Upper Jurassic reef play, East Texas basin: An updated overview part 2 - Inboard trend

This paper is the second part of a two-part paper summarizing new data on t he Upper Jurassic "reef" play in the East Texas basin. Information presente d in this paper focuses on carbonate buildups of the inboard trend. Inboard buildups represent significant backstepping of reefal facies from the ramp margin-outboard trend to more updip sites along a developing shelf margin. Inboard features resemble pinnacles that can be identified with two-dimens ional seismic data, but that require three-dimensional data to properly ima ge. Such pinnacles represent stacked features that resulted from three to f ive cycles of reef growth. The general upward progression of facies within each cycle exhibits a shallowing trend, with the overall proportion of shal low-water facies also increasing upward among these cycles. Most inboard bu ildups possess a low-porosity micritic "cap" immediately overlying vuggy, c oral-bearing facies with good-to-excellent porosity. Evidence of both prima ry and secondary porosity exists, with some correlation between porosity an d permeability development. Log and rock sample data from the Frost buildup (Freestone County) confirm the existence of diverse microfacies in these b uildups, with complex lateral variation in porosity/permeability distributi on. Two models of buildup occurrence in the basin are presented.