C. N. Threlkeld L. B. Magoon George E. Claypool 1980 <p><span>Two types of natural gas occurrences are present in the Cook Inlet basin. The major reserves (1.8 × 10</span>¹¹<span>m</span>³<span>) occur in shallow (less than 2,300 m), nonassociated dry gas fields that contain methane with ^dgr</span>¹³<span>C in the range of -63 to -56 per mil. These gas fields are in sandstones interbedded with coals of the Sterling and Beluga Formations; the gas fields are interpreted as biogenic in origin. Lesser reserves (1.1 × 10</span>¹⁰<span>&nbsp;m</span>³<span>) of natural gas are associated with oil in the deeper Hemlock Conglomerate at the base of the Tertiary section; associated gas contains methane with ^dgr</span>¹³<span>C of about -46 per mil. The gases associated with oil in the Hemlock Conglomerate are thermogenic in origin.</span></p> application/pdf 10.1306/2F91944F-16CE-11D7-8645000102C1865D en American Association of Petroleum Geologists Biogenic and thermogenic origins of natural gas in Cook Inlet basin, Alaska. article