Niagaran reef exploration dominated drilling activity for the 11 th straight year. Exploration and development drilling for these Middle Silurian reef reservoirs were heaviest in northern counties along the reef trend. Other pockets of high activity were associated with deeper development drilling in older fields in the central basin, in parts of southeastern Michigan, and in the Ingham-Calhoun-Eaton County region of southern Michigan.
Exploration resulted in 70 new discoveries, one of which resulted from reworking of an earlier dry hole drilled in 1960. of the new discoveries credited to 1979, 55 were new Niagaran reef reservoirs, 39 of which were located along various parts of the northern reef trend. Two new reef reservoirs in the Livingston-Oakland County region indicate additional prospects in this area of the basin.
Exploration and development footage figures, derived from Department of Natural Resources, Geological Survey Division records, amounted to 1,146,515 ft exploratory and 1,150,710 ft development compared with 1,128,691 ft exploratory and 1,176,270 ft development drilled in 1978. An additional 202,791 ft, mainly gas-storage facility wells, is credited to 1979.
Oil and gas production continued to set new records. Preliminary figures show that 35,428,411 bbl of oil (including condensate) and 161,707,877 Mcf of gas were produced in 1979. Both figures are new records for annual production. Niagaran reef reservoirs distributed along the northern reef trend accounted for about 72% of the oil and 84% of the gas produced in 1979.