Dependence of transport properties on grain size distribution

Tripp, Brandon Jamal
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The topic of this thesis is investigating the relationship between grain size distribution and absolute permeability for medium silt to very fine-grained sandstones that are typical reservoir rocks in deepwater, offshore environments. I analyzed the relationship between grain size, mean grain size, median grain size, and grain size mode; grain size standard deviation; and absolute permeability through the amalgamation of numerical modeling and experimental core data for marine clay from the Pacific Ocean and Gulf of Alaska. The Pacific Ocean core sample was selected to represent porous media exhibiting narrow grain size distributions; the Gulf of Alaska samples were selected to represent porous media exhibiting broad grain size distributions. I constructed porous media composed of random packings of spheres with grain size distributions modeled on the grain size distribution of the Pacific Ocean core, and determined permeability by performing Lattice-Boltzmann simulations. The narrow grain size distributions exhibited a power law relationship between grain size standard deviation and permeability relationship. I then compared these results to measured data on the Gulf of Alaska samples, which exhibited very broad grain size distributions. The Gulf of Alaska samples had a different relationship between permeability and the standard deviation of the grain size distribution, although the relationship was still a power law. This illustrates how the breadth of the grain size distribution must be considered in empirical permeability relationships.