Monitoring the Fate of Injected CO2 using Geodetic Techniques

Geodetic methods comprise one class of geophysical data that are sensitive to changes in effective pressure within operating reservoirs, albeit indirectly through induced deformation. Geodetic observations, which have observation intervals that vary from seconds to days, weeks, or months, generally provide more frequent sampling compared to existing geophysical methodologies (such as seismic time-lapse monitoring), which typically invoke repeat times of months to years. These differences in sampling intervals are primarily due to the extensive effort, and hence cost, of conducting geophysical field operations, which often precludes executing a large number of surveys. Satellite-based interferometric synthetic aperture radar (InSAR) is cost effective and used in many applications, including monitoring the injection of carbon dioxide (CO2) for both long-term storage and enhanced oil production. An application to the geologic sequestration of CO2 in Algeria revealed northwest migration along a fault/fracture zone intersected by the injection well. A study in a Texas field demonstrated that enhanced oil recovery utilizing CO2 leads to observable surface deformation that may be used to characterize the sequestered CO2 and to estimate the pressure changes within the reservoir induced by injection and production