The Citronelle field was discovered in 1955 by the Zack Brooks Drilling Company No. 1 Donovan, SW 1/4, NW 1/4, Sec. 25, T2N, R3W, Mobile County, Alabama. The well produced from the lower Glen Rose Formation at a depth of 10,879 ft (3,315.9 m). During the next 10 years, 434 productive wells were drilled. The productive limits completely enveloped the town of Citronelle, 32 mi (51.5 km) north of Mobile, Alabama. Forty-acre spacing, low gas-oil ratio, and rapid bottomhole-pressure drop, necessitating pumping of all wells, resulted in slow and spasmodic development. Unitization of 139 wells for waterflood was initiated in 1961, and a saltwater-injection program proved successful. Later, fresh water from the Wilcox Formation was used for injection fluids. By May 1966 all wells were unitized, and on December 31, 1973, the field had produced over 107 million bbl of oil. The structure, which lies in the southwest Alabama salt basin, is residual in origin. The field, as well as the townsite, is topographically high. The presence of this high led to the drilling of two shallow tests. Although both wells were dry, the fact that they appeared to be structurally high led to the drilling of the deeper discovery well. The structure at the producing-depth datum is that of a simple, moderately flat-topped, ovate dome, but the field presents a complex meander-belt pattern with 52 productive sandstone zones in 330 separate reservoirs. The entire field was eventually unitized under three agreements as though there were three separate reservoirs. All the productive wells produce through electrically driven downhole pumps. Production for the field reached its peak in the spring of 1972 when all three injection programs were utilizing all wells and all economically floodable sandstone reservoirs. Thirty-three percent of the oil in place had been produced by the end of 1973. Profitable production is expected to continue for another 8 years. At present, the Citronelle Operators Unit is studying the economics of a tertiary flood using carbon dioxide as a miscible agent.
Figures & Tables
With three previous volumes published by AAPG on structure of American oil fields, this publication takes 17 of these oil fields and describes them in detail. The reservoirs described in these 17 papers range in age from Devonian to Pleistocene; their litholgies are standstone, limestone, or dolomite; and the trapping mechanisms are structural or stratigraphic or a combination of the two. The North American oil fields described are distributed from Alaska and the McKenzie Delta area of Canada on the northwest, to the Gulf of Mexico and Southern Floriday on the southeast. This publication also includes an index to those North American oil and gas fields which have been described in previous AAPG publications.