COLLETT, TIMOTHY S., U.S. Geological Survey, Denver, CO

ABSTRACT: Natural Gas Production From Arctic Gas Hydrates

One of the primary objectives of the U.S. Geological Survey/Russian Ministry of Geology (VNIGRI) cooperative research agreement is the assessment of the resource potential of the known onshore Arctic gas-hydrate accumulations. The gas hydrates in the Russian Messoyakha field, located in the West Siberian basin, and those of the Prudhoe Bay/Kuparuk River area in northern Alaska are the most studied gas-hydrate accumulations in the world and the focus of our cooperative research efforts. The production history of the Messoyakha field has demonstrated that gas hydrates are an immediate producible source of natural gas. Geologic similarities between the Messoyakha and Prudhoe Bay/Kuparuk River gas-hydrate accumulations further suggest that the Alaskan gas hydrates may also be a producible source of natural gas.

The Messoyakha field, discovered in 1968, was the first producing field in the northern part of the West Siberian basin. Gas yields from the upper part of the Messoyakha reservoir were unusually low, and analyses of production data suggested the presence of naturally occurring gas hydrates. Subsequent analyses of temperature data and well logs confirmed the presence of gas hydrates in the upper part of the Messoyakha reservoir, thus separating the field into an upper, gas hydrate, and lower, free-gas accumulation. Long-term production from the gas-hydrate part of the Messoyakha field has been achieved by a simple depressurization scheme. As production began in 1969, reservoir pressures followed predicted values. In 1971, however, measured reservoir pressures began to deviate from pred cted values, a deviation that has been attributed to the liberation of free gas from dissociating gas hydrates. Russian researchers have estimated that about 36% (183 billion cu ft) of the gas withdrawn from the Messoyakha field has come from the gas hydrates.

Both the Messoyakha and Prudhoe Bay/Kuparuk River gas-hydrate accumulations occur in similar sequences of interbedded Cretaceous and Tertiary sandstone and siltstone reservoir rocks. The presence of a significant volume of free gas trapped below both the Messoyakha and Prudhoe Bay/Kuparuk River gas-hydrate accumulations is very important to the consideration of potential production characteristics of gas hydrates in Alaska. Free gas below the Prudhoe Bay/Kuparuk River gas hydrates suggests that the depressurization production scheme used in the Messoyakha field may work in northern Alaska.

The most striking difference between the Messoyakha and Prudhoe Bay/Kuparuk River gas-hydrate/free-gas occurrences is the size of the accumulations. The total mapped area of the gas-hydrate occurrences in the Prudhoe Bay/Kuparuk River area is about 650 sq mi, whereas the Messoyakha field covers an area of only about 90 sq mi. This difference in field size accounts for the vast difference in the estimated gas volumes in the Messoyakha (2.8 trillion cu ft) vs. Prudhoe Bay/Kuparuk River (44 trillion cu ft) gas-hydrate accumulations, which suggests that the ultimate natural gas production capacity of the Prudhoe Bay/Kuparuk River gas-hydrate occurrences will be much greater than the historical production from the Messoyakha field.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.