Molecular and isotopic analyses of the hydrocarbon gases within gas hydrate-bearing rock units of the Prudhoe Bay-Kuparuk River area in northern Alaska

Gas hydrates, which are crystalline substances of water molecules that
encase gas molecules, have the potential for being a significant source of
natural gas. World-wide estimates for the amount of gas contained in
hydrates range from 1.1 x 105 to 2.7 x 108 trillion cubic feet. Gas
hydrates exist in many Arctic regions, including the North Slope of
Alaska.

The two primary objectives of the U.S. Geological Survey Gas Hydrate
Research Project are (1) to map the distribution of in-situ gas hydrates
on the North Slope of Alaska, and (2) to evaluate the geologic parameters
that control the distribution of these gas hydrates. To aid in this
study, British Petroleum Exploration, ARCO Alaska, Exxon Company USA, and
the Continental Oil Company allowed the U.S. Geological Survey to collect
geochemical samples from drilling North Slope production wells.

Molecular analysis of gaseous drill cutting and free-flowing gas samples
from 10 production wells drilled in the Prudhoe Bay, Kuparuk River, and
Milne Point oil fields indicates that methane is the primary hydrocarbon
gas in the gas hydrate-bearing stratigraphic units. Isotopic data for
several of these rock units indicate that the methane within the inferred
gas hydrate occurences originated from both microbial and thermogenic
processes.