Gas hydrates can occur naturally in subsurface formations under equilibrium pressure conditions. These conditions exist in most arctic and deep offshore regions.15 

During exploratory drilling for oil and gas in the arctic, operators have encountered insitu hydrates that pose engineering problems. Although these zones are often non-productive, they must be evaluated for well control purposes and well completion design.67  The potential of hydrates as an energy resource has also received much attention over the past ten years. Studies of production methods have been undertaken and hydrate coring procedures have been investigated.810 

With the increased interest in naturally occuring hydrates, the need for improved detection and evaluation methods has also increased. In this paper, logging of hydrates is discussed and selected logs from four arctic wells are examined. A new procedure based on temperature log analysis is described. The concept of a downhole heater for use with drill stem testing is also described for testing and evaluation of hydrate intervals.

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