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UK researcher tests core samples to determine CO2 flow characteristics

From left: Kirk Osadetz, Programs Development Manager for CMC's Containment and Monitoring Institute, and Sam Krevor, Lecturer at Imperial College London, examine core samples.

From left: Kirk Osadetz, Programs Development Manager for CMC’s Containment and Monitoring Institute, and Sam Krevor, Lecturer at Imperial College London, examine core samples.

Research on core samples from CMC’s Field Research Station will help predict how far and how quickly a CO2 plume will expand within the storage reservoir, providing another tool to demonstrate carbon capture and storage is a safe, stable way to reduce carbon emissions.

Dr. Sam Krevor, a Lecturer in the Department of Earth Science & Engineering at Imperial College London, was in Alberta recently to examine core samples taken from the injection well at the Field Research Station (FRS). Krevor, who won a travel grant to visit the site through a UK Carbon Capture and Storage Research Centre competition, is interested in learning more about the flow of injected CO2 through reservoirs.

Examining CO2 flow

“We will be looking at how CO2 flows through the injection zone. We want to study how quickly it moves, how it becomes trapped and, if it escapes through the overlying layers, how it flows through,” says Krevor.

Researchers from the U.K., the U.S. and Canada have been busy this year testing and refining measurement and monitoring equipment at the field research station. When complete in late 2016, the site will feature an injection well with a small plume of CO2 injected at a shallow depth of 300 m. Two adjacent observation wells house equipment such as a U-tube fluid sampling system, vertical seismic array, fibre optic cable, and downhole equipment to use with an electrical resistivity tomography array.

Krevor took core samples from the FRS back to his lab where plugs will be removed and then examined by PhD student Olivia Sloan who will use a CT scanner to visualize how saline water and CO2 flow through the samples. They are working with Jerome Neufeld, Lecturer at the University of Cambridge, who will design a large-scale mathematical model of fluid flow through the substrate at the FRS.

Movement at the pore scale

While their work will help model how CO2 migrates through a large area within a reservoir, Krevor and his team are really examining movement at the pore scale within the rock. “People are interested in what’s happening at the bulk scale, but the battle forces will be on the microscopic scale,” says Krevor.

And it is a battle of sorts. As molecules of CO2 are injected into a reservoir, they begin looking for the path of least resistance. It’s a bit like water running down the side of a mountain – it finds already existing channels to move through. This is similar to CO2 pushing its way through the channels or fractures within a heterogenous rock formation, like the injection zone at the field research station.

The CO2 may not follow all of the open pathways in the pore space because it may be blocked by water already in the reservoir. “The forces that bind the water to the rock might be insurmountable. It might not always easily get out of the way of the gas,” says Krevor. In that case, the CO2 will find another route.

Preparing site for injection

Construction of the injection well has been progressing in preparation for the injection this fall of up to 1,000 tonnes of CO2 ­into the reservoir over the next year. During and after injection, researchers will image the plume using seismic and other technologies with all data being compared. The comparison will enable Krevor to see how accurate his modeling is and will also provide all researchers with a more complete picture of the plume’s behavior.

Krevor, who has worked on the CCS demonstration project at the Cooperative Research Centre for Greenhouse Gas Technologies’ (CO2CRC) Otway Research Facilities and also on target CO2 storage reservoirs in the UK North Sea, says the facilities at the field research station offer superb conditions for research. There are more instruments offering more detail than he’s found in industry situations and the research is more controlled. “This is an ideal situation.”