Abstract

Alaska’s first commercial oil and gas province, the Cook Inlet Basin, of south-central Alaska, was identified by the presence of numerous oil and gas seeps in the southern part of the basin and the Alaska Peninsula. These were first recognized by Russian explorers in the 1850s. Early exploratory drilling was centered in the vicinity of these seeps, which emanate from rocks of Jurassic and Cretaceous ages. Eighteen wells were drilled in this southern area prior to 1950. After 1950, exploration shifted northward, and the fourth well drilled in the northern portion of the basin discovered the Swanson River field in 1957. This generated an exploration boom, and by 1970, seven of the inlet’s ten oil fields and 17 of the 34 gas fields had been discovered. These discoveries represent more than 98% of both the oil and gas produced to date.

After the Prudhoe Bay discovery, in early 1968, activity in the Cook Inlet area declined sharply, and over the next 30 years, only three small oil fields and nine small gas fields were discovered. As of year-end 2011, the cumulative production from these discoveries was less than 20 MMBO and 65 BCFG.

A declining reserve base and concerns regarding the ability to meet local gas demands led to an increase in gas exploration in the late 1990s and early 2000s. From 2000 to year-end 2011, eight additional gas fields were discovered, with the most important discoveries occurring in 2011. Cumulative production from the five pre–2011 discoveries totals approximately 25 BCFG. The three fields discovered in 2011 have yet to be developed; however, the cumulative, preliminary reserve estimates from these three discoveries are thought to be in excess of 1.0 TCFG.

The total cumulative production in the Cook Inlet Basin, from 1958 through 2011, is 1.3 BBO from eight fields and just under 7.5 TCFG from 28 producing fields.

Given the relatively short, punctuated exploration history of this prolific hydrocarbon basin, renewed exploration activity using modern technology will very likely produce significantly positive results. Recent evaluations by the United States Department of Energy/National Energy Technology Laboratory and the United States Geological Survey place the mean for conventional undiscovered technically recoverable resources in the range of 13 to 17 TCFG and approximately 600 MMBO.