In the past 12 months significant new discoveries of oil and gas have been completed in the Powder River, Wind River, and Washakie basins. The eastern Powder River basin continues to lead the State in the number of new discoveries. However, remote discoveries of Minnelusa oil in the center of the Powder River basin, gas in deeper portions of the Wind River basin, and gas in several areas along the rim of the Washakie basin have provided new exploration frontiers. Thermal stimulation as a completion technique for exploratory wells also has provided a new exploration frontier.

Deeper drilling in the center of the Powder River basin found oil in the Minnelusa in a structural trap and caused the largest land play that the State has had in several years. Multi-pay gas discoveries in the deeper portion of the Wind River basin, combined with new gas outlets, have provided new exploration incentive for this area. Three gas discoveries along the rim of the Washakie basin have stimulated interest in the exploration potential of this sparsely drilled area.

Thermal stimulation as a completion technique in previously unproductive areas has attracted large leasehold investments in several basins. Pilot projects which were underway during the past 12 months have met with mixed results, several appearing to be successful whereas others appear to be in question. The coming year is expected to reveal additional data concerning the parameters for successful thermal-stimulation projects.

A review of exploratory statistics of the past 20 years reveals that Wyoming has been on an exploratory success-ratio plateau for the last 10 years with an average of 12.6 per cent of all exploratory wells completed as producers. The stratigraphic and combination type traps discovered during this period are 60-70 per cent of the total; structural traps are in the minority. This ratio in classification of new discoveries is expected to continue in the near future.

The decline in leaseholds on Federal and Indian lands of 25 per cent during the last 5 years indicates the change from "protection leaseholds" to "drillable leaseholds." The result is the increasing availability of leases at lower prices and the upgrading of exploratory prospects. This is expected to have a favorable effect on the success ratio of exploratory wells.

Wyoming's stable growth in production and reserves of petroleum and the rapid cash flow from unrestricted production combine to make a favorable climate for exploration investment. The increasing diversity in exploration techniques and the numerous areas available for exploration are expected to challenge every geologist working in Wyoming.

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