Geophysical Characterization of Gas Hydrates

The occurrence of gas hydrates in large quantities worldwide and their immense energy potential have prompted concerted efforts into their exploration and understanding. Geophysical characterization of natural gas-hydrate occurrences by seismic and other methods have gained prominence and such studies have been reported; however, no compilation of such studies has been attempted previously. This SEG publication, Geophysical Characterization of Gas Hydrates (Geophysical Developments No. 14), is the first book to focus on documenting various types of geophysical studies that are conducted for the detection and mapping of gas hydrates. Organized into five sections, the editors present 20 papers by experts in their respective fields plus introductory chapters for each section. Section 1 is an introduction and motivation for geophysical investigations into gas hydrates. Section 2 on seismic imaging discusses several seismic techniques with applications to various geologic settings. These comprise the indicators of gas hydrates in marine data such as BSRs, the use of AVO, seismic inversion, full-waveform inversion, VSPs, and multicomponent data in the assessment, detection, and quantification of gas hydrates. As the occurrence of gas-hydrate deposits affects the physical and chemical properties of the host sediments, various additional geophysical techniques, including electromagnetics, magnetics, and infrared imaging, are used for their detection, and these comprise Section 3. Section 4 discusses borehole methods aimed at characterization of gas-hydrate environments and includes the conventional log-based measurements, special logging measurements such as NMR, and logging-while-drilling and measurement-while-drilling applications. Finally, Section 5 discusses rock-physics modeling and gas-hydrate laboratory studies. Although rock-physics modeling helps link log measurements with seismic reflection profiles for estimating gas-hydrate concentrations, creation of artificial gas-hydrate-bearing sediments using different techniques is also necessary, for instance, when characterizing engineering properties of gas-hydrate-bearing sediments. The book will be of interest to geophysicists, petroleum geologists, geochemists, and those enthusiastic minds that seek the unknown in the field of energy resources.