Abstract
In 2006, giant oilfields were discovered in Brazil in a water depth of ∼ 2200 m and under a caprock of 2000 m of continues salt rock overlaying the reservoirs, called pre-salt. Currently more than a half of the Brazilian oil and gas production comes from these reservoirs. However, some of these assets have big Oil & Gas ratio with a high level of CO2 contamination, which are currently being reinjected in the reservoirs. This procedure gradually increases the CO2 content associated with the oil extracted, reducing well productivity and leading to high costs of CO2 and CH4 separation by the membrane technology. The Research Center for Gas Innovation (RCGI) located at the State University of São Paulo in Brasil, sponsored by Shell Brazil, is developing a technology that uses the thick layer of salt rock overlying the pre-salt reservoirs to build caverns where the contaminated gas will be injected and decontaminated. After 2 years of extensive research, several studies have been carried out to analyze the main critical aspects of the technology in order to evaluate its feasibility, and now it has been decided to advance to the field proof stage. The salt dome studied can accommodate the construction of 15 caverns, thus providing the confinement of approximately 108 million tons of CO2. Before the system be construct in full scale, it was decided to initially build an experimental cavern with smaller size to obtain field parameters of the final design of the caverns. This paper describes this development denominated Offshore Salt Cavern Ultra-deep Water CCS System, that aims to perform the natural gas storage, a natural gravitational separation between CO2 / CH4 inside the caverns, and the confinement of CO2 (CCS). It presents important results related to structural integrity analysis of the giant and experimental caverns, well design using the same methodology applied in more than 200 projects of the pre-salt oil wells, instrumentation plan of the experimental cavern, storage capacities and other relevant data. If the economics proves feasible, this offshore gas storage station will be the first of its kind and possibly the biggest CCS Project in the world.
