Geochemistry Study for the CO2-H2S Injection for Storage: Experimental and Modelling

Abstract

Abstract Realizing the risk and possible impacts of the H2S presence in the injected CO2 towards the overall of Carbon Capture and Storage (CCS) operation in carbonate reservoir, it is recommended to have an accurate knowledge of these behavior for safe and efficient CO2 injection and storage in the reservoir formation. Limited data available from the literature suggested that additional laboratory studies are required to measure and understand the behaviour of the CO2-H2S mixture on the carbonate rock reactions, and therefore the aim of the study is to measure the key geochemical reaction kinetics parameters between injected CO2- H2S, brine and reservoir rocks and their effects to the fluid, rock properties (chemistry, mineralogy, porosity, permeability). The core samples from Y Field have been selected and used as a case study since Y Field has been identified as one of the potential CO2- H2S storage sites and there are preserved core samples available. Briefly, the mixture of CO2-H2S gas with the H2S concentration level up to 500 ppm is co-mixed with brine water and aged with core samples under Y Field reservoir condition for duration of 30 days via static batch ageing using PT chamber. Cores and effluent collected at the end of ageing days were analyzed to measure the changes on the key geochemical parameters (i.e, rock porosity, permeability, mineralogy & images from CT scan) between post-ageing and pre-ageing. The experimental results will validate the geochemical models at such H2S concentrations, and it will greatly enhance the accuracy of the models used to predict CO2-H2S storage capacity and containment for high H2S fields. This study provides critical information on the kinetic rates, which are crucial inputs for both short- and long-term projections. The incorporation of these accurate data into the models will improve their ability to predict the behaviour of CO2 and H2S in the storage and containment process, thereby providing more reliable and actionable insights for future high H2S fields.