A Tale of Four Sand Bodies: Depositional Environment and Reservoir Characterization of Shallow Marine Sand Bodies in the Upper Woodbine at Lake Grapevine, Texas

Upper Woodbine outcrops at Lake Grapevine continue to be a source for research at TCU with recent emphasis placed on describing many vertical sections, relating them to marine sand body types and determining their quality as potential subsurface reservoirs. Reservoir models based on outcrop studies will provide for better exploration examples in the subsurface of the East Texas Basin where prolific Woodbine oil fields already exist. Comparing and contrasting the four sand bodies is imperative to understanding the relative reservoir quality of the separate environments and sand body types.

The Woodbine sections we examined crop out at Silver Lake Marina, Rockledge Park, Murrell Park and within the USACE restricted Spillway.

These Cenomanian sediments were never subjected to deep burial conditions and have very nearly undisturbed reservoir properties We have developed new field techniques that have enabled us to reveal high resolution sedimentary features both primary physical and biogenio. In some instances, we have used staining methods to reveal ichno fabric.

From the four outcrop sections sand bodies consists of a combined barrier island shoreface, tidal flats, tidal inlet and transgressive ravinement surface. A Bayshore sand flat and adjacent marsh overlain by an incised tidal channel with tidal bundled sands is observed. A flood tidal delta with numerous thin and laterally accreting beds overlain by muddy tidal flat facies and a soil ground and finally a compound tidal sand dune body with Hadrosaur tracks and fiddler crab deposits overlying it.