Abstract A quantitative model for categorizing submarine-channel stacking patterns is developed and applied to well-exposed outcrops of Neogene-aged submarine channels in the Capistrano and upper Monterey formations, Southern California. Three outcrops are characterized in terms of their stratigraphic architecture: (1) Point Fermin, (2) Dana Point Harbor, and (3) San Clemente State Beach. Each outcrop has a unique channel-stacking style. The channel elements at Point Fermin stack in a vertical, disorganized pattern; the channel elements at Dana Point Harbor stack in a mixed vertical–lateral, disorganized pattern; and the channel elements at San Clemente State Beach stack in a predominantly lateral, organized pattern. The different stacking styles are compared and contrasted using a method that quantifies channel-stacking patterns by normalized vertical and lateral offset. First-order controls on channel-stacking patterns are interpreted to be position on the physiographic profile, accommodation regime, and/or local changes in subsidence due to syndepositional faulting. The discrete channel-stacking patterns in the three outcrops closely relate to parameters relevant in subsurface reservoir characterization, such as net-sand content, connectivity of channel elements, and preservation potential.

Abstract 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-km 2 (19,300-mi 2 ) area linking the Veracruz and Burgos basins. Copyright © 2009 by The American Association of Petroleum Geologists. Reprinted from AAPG Bulletin, v. 89, no. 6, (June 2005), pp. 725 – 751. DOI:10.1306/13191099M903340 The Cañonero 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 Cañonero 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–Náyade 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 Cañonero 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. Reprinted from AAPG Bulletin, v. 89, no. 6, (June 2005), pp. 725–751.

Abstract The stratigraphy of deep-water reservoirs is commonly interpreted using seismic data. Exploration-grade seismic data are typically acquired with peak frequencies varying from 30 to 60 Hz, resulting in an average vertical stratigraphic resolution of between ∼23 m (30 Hz) to 11 m (60 Hz) in siliciclastic sediments. Many stratigraphic bodies, such as architectural elements and beds, can not be resolved at these frequencies, however. Seismic forward modeling of deep-water outcrop analogs provides a method by which this uncertainty can be addressed. Such modeling allows us to produce seismic images constructed from outcrops, where architectural elements, bedding, and facies are known. One of the advantages of this technique is the ability to bridge the gap between stratigraphic concepts learned from outcrop analogs and observations from seismic data sets. Seismic forward models of five exposures from the Brushy Canyon Formation of west Texas are presented here. The exposures span an upper slope to basin-floor transect through the depositional system. Each outcrop contains unique stratal architecture and facies related to its position on the slope-to-basin physiographic profile. The seismic forward models have been constructed using geologic interpretations from LIDAR (light detection and ranging) data, stratigraphic columns, photo-panels, and paleocurrent measurements. These models are generated at several peak frequencies (30, 60, and 125 Hz). The resulting seismic forward models can be compared directly with corresponding outcrop analogs, allowing a direct comparison between outcrop and seismic architecture. The outcrop and seismic architecture of each of the five models can be compared with one another to address changes in seismic architecture associated with their positions on the slope-to-basin physiographic profile.

Abstract Deep-water structures in southern Gabon are among the best imaged in the world. Our 30-km-long study area in the Anton Marin–Astrid Marin blocks runs obliquely through the northern part of the Congo Fan. The study area is entirely covered by high-quality 3D seismic data. It spans the complex transition between the landward extensional domain and the basinward contractional domain. Both domains detach on Aptian salt. We use seismic sections and dip-corrected isochron maps to illustrate and analyze the following processes. Control of thrust location by precursor anticlines and diapirs: a regular wavelength of the early Albian gentle precursor anticlines nucleated linear, regularly spaced thrust faults; the location of precursor passive diapirs caused some thrust faults to curve to intersect with the diapirs, linking them into the overall contractional network, which includes lateral transfer zones. Thrusting that verged consistently seaward: most other salt-based thrust belts have less systematic vergence; we attribute the consistent vergence to the high frictional resistance of the salt detachment because it had been thinned by expulsion of salt into diapirs before thrusting began. Landward propagation of thrusting : during the late Cretaceous and Paleogene, thrusting propagated updip through the formerly translational domain because of the buttressing effect of older thrusts downdip of the study area. In the study area, distal thrusts and diapirs were still shortening while more proximal thrusts began shortening. Extrusion of salt sheets under compression: as thrusting culminated, the precursor passive diapirs were compressed to extrude salt; extrusion continued until the diapirs were finally squeezed shut, more or less coevally across the thrust belt in the study area.

ABSTRACT The situation presented at the Diana field in the western Gulf of Mexico is a common one in exploration and early development: a hydrocarbon reservoir expressed by a single-cycle seismic event and limited appraisal wells spaced thousands of feet apart. There is excellent core coverage that enables close calibration of seismic and well data. Integration and analysis of the data suggest a relatively channelized reservoir in an updip position, becoming more sheetlike and layered downdip. This subsurface data, however, does not have the resolution to provide the dimensional and architectural information required to populate an object-based three-dimensional geologic model for more accurate flow simulation and well-performance prediction. To solve these uncertainties, deep-water outcrop analog data from the Lower Permian Skoorsteenberg Formation in the Tanqua Karoo Basin, South Africa, and the Upper Carboniferous Ross Formation in the Clare Basin, western Ireland, were integrated with the seismic and well data from the Diana field. Bed-scale reservoir architectures were quantified with photomosaics and by correlation of closely spaced measured sections. Bed continuity and connectivity data, along with vertical and lateral facies variability information, also were collected, as these factors ultimately control the reservoir behavior. From these measurements, a spectrum of channel dimensions and shapes were compiled to condition the modeled objects. These dimensions were compared to Diana specific seismic and well data and adjusted accordingly. The advantage of the resulting Diana geologic model is that it incorporates geologic interpretation, honors all available information, and models the reservoir as discrete objects with specific dimensions, facies juxtaposition, and connectivity. This study provides the framework for optimal placement of wells to maximize the architectural and facies controls on reservoir performance.

Abstract A unique perspective of sand-rich, basin-floor fan deposition was gained through an integrated study of the Paleogene deepwater reservoirs in the UK Central North Sea. The data set included contiguous 3D seismic (8400 km 2 ), 2D seismic (11,100 km), well logs (350 wells), high-resolution palynology (180 wells), and core (30 wells). The study provided new insight into downfan changes in reservoir facies and architecture and a framework to understand fan evolution through both low-and high-frequency depositional cycles. The Paleogene in this part of the basin is subdivided into four low-frequency (1-3 MY) composite sequences. Major basin floor fan cycles include the Maureen Formation, the Andrew-Lista units, the Forties-Sele-Balder units, and the Tay-Chestnut units. These low-order successions exhibit large-scale compensational stacking behavior and, in contrast to classical fan models, maintain channel-form patterns to their distal pinchouts. Sheet geometries are surprisingly rare. Sandstone body geometries, coupled with core-based lithofacies suggest that both turbidity currents and semi-cohesive sandy debris flows were active during reservoir deposition. Each of the major sand-rich fan units ( e.g ., Forties, Tay) is composed of higher frequency depositional sequences that display important changes in lithofacies and architecture through time. The early sequences are heterolithic consisting of variable proportions of mud-rich debrites and sandstones that are commonly thin and arranged into broadly channelized bodies (high aspect ratios). The later sequences are much sandier. The sandstone bodies show slightly sinuous to linear channel-form patterns (lower aspect ratios). Although less laterally extensive, the youngest sequences have high quality reservoirs that locally have strongly mounded cross-sectional geometries. The vertical change in reservoir character reflects a progressive change in the composition and relative volume of the sediment gravity flows being triggered at the shelf edge and then delivered into the basin. Following initial phases of muddy debris flows and sandy turbidity currents, sediment gravity flows became progressively sandier and confined in discrete channels. Latest-stage sequences are locally dominated by sandy debrites. This pattern records the evolution of the lowstand shelf-margin system as it became progressively sandier and increasingly prone to large, sand-rich failures that maintained a semi-cohesive rheology as they flowed onto the basin floor. Superimposed on this changing sediment composition is a progressive decrease in sediment volume as more sediment is trapped on the shelf in response to the low-order rise in sea level. This integrated seismic, lithofacies, and stratigraphic analysis leads to an improved regional (play) to local (field-scale) stratigraphic correlation and reservoir mapping methodology. This analysis also addresses variations in reservoir quality, channel geometry, and lateral and down-fan facies changes.

Abstract In the subsurface of the San Juan basin, New Mexico, the Coniacian Tocito Sandstone is composed of four high-frequency sequences. Basal sequence boundaries are marked by erosional truncation of underlying strata and have mappable axes of erosion which are typically narrow and linear. These erosional features are interpreted to be incised valleys cut by fluvial and estuarine processes during lowstands in relative sea level. Two end-member facies are found in the valley fills: (1) a low-energy mudstone-dominated facies with thin-bedded and bioturbated sandstones, and (2) a high-energy facies chiefly consisting of medium- to coarse-grained glauconitic sandstone. Tidal indicators in this facies include double clay drapes, flaser and lenticular bedding, and large- to small-scale sigmoidal cross-bedding. Iron-cemented shale rip-up clasts, quartz and phosphatic pebbles, sharks’ teeth, and detrital fragments of Inoceramus and oyster shells also characterize the Tocito Sandstone. Paleophycus, Thalassinoid.es, and Planolites burrows with locally abundant Ophiomorpha burrows typify the low-diversity, low- to moderate-abundance trace-fossil suite. The combination of lithofacies, sedimentary structures, and ichnofauna indicates lowstand deposition within tide-dominated estuarine systems. The sandstone-prone fills are considered proximal facies connected to fluvial systems, whereas the shalier facies are interpreted to be more distal fills laid down as the estuaries expanded to form large embayments. Valley systems show a sequential change in geometry and fill type in vertical profile: older valleys are narrow and sandstone filled and give way to broader systems which are filled with strata which are more shale-prone. The result is a retrogradational stacking of the sequences or a transgressive sequence set. This stacking pattern, coupled with the erosional juxtaposition of the valley fills, created many stratigraphic traps for hydrocarbons. The two principal trap types are: (1) bends in valley axes where valley-fill sandstones thin laterally to zero against underlying marine mudstones, and (2) truncation of valley-fill sandstones by younger, shale-filled valleys. Hydrocarbons are produced from the older, sandstone-prone valleys with top and lateral seals provided by the overlying, younger shale-filled valleys. The strongly parallel and southeast-flowing drainage pattern found in the Tocito lowstands parallels the basement-involved fault trend. A phase of structural reactivation is inferred to have accompanied Tocito deposition and caused sediment dispersal patterns to be nearly perpendicular to the northeast prograding Gallup highstand system.

Abstract OBJECTIVE : For the next two days we will examine the stratigraphy and lithofacies of Turanian- and Coniacian-age strata in northwestern New Mexico, on the lands of the Navajo Nation (see location map Figure 6-1). We will focus on the Gallup (shallow marine and coastal plain), Torrivio (predominantly braided-fluvial) and Tocito (estuarine to shallow marine) sandstone formations. An overview of the stratigraphy, lithofacies and hydrocarbon-trapping styles pertaining to these sandstones, in outcrop and from extensive subsurface well-log correlations, is presented in the accompanying paper entitled ‘High- resolution sequence stratigraphy of the Upper Cretaceous Tocito Sandstone…’. A briefer overview is also presented under STOP 1 below. The stratigraphy of the San Juan Basin is summarized in Figures 6-2, 6-3 and 6-4. These are increasingly higher resolution stratigraphic columns, with Figure 6-4, being specifically designed for this field trip. This figure reflects some of the latest ideas on the distribution of significant sequence-stratigraphic surfaces in the Late Turanian and Coniacian parts of the section. The discussion in the text at each of the field stops is designed to present two somewhat different sequence-stratigraphic interpretations of the rocks; an Exxon (Jones, Van Wagoner and Jennette) and L.S.U. (Nummedal and Riley) interpretation. The reader can draw his/her own conclusions from the observations made at outcrop and in the subsurface (see accompanying papers). Any person wishing to conduct geological investigations on the Navajo Reservation, including visiting the stops described in this guidebook, must first obtain a permit from the Navajo Nation Minerals Department, P.O. Box 146,

Abstract In the subsurface of the San Juan Basin, New Mexico, the Coniacian Tocito Sandstone is composed of four sequences (Tocito-1, Tocito-2, Tocito-3 and Tocito-4). Over their extent, each basal sequence boundary is marked by erosion and truncation of underlying strata and onlap by shallower water, typically estuarine strata. Axes of erosion are typically narrow, straight to slightly sinuous and locally join to form tributary-like junctures. These patterns are interpreted to be incised valleys cut by fluvial and estuarine systems during lowstands in relative sea level. The four sequences stack in a backstepping pattern to form a retrogradational sequence set. Toward the outcrop belt (southwest), the sequence boundaries merge to form a composite surface which everywhere separates Tocito strata from underlying Gallup strata. Sandstone accumulations occur along sinuous lows associated with incised sequence boundaries. Two end-member types of lowstand facies exist: an open-marine facies dominated by marine mudstone with minor thin-bedded and bioturbated sandstone beds and a sand-prone, tidally influenced facies consisting of beds of medium to coarse grained, highly glauconitic sandstone. Tidal indicators include double clay drapes, flaser and lenticular bedding and large- to small-scale sigmoidal and trough cross bedding. Iron-cemented shale rip-up clasts, quartz and phosphatic pebbles, sharks teeth, Inoceramus and oyster shell fragments also characterize the Tocito Sandstone. Ichnofauna are dominated by Thalassinoides, Paleophycus and Planolites burrows with locally abundant robust Ophiomorpha burrows. Bedding and ichnofauna indicate sand deposition within estuaries. Reactivated basement-involved faults were the dominant influence on Tocito drainage patterns. These northwest-trending basement-involved faults, which were active episodically throughout the Phanerozoic, created linear pathways that acted as catchments for southeast-directed stream and estuarine systems. Reactivation of these structures during the Tocito lowstands led to a reorientation of regional sediment transport directions nearly perpendicular to that of the underlying Gallup shoreline deposits. The close vertical juxtaposition of erosional sequence boundaries and variably filled incised valleys created abundant stratigraphic traps. Most hydrocarbon traps are dependent on a combination of trapping elements which can include a bend in the valley axis (lateral-trapping clement), valley edges where valley-fill sandstones thin to zero (lateral and updip seals), and truncation of sandstone valley-fill by younger, shale-filled valleys (lateral, updip and top seals). Through time, valleys tend to become broader and shallower and are filled with strata that are more shale-prone and more open marine in character. Hydrocarbon production is chiefly from the older, sand-prone valley systems. Previous workers viewed the composite erosional surface at the base of the Tocito sequences as a single erosional unconformity which was progressively onlapped through time by beaches, offshore bars and shelf-sand ridges. In these models, hydrocarbon-trapping mechanisms relied on gradual facies changes of the sandy bars into marine shale. The incised-valley model accounts for the lidal and estuarine indicators, complex erosional patterns and hydrocarbon-trapping styles of the Tocito Sandstone.