Facies variability and depositional systems of the Buda Limestone and Woodbine Formation, Hainesville Dome/Neuoff Field, Wood County, Texas

We describe and interpret several drill core containing the Cretaceous Buda Limestone and Woodbine Formation from the Hainesville Dome/Neuoff Field in Wood County, TX. This study is significant because the Neuhoff Field is an actively producing oil/gas field at 10,000+ ft depth immediately adjacent to the Hainesville Salt Dome in the deepest part of the East Texas Basin, and available core is exceedingly rare. Salt movement likely controlled the type-locus of deposition, stratal thickness, and the presence of unconformities, affecting reservoir characteristics and across-field predictability.

The Buda Limestone is predominantly carbonate deposited along the shallow-marine shelf/ramp and associated reefs. Carbonate facies vary depending on well/core location and may include muddy ramp deposits and/or allochem-rich intervals. An unconformity separates the overlying Woodbine from the Buda.

Contrastingly, the Woodbine is primarily siliciclastics with some minor carbonate cement and common iron-carbonate nodules. The base of the Woodbine contains abundant hummocky to swaley cross-stratified sandstones, current-rippled sandstones, and interbedded siltstones with a low-diversity and low-abundance trace fossil assemblage. We suggest that this part of the Woodbine records river-dominated to commonly wave-modified prodelta and distal delta front deposits with some channelization, offshore deposits, and a more heavily bioturbated shoreface. The upper part of the Woodbine overlies a significant erosion surface and is dominated by a thick package of fine-to medium-grained sandstones with trough crossbeds, current ripples, and low-angle parallel laminations. Interbedded intervals of mud-rich very fine sandstone and silt are seen throughout this interval, and there appears to be little to no bioturbation. Deposits are those of distributary channel bars with rare overbank deposits that likely overlie a significant sequence boundary and may represent a valley-fill succession. Shallow marine tidal and deltaic facies with some wave influence return in the uppermost Woodbine below the transition to the overlying Woodbine Marker and Eagle Ford.