CO2 Dependable Injection and Storage System Optimized for Local Valorization of the geothermal Energy Delivered – CO2-DISSOLVED

Even though the project basically is a feasibility study using engineering methods, such as dimensioning calculations and numerical simulations, ambitious research work will be necessary as well:
• The usual methods for site monitoring and risk assessment must be reviewed in the light of new constraints inherent in this original approach proposed for the CO2-DISSOLVED Project. Innovating solutions for geochemical and geophysical monitoring will be evaluated and tested, both in the field and in the laboratory. A new methodology for risk analysis will be specifically designed and applied, in accordance with the modelled and observed properties of the system as a whole, i.e. capture, injection, CO2 storage and heat recovery.
• The brine acidified by dissolved CO2 will be chemically reactive with the mineral phases of the aquifer as soon as it exits the injection well, contrary to the «classic« approach where the reactive acid front follows the extension of the supercritical CO2 «bubble«. Specific work will focus on the «near-well« area, based on new experimental and modelling approaches. An experimental laboratory installation (MIRAGES-2) will thus be specifically designed and used for this project.
• Earlier economic models of the CO2 will be rendered obsolete by the local application of an associated capture-storage and geothermal-heat-production technology to small CO2 emitters. This will require the development and validation of new economic models that will then be applied to two test cases in France and Germany.

The main results acquired so far first demonstrate the existence of a real potential of application of the CO2-DISSOLVED concept to many low to medium industrial emitters in France, Germany, and the USA. Besides, the results of the preliminary hydrodynamic modelling work of the doublet functioning evidenced that dissolved CO2 will inevitably reach the production well after a while (ca. 2 to 10 years, depending on the doublet characteristics), at low-medium concentrations. However, this CO2 production will not generate any gaseous emission to the atmosphere, since CO2 remains dissolved in the brine circulating in a closed loop between the injection and the production wells. In addition to this, the mass balance calculations show that a significant fraction of the injected CO2 actually remains stored in the aquifer, corroborating the viability of the concept. The MIRAGES-2 experimental set-up is now fully operational for the first series of experiments which are scheduled in September 2014.

The expected results will provide us with a range of innovating technologies associated with new experimental and theoretical tools. These will include: a device for capturing and dissolving CO2; monitoring tools; an experimental laboratory «miniature well«; coupled models for simulating flow, mass and heat transport and geochemistry; and an economic model. Promising industrial applications can be envisaged as soon as the project will be finished after 36 months, provided that the conclusions on the feasibility of the concept of CO2 injection coupled with geothermal-heat recovery are positive.

A paper discussing the CO2-DISSOLVED Project was accepted for an oral presentation at the «Sustainable Earth Sciences 2013« conference organized by the EAGE (European Association of Geoscientists & Engineers) in October 2013 at Pau. Four papers have been accepted (two for oral presentations, two for poster presentations) at the next GHGT conference to be held in Austin, TX (USA) in October 2014.

The objective of the CO2-DISSOLVED project is to assess the technical-economic feasibility of a novel CCS concept integrating (1) an innovative post-combustion deep-well CO2 capture and dissolution technology, (2) injection of dissolved CO2 instead of supercritical, and (3) combined geothermal heat recovery in the extracted brine via a doublet/surface heat exchanger system.

This approach combines several objectives including renewable energy production, greenhouse gas reduction, and the assessment of a novel, low cost capture and storage method. Further, the proposed use of dissolved CO2 versus injection in a supercritical phase offers substantial benefits in terms of lower brine displacement risks, lower CO2 escape risks, lower to none pressure buildup in the storage aquifer, and the potential for more rapid mineralization.

As another contributing novel factor, this proposal targets low to medium range CO2-emitters (10-100 kt/yr), that could be compatible with a single doublet installation. Unlike the standard approach which focuses on very large regional emitters (1-5 Mt/yr), the proposed CO2-DISSOLVED concept opens new potential opportunities for local storage solutions dedicated to low emitters such as food, paper, or glass industry, building materials makers, etc. Since it is intended to be a local solution, the costs related to CO2 transport would then be dramatically reduced, provided that the local underground geology is favourable. On the other hand, the heat recovered could benefit directly to the industrial emitters for their own heating and/or process needs and possibly for heating other collective buildings close to the storage facility.

This project is divided in four main technical tasks addressing the following points:

- Task 1: Applicability of the Aqueous-based CO2 Capture and Dissolution Facility technology,

- Task 2: Efficiency of the Coupled CO2 Injection/Geothermal Heat Extraction System,

- Task 3: Monitoring and Risk assessment,

- Task 4: Integrated Technical-Financial Feasibility Analysis Applied to two Test-cases (France, Germany).

Though being mainly a feasibility study relying on engineering methodologies, the achievement of this project will also have to rely on ambitious research work in order to address the following points:

- Standard monitoring and risk analysis approaches need be revisited as a function of the new features and constraints of the CO2-DISSOLVED approach. Innovative geochemical and geophysical monitoring solutions are intended to be evaluated and tested, both on-field and in-lab. A new risk analysis methodology will be specifically designed and applied in accordance with the modelled and observed properties of the whole system.

- The potential acidified brine reactivity will now be delivered out of the injection well, unlike the standard supercritical approach where the acid front followed the extension of the CO2 plume. Specific work, focusing on the near-well area and relying on both new experimental and modelling approaches will be carried out in this project. A new experimental facility will be available for future experiments involving injection of dissolved CO2.

- The association of CCS to geothermal heat production, applied locally to small CO2-emitters, makes partly obsolete previous conceptual economic models. New models will then have to be developed, validated, and applied to two application test-cases (one in France, one in Germany).

The expected results will permit to have at our disposal a complete portfolio of innovative technologies associated with adapted experimental and theoretical tools, so that in case of positive conclusions on the feasibility of this concept, promising industrial applications could be envisaged on the short term by the end of this 30 month project.