AVO modeling of the bottom simulating reflection related to gas hydrate of the offshore Oregon and Beaufort Sea
Presenter : Welayaturromadhona Advisor : How-Wei Chen
Abstract
The upper continental margin of the Oregon and Beaufort Sea are underlain by a strong bottom simulating reflection (BSR). A bottom simulating reflection (BSR) that parallels the sea floor coincides with the base of the gas hydrate stability field and is commonly used as indicator of natural submarine gas hydrates. This study investigates the relative abundance of hydrate and free gas associated with the BSR by modeling the reflection coefficient or amplitude versus offset (AVO) of the BSR at two separate sites, offshore Oregon and the Beaufort Sea. AVO studies of the BSR can determine whether free gas exists beneath the BSR if the saturation of gas hydrate above the BSR is less than approximately 30% of the pore volume. The AVO analyses at the two study locations indicate that the high amplitude BSR results primarily from free gas beneath the BSR.The amplitude-versus-offset (AVO) analysis indicates that the BSR is produced mainly by the existence of free gas in the sediments beneath the BSR.Saturation of gas hydrate in the sediment above the BSR is estimated from the AVO modeling to be less than 10% of the pore volume.
References
Andreassen, K., Hart, P and MacKay, M., 1996. Amplitude versus offset modeling of the bottom simulating reflection associated with submarine gas hydrates. Marine Geology, 137, 25-40
Andreassen, K., Hart, P. and Grantz, A., 1995. Seismic studies of a bottom simulating reflection related to gas hydrate beneath the continental margin of the Beaufort Sea. J. Geophys. Res., 100: 12,659-12,673.