The Kuparuk River oil field was developed later than Prudhoe Bay and benefited from newer technology.
Most obvious is the reach of drilling rigs which dramatically reduced the size of drill sites.
In 1970, a Prudhoe Bay drill site was 65 acres and from that 65 acres drill rigs could access a subsurface area two miles across.
A 1980 Kuparuk drill site was 24 acres and rigs could access an area three miles across.
By 1985, Kuparuk drill sites had dropped to 11 acres, but the subsurface reach was five miles across.
By 1999 at Alpine, a drill pad of 13 acres could access a subsurface area eight miles across.
The reservoir was also different: Kuparuk is at about 6,300 feet, compared to 8,000 to 9,000 feet at Prudhoe Bay.
And the net thickness, the pay at Kuparuk, is about 50 feet compared to nearly 600 feet at Prudhoe.
The sizes of the reservoirs are about the same: some 200 square miles.
Based on remaining recoverable reserves, ARCO estimated in 1981 that Kuparuk was probably the second largest field in the United States, behind Prudhoe.