Monitoring and modelling 3-D ground movements induced by
seasonal gas storage in deep reservoirs
P. Teatini, G. Gambolati, N. Castelletto, M. Ferronato, C. Janna
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
E. Cairo, D. Marzorati
Stogit S.p.A., San Donato Milanese, Italy
D. Colombo, A. Ferretti
Tele-Rilevamento Europa S.r.l. (TRE), Milano, Italy
A. Bagliani, F. Bottazzi
Eni S.p.A. - Divisione E&P, San Donato Milanese, Italy
F. Rocca
Dip. di Elettronica ed Informazione, Politecnico di Milano, Milano, Italy
ABSTRACT
Underground gas storage (UGS) in depleted hydrocarbon fields is a strategic practice to cope with
the growing energy demand, and occurs in many places in Europe and North America. In response to
summer gas injection and winter gas withdrawal the reservoir expands and contracts almost elastically,
namely it "breathes", as a major consequence of the fluid pore pressure fluctuations. Depending on a number
of factors, including the field burial depth, the difference between the largest and the smallest gas pore
pressure, and the geomechanical properties of the injected formation and the overburden, the porous medium
overlying the reservoir is subject to a three-dimensional deformation related to the cyclic motion of the land
surface in both vertical and horizontal directions. We present a multidisciplinary methodology to evaluate
the environmental impact of UGS from a geomechanical point of view in connection with the ground surface
displacement that may cause some concern for the integrity of the existing engineered structures and infrastructures.
Long-time records of injected/removed gas volume and fluid pore pressure, together with multiyear
detection of vertical and horizontal west-east displacement of the land surface above the field by an
advanced PSInSARTM analysis have allowed calibration of a 3-D fluid-dynamic model and development of a
3-D transversally isotropic geomechanical model. The latter has been successfully implemented and used to
reproduce the vertical and horizontal cyclical displacements, in the range 8-10 mm and 6-8 mm, respectively,
measured between 2003 and 2007 above the "Lombardia" gas reservoir, northern Italy, where since 1986 a
UGS program has been under way by Stogit S.p.A. (Eni), following an initial 5-year field production life.
