Time-lapse AVO on OBN Seismic Acquired in the Mars Field

The time-lapse OBN (Ocean Bottom Node) seismic data acquired by Shell in 2007 and 2010 in the Mars field, is a true wide azimuth marine dataset that provides a good opportunity to study the azimuth and offset dependence of time-lapse depth-shifts and amplitudes. The goals of such analysis are to gain a better understanding of the response of seismic waves to geomechanical changes happening in the field and to improve our ability to discriminate between pressure and saturation signals using the time-lapse AVO response. In this paper we compare the conventional time-lapse AVO analysis with an alternative method based on the combined use of time-lapse amplitudes and time-lapse depth-shifts to separate pressure and fluid-related changes on the Mars time-lapse OBN data.