David C. Jennette

Deep-Water Sandstones, Brushy Canyon Formation, West Texas

Exceptional oblique-dip exposures of submarine fan complexes of the Brushy Canyon Fm. allow reconstruction of channel geometries and reservoir architecture from the slope to the basin floor. The Brushy Canyon conslsts of 1,500 ft. of basinally restricted sandstones and siltstones that onlap older carbonate slope deposits at the NW margin of the Delaware Basin. This succession represents a lowstand qequence set comprised of lugher frequency sequences that were deposited in the basin during subaerial exposure and bypass of the adjacent carbonate shelf. Progradational sequence stacking patterns reflect changing position and character of the slope as it evolved from a relict, carbonate margin, to a constructional, siltstone-dominated slope. Lowstand fan systems tracts consist of sharp-based, laterally extensive, sand-prone basin floor deposits and large, sand-filled channels encased in siltstones on the slope. The abandonment phase of each sequence (lowstand wedge-transgressive systems tract) consists of basinward-thinning siltstones that drape the basin floor fans. The slope-tobasin distnbution of lithofacies is attributed to a three stage cycle of: 1) erosion, mass wasting, and sand bypass on the slope with concurrent deposition from sand-rich flows on the basin floor, 2) progressive backfilling of feeder channels with variable fill during waning stages of deposition, and 3) cessation of sand delivery to the basin and deposition of laterally-extensive siltstone wedges. Paleocurrents and channel distributions indicate SE-E sediment transport from the NW basin margin via closely spaced point sources.

Sequence Stratigraphy Applications to Shelf Sandstone Reservoirs: Outcrop to Subsurface Examples

The Lower Sego provides an opportunity to study well-exposed, high-frequency sequences and their systems tracts. Criteria for identification of sequence boundaries will presented. Sequences and their boundaries will be contrasted with parasequences and their bounding surfaces. The Upper and Lower Sego contain well-exposed tidal deposits within the lowstand systems tracts of high-frequency sequences. These tidal deposits and their relationship to incised valleys and systems tracts will be examined. The incised valley interpreted to form during relative falls in sea level will be contrasted with distributary channels related to autocyclic mechanisms. 0.0 Leave the parking lot of the Grand Junction Hilton. Grand Junction , Colorado. Turn left onto Horizon Drive. Pass under the 1-70 bridge, Turn left into the entrance ramp for 1-70 west. 0.2 Enter 1-70 heading west toward the Colorado –Utah State line. For the next 20 miles the Interstate will parallel the Colorado River flowing along the west side of the Grand Valley. The Interstate is built on the gray Cretaceous Mancos Shale. To the west of the Colorado River are the red cliffs of the Colorado National Monument. The Monument is operated by the National Park Service. These cliffs are the eastern edge of the Uncomahgre Uplift. As you drive north along the Interstate, the steeply dipping eastern limb of the Uncomahgre is clearly visible. This tight monoclinal fold is the result of horizontal compressional tectonics associated with Laramide deformation (Heyman, 1983). The red rocks in the Mounment include, from stratigraphically oldest to youngest: the Chinle Formation forming the lower, less resistant slops, the Wingate formation forming the massive cliffs up to 400 feet thick , the Kayenta Formation overlain by an unconformity along which the Navajo and Curtis Formations are missing , the Summerville and Entrada Formations, and the Morrison Formation consisting of fluvial sandstones and associated mudstones, within which some of the earliest dinosaur bones in North America were discovered in the late 19th century. The Jurassic Morrison Formation is unconformably overlain by the brown, Cretaceous, coal-bearing Dakota Sandstone. The Dakota caps many of the high mesas within the Mounment and forms well-exposed dip slopes along the Interstate in the vicinity of the exit to Mack, Co..

Traps and turbidite reservoir characteristics from a complex and evolving tectonic setting, Veracruz Basin, southeastern Mexico

The Miocene and Pliocene interval of the Veracruz Basin, southeast Mexico, experienced an evolving array of shortening, strike-slip, and volcanic forces in response to plate-scale interactions. The basin is divided into six structural domains that define regions of comparable timing and type of structural deformation, and the basin fill is separated into two long-term depositional phases, each of which can be tied to a waning and then waxing of major basin-bounding tectonic events. The first phase of deposition took place from the early to late Miocene and is tied to the waning effects of the Laramide orogeny. The Miocene basin inherited a tectonically steepened basin margin, across which deep canyons were carved and variably filled with mudstone and thin remnants of coarse sandstone and conglomerate. This zone of erosion and bypass grades into thick, sandstone-rich basin-floor fans. Later in phase I, subaqueous volcanoes, tied to distant plate subduction, developed offshore and formed a bathymetric barrier that prevented turbidity currents from entering the ancestral Gulf of Mexico. The volcanoes also served as immovable buttresses, around which intrabasinal thrust belts developed in response to regional shortening.The second depositional phase is tied to the onset of internal basin shortening and uplift of the north basin margin known as the trans-Mexican volcanic belt. This uplift caused a dramatic reconfiguration of the sediment-dispersal system, whereby large shelf clinoforms prograded from north to south across the basin. In contrast to the onlapping stacking pattern of phase I units, phase II units stack in a strongly offlapping pattern.Proven and postulated reservoir-trap combinations, ranging from four-way to three-way combination (stratigraphic), to pure stratigraphic traps are common. Four-way closures mapped from the two-dimensional and three-dimensional seismic data are large (P50: 5000 km2) and are covered with thick, lower Miocene fan sandstones. Traps that depend on a stratigraphic component are thinner and smaller in size (P50: 1000 km2), but more numerous than the four-way closures. Because many structures have experienced prolonged pulses of compression, top seal is considered an important geologic risk to the retention of substantial gas-column heights.

Neogene tectonic, stratigraphic, and play framework of the southern Laguna Madre–Tuxpan continental shelf, Gulf of Mexico

Neogene shelf, slope, canyon, and slope-to-basin-floor transition plays in the southern Laguna Madre–Tuxpan (LM-T) continental shelf reflect a variety of structural and stratigraphic controls, including gravity sliding and extension, compression, salt evacuation, and lowstand canyon and fan systems. The Neogene in the LM-T area was deposited along narrow shelves associated with a tectonically active coast affected by significant uplift and erosion of carbonate and volcanic terrains. This study characterizes 4 structurally defined trends and 32 Neogene plays in a more than 50,000-km2 (19,300-mi2) area linking the Veracruz and Burgos basins. The Caonero trend in the southern part of the LM-T area contains deep-seated basement faults caused by Laramide compression. Many of these faults are directly linked to the interpreted Mesozoic source rocks, providing potential pathways for vertically migrating hydrocarbons. In contrast, the Lankahuasa trend, north of the Caonero trend, contains listric faults, which detach into a shallow horizon. This trend is associated with thick Pliocene shelf depocenters. The dominant plays in the Faja de Oro–Nyade trend in the central part of the LM-T area contain thick lower and middle Miocene successions of steeply dipping slope deposits, reflecting significant uplift and erosion of the carbonate Tuxpan platform. These slope plays consist of narrow channel-fill and levee sandstones encased in siltstones and mudstones. Plays in the north end of the LM-T area, in the southern part of the Burgos basin, contain intensely deformed strata linked to salt and shale diapirism. Outer-shelf, slope, and proximal basin-floor plays in the Lamprea trend are internally complex and contain muddy debris-flow and slump deposits. Risk factors and the relative importance of play elements vary greatly among LM-T plays. Reservoir quality is a critical limiting play element in many plays, especially those in the Caonero trend directly downdip from the trans-Mexican volcanic belt, as well as carbonate-rich slope plays adjacent to the Tuxpan platform. In contrast, trap and source are low-risk play elements in the LM-T area because of the abundance of large three-way and four-way closures and the widespread distribution of organic-rich Upper Jurassic Tithonian-age source rock. The potential for hydrocarbon migration in LM-T plays is a function of the distribution of deep-seated faults inferred to intersect the primary Mesozoic source. Their distribution is problematic for the Lankahuasa trend, where listric faults sole out into the Paleocene. Seal is poorly documented for LM-T plays, although the presence of overpressured zones and thick bathyal shales is favorable for seal development in middle and lower Miocene basin and slope plays.

Geologic framework of upper Miocene and Pliocene gas plays of the Macuspana Basin, southeastern Mexico

This integrated study provides a geological and geochemical framework for upper Miocene and Pliocene siliciclastic gas plays in the Macuspana Basin. Structural controls for the plays are deep-seated faults that tap Mesozoic thermogenic gas sources, areas of intense shale diapirism and folding, and areas with structural inversion that could enhance trapping and reservoir productivity. Early Neogene thrusting south of the basin triggered evacuation of Oligocene shale along northwest-dipping listric faults in the eastern and southeastern basin margin. These faults are associated with large-scale rollover structures and thick (500 m) upper Miocene shoreface and wave-dominated deltaic complexes. A second phase of extension in the early Pliocene formed a set of broad, southeast-dipping listric faults in the western basin, controlling thick accumulations of stacked Pliocene shoreface deposits. Trap formation and enhancement in the southern basin margin are linked to late Miocene to Pliocene inversion.The primary stratigraphic controls on play occurrence in the upper Miocene in the onshore part of the basin are the regional facies distribution of northwest-prograding shoreface and wave-dominated deltaic systems. There was a shift in Pliocene sedimentation from the southeast to the west and northwest parts of the basin, where thick successions of aggradational shoreface and wave-dominated deltaic deposits accumulated in depocenters defined by shale evacuation along growth faults. Valley-fill deposits in both the upper Miocene and Pliocene resulted from shortlived periods of base-level change induced by either uplift on the southern basin margin or eustasy. The offshore part of the basin is inferred to consist of deep-water turbidite deposits that formed downdip (westward) of a hypothesized mixed clastic-carbonate prograding complex from the Yucatan platform.Three petroleum systems (Mesozoic, Paleogene–lower Neogene, and upper Miocene–Pliocene) contributed to the hydrocarbon accumulations and hydrocarbon generation and migration in the basin. Principal Upper Jurassic/Lower Cretaceous source rocks generated wet thermogenic gases and oil. Secondary lower Tertiary source rocks generated dominantly dry biogenic gases. Mixtures of the two gas types are common. Numerous deep-seated growth faults and faults serve as pathways for Mesozoic-sourced hydrocarbons. Surface seeps and abundant gas shows suggest that hydrocarbons are being generated today.

Wave-shape classification and attribute analysis of the lower Miocene deep-water reservoirs, Laguna Madre Basin, offshore México

The lower Miocene deep-water play in Laguna Madre Basin contains attractive depositional features and yet is considered high-risk potential. Previous economic activity within this region largely focused on large traps within carbonate rocks of the Tuxpan Platform. Recently interest has renewed in exploring natural gas reserves in the Neogene plays. In this study, we analyzed a nonproductive horizon representing the base of the Miocene and containing an apparent toe-of-slope channel complex in the proximal part of the basin.

Seismic Facies And Attribute Analysis of the Miocene Incised-valley-fill And Submarine-canyon Systems In Tuxpan Basin, Offshore México

In this study, we demonstrate the seismic facies and attribute analysis in upper Miocene incised-valley-fill and submarine-canyon systems in the Laguna Madre-Tuxpan area north of Veracruz. Following initial structural identification by PEMEX geoscientists, seismic imaging techniques were used to build a stratigraphic model on the basis of seismic sequence and attribute analysis. Seismic wave-shape analysis using neural-network wavelet classification was employed to describe the canyon-fill deposits. These techniques were applied in the imaging of lower-canyon-fill successions that are inferred to be sandstone-rich where they onlap onto faulted submarinecanyon margins. In contrast, overlying upper-canyon-fill deposits from progradational highstand delta-front deposits consist of thin delta-front sandstones intercalated with distal prodeltaic siltstones and are genetically associated with a fine-grained succession providing a shaly drape over the sandy lower-canyon-fill.