The RCGI institute is developing a R&D project that aims to perform the natural gas storage, the final confinement of CO2 (CCS) and a gravitational separation between CO2 / CH4 inside offshore Salt Caverns opened by seawater dissolution in ultra-deep-waters in Brasil. This project is sponsored by the oil company Shell Brasil to solve a current demand of some Brazilian pre-salt reservoirs to destinate a gas stream with high CO2 contamination that is produced in association with the oil extraction in the pre-salt reservoirs. These reservoirs have a continuous salt rock layer of 2000 meters as caprock, making possible the construction of salt caverns. The geomechanical simulation results carried out within the project demonstrates the technical feasibility of offshore giant salt caverns of 450 m high by 150 m in diameter, able to store 4 billion Sm3 or 7.2 million tons of CO2 at the pressure of 450 bar and 42 °C of temperature. As a first step in the project it has been decided to develop an experimental cavern to conduct experiments. This paper presents the results of the design of one of the most important parts of this technology, the well that will be used to construct and operate the experimental cavern.
The petroleum in the pre-salt reservoirs in Brazil possess very high GOR (gas-oil ratio) with high content of carbon dioxide. Some of these gasses are treated and separated on the platform using the membrane technology, reducing the CO2 content to 3%, and it is possible to transfer a portion of the natural gas to shore through carbon steel pipelines. The remaining part possessing mainly CO2 gas is reinjected back into the reservoir. At the beginning of the life of the fields, the reinjection of this gas supports EOR (enhanced Oil Recovery) in a process called WAG Water Alternated Gas. However, as the same molecule of CO2 recycles several times within the drainage radius of the wells, the CO2 content starts to increase significantly, making it unfeasible for its treatment in the platform, which may force the closure of production wells.