Sedimentation and Diagenesis of Upper Smackover Grainstone, Jay Field Area, West Florida: ABSTRACT

Abstract

The examination of core and logs from a well 3 mi (5 km) southwest of the Jay field has given considerable insight into the upper Smackover facies distribution, diagenesis, and the application of recent models for the sedimentation and diagenesis of this Jurassic reservoir. A 63-ft (19 m) thick unit of oolitic and oolite-oncolite grainstones is recognized in the upper Smackover. High-angle inclined bedding, visible on both core and dipmeter, with a consistent 15 to 20° northeast dip, demonstrates the presence of oolite bars. These bars formed a barrier which affected subsequent deposition and diagenesis in the Jay field area. A complicated diagenetic history of marine and vadose cementation, and pervasive and selective dolomitization have left a unique imprint on the porosity and permeability of these rocks. Dipmeter results and petrographic analysis of the grainstones indicate that cementation and diagenesis have not been uniform. Within the large-scale cross-strata, permeable beds are interstratified with tightly cemented or compacted, impermeable beds. Horizontal flow should be greatest along the strike of the inclined units, because the flow would remain within the permeable planes of the inclined strata. Thus, dipmeter correlation permits an interpretation of the direction of bedding permeability anisotropy produced by the inclination of the pore system. The characteristics of sedimentation and facies distribution in the Jay field area have previously been compared with a modern analog from Joulters Cay in the Bahamas. The Trucial Coast of the Persian Gulf in the Abu Dhabi region may be a better model. The style of deposition and distribution of carbonate and evaporite sediments, and diagenetic characteristics in the grainstone barriers and lagoons closely fit the sedimentation and diagenetic pattern in the Jay Field area. End_of_Article - Last_Page 950------------