3D geomechanics in UGS projects. A comprehensive study in northern Italy
N. Castelletto, M. Ferronato, G. Gambolati, C. Janna, P. Teatini
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
D. Marzorati, E. Cairo
Stogit S.p.A., San Donato Milanese, Italy
D. Colombo, A. Ferretti
Tele-Rilevamento Europa S.r.l. (TRE), Milano, Italy
A. Bagliani, S. Mantica
Eni S.p.A. - Divisione E&P, San Donato Milanese, Italy
ABSTRACT
The 3D geomechanical response to seasonal gas storage is investigated for
a gas field managed by Stogit. The 1200 m deep reservoir is located in the Po
basin, Italy, and a UGS program is under way since 1986 following a 5-yr
primary production life. The use of i) a basin-scale geomechanical
characterization of the Po basin, ii) a detailed knowledge of the subsurface
geology made available by 3D seismic surveys, iii) almost 30-yr measurements
related to the gas field activities, and iv) an advanced PSInSAR analysis
providing the vertical and horizontal West-East displacements of the ground
surface above the field from 2003 to 2007 has allowed for the development,
set up, and calibration of a representative 3D fluid-dynamical model and a
transversally isotropic nonlinear geomechanical model. The latter successfully
reproduces the largest vertical and horizontal seasonal land displacements,
on the range of 8-10 mm and 6-8 mm, respectively, as observed above the gas
reservoir. The model is then used to investigate the ground surface displacements
in connection with UGS future programs where the maximum overpressure achieved
in the field is planned to be raised to 107% pi and
120% pi, with pi the original in-situ pore pressure.
