Sealing efficiency of reservoir cap rocks over geological time with respect to gaseous and supercritical CO2

Objectives

The long-term sealing efficiency of cap rocks above potential CO2 storage reservoirs is a major concern in the selection and design of subsurface storage facilities for this reactive gas. In this project sealing efficiency will be characterized of geological barriers (low-permeability cap rocks) exposed to CO2 gas and dissolved CO2 at reservoir pressure and temperature.

Scientific and technical goals

Fine-grained clastic rocks form the seals above most natural gas and petroleum reservoirs. Laboratory tests will be perform on selected types of cap rocks (shales, marls, siltstones, carbonates) to assess their sealing efficiency with respect to CO2 and study the influence of reactive CO2 gas or dissolved CO2 on their geochemical and petrophysical properties. Our primary objective is to develop an improved quantitative understanding of CO2 transport processes in sedimentary rocks by combining well-constrained laboratory experiments, rock characterization, and numerical modelling. Short-term, long-term, and corresponding leakage processes will be addressed. The laboratory experiments comprise capillary gas-breakthrough tests, permeability measurements with water, determination of effective gas permeabilities after breakthrough, and diffusion experiments. All experiments will be conducted under controlled effective stress conditions at reservoir temperatures and fluid pressures. Detailed petrophysical, mineralogical and geochemical analysis will be performed for sample characterization and correlation. The experiments will be accompanied by numerical modelling studies from laboratory to field scale involving multi-component and multiphase flow and reactive transport to provide a quantitative basis for a qualitative and quantitative appraisal of long-term cap rock sealing efficiency.

The CO2TRAP project was successfully completed in May 2008 and initiated these follow-up projects:

CO2 Seals

Integrity of sealing rock formations for CO2 storage
http://www.co2seals.de

CO2SINUS

CO2 Storage in in situ Converted Coal Seams
http://www.co2sinus.org

ALCATRAP

Optimisation of CO2 binding by reaction with alkaline residual materials through the ALCATRAP process
http://www.hydro.uni-bayreuth.de/pros/detail.php?lang=de&id=32