Exploratory objectives in the Cook Inlet Basin are confined largely to the Kenai Formation, a 15,000-20,000-foot series of non-marine, coal-bearing sediments of Eocene or younger Tertiary age, underlain by marine Mesozoic sediments. The Kenai Formation on the Kenai Peninsula is divisible into an upper sand member, a middle siltstone and coal member, and a lower sand member. The gas fields on the Kenai Peninsula occur in the upper member; Swanson River oil production is from the lower member. The Kenai beds have been gently to moderately folded and locally faulted.

Exploration techniques consist of surface mapping, gravity and airborne magnetometer surveying, and reflection seismic shooting. Marine reflection shooting and gas exploder-sparker surveys have been used to explore Cook Inlet. Some structural leads can be obtained by field mapping but seismic work is needed to confirm closure. To date only structures defined by seismic methods have been drilled.

The Swanson River oil field is producing in excess of 28,000 barrels per day from the Hemlock zone, a series of sands and conglomerates near the base of the Kenai Formation. The structure is a large, faulted anticline.

Five gas fields have been discovered--the Kenai, Swanson River, West Fork, Falls Creek, and Sterling fields. Gas from the Kenai field is being delivered to Soldotna and Anchorage; the other fields are shut in although some gas from the Swanson River gas field is used in oil-field operations.

The gas consists of 99% methane and is believed to have originated within the Kenai Formation. There is insufficient evidence to determine whether the oil originated in the Kenai Formation or in underlying Mesozoic shales.

Seismic crews cost between $60,000 and $85,000 per month. Costs of deep exploratory wells on the Kenai Peninsula vary between $20 and $50 a foot, exclusive of road costs. Completed oil wells in Swanson River cost nearly $400,000. Road costs range from $10,000 to $50,000 per mile.

An increase in the tempo of exploratory drilling in 1962 is indicated.

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