Geomechanical response to seasonal gas storage in depleted
reservoirs: A case study in the Po River basin, Italy
N. Castelletto, M. Ferronato, G. Gambolati, C. Janna, P. Teatini
Dept. of Civil, Environmental and Architectural Engineering,
University of Padova, Padova, Italy
D. Marzorati
Stogit S.p.A., San Donato Milanese, Italy
Underground gas storage (UGS) and CO2 sequestration (CCS) are strategic practices
to address the growing demand of energy and reduction of greenhouse gas emission.
There is an interest from the energetic, economic, and environmental viewpoint to store as
much gas as possible consistent with the requirement of a safe disposal. A transversely
isotropic geomechanical model is developed and calibrated using the vertical and horizontal
displacements measured by SAR-based interferometry over an exhausted gas field located in
Northern Italy where UGS is active since 1986. The predictions show that a maximum storage
pressure up to 140% pi, pi being the virgin fluid pore
pressure, may yield a 400% increase of the gas stored relative to pi provided
that an accurate assessment of the parameters defining the yield surface, i.e. friction
angle and cohesion in the Mohr-Coulomb criterion, is performed for the reservoir formation.
No appreciable risk for the integrity of the sealing layer is ever expected, along with a
negligible impact on the ground structures. Land motion does not exceed few centimeters
with the differential displacements safely below the bound required by structural safety.
