Abstract

The Kenai gas field, located south of the town of Kenai on the eastern shore of the Cook Inlet, was the first gas field discovered in the Cook Inlet Basin. Discovery was in 1959 while unsuccessfully exploring for oil in the deep Hemlock Formation. Since 1961, more than 2.4 TCF of gas have been produced from the field. Unocal Corporation operated the field from discovery until 1994, when Marathon Oil Corporation assumed full ownership and operations. Production has provided the local community with natural gas for decades and has helped create new industries in Alaska, such as LNG (liquefied natural gas) export and fertilizer production. The Kenai structure is a large, north–south-trending anticline that is separated from the adjacent Cannery Loop Unit by a down-to-the-north normal fault. The gas is 99% methane, predominately biogenic in origin, and produced exclusively from the Sterling, Beluga, and Tyonek members of the Tertiary-age Kenai Group. The three productive formations were deposited by fluvial systems that migrated across the basin, resulting in a thick section of interbedded sand, silt, mudstone, and coal. Variations in provenance and location within the greater fluvial system resulted in a broad spectrum of reservoir quality and continuity within these three formations. The high-quality reservoirs in the Sterling and Deep Tyonek Formations have proved to be the most prolific gas sands in the field, producing a combined 2 TCF. In contrast, the sands of the Beluga Formation are thinner, tighter, and laterally discontinuous. The Beluga, however, is composed of more than 25 individual gas-filled sands that contain a significant amount of original gas in place. Advances in completion technology have made these sands economically viable, extending the life of the field to 2009 and beyond. Today, the Kenai gas field produces an average of 82 MMCFD from more than 30 wells. In addition, Kenai gas field has Alaska’s only large-scale gas storage project in the Sterling Formation.