Monia Procesi

Algorithms for CO2 Storage Capacity Estimation: Review and Case Study

The estimation of CO2 storage capacity in deep geologic formations is a pre-requisite for an efficient and safe application of Carbon Capture and Storage (CCS). The evaluation of storage resources for CO2 geological sequestration is a challenging task and has been tackled using several static algorithms and dynamic methods, on a variety of scales ranging from country to site-specific. The purpose of this study is to present an up-to-date as well as an overall review of the storage capacity algorithms for oil and gas reservoirs, coal seams, and deep saline aquifers, including some worldwide estimation examples. Moreover, a practical application at local scale was also performed for an Italian deep reservoir located in the Po Plain (Northern Italy). The effective storage capacities were obtained applying the commonly established static methods, using both the theoretical and the geocellular volume of the reservoir. Although a conservative approach, this study demonstrates that the selected structure has favorable characteristics for CO2 geological storage and has the capacity to host the most part of the Po Plain CO2 emissions for several decades.

Geochemical characterization of thermal springs in the Tete Province, Northern Mozambique.

The partitioning of Fe in sediments and soils has traditionally been studied by applying sequential leaching methods. These are based on reductive dissolution and exploit differences in dissolution rates between different reactive Fe (oxyhydr)oxide minerals. We used lab-made ferrihydrite, goethite, hematite and magnetite spiked with 58Fe and leached two-mineral mixtures with both phases abundant in excess of the methods dissolution capacity. Leaching was performed with 1) hydroxylamine-HCl and 2) Na-dithionite as the reactive agent. Following Poulton & Canfield (2005) [1], the first dissolution is designed to selectively leach the most reactive Fe-phases, ferrihydrite and lepidocrocite, whereas the second dissolution is designed to leach goethite and hematite. Magnetite would then be dissolved in a third dissolution step with oxalic acid. First results show that the hydroxylamine-HCl method for ferrihydrite dissolves only insignificant amounts of goethite and hematite. However, magnetite-Fe constitutes about 10% of the total dissolved Fe. The Na-dithionite dissolved Fe from goethite-magnetite and hematite-magnetite mixtures contain about 30% of magnetite-Fe. We applied selective sequential leaching and Fe isotope analysis to fine-grained marine sediments from a depocenter in the North Sea, which contain abundant reactive Fe (oxyhydr)oxides and show evidence for Fe sulfide formation within the upper 10 cm. Fe isotopes of the hydroxylamine-HCl leach targeting ferrihydrite shows a downcore increase of !56Fe typical for sediments undergoing microbial reductive Fe dissolution, whereas Fe isotopes of the Na-dithionite leach (goethite and hematite) and oxalic acid leach (magnetite) are identical and show no downcore variation in !56Fe. This means, that only the most reactive Fe phases participate in the Fe redox cycle in this location. The similar isotopic composition of goethite + hematite and magnetite suggests a detrital source, which is not utilized possibly due to the abundant ferrihydrite and lepidocrocite present. [1] Poulton & Canfield (2005), Chemical Geology 214, 209– 221Seasonal Methane Fluxes and Sulfate Reduction Rates in a Eutrophied Baltic Estuarine System