Seismic Imaging of Gas Hydrate Accumulations Beneath Thick Permafrost Areas of the Mackenzie Delta, NWT, Canada

Bellefleur, G. (Geological Survey of Canada) | Riedel, M. (Geological Survey of Canada) | Brent, T. (Geological Survey of Canada)

OnePetro 

The Mackenzie Delta in Canada's Northwest Territories hosts manypermafrost-related gas hydrate accumulations that were indirectly discovered orinferred from conventional hydrocarbon exploration programs. In particular, gashydrate intervals characterized with high saturation show high resistivity andhigh P- and S-wave velocity on well-log data, and are typically found insand-rich horizons. As demonstrated at the Mallik site, the velocity contrastbetween highly saturated gas hydrate-bearing sediments and unconsolidatedwater-bearing sediments is significant and allows their detection with seismicdata. Here, we use 2D and 3D seismic reflection data acquired by industry onRichards Island to map and characterize gas hydrate accumulations beneath athick permafrost area of the Mackenzie Delta. Specifically, we show new seismicevidences of gas hydrate accumulations near YaYa, Ivik and Umiak. The presenceof gas hydrate was previously inferred from well-log data in several boreholeslocated in those areas. All seismic data were re-processed following anAVO-friendly flow that preserved relative amplitude relationships. On suchdata, the strong acoustic impedance of gas hydrate produces strong amplitudeseismic reflections. The seismic signature of gas hydrates is confirmed byseismic-to-well correlation in areas where boreholes are available. Resultsindicate that gas hydrate accumulations occur in structurally-controlled playstypical of conventional oil and gas traps found in this area, and furtherdemonstrate that gas hydrates are part of the regional petroleum system.

 

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