ABSTRACT:

This paper examines the newly assessment of permeability of sediments via the correlation between the absolute permeability and the pore network in sediment. The continuous pore channel, which allows gas and water flow, was analyzed from the three-dimensional sediment images using a microfocus X-ray computed-tomography system. The results clarified that the proportion of the horizontal-continuous pore channel in terms of direction is a dominant factor in determining the absolute permeability. The absolute permeability of the sediment correlated well with the distribution of the continuous pore channel.

INTRODUCTION

The gas hydrate is crystalline clathrate of gas and water molecules. Hydrates have been studied over a wide range from fundamentals to field applications because of their unique structure and characteristic. Gasses in the natural-gas hydrate sediment are primarily methane molecules (Kvenvolden, 1995) and are expected to become a new energy resource. The production of natural gas from oceanic and permafrost sediments is currently being developed using such methods as depressurization, thermal stimulation, and injection of hydrate inhibitors (Moridis, Collett, Dallimore, Satoh, Hancock and Weatherill, 2004). It is important to understand the physical properties of sediment in investigations of structural properties, such as permeability, hydrate saturation, and sediment porosity, since these properties are essential to the development of natural gas production. The porosity is particularly important for material flow in sediment. Therefore many reports have been published on the relationship between porosity and permeability (Arns, Knackstedt and Martys, 2005; Bernabe, Mok and Evans, 2003; Koponen, Kataja and Timonen, 1997; Noiriel, Gouze and Bernard, 2004; Pape, Clauser and Iffland, 2000; Quispe, Rozas and Toledo, 2005; Singh and Mohanty, 2000). The gas and water appear to flow in continuous pores of sediment during the hydrate decomposition, and thus it is necessary to investigate the pore network to understand the material flow in the sediment.

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