We are investigating the technical feasibility of injecting CO2 for carbon sequestration with enhanced gas recovery (CSEGR) in the depleted Altmark natural gas reservoir, Germany. Our approach is numerical simulation using TOUGH2/EOS7C. Our earlier simulation studies have shown early CO2 breakthrough due to fast-flow through the high-permeability sand layers. In order to extend the period of enhanced CH4 recovery, we propose the preinjection of gelling fluids for the purpose of limiting the mobility of injected CO2 and thereby improving CO2 sweep and delaying CO2 breakthrough. We have implemented a simple gel model into EOS7C and simulated gel injection followed by CSEGR.Preliminary simulations to date show minimal improvements in CSEGR with breakthrough times delayed by only a few months to a year. While mobility control using pre-injected gelling fluids appears to be a promising strategy in controlling early breakthrough, more work is needed to design and simulate an effective procedure.

Geologic carbon dioxide storage is one strategy for reducingCO2 emissions into the atmosphere. Depleted natural gas reservoirs are anobvious target for CO2 storage due to their proven record of gascontainment. Germany has both large industrial sources of CO2 anddepleting gas reservoirs. The purpose of this report is to describe theanalysis and modeling performed to investigate the feasibility ofinjecting CO2 into nearly depleted gas reservoirs in the Altmark area inNorth Germany for geologic CO2 storage with enhanced gasrecovery.