Industrial CO2 emissions. Geological storage of CO2 is a new and key technology to fight global warming (2005). © BRGM - Dominique Quiniou

Successfully combining CO2 storage and geothermal heat extraction

08.10.2016
Storing dissolved CO2 in saline aquifers close to industrial emissions sources is the idea being investigated by the CO2Dissolved project as a promising alternative to large scale storage.

Design for a storage facility for dissolved CO2 in a saline aquifer combined with geothermal heat production © BRGM

Design for a storagefacility for dissolved CO2 in a saline aquifer combined with geothermal heat production. © BRGM

While there is no doubt that geological storage of CO2 is necessary to cut atmospheric greenhouse gas emissions, the  implementation,safety and  monitoring conditions required raise scientific, technical, economic and  social  issues that are  slowing its  development in the  short term. Storing CO2 on a small scale close to  the  emission sources would be an  additional and  possibly alternative solution. The 3-year ANR CO2Dissolved project  explored  this  possibility. With  7 partners* co-ordinated by the BRGM, the project demonstrated the  feasibility of combining the  storage of dissolved CO2 in an aquifer with the extraction of geothermal heat.

As  project  manager  Christophe  Kervévan explains, "This solution has several advantages. The idea is to store the CO2 produced by an industrial facility on the same site by injecting it in dissolved form into  an  underlying deep  saline  aquifer. The water is pumped up and subsequently reinjected with the dissolved CO2 through one "injection"  and  one "production" well, similar to the geothermal doublets used to supply heating networks." In situ CO2 storage would  reduce both the  costs and risks of transporting the gas, which, in addition to heat recovery, makes this  an attractive solution, subject to the  existence of suitable aquifers in the right location and proper control of the process.

Map of France matching the locations of low emission industrial facilities - yellow dots - with geothermal resources in aquifers - deep sedimentary basins in blue. © BRGM

Map of France matching the locations of low emission industrial facilities - yellow dots - with geothermal resources in aquifers - deep sedimentary basins in blue. © BRGM

Feasibility and risk  control

Because CO2 is only is soluble in brine within certain  limits, and  because of the  standard flow rates in geothermal doublets (250-350 m3/h in the  Paris Basin), this  is a relevant solution for  small-scale industrial emissions of CO2 (< 150 000 t/year). The storage sites  targeted are deep  aquifers (1 500 - 2 500  m) with temperatures in the region of 60 to 80°C. In France, 650  potentially compatible industrial sites (accounting for 25% of emissions in France) have been identified.

"Our American partners have  developed an innovative CO2 capturing process  in which  water is the  only  solvent",  says C. Kervévan. "Possibilities for integrating this  process  into  the  CO2Dissolved system have been investigated, and depend on CO2 concentrations in flue gases and the possible need for separation prior to injection. Unlike large-scale storage, where the CO2 is injected in supercritical form, in this case it is entirely dissolved in the brine of the aquifer. This removes the risks of a gas bubble forming underground, which could rise to the surface."

The impacts on the  rock of injecting acid water and the resulting chemical reactions that depend on the  hydrogeological characteristics of the  environment have been  digitally simulated and repeatedly tested at an experimental facility.  The economic impact has also been investigated, in the  case of a sugar mill and  distillery in central France, and  has demonstrated the viability of most of the scenarios simulated, thanks to the  economic benefits of the heat recovered.

"The next stage",  says  C. Kervévan, "will be to implement a demonstration pilot  on an industrial site. The first steps  are already under way with  the new  "Pilot CO2-Dissolved" project  financed by the Géodénergies scientific  interest group".

The experimental MIRAGES-2 set-up for injecting a mixture of water and dissolved CO2 into a core under pressure and temperature conditions typical of a deep aquifer. © GÉORESSOURCES

The experimental MIRAGES-2 set-up for injecting a mixture of water and dissolved CO2 into a core under pressure and temperature conditions typical of a deep aquifer. © Géoressources

3D tomography of induced porosity (in blue) 20 days after injecting acidified water (through the vertical tube) into an initially cylindrical and highly homogeneous limestone core. © GÉORESSOURCES

3D tomography of induced porosity (in blue) 20 days after injecting acidified water (through the vertical tube) into an initially cylindrical and highly homogeneous limestone core. © Géoressources

PARTENAIRES

  • BRGM (France, coordinateur)
  • BGR (Allemagne)
  • CFG Services (France)
  • Geogreen (France)
  • GeoRessources (France)
  • LEO (France)
  • Partnering in Innovation, Inc. (USA).

TO FIND OUT MORE

Go to the CO2 dissolved project website

BRGM - 3 avenue Claude-Guillemin - BP 36009 45060 Orléans Cedex 2 - France Tel.: +33 (0)2 38 64 34 34