The Cook Inlet Region of Alaska contains an estimated 19 trillion cubic feet of natural gas, about 600 million barrels of oil, and 46 million barrels of natural gas liquids, according to a new assessment by the U.S. Geological Survey (USGS). This estimate is of undiscovered, technically recoverable oil and gas resources, and includes both unconventional and conventional resources. These gas estimates are significantly more than the last USGS assessment of southern Alaska in 1995, in which a mean of 2.14 trillion cubic feet of gas was estimated. This increase in the undiscovered resource is attributed to new geologic information and data.
“For the first time, USGS has evaluated unconventional (or continuous) as well as conventional petroleum resources in the Cook Inlet region of Alaska,” says Brenda Pierce, USGS Energy Resources Program coordinator. “The USGS conducts assessments to evaluate the nation’s petroleum potential, especially as new data and information become available, in order to understand the resource endowment of the nation.”
Since oil and gas production began in the Cook Inlet region in 1958, more than 1.3 billion barrels of oil and 7.8 trillion cubic feet of gas have been produced, yet the new USGS assessment shows that significant undiscovered gas remains. This assessment includes estimates of conventional and unconventional accumulations, including coalbed gas and tight gas formations. Coalbed gas is a form of natural gas extracted from coal deposits, whereas tight gas is natural gas occurring in impermeable, compact rock formations. Both require different development techniques than conventional gas accumulations.
The USGS assessment of undiscovered gas resources ranges from 5 trillion to 40 trillion cubic feet (95% and 5% probability, respectively). Of this total, about 72 percent is estimated to be found in conventional accumulations, 25 percent in coalbed gas accumulations, and 3 percent in tight gas accumulations.
The assessment of undiscovered oil resources ranges from 108 million to 136 billion barrels of oil (95% and 5% probability, respectively). These resources all are conventional resources; there are no unconventional oil resources assessed in the Cook Inlet region.
These new estimates are for technically recoverable oil and gas resources, which are those quantities of oil and gas producible using currently available technology and industry practices, regardless of economic or accessibility considerations. As such, these estimates include resources beneath both onshore and offshore areas of the Cook Inlet region and beneath areas where accessibility may be limited by policy and regulations imposed by land managers and regulatory agencies.
USGS is the only provider of publicly available estimates of undiscovered technically recoverable oil and gas resources of onshore lands and offshore state waters. The USGS worked with the Alaska Division of Geological and Geophysical Surveys and the Alaska Division of Oil and Gas to develop a geologic understanding of the Cook Inlet region. The Cook Inlet assessment was undertaken as part of a nationwide project assessing domestic petroleum basins using standardized methodology and protocol.