Variable Depth Streamer Acquisition – Benefits for Rock Property Inversion

Quantitative interpretation teams face two challenges when using model-based inversion: to extract meaningful wavelets and to build accurate low frequency models. The use of variable depth streamer gives access to lower frequency and enable to use calibrated seismic velocities as an initial model. With constant depth streamer and sparse well-log, the well-derived low frequency model may be inaccurate and cause biased inversion results. Seismic data acquired using variable depth streamers are ideally suited for inversion as they provide directly the missing low frequencies, hence removing the need to build low frequency models from well data. In order to quantify the impact of the low frequency content on seismic inversion, comparative elastic inversion tests have been conducted using 2-D seismic data from Constant Depth Streamer (CDS) and Variable Depth Streamer (VDS) acquisitions using the exact same streamer geometry. Both datasets from offshore NW Australia were acquired simultaneously, with a constant streamer depth of 7m for the conventional acquisition and streamers’ depth ranging from 7.5 to 58 m for the VDS acquisition.