Surface orbital vibrator (SOV) and fiber-optic DAS: field demonstration of economical, continuous land seismic time-lapse monitoring from the Australian CO2CRC Otway site

摘要

We present an analysis of a field dataset demonstrating the combined use of a permanent surface orbital vibrator source (SOV) and a trenched fiber-optic cable sampled using distributed acoustic sensing (DAS). We examine SOV signal characteristics, repeatability, and wavefield decomposition for a short duration test. We show the SOV source to have excellent spectral repeatability but asymmetric response depending on spin direction. Wavefield decomposition tests demonstrate that the rotating source can effectively be decomposed into equivalent horizontal and vertical forces, well-suited to isolation of wavefield components. Finally, quantitative analysis of repeatability metrics normalized rms difference (NRMS) and predictability (PRED) show that wavefield phases with sufficient signal-to-noise ratio (S and surface waves) have high repeatability. The combination of SOV & DAS appears to be a promising approach for high temporal resolution time-lapse monitoring efforts in a variety of contexts.