Petroleum production in the North Carterville Field, Bossier Parish, Louisiana, is from the Pettet interval, a porous limestone lentil, within the Lower Cretaceous Sligo Formation. The unit is approximately 30 meters thick and is composed of five microfacies; oosparite, oomicrite, oobiosparite, poorly-washed oobiosparite, and biomicrite. The microfacies were deposited in a series of shoaling-upwards cycles where the biomicrite represents normal open-marine shelf sedimentation and the ooliticic microfacies represent phases in the development of the shoal. Diagenesis occurred in marine, meteoric and burial environments. Porosity is predominantly secondary moldic produced after significant occlusion of primary and early diagenetic pores. Permeability is variable; each of the microfacies has intervals with values in excess of 0.10 md with no apparent microfacies control of distribution. Production is typically from long, narrow and discontinuous zones of permeability.