Continuous DAS VSP monitoring using surface orbital vibrators: field trials for optimal configuration at the CO2CRC Otway Project

Reservoir monitoring usually involves a combination of seismic surveys acquired using a large array of seismic receivers and mobile sources to image the subsurface changes. Such surveys rely on accurate positioning of both source points and receivers. Permanent reservoir monitoring seeks to overcome the limitations of the conventional approach, such as poor repitability and high survey costs, by fixing either the seismic receivers, sources or both. At the CO2CRC Otway Research Facility, we are exploring the use of distributed acoustic sensing (DAS) combined with permanent surface orbital vibrators (SOVs) to acquire high quality time-lapse seismic data at relatively low cost, while significantly reducing the land access issues. To study the feasibility of using such monitoring method, we present the analysis of a series of Vertical Seismic Profile (VSP) acquisitions acquired with a cemented fibre-optic cable. We test different SOV sweep designs, and evaluate DAS ability to record the acoustic signal. The results show that the DAS/SOV configuration was able to deliver high quality VSP datasets, sufficient to image the target interval.