Land surface uplift above compacting overconsolidated reservoirs
M. Ferronato, G. Gambolati, P. Teatini, D. Bau'
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
ABSTRACT
An investigation on land surface deformation resulting from the compaction
of producing overconsolidated gas/oil reservoirs is presented. If the depleted
formation is significantly less compressible than the surrounding medium
the vertical reservoir shrinkage is relatively smaller than the
horizontal one, thus generating a possible swelling of the overburden
and a consequent pronounced decrease of land subsidence or even a surface
uplift. Such an effect may also cause an additional land settlement during the
post-productive recovery phase over fields which exhibit a stiffer behavior
in expansion. In the present paper the surface displacements caused by
the depletion of an overconsolidated disk-shaped reservoir are analysed by a
finite element model taking into account the influence of the disk burial
depth and areal extent, the Poisson ratio of the medium, and the underburden
stiffness. The results obtained with a more realistic three-dimensional
setting are also discussed to address the possible effects of an irregular
reservoir geometry.
