Chapter 10: Integration of Chimney, Waveform Segmentation, AVO, and Absorption Attributes for Evaluation of Deep and Shallow Gas: A Southeastern Louisiana Case History*
Andy Clifford, Fred Aminzadeh, David Connolly, 2013. "Integration of Chimney, Waveform Segmentation, AVO, and Absorption Attributes for Evaluation of Deep and Shallow Gas: A Southeastern Louisiana Case History", Hydrocarbon Seepage: From Source to Surface, Fred Aminzadeh, Timothy B. Berge, David L. Connolly
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Gas-chimney analysis is a useful tool for evaluating shallow and deep hydrocarbon prospects by showing likely migration routes for deeply sourced thermogenic hydrocarbons as well as shallower biogenic hydrocarbons. Specialized seismic processing conditions the 3D data set so that only meaningful gas chimneys are analyzed. Once the data have been so conditioned, the interpreter can differentiate between faults that show evidence of leakage and those that do not show evidence of leakage and may be sealing faults. Many of the shallower chimneys can be tied directly to active surface seeps as well as shallow gas prospects and known hydrocarbon deposits. When this type of chimney analysis is coupled with techniques such as waveform segmentation, amplitude variation with offset, and absorption attribute analysis, the result is a very powerful 3D data volume that can be used to derisk shallow and deep gas prospects.
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With the increased resolution power of many geophysical methods, we are seeing direct evidence of seeps on a wide variety of data, including conventional seismic. New methods and technology have also evolved to better measure and detect seeps and their artifacts and reservoir charge and to map migration and remigration routes. In addition, detection of seepage is important for minimizing the risks associated with shallow gas drilling hazards, ensuring platform stability, and preventing well blow-outs.