Ensemble smoothing of land subsidence measurements for reservoir
geomechanical characterization
D. Bau'
Dept. of Civil and Structural Engineering, University of Sheffield, UK
A. Alzraiee
Sandia National Laboratories, Carlsbad, New Mexico, USA
C. Zoccarato, G. Gambolati, M. Ferronato, P. Teatini
Dept. of Civile, Environmental and Architectural Engineering,
University of Padova, Padova, Italy
F. Bottazzi, S. Mantica
Development, Operations & Technology, eni S.p.A., San Donato
Milanese, Italy
ABSTRACT
The compaction of a gas/oil bearing reservoir or an aquifer system due to subsurface fluid production may result in
land subsidence as has been observed worldwide during the 20th century. Uncertainties on geomechanical parameters
typically affect model prediction of anthropogenic land settlement. Usually, soil compressibility, Young’s modulus, and
the Poisson ratio, that is, the most important parameters characterising the rock geomechanical properties, are derived
from laboratory tests and/or in situ measurements, whose reliability may be limited in some cases. In the present
work, the authors test the capability to reduce the uncertainty on geomechanical parameters by assimilating a given
number of surface displacements. A data-assimilation algorithm, known as ensemble smoother (ES), is used along
with a radial-symmetric finite element (FE) code in a realistic orthotropic geological setting, where a 1200-m deep disk-
shaped reservoir is assumed to be developed. The results show that the ES constitutes a quite promising tool to reduce
geomechanical uncertainties in modelling land subsidence.
