. Depleted oil/gas fields or saline aquifers are strategically used to cope with the growing demand of energy and the planned reduction of the greenhouse efflux into the atmosphere. Due to the pressure increase caused by gas injection, porous rock formations expand and land surface rises. The surface displacements, when accurately measured for example by SAR interferometry, can be effectively used to evaluate the petrophysical and geomechanical properties of the injected formation. In this study, an Ensemble Smoother (ES) data assimilation technique is applied to reduce the uncertainty on the constitutive parameters characterizing the geomechanical model of a UGS field situated in the Po River basin, north of Italy. The assimilation has been implemented using vertical and East-West displacements measured by an advanced satellite technology based on Radarsat scenes collected between 2003 and 2008.