Application of ERT For Tracking CO2 Plume Growth and Movement at the SECARB Cranfield Site

摘要

Electrical Resistance Tomography (ERT) installed to track the development of an injected subsurface CO2 plume at the SECARB Cranfield, MS. sequestration site will be the deepest subsurface application of this method to date. ERT utilizes vertical arrays of electrodes, usually in a cross-well arrangement, to perform four-electrode measurements of changes in the spatial distribution of electrical resistance within a subsurface formation. Because a formation containing super-critical CO2 is approximately five times as resistive as its surroundings, significant resistance changes are anticipated during plume growth and movement within a brine-filled formation. ERT has also been shown to be quite sensitive to CO2 saturation changes. The Cranfield ERT electrode arrays will be emplaced at a depth exceeding 10,000 feet. (3280 m); the system design and installation must address significant challenges associated with both the depth and borehole conditions including temperatures of 258 F (126 C), pressures exceeding 5000 psi and a groundwater pH of 3. In addition, the system must allow co-located emplacement and concurrent operation with other monitoring techniques that utilize the same boreholes. ERT electrode and cabling will be attached to the outside of the well casing, allowing free access to the interior of the well, which is required by some of the other monitoring techniques being fielded.