Fluid-Dynamic and Geomechanical Effects of CO2 Sequestration below the Venice Lagoon

Abstract

Simulation of CO 2 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 caused by 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 CO 2 sequestration in a brackish aquifer between 600 and 800 m below the Venice Lagoon is presented. Using available geological, geophysical, hydrologic, 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 CO 2 storage and the possible land uplift are concerned. The results show that with the most probable hydrogeological configuration the total amount of CO 2 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 percent of the ''acqua alta'' that 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.

The Geomechanics of CO2 Storage in Deep Sedimentary Formations

“…The magnitude of uplift will also depend on the thickness of the underground reservoir being pressurized at depth. For example, the possibility of CO 2 or water injection into a saline sandy aquifer lying 600-800 m under the lagoon of Venice, Italy, has been suggested for lifting Geotech Geol Eng (2012) 30:525-551 529 Venice from the sea, an estimated 30 cm (Abbot 2004;Comerlati et al 2006;Castelletto et al 2008). At the In Salah CO 2 storage project, around 2.5 cm of uplift have been observed as a result of CO 2 injection (Fig.…”

Numerical Modeling of Rock/Casing Interaction in Radioactive-Marker Boreholes of the Northern Adriatic Basin, Italy

“…As far as the constitutive law for c M is concerned, we elect to use the relationship developed by Baù et al (2002) as slightly modifi ed after Comerlati et al (2004Comerlati et al ( , 2006 (Fig. 6).…”

Ground displacement data around the city of Ravenna do not support uplifting Venice by water injection

“…The subsidence surfaces have been obtained with different models and codes; e.g. in Comerlati et al. (2003) with ECLIPSE (Schlumberger‐GeoQuest, 2003); in Gambolati et al.…”

“…whether a uniform uplift can be obtained in Venice as claimed by the proponents with numerical subsidence models of regional scale, shown in Fig. 1 (Comerlati et al. , 2003; Castelletto et al.…”