Field data observation and numerical study using a permanent seismic source ACROSS towards hydrocarbon reservoir monitoring

Abstract

Time-lapse seismic analysis plays an essential role in reservoir monitoring. We aim at developing a reservoir monitoring approach using a permanent seismic source “ACROSS” (Accurately Controlled and Routinely Operated Signal System) that can produce repeatable, extremely precise source signature. Both vertical and horizontal single forces are reconstructed by clockwise and counter-clockwise rotations of an asymmetric cylindrical mass. Here, we performed test observation of low-frequency data (3.5-15Hz) at JOGMEC Kashiwazaki test field, Niigata, Japan. We installed the ACROSS source with a horizontal rotation axis that can generate pronounced P-wave energy. With the assumption that one or two ACROSS sources are installed at a CCS (carbon capture and storage) field, we performed 2D simulation study using reverse time migration (RTM) and full waveform inversion (FWI) for delineating temporal change of the P-wave velocity. Since ACROSS precisely controls the sweep source signature, it is possible to discuss application of time-lapse FWI rather than just the first arrival or P-wave reflection traveltime inversion. To simplify the multi-component, multi-parameter problem on elastic FWI, we invert only for P-wave velocity residual using so-called scalar potential of the elastic wavefields. The synthetic FWI result shows sharp delineation of P-wave velocity residual associated with fluid replacement. The superior repeatability of ACROSS and developments of time-lapse imaging methods may bring a breakthrough towards hydrocarbon reservoir monitoring.