Outcrop Analogs from Western Europe for Reservoir Characterization and Modeling of Upper Jurassic Microbial and Associated Higher Energy Reservoirs in the Little Cedar Creek Field Area, Eastern Gulf Coastal Plain, Usa

Mancini, Ernest A.¹; Parcell, William C.^2
1 Geological Sciences, University of Alabama, Tuscaloosa, AL.
² Department of Geology, Wichita State University, Wichita, KS.

Upper Jurassic microbial buildups and associated higher energy facies developed in a carbonate ramp setting in eastern Spain and southern Portugal. Opportunistic microbes nucleated on a cemented and encrusted surface during an overall rise in sea level in which low background sedimentation rates and low energy conditions prevailed. The resulting buildups consist of thrombolitic boundstone and include peloids, bivalves, gastopods, bryozoans, corals, echinoids and serpulids. These microbial buildups attained a thickness of 16 to 30 m and covered an area of 2.3 km2. Overlying facies consist of ooid, peloidal and bioclastic grainstone and packstone. Lateral facies include wackestone and lime mudstone. Upper Jurassic microbial buildups and associated higher energy facies also developed in a carbonate ramp setting in the Little Cedar Creek Field area, eastern Gulf Coastal Plain of the United States. They consist of thrombolitic boundstone and include peloids, ostracods and foraminifera. These buildups attained a thickness of 11 m and covered an area of 13 km2. Individual buildups were present in an area of 2 km2. Overlying and lateral facies include subtidal lime mudstone and wackestone. Nearshore higher energy subtidal facies consisting of ooid, peloidal and bioclastic grainstone and packstone post dated microbial buildup development. Porosity and permeability in the boundstone and grainstone/packtone reservoirs were enhanced through dissolution processes. Knowledge of the origin and growth of the microbial buildups in western Europe facilitates characteristization and modeling of the microbial boundstone and associated higher energy grainstone reservoirs in the eastern Gulf Coastal Plain.

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009