Abstract Magnetotelluric (MT) soundings were conducted in a 4 × 4 km area at the Aquistore CO2 sequestration site at Estevan, Saskatchewan, Canada in 2013, 2014 and 2015, prior to CO2 injection. The… Click to show full abstract
Abstract Magnetotelluric (MT) soundings were conducted in a 4 × 4 km area at the Aquistore CO2 sequestration site at Estevan, Saskatchewan, Canada in 2013, 2014 and 2015, prior to CO2 injection. The MT response is locally one-dimensional but spatially variable at short periods ( 30 s). Responses corresponding to Williston Basin rocks are uniform across the area. A representative MT response was inverted using constraints derived from a resistivity well-log. Beneath the Jurassic Watrous to Vanguard formations (at depths greater than 1240–1600 m), the resistivity of the inversion model is consistently 20–30% lower than in the reference well-log model, consistent with the MT method sensing the longitudinal resistivity of the more strongly stratified units at these depths. Electromagnetic noise in the MT data set includes high-frequency odd harmonics of the 60 Hz source and a broad-band source, spatially associated with the CO2 pipeline, observed only in 2014. Within the period range 10−4 to 102 s, but outside the bands influenced by the broad-band noise, the off-diagonal MT impedance response at Aquistore can be measured with an RMS repeatability of 1% or better.
               
Click one of the above tabs to view related content.