Model map: The Weyburn sequestration site sits within the red dot at the center of the image, in southeastern Saskatchewan, where carbon dioxide is being pumped underground for enhanced oil recovery (labeled “EOR”). Researchers are trying to model how CO2 behaves within about 10 kilometers of that spot, and they’re studying the geology of a far larger area (200 kilometers by 200 kilometers) within a regional geological depression called the Williston Basin. Vertical scale for depth is greatly exaggerated. The buried CO2 lies at a depth of 1.5 kilometers, and the depth of the study area is about 2.5 kilometers.
Larry Myer, a geophysicist at Lawrence Berkeley National Laboratory, who is developing sequestration plans in California, says that the Weyburn experience is showing the way toward broader implementation of accurate monitoring technologies. “In these early stages, one of the most important questions we have to answer is, what techniques work best under what conditions?” Myer says. “Certainly one of the key things they showed was the value of seismic technologies for mapping where the CO2 is going. It provides tremendous confidence that we can apply this broadly for monitoring.”
White says that the Canadian agency is hoping to install a permanent seismic array and a new sensor-laden monitoring well to further improve the tracking of the CO2, and ultimately develop a computer model that can be used by future projects around the world. “We want to understand the different [geologic] trapping mechanisms that will be active and the applicability and usefulness of different monitoring techniques, and how they should be applied over time,” he says.
Ultimately, CO2 sequestration will require more than just knowing the fate of the carbon dioxide: it will require understanding the full range of impacts on everything from groundwater to natural-gas deposits. “No one has injected 10 million tons of CO2 for 50 years–anywhere,” John Bradshaw, CEO of Greenhouse Gas Storage Solutions, an Australian petroleum consultancy, pointed out at the conference. “How we model that, how we regulate that–on groundwater, oil, gas, CO2–is something we will have to work together on how to handle.”