Time-lapse Velocity Analysis Using Apparent Image Displacements

The production of hydrocarbons modifies the stress conditions in the subsurface and changes the model parameters previously estimated from the prospect. The capability to remotely monitor the changes in the reservoir using seismic data has strategical importance since it allows us to infer fluid movement and evolution of the stress conditions, which are key factors to enhance recovery and reduce uncertainty and risk during production. In this work, we present an approach for estimating changes in the subsurface model parameters using the apparent shifts between the migrated images obtained in a 4D time-lapse seismic survey. We assume the shift in the position of the reflectors between two images is completely due to the perturbation of the model parameters, and we use the image from the first (baseline) survey as a reference to estimate this perturbation. The apparent shifts are measured using penalized local correlation in the image domain.