Revealing the Time-Lapse Signal from Non-Repeatable Vintages with 4D Depth-Domain Inversion

For time-lapse seismic methods to reveal the 4D signal that is representative of production-induced changes, high repeatability between seismic vintages is essential. However, in some cases, a change in survey geometry is required for improved imaging and superior future repeatability, for instance, from towed-streamer to ocean-bottom node (OBN) acquisition. The resulting differences in acquisition geometry and recording datums lead to significant inconsistencies in the reservoir illumination, especially for deep-water fields or in the presence of complex overburden geology. Conventional 4D binning techniques generally cannot compensate for the fundamentally varying illumination arising from these differences. This study assesses if time-lapse analysis between two seismic vintages with completely non-repeatable geometry can be enabled by using depth-domain inversion to overcome the illumination differences. We use point-spread functions to capture and correct for the illumination footprint resulting from the complex overburden and variable acquisition geometry. Simultaneous 4D depth-domain inversion is performed between the two vintages of realistic towed-streamer and OBN synthetic data. The results show that application of the technology significantly reduces the 4D noise, allowing a sufficient change in a reservoir’s acoustic impedance to be detected as an interpretable time-lapse response.