The West Texas (Permian) Basin is a complexly structured intracratonic (IC) basin with prolific oil and natural gas production. It began as a subsidence basin ('Tobosa Basin') from Middle Ordovician to Devonian time, a response to the Cambrian rifting that separated Gondwana and Laurentia. In the Pennsylvanian to early Permian, it formed part of the Ancestral Rocky Mountains (ARM) orogen. The Texas-New Mexico segment of the ARM contains small to medium basement-cored uplifts, folds, thrust faults and two trends of strike-slip faults, with a pattern that is consistent with SW-NE compression. The largest thrust fault known in the basin is SW-vergent, and faces the deepest part of the Delaware Basin. This direction of compression is similar to that observed in the southern Oklahoma part of the ARM, which shows NE-vergent thrusting and left-lateral faulting.

This SW-NE compressive stress is grossly inconsistent with the northwestward convergence of the Ouachita-Marathon thrust belt southeast of the ARM. The ARM-generating stress may have originated either from the Pacific side (by flat subduction) or from strong continental collision in the Appalachian Orogen. Lines of weakness generated during the Proterozoic and/or Cambrian concentrated stress and created the complex structures.

The West Texas branch of the ARM is buried by over 2.5 km of post-deformational Permian strata -- the Permian Basin. Subsidence began during ARM deformation, then increased in rate and continued to the end of the Permian. Permian subsidence resulted in the maintenance of isolated deep-water marine basins until Late Permian time. The Marathon orogen also subsided, and shed little clastic material into the basin. Despite Mesozoic basin-margin modifications, the Permian isopach pattern suggests a bowl-shaped subsidence centered on the Central Basin axis of uplift. The size and shape of the Permian Basin are similar to other IC basins (Illinois, Michigan, Williston). Similar to some IC basins, the central basin area hosts a 1100-Ma mafic complex, which was subjected to compression in Pennsylvanian time. Sinking of a mafic crust or its subjacent lithosphere, begun during compression, may have been a driving force for Permian subsidence.

Over most of the basin, later Permian subsidence was responsible for putting source rocks into the oil window. Further maturation to gas occurred within the deep basins generated by ARM deformation and Marathon thrust loading.

Comparison of the hydrocarbon systems and geometries of the complex intracratonic West Texas (Permian) Basin and the complex postrift subsidence basins of the Gulf Coast / Gulf of Mexico yield useful insights for basin evolution and play development. The West Texas basin contains source rocks in the Ordovician and Devonian, but much generation comes from the Late Mississippian, Pennsylvanian and Permian basinal sediments. These were deposited in a poorly ventilated remnant basin during compression and strike-slip of the Ancestral Rocky Mountains orogeny, and subsidence of the intracratonic Permian Basin. Maturation resulted from Permian intracratonic subsidence, with hydrocarbons sealed from later leakage by late Permian salt and a fortunate tectonic setting. By contrast, the major Jurassic source rocks of the Gulf basins are at the base of the postrift subsidence, and are matured by further subsidence. Later Cretaceous source rocks (Eagle Ford) are mature in the main Gulf basin, but again lie near the bottom of the thick sedimentary package in the area. The younger part of the succession yields mostly gas formed during outbuilding of the shelf margin by Cenozoic deltaic progradation. No cap is present on the basin (except for subsalt plays), and seepage is widespread.

The Yegua Formation (Late Middle Eocene) is a minor siliciclastic progradation of the Gulf of Mexico shelf margin between the larger Early Eocene and Oligocene shelf-margin progradations. During Yegua time (and unlike the other units of the Middle and Late Eocene), four to eight sea-level fluctuations with a 100-300 ka period alternately pushed marine rocks toward the basin margins and pushed deltaic sedimentation to and past the shelf edge. Because of limited to moderate sand supply and the flat coastal plains, the updip (highstand) depositional complexes are nearly entirely separated from the downdip (lowstand) shelf-edge deltas and slope fans. Maximum flooding surfaces can be mapped over much of the area and correlated along and across the basin. The Yegua is truly a laboratory for sequence stratigraphy. A number of plays in the downdip and 'mid-dip' (incised valley complexes) trends have produced over 4 TCF of gas and condensate, and new discoveries await the return of exploration capital. The Yegua story is significant to all those interested in siliciclastic stratigraphy in passive-margin settings.

Considering a career in industry? The oil and gas industry? In Exploration? Maybe Production? Perhaps Planning? This presentation of the Top Ten Tips for Working in Industry was developed during my 34 year career working for Mobil and ExxonMobil as a technical professional, supervisor, manager, and researcher. I’ll use examples and stories from my career, working with foreign governments in Azerbaijan and Kazakhstan, working in Mobil’s Headquarters in Fairfax, Virginia, being a supervisor and manager in exploration, and working as a senior research associate in ExxonMobil’s Upstream Research Company, recruiting for ExxonMobil at top American Universities interviewing students; and working as the Planning Manager, in Mobil’s Norwegian Affiliate in Stavanger, Norway. All of my experiences over the past 34 years have taught me how to be a successful in these fields, and I enjoy sharing these lessons with others who may be considering careers in the oil and gas industry.

Authigenic quartz overgrowths are the most common pore-occluding mineral in deeply buried (>2500 m) quartzose sandstones. But, deeply buried reservoirs of this kind in the North Sea contain more porosity than expected when the influence of authigenic microcrystalline quartz (microquartz, or the good quartz) is ignored. However, we know relatively little about the nature and origin of this porosity-preserving microquartz, which inhibits the bad and ugly quartz overgrowths from growing and occluding pores. Therefore, advanced analytical techniques have been utilized to improve our understanding of the controls on microquartz development in several examples where porosity is preserved in these and similar sandstone reservoirs.

In this study, several advanced analytical techniques were used to evaluate the crystallographic and compositional controls on the formation of microquartz. SEM/Cathodoluminescence (CL) confirms that (bad and ugly) quartz overgrowths have a complex growth history. Electron Backscatter Diffraction (EBSD) combined with Wavelength Dispersive Spectrometry (WDS) confirmed and elaborated on the complex growth history: the complex banding visible in CL is not due to changes in crystallographic orientation but more likely variations in quartz composition associated with changes in pore fluid composition and/or reservoir conditions. Finally, Secondary Ion Mass Spectrometry (SIMS) analysis provides oxygen isotope data providing insight into those initial reservoir conditions and temperature of formation of microcrystalline quartz.

Integrating the results from these advanced analytical techniques has developed an understanding of the processes controlling the formation of porosity-preserving microquartz and improved our ability to reconstruct the reservoir diagenetic history of microquartz growth leading to a proposed model for predicting porosity preservation in deep, hot sandstone reservoirs.

Scientific drill cores from Lake Malawi provide the first continuous and high-resolution 1.2 million-year terrestrial record of past climates in East Africa. The multi-proxy climate signals extracted from these lake sediments reveal remarkable high-frequency and high-amplitude variability in effective moisture over this major southern hemisphere catchment. The level of Lake Malawi dropped more than 400 m at least 25 times over the past 1.2 million years, substantially impacting endemic organisms in the lake, and implying significant landscape variability over this time interval. This presentation provides an overview of the Lake Malawi Scientific Drilling Project, including basin framework seismic images from this enormous ultra-deep rift lake. This work and subsequent East Africa drilling studies are providing the environmental context for the origin of our own species.

Continental rifts have long been important for hosting lacustrine source rocks in many hydrocarbon provinces, and in recent years rifts have seen accelerated exploration for syn-rift reservoirs. The application of sequence stratigraphy to rift-lake systems requires special consideration, in light of 1) heightened and spatially variable subsidence accompanying normal faulting; and 2) sensitive lake levels driven by climatic shifts over geological time scales. This presentation provides examples of sequence stratigraphy applied to rift-lake systems, especially considering the roles of rift segmentation, magmatism (or lack thereof), and varying continental hydroclimates. The wide geochemical variability of lake systems in rifts is in part driven by the different styles of magmatism observed in different extensional environments, which influences the occurrences of lacustrine carbonates. Predictive models of siliciclastic reservoir facies in extensional basins are grounded in our understanding of structural controls of drainage systems. Stacking patterns and lithofacies variability are commonly complicated by climatic processes. Many tropical lakes are hypersensitive to changing evaporation-precipitation ratios, and therefore lake level changes are amplified through subtle changes in climate. Accordingly, lake level shifts in many tropical basins are dramatic, with documented changes of hundreds of meters over timeframes of a few thousand years. This presentation includes extensive overviews of nested seismic reflection data sets, ranging in scope from high-resolution data to basin- and crustal-scale imagery.

Exploration activity in lacustrine basins in extensional settings has accelerated in recent years with important discoveries in the South Atlantic Ocean and in East Africa. This presentation reviews reservoir facies in lacustrine-rifts including siliciclastic deposits, mixed siliciclastic-carbonate systems, as well as lacustrine carbonates, as observed in different systems in East Africa. Lacustrine extensional basins are characteristically dominated by siliciclastic deposits, on account of the high-relief on faulted rift margins, and associated deep-basin subsidence. Source rock facies in lake systems are shown to vary dramatically in space and time, based on studies of modern lake basins as well as ancient high-resolution records revealed through scientific drilling. This presentation offers data-intensive perspectives of extant lake basins in both the western and eastern branches of Africa's Great Rift Valley.

Numerical and experimental models of turbidity currents and other sediment gravity flows are powerful tools that can help quantify how the fundamental physics of sediment transport affects the distribution of sediments and patterns of erosion and deposition. Several studies using 1D/3D numerical models at full-field scale and flume-tank experiments at reduced-scale provide quantitative insights into reservoir properties and rules that can be used to build realistic reservoir models and to help de-risk exploration targets. Flow models provide unparalleled details, through movies, deposit analysis and computer simulations that allow for extrapolating observations from core, logs and seismic data to their depositional environment context.

The key controls in sediment transport are the morphology of the seafloor along the path of the flow, the composition of the sediment both at the source and along the system, and the dynamic interaction between flow and topography. Over time, erosion/deposition and tectonic forces interact, leading to changes in the equilibrium profile, that result in the formation of geologic strata. The response of flow processes to changes in the topography are the key to understanding the distribution of facies and the stratigraphic architecture of deepwater reservoirs. These processes can be verified in well imaged and calibrated near-seafloor systems, providing the key elements for building realistic reservoir models, which are ultimately tested against dynamic data from producing reservoirs.