An innovative, different, yet complementary approach to the "classic" CCS approach

Projects for the geological storage of CO₂ generally plan for its injection under supercritical conditions, i.e. in a state between gas and liquid, thus maximizing the stored quantities that can involve several million tons per year. When no site is available for the secure and durable storage of CO₂ near a major industrial producer, it must be transported to its injection site, entailing very high induced costs.

The CO₂-DISSOLVED project studies a different option that consists in injecting CO₂ dissolved in brine, close to the emitting source. The infrastructure for this is based on a set consisting of a production well and an injection well (click on the figure below), which allows pumping the brine from the reservoir and then re-injecting it after having been saturated in dissolved CO₂. With this process, it will be possible to overcome the inherent problems of the "classic" approach, such as the pressure increase and migration of the initially present brine, or the risk that CO₂ will migrate into overlying geological formations in the absence of a light gaseous or supercritical phase. In addition, it is planned to recover the heat in the brine pumped by the production well for local use by the industrial CO₂ emitter and/or for feeding a heating network.

The major drawback of this approach lies in the quantity of CO₂ that can be injected, which is physically limited by the solubility of CO₂ in the brine. However, injection rates of around 100,000 tons of CO₂ per year are a realistic target for a single doublet facility. The CO_2-DISSOLVED project will thus study the technical and economic feasibility of using this technology in the immediate vicinity of low to medium industrial emitters (10,000-150,000 tons of CO₂ per year) which are never considered with the supercritical injection methodology. As such, the CO₂-DISSOLVED concept opens a new potential market for CCS, complementary to the classic sector which remains more appropriate for much higher tonnages of CO₂ emissions.