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Imaging Below Shallow Gas with Full Azimuth Acquisition: A Solution Design and Modeling Case Study in Offshore MalaysiaNormal access

Authors: M.C.K. Choo, M. Branston, M. Tham, P. Baltensperger and M. Wysocki
Event name: Petroleum Geoscience Conference & Exhibition 2013
Session: Geophysics: Shallow Gas
Publication date: 18 March 2013
Organisations: GSM, EAGE
Language: English
Info: Extended abstract, PDF ( 3.06Mb )

The image of the target in this case study is affected by zones of shallow gas/high Earth attenuation in the overburden. The goal of the study is to determine whether the imaging of the seismic below these areas can be improved through the application of advanced acquisition designs, eg. increased azimuth, long offset acquisition. Following the successful completion of a proof of concept test using a realistic synthetic model, illumination analyses were carried out over the survey area to determine the illumination characteristics of the legacy survey and the circular shooting acquisition to help understand the impact of the shallow gas bodies on the amplitude across the target horizons. The non-conventional circular acquisition approach has the potential to improve upon the azimuthal sampling achievable with the traditional straight line narrow azimuth survey. To determine the relative benefits of the full azimuth approach against the narrow azimuth legacy data for this specific area, additional target orientated analysis was conducted. This consisted of establishing the full range of reflector dips and azimuths (outside of those in the existing structural model) which could be imaged by each technique combined with simulating local PSDM images for the key areas of interest.

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