Introduction

Abstract

Natural gas hydrate, or clathrate, sometimes called “flammable ice” or “combustible ice,” is a nonstoichiometric ice-like crystalline compound that is formed by water and gas molecules under high pressure and low temperature. In this chapter, we firstly summarize the properties of natural gas hydrate (i.e., compositions, structures, and the chemical and physical properties) and then give a brief history of gas hydrate researches from 1810 to present. It is found that great progress has been made in basic gas hydrate researches over the last two decades. Here, we discuss the formation conditions (e.g., gas origin, P-T conditions) of marine gas hydrate, summarize and predict the distribution and amount of gas hydrates in the world, and describe four prospecting techniques (i.e., seismic technique, drilling, logging, and geochemical exploration) for marine gas hydrate. In a word, gas hydrate researches involve multidiscipline, including geology, geochemistry, geophysics, regional engineering geology in the hydrate zone, and the related global climate.