Total drilling in eastern and northwestern Colorado and western Nebraska declined from 1,061 wells in 1963 to 998 wells in 1964. This 5.9 per cent decrease continues the downward trend of recent years. Exploration drilling in eastern Colorado increased by 17 wells in 1964, and the success rate increased from 9.0 to 9.6 per cent. The first Mississippian production in eastern Colorado was established in 1964. In northwestern Colorado, 44 exploratory tests resulted in two oil and eight gas discoveries for a success rate of 22.7 per cent. Exploratory drilling in Nebraska declined by 49 tests, or 17 per cent, during 1964. The most encouraging development in the Nebraska portion of the Denver basin was the northward extension of production resulting from the discovery of four n w fields. Exploratory drilling in central Nebraska decreased by 38 wells, or 44 per cent, during 1964. The success rate declined from 11.5 per cent in 1963 to 8.2 per cent in 1964.

Although geophysical activity decreased 64 per cent in 1964, exploratory drilling in 1965 is expected to maintain the 1964 level or show a slight increase.