Multi-Well 4D DAS VSP: A Case Study at Mars Basin, Gulf of Mexico

We present a 4D case study of time-lapse multi-well Vertical Seismic Profiling (VSP) acquired with Distributed Acoustic Sensing (DAS) at the Mars field, deepwater Gulf of Mexico. In this work, we are able to obtain meaningful 4D signals from multi-well DAS VSPs by addressing various challenges that include weak 4D signals from a relatively short time interval (~1 year), an extremely noisy monitor survey, and poor repeatability between baseline and monitor acquisitions. 4D friendly premigration co-denoise was the key to attenuating the strong background noise in the monitor survey while preserving the potentially weak 4D signals. 4D shot co-selection and regularization effectively mitigated some of the acquisition differences between the baseline and monitor surveys. In addition, least-squares Kirchhoff (LS-Kir) migration compensated for the illumination variations and attenuated strong migration swings caused by irregular VSP acquisition geometry; it also improved the amplitude consistency between upgoing and downgoing wavefields within each well and among different wells. This facilitated the combination of three nearby wells with both upgoing and downgoing wavefields for 4D imaging and improved the coverage and S/N of the 4D results.