James Limestone, northeastern Gulf of Mexico: Refound opportunity in a Lower Cretaceous trend

Abstract

Recent offshore exploratory success has focused industry interest on porous Lower Cretaceous carbonates of the James Limestone in the eastern Gulf of Mexico. The current offshore play targets the interior James platform trend in the Viosca Knoll and Mobile areas, south of Mississippi and Alabama, where water depths are 30-60 m (98-197 ft). James reservoirs in this area consist mainly of patch reef debris halos and interior platform grainstone facies at drilling depths of 4358-4632 m (14,300-15,200 ft). These facies comprise a belt parallel to, but up to 25 km (15.5 mi) behind (updip from), the James shelf margin. Diagenetic alteration, including dolomitization and dissolution of original calcite grains and cement, cause porosities of 8-19% and permeabilities in the range of 20-30 md. To date, seven fields have been discovered. Individual wells in these fields have been completed at rates ranging from 10-39 MMCFGD and have produced as much as 15.9 bcf in less than 3 yr. The new play represents an extension into the offshore of scattered, older production in the James that occurs from east Texas to southern Mississippi. When combined with the onshore part of the play, the new success in the James suggests that significant regional potential still exists in many areas of the northern and northeastern Gulf. Scott L. Montgomery is a petroleum consultant and author. He received his B.A. degree in English from Knox College in 1973 and his M.S. degree in geological sciences from Cornell University in 1978. He is widely published in the geosciences and since 1996 has been principal author of the E & P Notes series in the AAPG Bulletin. His other publications include seven books on topics in petroleum geology, science education, and the history of science, plus articles and monographs related to frontier plays, new technologies, field studies, and reservoir characterization.Andrew J. Petty is currently a geologist with the Minerals Management Service (MMS) in New Orleans, Louisiana. He joined the MMS in 1979, where he worked in the Rate Control Section, served as the Corpus Christi District Geologist, and is now with the Regional Analysis Unit. Andy received his B.S. degree in geology from Stephen F. Austin State University in 1973 and his M.S. degree in geology from the University of Texas at El Paso in 1975. Paul J. Post is a geologist with the Minerals Management Service (MMS) in New Orleans, Louisiana. He has more than 30 years of diverse exploration experience in an array of United States and international basins with major and independent companies, as a consultant, and with MMS. His primary technical expertise is in regional synthesis, new venture/play development and prospect evaluation, basin analysis, basin modeling, economic analysis, and risk assessment. Paul has a B.S. degree in geology from Virginia Polytechnic Institute.