Fluid-dynamical and geomechanical effects of CO2 sequestration
below the Venice Lagoon
A. Comerlati, M. Ferronato, G. Gambolati, M. Putti,
P. Teatini
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
ABSTRACT
Simulation of CO2 sequestration in deep geological formations is a
multi-disciplinary effort involving the study of multi-phase flow of
groundwater and carbon dioxide along with porous medium deformation due
to pore pressure increase. The latter can cause the ground surface to rise
because of the reduction of the effective stress in the aquifer and consequent
rock expansion. A preliminary analysis of CO2 sequestration in
a brackish
aquifer between 600 and 800 m below the Venice Lagoon is presented. Using
available geological, geophysical, hydrological, and geomechanical data, and
with the aid of advanced numerical models, several scenarios are addressed
to investigate the potential of the proposed solution as far as both the
CO2 storage and the possible land uplift are concerned. The results
show that with the most probable hydrogeological configuration the total amount
of CO2 released from nearby thermo-power plants, i.e. 20 Mt/year,
can be safely sequestered, with an expected city uplift over 10 years ranging
between 7 and 13 cm, depending on well configuration. This would make up for
most of the anthropogenic land subsidence experienced by Venice over the last
half-century and could offset between 50% and 70% of the ''acqua alta''
which periodically floods Venice. The simulations, however, show a high
sensitivity to sand permeability and compressibility, which points to the
need for new field investigations before the present preliminary proposal
may be turned into an actual feasibility study.
