The organic-rich, silty Woodford Shale in west-central Oklahoma is a prolific resource play producing gas and liquid hydrocarbons. We calibrated seismic attributes and prestack inversion using well logs and core information within a seismic geomorphologic framework to define the overall basin architecture, major stratigraphic changes, and related variations in lithologies. Core measurements of elastic moduli and total organic content (TOC) indicated that the Woodford Shale can be broken into three elastic petrotypes important to well completion and hydrocarbon enrichment. Upscaling these measurements facilitates regional mapping of petrotypes from prestack seismic inversion of surface data. Seismic attributes highlight rugged topography of the basin floor of the Paleo Woodford Sea, which controls the lateral and vertical distribution of different lithofacies containing variable quantity of TOC as well as quartz, which controls brittleness. Depressions on the basin floor contain TOC-lean cherty lithofacies alternating with TOC-rich lithofacies, resulting in brittle-ductile rock couplets. In contrast, basin floor highs are characterized by overall TOC-rich ductile lithofacies. Seismic attributes illuminate complex post-Woodford tectonic deformation. The Woodford Shale is known to be naturally fractured on outcrop. Image log analysis in other shale plays showed a good correlation between such tectonic features and natural fractures. These features need to be correlated with well trajectories and production data to determine which hypothesized "fracture sets," if any, improve well performance.

D etailed interpretation of seismic attributes along horizon slices or stratal slices reveals changes in depositional pattern and seismic geomorphology within a sediment column that are controlled by eustatic and local changes in sea level.In this study, we analyze seismic geomorphologic features of a shallow sedimentary column within a salt minibasin in the northern Gulf of Mexico, and attempt to predict the relative sea-level curves. We then calibrate these predictions against biostratigraphic markers and compare with existing eustatic cycles and events. Systematic analysis of amplitude and attribute data within a seismic geomorphologic framework reveals high-resolution sequence stratigraphic patterns that might otherwise be overlooked. SUPRATIK SARKAR, KURT J. MARFURT, and ROGER M. SLATT, University of Oklahoma

Shallow intrusive and extrusive volcanic events are common in the northeastern part of Chicontepec Foredeep where the close proximity of these volcanic bodies add to the complexity of the Paleocene-Eocene age tight and complex turbidite reservoirs. In accordance with studies in other basins, outcrop analogs of the Chicontepec reservoirs indicate the potential of enhanced natural fracturing and hence the increase of effective porosity in the host rock. We focus on exploring the validity of this observation in seismic and well data, which is rare in the literature. The preliminary results support the hypothesis of the potential increase of effective porosity including indication of dual-porosity systems in some areas, which would influence detailed studies aided by seismic data for considering Chicontepec reservoirs influenced by volcanic intrusions as additional target zones. Geologic setting During the Late Cretaceous Laramide (Cordilleran) Orogeny, the Farallon (Pacific) plate began subducting under the North American plate resulting in island arc complexes along the western margin of Mexico (Morán-Zenteno, 1994; Alzaga-Ruiz et al., 2009). The northeastward movement of the Farallon plate continued into the Latest Cretaceous and Early Paleocene period. This movement of the Farallon plate accreted and uplifted the Mesozoic sedimentary layers of the former passive margin of the Gulf of Mexico forming the Sierra Madre Oriental fold and thrust belt. Tectonic pulses in the Sierra Madre Oriental continued until the Early Eocene (Alzaga-Ruiz et al., 2009). The Chicontepec foreland flexural basin developed in front of this thrust front, with syn-tectonic sedimentation within the foredeep. The Tuxpan platform is situated in the eastern part of the basin (Figure 1). The Early Paleocene Velasco Formation provided the initial sedimentation within the Chicontepec Foredeep, which was followed by Upper Paleocene Lower Chicontepec deposition. A basin-axis-parallel amalgamated channel system was a major source of sediment in the Lower Chicontepec turbidites. A major tectonic pulse beginning during the late Upper Paleocene initiated syn-tectonic basin-axis-perpendicular sediment flows from the direction of the Sierra Madre Oriental. These basin-axis-perpendicular channel-fan systems were the major contributor to the Middle and Upper Chicontepec Formation. These Paleocene-Eocene turbidites represent tight hydrocarbon reservoirs (porosity: 1%-10%; permeability: 0.001-5 mD) that can be primarily attributed to the mineralogical immaturity of the sandstone and extensive diagenetic processes. In spite of their low porosity and permeability, the Chicontepec Formation represents one of Mexico's most important hydrocarbon plays. Tristán-González et al. (2009) summarize the volcanic activities in east-central Mexico from the Late Cretaceous to the Miocene (Figure 2). Subduction volcanism indicative of tectonic activities was dominant until the culmination of the Laramide orogeny during Late Eocene time followed by transitional volcanism fro...