The Value of High-Resolution and Rich Azimuth Imaging for Overburden Description

High resolution (HR) seismic data is required to assess the presence of shallow hazards in the overburden and ensure the safe drilling of new wells.

Typically, the data used is 2DHR seismic, even though the benefits of 3D imaging are well known. To develop the 3D approach, existing wide-azimuth ocean bottom seismic data have been re-processed at the full sample rate, using the downgoing wavefield, to deliver a high resolution image. Analysis and inversion of the surface waves at seabed has also been applied to provide a high resolution velocity volume. This is complimentary to seismic data in the accurate identifaction of shallow gas.

In addition, a narrow azimuth, high resolution 3D site survey was acquired across the area and the results from both techniques compared to assess the relative merits of each approach.

In conclusion, each dataset brings an improvement in overburden imaging, when compared to existing 2DHR and reservoir focused 3D seismic data. However, the different data are best used in combination to enable the robust analyses of shallow hazards for safe delivery of a well.