Drilling activity in North America in 1966 amounted to a total of 44,690 holes and 183,684,533 ft.

Total exploratory drilling in Canada, Mexico, and the United States increased slightly compared with 1965. Drilling activity in Canada, which had been increasing sharply since 1962, decreased; however, this decrease was offset by an increase in exploratory work in Mexico and the United States. Actual numbers, with corresponding 1965 numbers in parentheses, are: Canada, 1,505 wells (1,748) and 6,857,785 ft. (7,441,197); Mexico, 153 wells (139) and 1,280,994 ft. (1,156,677); United States, 10,313 wells (9,466) and 55,223,161 ft. (49,204,024). A total of 1,961 wells, or about 16.4% of all exploratory holes drilled in the 3 countries, were found capable of producing some hydrocarbons, i.e., about 1 in 6. The "success" percentage for Canadian exploratory effort decreased to 22.86% compared with 25.0% in 1965 and 25.8% in 1964. In Mexico, the percentage of exploratory tests "successfully completed" was 29.4% compared with 21.6% in 1965. In the United States, the "success" percentage was 15.59% compared with the all-time low of 15.43% in 1965.

Wildcat drilling in the United States in 1966 is believed to have resulted in the discovery of approximately 1,358 million bbls. of oil and condensate and 13,306 Bcf. of gas. This is a significantly greater quantity of oil and a slightly smaller quantity of gas than was found in 1965, but still much less than the quantity of hydrocarbons produced during 1966. Corresponding estimates are not available for Canada and Mexico.