A novel renewable energy concept based on using supercritical CO2 as heat
transmission fluid was proposed by Brown (2000). Pruess (2006) evaluated
thermophysical properties and performed comparative numerical simulations to
studying fluid dynamics, heat and mass transfer potentials of water and CO2 as
heat transfer fluids in an engineered geothermal reservoir. He highlighted some
advantages of using CO2 with respect to well bore hydraulics. Pruess and
Azaroual (2006) extended previous analysis to include physicochemical
interactions induced by CO2 between fluids and reservoir minerals. They
concluded a potential of porosity increase and reservoir volume expansion.
Simulation of multiphase reactive transport (CO2 in a porous carbonated rock
initially saturated with water) illustrates existence of different zones featuring
distinct reactive behaviour around the injection well (Andre et al., 2007).
Supercritical CO2 reacts differently to CO2-saturated solution in each zone.
First, it dissolves into the aqueous phase and increases both water acidity and
mineral dissolution potential, favoring higher porosity. Next, hydraulic processes
induced by supercritical CO2 injection are accompanied by a desiccation
phenomenon of the porous medium. Irreducible water, entrapped in pores,
sustains the increase in CO2 pressure. When the pressure is sufficiently high
under a continuous dry (without water vapour) CO2 flux, an evaporation
process starts leading to the precipitation of salts and other secondary minerals
from capillary metastable water (Lassin et al., 2005).
This new concept based on specific advantages thermophysical and
physicochemical properties of CO2 as a heat transmission fluid integrating
geochemical interactions and carbon geological storage constraints will be
André L., P. Audigane, M. Azaroual, A. Menjoz (2007). Energy Conversion
Management (under press).
Brown, D. Proceedings, Twenty-Fifth Workshop on Geothermal Reservoir
Engineering, pp. 233–238, Stanford University, January 2000.
Fouillac, C., B. Sanjuan, S. Gentier, I. Czernichowski-Lauriol. Third Annual
Conference on Carbon Capture and Sequestration, Alexandria, VA, May 3-6,
Lassin A. M. Azaroual, L. Mercury (2005) Geochim. Cosmochim. Acta, Vol. 69, No.
22, pp. 5187-5201.
Pruess K. (2006) Geothermics, Vol. 35, pp. 351-367.
Pruess, K., M. Azaroual. (2006) Thirty-First Workshop on Geothermal Reservoir
Engineering, Stanford University, Stanford, CA, January 30 - February 1, 2006.