Multicomponent seismic monitoring of strain due to CO2 injection at Delhi field, Louisiana

Abstract

Time-lapse, multicomponent seismic data are used in this thesis to monitor geomechanical changes within the reservoir and in the overburden layers at Delhi Field, Louisiana. Multicomponent seismic data are important for monitoring gas saturation and pressure changes associated with CO2 flooding. A seismic survey acquired before CO2 injection operations began serves as a baseline survey and a pair of multicomponent monitor surveys acquired during first two years of injection allow time-lapse analysis of amplitude differences and time-shifts between seismic surveys. Time-lapse seismic data are used for mapping fluid and pressure changes within the reservoir interval. Reservoir pressure increases at Delhi Field cause overburden compaction and time-shifts between seismic monitor surveys. Vertical strain in the overburden is calculated from compressional and converted wave time-shifts and provide quantitative insight into how injection operations affect overburden layers. Strain estimated from converted wave seismic data shows both a different pattern and magnitude than strain estimated from compressional seismic data. Monitoring these geomechanical changes enables the calibration of geomechanical models to understand the influence of reservoir dynamics on the overburden and the underburden.