Combined Geothermal and Dissolved CO2 Storage System - Example of Application to a Geothermally Heated Greenhouse Area in the Netherlands
8 Pages Posted: 15 Apr 2019 Last revised: 27 Oct 2020
This paper explores the concept of combining a geothermal energy system with CO2¬ storage. Introducing CO2 in dissolved form into the cold return stream of a geothermal doublet would lead to inherently safe CO2 storage, while generating the possibility of an additional revenue stream for the a geothermal operator. Moreover this concept could also provide a solution for smaller emitters, located far from storage sites or transportation facilities, but close to (potential) geothermal systems. It uses a low-cost CO2 capture technology. Storing CO2 in dissolved phase by co-injection with the geothermal water, increases storage security and safety compared to supercritical storage. The absence of buoyancy as an upward migration force removes the risk of leakage. Because of this, a caprock is not required and therefore more storage sites become available. This is only true if degassing, both on the short- and the long-term, can be excluded. The design of the entire chain therefore takes into account the solubility limit of CO2 in the geothermal water at all conditions which occur during the operational phase and beyond. Reservoir simulations were performed on a existing geothermal reservoir in the greenhouse area in The Netherlands to investigate the feasibility of CO2 co-injection and potential impacts on the geothermal operations and the business case. Results show that, for the conditions considered, no (significant) breakthrough of either the cold front or the dissolved CO2 are predicted to occur within 30 years of continuous operations. Also, the simulations show that all CO2 remains dissolved and hence no degassing takes place. An initial cost estimate indicates that with current emission reduction credits the return on investment of the CO2-Dissolved concept can be achieved within a few years, and is therefore an economically attractive addition for a geothermal operator.
Keywords: Novel storage concepts, GHGT-14
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