Angle-Variant 4D Seismic Time-Shift Analysis for Velocity Change and Subsurface Strain Estimation

Abstract

Summary In a time-lapse (also called 4D) seismic analysis, the time-shift of a certain event is caused by the changes in the seismic velocity and the depth of the event. An interpretation of 4D time-shifts is normally simplified by neglecting displacement changes (strains) or assuming a linear relation of velocity and thickness strains. Here we go beyond these assumptions and propose a least-squares inversion method to simultaneously estimate the velocity and thickness strains from 4D angle stacks. We show, through examples from synthetic and field data, that the 4D velocity and thickness strains can be estimated simultaneously without an assumption of their linear relationship. Our method can be applied to any other 4D seismic data set in which angle-stack images are available. We see that our method has high potential in many other applications, because the velocity and thickness strains form a basis of other properties used in 4D seismic and geomechanics applications.