Magnetotelluric and controlled-source electromagnetic pre-injection study of Aquistore CO2 sequestration site, near Estevan, Saskatchewan, Canada

Abstract

Surface electromagnetic (EM) methods were tested prior to CO2 injection at the PTRC Aquistore site at Estevan, Saskatchewan to determine their applicability to carbon sequestration monitoring. Magnetotelluric surveys in 2013, 2014 and 2015 resulted in successful definition of the pre-injection response and electrical resistivity model for the Williston Basin at Aquistore. These datasets define spatially uniform MT responses with a high level of repeatability. Controlled-source EM (CSEM) studies using a horizontal electric dipole transmitter have also been implemented at Aquistore. Preliminary analyses demonstrate that the CSEM experiment is well-designed, with measurable signal levels at all sites and a configuration that maximizes sensitivity to the sequestration reservoir. However, theoretical sensitivity modeling indicates that extremely large volumes of injected CO2 are required to produce measurable anomalies in the CSEM response. Greater sensitivity of both magnetotellurics and CSEM to the resistivity of shallower strata suggests these methodologies have superior application in leakage monitoring.