Cook Inlet stretches 180 miles from the Gulf of Alaska to Anchorage in south-central Alaska. Cook Inlet branches into the Knik Arm and Turnagain Arm at its northern end, almost surrounding Anchorage. The watershed covers about 100,000 km² of southern Alaska, east of the Aleutian Range and south of the Alaska Range, receiving water from its tributaries the Knik River, the Little Susitna River, and the Susitna and Matanuska rivers. The watershed includes the drainage areas of Mount McKinley. Within the watershed there are several national parks and the active volcano Mount Redoubt, along with three other historically active volcanoes. Approximately 400,000 people live within the Cook Inlet watershed.
Before the growth of Anchorage, Knik was the destination for most marine traffic in upper Cook Inlet. The Cook Inlet Region of Alaska contains an estimated mean of 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.
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.
The Cook Inlet basin contains large oil and gas deposits including several offshore fields. As of 2005 there were 16 platforms in Cook Inlet, the oldest of which is the XTO A platform first installed by Shell in 1964, and newest of which is the Osprey platform installed by Forest Oil in 2000. Most of the platforms are operated by Union Oil, which was acquired by Chevron in 2005. There are also numerous oil and gas pipelines running around and under the Cook Inlet. The main destinations of the gas pipelines are to Kenai where the gas is primarily used to fuel commercial fertilizer production and a liquified natural gas (LNG) plant and to Anchorage where the gas is consumed largely for domestic uses.
This USGS assessment includes estimates of conventional and unconventional, or continuous, 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 4.976 to 39.737 trillion cubic feet (95 percent and 5 percent 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 USGS assessment of undiscovered oil resources ranges from 108 to 1,359 million barrels of oil (95 to 5 percent probability, respectively). These resources are all 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 (exclusive of the Federal offshore) and beneath areas where accessibility may be limited by policy and regulations imposed by land managers and regulatory agencies.
By. Andy Soos