Experimental Integrated Workflow Activities for CCS Application

Abstract

Abstract One of the main drivers of climate change in terms of global temperature rise in recent decades are anthropogenic greenhouse gases, in particular carbon dioxide (CO2). Several decarbonization strategies have been proposed to limit global warming. The geological sequestration of CO2 emissions is one of the actions promoted by the European Union to achieve neutrality in terms of carbon emissions by 2050. To achieve secure and lasting storage of CO2 in underground spaces, it is necessary to have besides a good reservoir, a low permeability caprock (seal), that maintains its integrity. For this reason, the main aspect is to investigate, as accurately as possible, the interaction phenomena among rock, formation fluids and CO2 at field and basin scale, from a static and flow-dynamic point of view. In this work, we present methodological workflow developed in the Eni laboratories, to achieve maximum integration between experimental analytical and modeling activities in all Carbon Capture and Storage (CCS) projects. The defined workflow allows to integrate the skills developed in the hydrocarbon reservoir characterization and management for a different objective such as the capture and storage of CO2. The integrated experimental workflow is consisting of 5 macro steps (1) sedimentology & stratigraphy studies based on core, cuttings, and log data, (2) initial rock and fluids characterization (fluid characterization is also critical for CO2 plume monitoring), (3) static and flow-dynamic testing, (4) final rock and fluids characterization and (5) simulation modeling. The integrated data obtained from initial and post-testing characterization allow to evaluate the rock and fluids behavior from a mineralogical, petrographic, petrophysical and geomechanical point of view to assure representativeness for the storage complex under study. Static testing (i.e., ageing tests) are supporting geochemical and geo-mechanical studies. The geochemical study is focused to identify and quantify the presence of reactive processes that occur between the mineral phases of rocks and CO2. This allows for an accurate calibration of geochemical numerical models. Also, from a geomechanical point of view it is necessary to evaluate the effects of CO2 on the rock mechanical properties, i.e., strength and deformability. The testing results will become an important input data for simulation modeling. Flow-Dynamic testing (i.e., core flooding tests) are conducted to simulate the region near the wellbore during CO2 injection allowing to better investigate the "dynamic" interaction of the CO2-brine system with the porous medium at reservoir pressure and temperature conditions. Petrophysical parameters, mineralogical, chemical, and petrographic rock properties are correlated with water analyses after the exposure to the CO2 injection. All data and test results are the input for the geological-geochemical reactive-transport models, aimed at the quantification of the reactive processes between rock and CO2 during the ageing period. This allows to define accurately the geochemical model for the prediction of the reservoir storage capacity/efficiency and of the cap rock tightness over a large period (100s to 1000s of years). The newly developed integrated workflow is a result of the interdisciplinary exploitation of the capabilities developed in the hydrocarbon reservoir characterization and management and permits to populate adequately the numerical models for the prediction of the reservoir/cap-rock behavior during CCS.