dc.description.abstract | The presence of gas hydrates alters the bulk physical properties of the host sediments. The deviation of the physical property in the hydrated layer from the regional (hydrate-free background) trend can be used to estimate hydrate concentration. Six different methods of gas hydrate concentration estimation that make use of data from the measurements of the seismic properties, electrical resistivity, chlorinity, porosity, density, and temperature are summarized in this paper. We demonstrate the methods of hydrate concentration estimation using data from three different geographical areas: 1) Mount Elbert test site, Alaska, 2) Cascadia margin, offshore Canada and 3) Krishna Godavari (KG) basin, offshore India. Based on our estimation, the hydrate saturation in the hydrate stability zone varies from 40% to 80% of pore space in Alaska, 10% to 40% of pore space in the Cascadia margin, and 5% to 40% of pore space in the KG basin. There are various factors that can affect the hydrate saturation estimate; the two most important factors being the background property value in the absence of gas hydrate, and the modeling relationship between the physical property and gas hydrate saturation. a simple work-flow for hydrate saturation estimation from seismic velocity in a Microsoft Excel sheet is also presented. | |