The presence of gas hydrates in permafrost regions has been confirmed by core samples
recovered from the Mallik gas hydrate research wells located within Mackenzie Delta in the
Northwest Territories of Canada. Strong vertical variations of compressional and shear velocities
and weak surface seismic expressions of gas hydrates indicate that lithological heterogeneities
control the lateral distribution of gas hydrates. Seismic scattering studies predict that typical
horizontal scales and strong velocity contrasts due to gas hydrate concentration will generate
strong forward scattering, leaving only weak energy to be captured by surface receivers. In order
to understand the distribution of gas hydrates and the scattering effects on seismic waves,
heterogeneous petrophysical reservoir models were constructed based on the P-wave and S-wave
velocity logs. Random models with pre-determined heterogeneity scales can also be used to
simulate permafrost interval as well as sediments without hydrates. Using the established
relationship between hydrate concentration and P-wave velocity, we found that gas hydrate
volume content can be determined by correlation length and Hurst number. Using the Hurst
number obtained from Mallik 2L-38, and the correlation length estimated from acoustic
impedance inversion, gas hydrate volume fraction in Mallik area was estimated to be 17%,
approximately 7x108 m3 free gas stored in a hydrate bearing interval with 250,000 m2 lateral
extension and 100 m depth. Simulations of seismic wave propagation in randomly heterogeneous
models demonstrate energy loss due to scattering. With the available modeling algorithm, the
impact of heterogeneity scales on seismic scattering and optimum acquisition geometries will be
investigated in future studies.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/1045 |
| Date | 07 1900 |
| Creators | Huang, Jun-Wei, Bellefleur, Gilles, Milkereit, Bernd |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
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