General Considerations for the Use of Offshore Depleted Reservoirs for CO2 Sequestration

Carbon dioxide (CO2) sequestration is one of the most effective ways of overcoming the excessive emissions of anthropogenic CO2 and the resulting climate change. The existence of large and accessible pore space, along with the wells, pipelines, and surface facilities, makes depleted oil and gas reservoirs a prime target for the deposition of CO2. This study aims to outline the primary considerations for sequestration of CO2 in abandoned oil and gas reservoirs, with a particular focus on offshore reservoirs in the Gulf of Mexico (GOM). We examine publicly available data from the Bureau of the Ocean Energy Management (BOEM) to gather insight into the existing porous formations in the GOM. Particular interest is given to the formations that have been assessed, developed, and are now abandoned. This approach has enabled us to identify significant storage potentials in shelf, shallow and deep parts of the GOM, making it possible to offer an abundance of safe and long-term storage options in this region. The first productions in the GOM started back in 1947. As of January 2018, over 900 GOM fields, including more than 5,000 reservoirs (also known as "Sands"), have since ceased production. The total pore volume of these reservoirs is over 175 million cubic feet or over 6.1 million cubic meters. Although many of the wells in these reservoirs are permanently plugged and abandoned (P&A), the existing knowledge about the pore space, the presence of proven seal and geomechanical stability, and the favorable depth of such sands are still highly relevant to commercially viable CO2 sequestration scenarios. Such knowledge can provide a wealth of knowledge, which had to be acquired otherwise prior to the development of the sequestration project. The present paper offers an overview of the potential CO2 sequestration candidates in the GOM and practical considerations for commercially viable and environmentally friendly sequestration sites. We examine the main factors contributing to the safety and sustainability of long-term storage and sequestration projects, along with remedial techniques that would pave the road for commercial leasing of pore space in the GOM for safe and effective disposal of CO2.