Full Elastic Non-linear Inversion the Key to 4D

Usually great emphasis is placed on the repeatability of seismic acquisition for time-lapse purposes. However, the non-linearity of the relationship between seismic time-lapse data differences and time-lapse property changes is usually ignored. In this paper it is demonstrated that ignoring the non-linearity can cause serious errors in time-lapse interpretation, whereas application of full elastic non-linear inversion to base-line and time-lapse surveys separately, fully accounts for the non-linearity and gives quantitatively very accurate results. In addition, it is well understood that full elastic non-linear inversion is less sensitive to noise and acquisition imprint. The method is illustrated with the help of a synthetic time-lapse example based on real logs.