The Sequre tracer technology, developed by scientists at the US Office of Fossil Energy’s (FE) National Energy Technology Laboratory, was tested at the San Juan Basin coalbed test site.
The San Juan Basin is considered one of the best sites worldwide for coalbed methane recovery, as well as a prime site for CO2 sequestration. The site contains three coalbed methane-producing wells and a central injection well.
Sequre uses perfluorocarbon tracers (PFTs) - non-toxic, chemically inert clear colourless liquids - to provide a way to measure CO2 movement as well as provide leak detection. In use, the PFT is released at a certain point and the concentration of the PFT is then determined at another set of points, allowing the flow from the source to the points to be determined.
At the San Juan Basin, the Sequre tracers detected gas first in the easternmost of three production wells and then in the southwest production well. Numerical models used for the test site had predicted the CO2 movement, but indicated that the movement would initially occur at the southwest well.
The tracer technology can be used as a tool to improve modelling techniques that determine storage capacity, injection capability and flow rates. The technology can measure concentrations as small as parts-per-quadrillion (one thousand million million) and differentiate injected CO2 from natural CO2.