Passive seismic imaging at reservoir depths using ambient seismic noise recorded at the Otway CO2 geological storage research facility

We demonstrate rapid convergence (<60 min) of passive seismic images down to reservoir depths (similar to 2.0 km) at the CO2CRC Otway CO2 geological storage research facility, Australia, using ambient seismic noise (ASN) recorded continuously with a buried geophone array. Our passive seismic images are created by applying seismic data processing and interferometry techniques, and show we can recover both surface and body waves from the ambient noise data. Using a recording time interval in which body waves dominate the ASN, we generate passive seismic images that correlate well with the major reflectors imaged by conventional active-source 3-D seismic data at the site. We present a mathematical model for image convergence, where the variance converges inversely proportional to recording time, and show for the first time an excellent agreement between a mathematical model and the observed convergence rate of interferometric images made from ASN.