Time and the river.

• Author: Tyson, Ray
• Position: Swanson River oil field

The legendary Swanson River oil field passes into a new phase of gas development.

Within the year, the legendary Swanson River field, Alaska's first major oil discovery and father of Cook Inlet petroleum development, will be converted to produce mainly gas as the oil reservoir nears the end of its natural life.

The North Slope today produces more oil in three months than Swanson River has during the past 35 years. However, it was Swanson River that launched Alaska into the oil age, serving as the inspiration for additional exploration that led to oil and gas development throughout the Cook Inlet basin. Discovered by Richfield Oil Co. in 1957, Swanson River spurred the largest rush for oil leases ever recorded in the nation.

Father Time has caught up with Swanson River, where crude production has fallen from a peak of 37,000 barrels a day in 1968 to current rates of about 4,500 barrels a day. Some 217 million barrels of crude have been extracted, or more than 98 percent of the field's oil reserves.

But Swanson River contains lots of natural gas -- an estimated 333 billion cubic feet -- most of which has been funneled into the reservoir over the years from the nearby Kenai gas field to maintain reservoir pressure for oil production.

Swanson River's new field operator, Unocal Corp., says the "redelivered" gas is just too valuable to keep in the ground. Unocal's share of the gas will be piped to the company's chemical plant at Kenai, which requires more than a quarter of the 200-plus billion cubic feet of gas consumed a year in the entire Cook Inlet region, including Anchorage.

"We're trying to secure enough gas and enough sources in various fields to maintain that plant's insatiable appetite," explains Kevin Tabler...