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

摘要

Observations of velocities in sediments containing gashydrates show that the strength of sediments increases withhydrate saturation. Hence it is expected that the attenuationof these sediments will decrease with increasing hydratesaturation. However, sonic log measurements in the Mallik2L-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 compositemedia. We have used our model to predict observed attenuations in the Mallik 2L-38 well, Mackenzie Delta, Canada.