Hidden depths of 4D seismic

Since its inception in the late 1990's, 4D seismic has become a geophysical mainstay in support of Field Development and Optimization, especially in the offshore. Typical applications include mapping of waterfronts caused by aquifer influx or injected water, and mapping of connected and disconnected compartments using pressure and/or compaction related signals.Shell1 has acquired dozens of 4D seismic surveys in the Deepwater GoM alone, and many more in the North Sea and globally. When dealing with such large numbers of seismic surveys, standardization in various domains is necessary. It brings distinct advantages in terms of turnaround time and interpretation quality.But we should not be tempted to rely on a “hands-off, minds-off” approach, as we will illustrate through presenting several unusual or unexpected observations and interpretations, all from Deepwater fields. We include a real data example showing signals for which satisfactory explanations are yet to be found. We finish the overview with an example of a credible 4D signal detected at a depth of 29000' - a fitting testimony of the fantastic quality of our data these days thanks to many years of progress in acquisition and processing technologies.