A tale of two rigs: cook inlet jack-up rig briefing.

• Author: Bradner, Mike
• Position: OIL & GAS

Geologists have long believed Cook Inlet to be an underexplored hydrocarbon basin. Alaska's first commercial oil field in modern times was discovered at Swanson River, an onshore oilfield on the Kenai Peninsula that is still producing. That led quickly to a rush of exploration nearby, including in waters of the Inlet offshore.

The discoveries that resulted were to help shape Alaska, including establishment of a major industrial base for the Kenai Peninsula with its natural gas-based manufacturing. But the exploration of Cook Inlet was cut short.

In 1970, just as the first Inlet oil and gas fields were being developed, the discovery of world class oil deposits on the North Slope diverted the industry's attention. Money that ordinarily would have been spent in a second round of Cook Inlet exploration went to the North Slope, and there has not been sustained exploration until recently.

More to be Discovered

State geologists are confident that there are more oil and gas fields to be discovered in the inlet, however. In Cook Inlet there are the handful of larger discoveries and a number of small deposits found recently, but many medium-sized finds that were expected have not been made. They are still out there.

But where? Many believe the larger unfound deposits are in deeper waters of Cook Inlet. Exploration drilling with drillships in the 1960s and 1970s actually found some of these or at least indications of them. But at the time they were not large enough for the companies to pursue. However, the well logs and other data have long been made public, and now, a new generation of oil entrepreneurs, using new exploration tools, have been working to get more exploration done.

Lack of a critical technology--a jackup rig for drilling in deep water--has been a major obstacle, until recently. A jack-up rig is a floating barge that serves as a platform for a drill rig. It has large, vertical steel legs attached. Pulled into position with tugs, the rig lowers the legs to the sea bottom and literally jacks itself up from the water surface, creating a stable platform for drilling. When the well is finished, the drill platform is jacked back down, the legs raised and the unit is pulled away.

There has been recent onshore exploration drilling in the Cook Inlet basin with drill rigs designed to work on land, and many of these have yielded modest discoveries of natural gas. The big prize--more oil--appears to lie offshore, in the deep water.

Unlocking the...