Water-gas dynamics and coastal land subsidence over Chioggia Mare field,
northern Adriatic Sea
P. Teatini, D. Bau', G. Gambolati
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
ABSTRACT
A major development programme comprising 15 gas fields of the northern
Adriatic Sea has recently been submitted to the Ministry of
Environment, VIA Committee for the assessment of the environmental
impact, by ENI-Agip, the Italian national oil company. One of the
largest reservoirs is Chioggia Mare, located about 10 km offshore of the
Venetian littoral with a burial depth of 1000-1400 m. The
planned gas production from this field is expected to impact the
shoreline stability with a potential threat to the city of
Venice, 25 km northwest of the center of Chioggia Mare.
To evaluate the risk of anthropogenic land subsidence due to gas
withdrawal, a numerical model was developed that predicts the
compaction of both the gas-bearing formations and
the lateral/bottom aquifer (water-drive) during
a 13-year producing and a 12-year post-production period,
and the transference of the deep compaction to the ground surface.
To address the uncertainty of a few important hydromechanical
parameters, several scenarios are simulated and the most pessimistic
predictions obtained. The modeling results show that at most 1 cm of
land subsidence over 25 years may be expected at the city of Chioggia,
whereas Venice is not subject to settlement. If aquifer drawdown is mediated
by water injection, land subsidence is arrested 5 km offshore, with the Chioggia
littoral zone experiencing a rebound of 0.6-0.7 cm.
