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The economics of small gas field developments in the Southern North Sea away from any existing infrastructure is particularly sensitive to subsurface uncertainties. Applying latest geophysical approaches is a key aspect of obtaining sufficient grip on these parameters and ensuring robust project economics. For the Alpha field, the structural uncertainty due to poor seismic imaging was identified as critical and therefore a dedicated seismic imaging project was undertaken. It involved re-processing the existing seismic data with the latest velocity modeling and imaging technologies, such as Reverse Time Migration. It led to a clear improvement of the seismic character at objective level as well as a more consistent depth image. As a consequence, the expected volume of gas in place increased by 50% and additional reservoir targets were identified, considerably improving the project economics. In addition, a High Definition 3D seismic image of the shallow subsurface was for the first time successfully created over the area to assess any potential geohazards and ensured that the proposed and selected development concept had mitigations against these hazards and their consequences.

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