Screening Depleted Reservoirs and Aquifers for CO2 Geo-Sequestration, and Assessing Implications for Converting an Offshore Platform for Carbon Capture and Storage Project

Abstract

Abstract Re-using the depleted reservoirs for CO2 storage offers advantages over saline aquifers, as the geological characteristics required for CO2 storage have been pre-determined with high accuracy throughout the reservoir production life, plus a proof of secure containment. Additionally, re-using the production facilities and offshore platforms for the injection of CO2 would be economically and environmentally winning fact. This paper is based on intensive bibliographic research related to challenges and concerns of CO2 storage in depleted oil and gas reservoirs, for the selection of the optimum solution for converting the offshore platform GREEN1 in the Adriatic Sea to be re-used instead of decommissioning. It also highlights the interactions between the reservoir parameters and the design of surface facilities. The design of all the upstream components, i.e., transportation pipeline diameter, compression capacity, and maximum allowable pressure is mainly based on the rock and fluid interactions in the reservoir porous media. Storage capacity has a pivotal role in the candidate sites screening process, accompanied by an economic feasibility study. CO2 storage capacity of ‘Porto Corsini Mare’ reservoir, as a candidate site for GREEN1, is estimated based on returning the depleted reservoir to its initial pressure before production. A methodology for comparing and selecting suitable reservoirs and aquifers for CO2 geo-storage is introduced in this paper for the purpose of identifying the optimum storage site for GREEN1 platform. The screening criterion is divided into three main categories: storage capacity, injectivity, and containment, in a shape of logic flow charts with the relevant parameters to each category, in order to help analysts and decision makers identify and compare candidate sites for CO2 storage, so that they are easily able to exclude the unsuitable reservoirs and proceed with the right candidates for further economic and risk assessment studies.