The effect of hydrate content on seismic attenuation: A case study for Mallik 2L-38 well data, Mackenzie delta, Canada

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Description/Abstract

Observations of velocities in sediments containing gas
hydrates show that the strength of sediments increases with
hydrate saturation. Hence it is expected that the attenuation
of these sediments will decrease with increasing hydrate
saturation. However, sonic log measurements in the Mallik
2L-38 well and cross hole tomography measurements in the Mallik field have shown that attenuation increases with hydrate saturation. We studied a range of mechanisms by which increasing hydrate saturation could cause increased attenuation. We found that a difference in permeability between the host sediment and the newly formed hydrate can produce the observed effect. We modelled attenuation in terms of Biot and squirt flow mechanisms in composite
media. We have used our model to predict observed attenuations in the Mallik 2L-38 well, Mackenzie Delta, Canada.