Recent advances in mapping deep permafrost and gas hydrate occurrences using industry seismic data

• Main Authors: Gilles Bellefleur, Michael Riedel, Kumar Ramachandran, Tom Brent, Scott Dallimore
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2009
• Subjects: Summary; Island Lakes; Talik; Ice; permafrost; Richards Island
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.601.7397; http://www.geoconvention.org/archives/2009abstracts/076.pdf

An industry-acquired (2002) 3D seismic survey over the Mallik area in is used to map heterogeneities in permafrost and to determine the extent of gas hydrate occurrences. Seismic amplitude anomalies associated with lakes and drainage systems are observed in the data. Beneath lakes, the seismic indicate weaker amplitudes, locally degrading images of the geology within, and below the permafrost. On Richards Island, lakes may not become ice-fast in winter promoting talik development that vertically penetrate permafrost. Amplitude effects on the seismic data arise from velocity and attenuation associated Frontiers + Innovation – 2009 CSPG CSEG CWLS Convention 604 with this frozen / un-frozen variability of the permafrost zone. A 3D travel-time tomography algorithm produced a map of the permafrost velocity structure. The 3D velocity map clearly reveals a heterogeneous velocity distribution, primarily related to thermal variations within the permafrost. Results from acoustic impedance inversion at hydrate reservoir interfaces indicate that sediments with high gas hydrate saturation near the Mallik well site extend over an area of 0.25 km2.