The 410 exploratory wells drilled in 1959 represent the greatest number drilled in any year and a 30.7% increase over the previous year. 298 wildcats discovered 10 new oil fields and 12 new gas fields, for a success ratio of 7.3% compared with 8.7% in 1958. While seismic activity dropped average well depth and total exploratory footage increased.

The 185 exploratory wells in the Powder River basin resulted in 19 successes, for a success ratio of 10.2% and 5 new-field discoveries. 37% of all Wyoming exploratory drilling was concentrated on the east side of the Powder River basin. A success ratio of 22.2% was achieved in the Green River basin by 18 of the 81 exploratory tests being successful. Nineteen per cent of all exploratory drilling was in the Green River basin.

Of the 22 new-field discoveries, 6 were found in the Mesaverde and 5 in the Tertiary. Eleven new fields were discovered in the Green River basin, 5 in the Powder River basin, 5 in the Wind River basin, and 1 in the Big Horn basin.

Stratigraphic exploration was extensive with attention directed toward the Dakota on the eastern side of the Powder River basin and the Tertiary-Upper Cretaceous of the Green River and Wind River basins. The search for gas was greatly accelerated.

The most significant development was the discovery of commercial oil in the Almond on the east flank of the Rock Springs uplift, previously looked upon as a gas province.

Most of the exploratory drilling in 1960 will probably be concentrated on (1) the eastern side of the Powder River basin in search of Dakota and Minnelusa oil and (2) in the Green River Basin in search of gas and Almond oil.

There was no exploratory drilling in Idaho in 1959.