Micromodels of Hydrate Deposition

I evaluated three different models of possible hydrate deposition in the pore space. In the first model (model A), I assume that hydrate is suspended in the water and thus only contributes to the bulk modulus of the pore fluid (Figure A). In this case, the formation and deposition of the hydrate in the sediment would have no effect on the stiffness of the sediment and could be treated as pure fluid substitution. In the second model, hydrate becomes part of the solid sediment frame (Figure B). This causes a reduction in porosity and a weak stiffening of the sediment structure. The third model assumes that hydrate cements grain contacts (Figure C), thus significantly changing the rock stiffness and simultaneously reducing the porosity. Even though this last model is not likely to apply to the sediments at the Blake Outer Ridge due to their high porosity, I include it into this study to show the different effects of these models not only on saturation but also on the elastic properties and seismic amplitudes. Even though, strictly speaking the cementation theory applies only for porosities of less than 40%, it can be used to approximately estimate the elastic properties of granular aggregate of higher porosities.

 

hydrate
Figure 1 Hydrate models used in this study.