Understanding gas hydrates as an alternative energy source is of increasing interest to the oil and gas industry. Gas hydrates are formed from a combination of water and natural gas and are commonly found in offshore shallow seabed sediments and arctic areas. More specifically, they are formed in areas that are conducive to high pressure and low temperature where water and gas can combine to create a solid ice-like substance.
The authors review the current and developing techniques in the area of gas hydrate reservoir formation evaluation. In particular, they delve into the physical responses of the resistivity, nuclear, acoustic, and nuclear magnetic resonance (NMR logging measurements. Key items discussed are the estimation of hydrate saturation; hydrate growth habits and their identification from log data; and the relevancy of such information to possible reservoir exploitation.
The paper emphasizes the importance of an integrated approach; i.e., the combination of various log measurements gives a far clearer picture than can any one single measurement. For example, a combination of density and NMR measurements have been shown to be useful in determining hydrate saturation while a combination of the acoustic well log velocities and hydrate saturation can help determine the hydrate growth habit.