In 1968, Prudhoe Bay State No. 1 encountered the Permian-Triassic Sadlerochit formation at 8200 feet which flowed gas at 1.25 million cubic feet per day with 20-27 per cent porosity and "tens of millidarcies" permeability. Oil, condensate and gas are produced from the Triassic, Ivishak sandstone. This reservoir was deposited as a complex amalgamation of fan deltas and alluvial fans. The continuity of this fan delta was shown to extend seven miles away when the ARCO-Humble Sag River State No. 1 well was drilled. During the field's early life the oil-bearing sandstone in some locations was thick. Today, the oil bearing zone's average thickness is about and the initial estimate of Oil in place was 2.3 billion barrels.