Geophysical Monitoring of CO2 Injection in Saline Aquifers

Abstract

Carbon capture and storage (CCS) is a prerequisite to meet the internationally agreed upon target of limiting the emissions of CO2. The international energy agency has a goal that CCS should cover 14% of the CO2 emission reduction within 2050. Saline aquifers and depleted oil- and gas reservoirs are of particular interest as storage sites. The capacity and injectivity of the saline aquifers are crucial success factors for CO2 storage. Fluid saturation, pore pressure and geomechanical changes are the most frequent observed variations in reservoir parameters caused by CO2 injection. Monitoring is essential to ensure safe storage and detect possible leakage of injected CO2. Time-lapse seismic data is an important monitoring tool. Pore pressure variation is expected to interfere with the CO2 fluid substitution on the time-lapse seismic for semi-closed reservoirs. The aim of this thesis is to study time-lapse seismic monitoring of pressure and saturation changes caused by CO2 injection in a saline aquifer. Field data from the Tubåen Fm. at the Snøhvit field is used in the analysis. Time-lapse seismic data is combined with laboratory measurements, reservoir flow analysis, rock physics analysis, synthetic seismograms and well-log analysis to estimate the changes in pressure and fluid saturation caused by CO2 injection. This thesis consists of four main papers in addition to two papers in appendixes.