Parametric study and geomechanical design of Ultra-deep-water Offshore Salt Caverns for Carbon Capture and Storage in Brazil

Abstract

This article describes a new concept to reduce carbon dioxide emissions of offshore oil production of high gas-to-oil ratio reservoirs and high content of CO2, denominated Offshore Salt Cavern Ultra-deep Water CCS (Carbon Capture and Storage) System. This hybrid system is intended for natural gas storage, the gravitational separation between CO2/CH4, and CO2 confinement for final destination. This development emerged from a current demand of some Brazilian pre-salt reservoirs to destinate a gas stream with high CO2 contamination, produced during the oil extraction. These reservoirs have a continuous salt rock layer of 2000 m as caprock making the construction possible of salt caverns by leaching using seawater. In the first stage of technology development, the system will only store a gas stream contaminated with a high concentration of CO2. In the second stage of its development, it will allow not only the separation of natural gas from the CO2 but also its storage and the monetization of CH4. This paper presents the conceptual design of this technology, showing the steps from the parametric study to select the best relation between flowrate, leaching time, structural stability, and the volume of gas with the high content of CO2 storage, up to the final geomechanical design using the set of parameters selected.