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Snøhvit OBS Case History - PP and PS Imaging Under a Shallow Gas Cloud
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 77th EAGE Conference and Exhibition 2015, Jun 2015, Volume 2015, p.1 - 5
Abstract
Structural interpretation under shallow gas clouds can be challenging. It creates uncertainty in the top reservoir interpretation and hydrocarbon reserve estimation. PS Ocean Bottom Seismic (OBS) may be used to image beneath gas clouds to overcome these problems.
Snøhvit gas field is located in the Barents Sea. Structural interpretation of the field is mainly based on the 3D surface seismic surveys. However, there is a shallow gas cloud in part of the field that masks the top reservoir. PS seismic data is expected to be less sensitive to presence of the gas and can be used for the structural imaging in this area. A 3D OBS data was acquired by Magseis in 2013/2014. Full Waveform Inversion (FWI) in combination with conventional tomography is used in velocity model building process to get optimum image of the reservoir. PS statics is identified as the main challenge for the PS processing in the area. Lateral variation in low S-wave velocity and sediment thickness in the layer(s) close to the water bottom are most likely the reason for the static issue. The sediments are heavily distorted by pockmarks and plough marks from drifting icebergs. In this study we present the Snøhvit case history.