Part 4 - Berg - Hughes Center

contains approximately 13 producing reservoirs in northern Louisiana. Porosity ranges
from 16 to 20% and permeability from 9 to 100 md. The produced hydrocarbons are
typically 25º to 46º API gravity oils, condensate, and gas.
Bailey’s (1978) brief historical account of early drilling activity at Black Lake field
in Natchitoches Parish gives insight as to the rather slow pace of Sligo development. The
first well to show the existence of Sligo reefs was Hunt’s Goodpine Lumber Co. #F-24,
drilled in 1942. Later, between 1947 and 1949, the limits of the hydrocarbon trap were
defined by four additional wells. The first well discovered 160 ft of Sligo reef, with 80 ft
of water-wet porosity. The second well found no reef facies and no porosity in the Sligo.
The third well penetrated 52 ft of wet reefal limestone about two miles south of the field
and the fourth well found no reef and no porosity, only one mile north. Because of these
rather poor results, it was not until 1958 that interest was renewed in the area and drilling
began less than three miles west of the field. Again, no reef and no porosity were found.
Then a well drilled some three miles east of original production, encountered almost 200
ft of Sligo reef, of which 130 ft was porous and water-wet. By this time, both downdip
porosity and the updip permeability barriers were known to exist, and preliminary
structure maps indicated the possibility of structural closure or nosing trend. In spite of
the presence of the elements of a structural-stratigraphic trap, interest was again lost and
Black Lake field remained undeveloped for several more years.
It was not until 1963 that a seismic survey, verified the existence of strong nosing in
the Black Lake field area. The first drill test encountered water with a slight show of oil
in the Sligo reef. The next well was lost because of drilling problems. At a distance of
100 ft away another hole was drilled and the perforated interval (7,990-8,000 ft) tested at
366