Applied Geosciences - Geohydromodelling

CLEAN

Coupled THMC processes in the reservoir near field: Geochemical simulation of CO2 injection

The injection of CO2 in a depleted gas reservoir results in geochemical reactions between the formation brine and the rock matrix. Dissolution or precipitation of mineral phases will result in changes of porosity and permeability of the reservoir, which may cause feedbacks on the flow- and transport processes. A reliable characterisation and assessment of the relevant storage mechanisms has to take into account the time dependency of such reactions and feedback processes.

Therefore, in this project the THMC simulator OpenGeoSys (OGS) was extended for the kinetic limitation of CO2-fluid-mineral reactions. For this end, a generalized but very flexible Lasaga-type rate law was implemented in OGS. Moreover, the already existing interface of OGS to the geochemical code ChemApp was extended to allow for the exchange of consistent thermodynamic data between the OGS kinetics module and ChemApp. The verification of the coupled simulator was achieved by benchmark comparisons against analytical solutions and code comparison against other models. The successfully verified simulator then was applied for a site specific investigation of mineral trapping of CO2 and the consequential changes of porosities due to an injection of CO2 into the Altmark gas field for enhanced gas recovery. The scenario simulations show that the mineral trapping of CO2 may require very long times and geochemical equilibrium is reached only beyond 10000 years after the injection. Changes in porosity predicted by the scenario simulations with about -1 % are rather small, which is due to the limited extent of mineral conversion reactions and the small amounts of CO2 trapped in mineral form.

 

Project partners:

  • GFZ Potsdam
  • BGR Hannover
  • DBI gGmbH Freiberg
  • DMT GmbH Essen
  • FU Berlin GDF
  • SUEZ E&P GmbH
  • GICON GmbH Dresden
  • IFINKOR gGmbH Iserlohn
  • TU Clausthal
  • TU Dresden
  • UFZ Leipzig
  • Universität Erlangen-Nürnberg
  • Universität Halle-Wittenberg
  • Universität Jena
  • Universität Kiel
  • Universität Tübingen

 

Project duration:

July 2008 - June 2011
 

Funding:

This study was funded by the German Federal Ministry of Education and Research (BMBF), as part of the CLEAN project in the framework of the Special Program GEOTECHNOLOGIEN.

 

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