The team is working with three brine reservoirs and two EOR sites (Figure 1) to confirm that sequestration is safe and effective, reports Susan Hovorka, senior research scientist at the GCCC.
An interesting side effect of carbon dioxide sequestration research is its positive impact on reservoir characterization techniques, says Hovorka
"A considerable effort is devoted to tracking what happens to CO2 after it is injected, which in effect, tests the validity of the characterization," she
Through this process, Hovorka
says the team determined that increased injection rate leads to improved sweep efficiency.
It has found that its conceptualizations of residual water saturation and residual CO2 sequestration were valid, and its buoyancy conceptualization is still under review, according to Hovorka
Unlike oil and gas, where the fluid is up against a seal, injected CO2 comes with energy or gradient that interacts with buoyancy.
"Which is more important is a very big theoretical question," says Hovorka
The team is in the middle of history matching the characterization.
"We are looking at how many characterizations we can history match to see how good the characterization is, especially with regard to sweep efficiency," she
"So far we have quite respectable matches."
Repeat crosswell seismic, VSP and surface seismic are scheduled for the fall.
"Then we will see how the reservoir responds to CO2 in a heterogeneous fluvial reservoir," Hovorka
will make another set of measurements in the coming months to look at different scenarios for how to conceptualize the interactions of different types of physics on multiphase fluids in a complex flow system.
The goal is to provide insight into how to characterize multiphase flow in all kinds of reservoirs, including those that have oil and gas, she
Other questions remain that could have implications for EOR
, including the dissolution of carbon dioxide into water, the adequacy of well completions at retaining injected CO2, the effects of pressure increase on sealing faults, the effective management of downdip migration, detecting fugitive CO2 and documenting plume edges, according to Hovorka
"The value of our research goes beyond storing captured CO2," she