The Point Thomson Undefined Oil Pool is located on the Arctic Slope of Alaska, about 60 miles east of Prudhoe Bay. The pool was discovered in 1977 by Exxon Corp's PTU No. 1 exploratory well that flowed 18.5°API gravity “pipeline-quality oil” at an average rate of about 2,300 barrels per day from the Thomson sand. The average gas-oil ratio reported was 5,800 cubic feet per barrel. The existence of hydrocarbons at Point Thomson was confirmed during 1978 and 1979 by the PTU No. 2 and No. 3 exploratory wells. Five tests of the Thomson sand conducted in four wells flowed between 170 and 2,283 barrels of oil per day and between 3.4 and 13.3 million cubic feet of gas per day, yielding reported gas-oil-ratios from 3,890 to 22,705 standard cubic feet per stock tank barrel. Because Commission regulation 20 AAC 25.990 (45) defines an “oil well” as a well that produces predominantly oil at a gas-oil ratio of 100,000 standard cubic feet per stock tank barrel or lower, the Point Thomson Undefined Pool is classified as an oil pool.

As of early 2010, ExxonMobil is drilling two new exploratory wells, PTU No. 15 and PTU No. 16, that are part of a cycling project designed to test the production potential of the reservoir.

The main reservoir of the Point Thomson Undefined Oil Pool is informally named the Thomson sand. This Cretaceous-aged (Neocomian) conglomeratic sandstone is about 12 miles long, 5 miles wide and ranges up to 330 - 350 feet thick in the Point Thomson area. It is stratigraphically equivalent to the Kemik Sandstone that is located approximately 30 miles to the south. The Thomson sand consists of very fine- to very coarse-grained, dolomite-rich sandstone that contains argillaceous rock fragments. Dolomite-rich pebble-, cobble- and boulder-conglomerates are locally abundant. The Thomson sand unconformably overlies pre-Mississippian-aged dolomite and argillite basement rocks and it is, in turn, overlain by the pebble shale. The abundance of coarse, dolomite clasts and close association with an erosional unconformity suggest a local source for the Thomson sand.

Secondary reservoirs at Point Thomson are the pre-Mississippian basement and the marine sandstones of the Cretaceous- to Oligocene-aged Canning Formation, which have both produced oil and gas during well tests. Abnormal fluid pressure gradients, as high as 0.84 psi per foot, have been reported for the basement and overlying Thomson sand, pebble shale, Hue Shale, and lower Canning Formation (in ascending order).