Preliminary results of geological characterization and geochemical monitoring of Sulcis Basin (Sardinia), as a potential CCS site

The Sulcis Basin is an area situated in SW Sardinia (Italy) and is a potential site for the development of CCS in Italy. This paper illustrates the preliminary results of geological characterization of fractured carbonate reservoir (Miliolitico Fm.) and the sealing sequence, composed by clay, marl and volcanic rocks, with a total thickness of more than 900 m. To characterize the reservoircaprock system an extensive structural-geological survey at the outcrop was conducted. It was also performed a study of the geochemical monitoring, to define the baseline conditions, measuring CO2 concentrations and flux in the study site

A Contribution to the Geological Characterization of a Potential Caprock-Reservoir System in the Sulcis Coal Basin (South-Western Sardinia)

The results provided by this study contribute to the geological characterization of a potential caprock-reservoir system for CO2 storage in the experimental area of the mining district of the Sulcis Coal Basin (south-western Sardinia, Italy). The work is aimed to improve the knowledge of the petrographic and petrophysical characteristics of the siliciclastic and carbonate geological formations that make up the potential caprock-reservoir system. Core samples from a number of wells drilled in the study area for mining purposes were analyzed especially for texture and physical properties (longitudinal velocity, density, porosity, and permeability). The preliminary integrated petrographic and petrophysical characterizations indicate that the Upper Paleocene to Early Eocene potential carbonate reservoir is heterogeneous but presents suitable reservoir zones for CO2. A preliminary analysis of the potential caprock siliciclastic lithologies of the Middle Eocene to Lower Oligocene suggests that they appear suitable for CO2 confinement. Finally, to account for the stability of the investigated area, an accurate geodynamical study of south-western Sardinia was carried out using global navigation satellite system and advanced differential interferometric synthetic aperture radar methodologies in order to estimate vertical and horizontal crustal displacements. The study area results stable, since it is characterized by surface crustal horizontal and vertical velocities smaller than 1 mm/year and few mm/year, respectively

Characterization of fractured rocks for the design of a pilot-scale CO2 injection site in the Sulcis Basin, Italy

The naturally fractured carbonates have a great potential for Carbon Capture and Storage (CCS) purpose because they could offer the possibility for CO2 storage in areas where no suitable sandy reservoirs are available, as for example in the Mediterranean area, where most of the stratigraphic succession is composed by carbonate rocks. The Sulcis basin, located in the south-western part of Sardinia island (Italy), is an ideal site for technology development. Although the site is not feasible for commercial-scale geological storage (mainly due to the lack of stationary CO2 sources), it represents an optimal location for pilot-scale experiments. Thanks to data available from several national and international projects, as well as from the mining activities, it has been possible to recognize a potential reservoir-caprock system, suitable for pilot-scale CCS development. A sequence of well bedded, about 50 m thick, mudstones and grainstones (“Miliolitico Fm.”) has been identified as a potential reservoir; the caprock is represented by a thick succession of siltstones, sandstones and conglomerates (“Cixerri Fm.”) and up to 900 m of OligoMiocene volcanic rock, ranging from basaltic to rhyolitic composition. In this work we present the results of several geophysical and geological surveys, including reflection seismic profiles, and geo-structural analysis. All the data were combined in a 3D model, defining the volumes of each formation. The evaluation of the storage capacity and the existence of a thick and impermeable caprock are essential to consider the site suitable for the experimental tests. With this aim, we measured primary porosity and permeability, whereas the fracture network was studied using scan lines and scan areas techniques on outcropping analogue of reservoir and seals. The measured linear parameters were used to build several Discrete Fracture Model (DFN) both of reservoir and caprock formations. In particular, DFN were constructed varying length and aperture values to evaluate their influence on the total secondary porosit