L'objet principale de cette étude a été d'établir dans la mesure du possible, une corrélation entre les affleurements de la rivce droite du Rhône de Tournon à La Voulte et ce que l'on peutconnaitre des formations sous-alluviales. Ainsi, nous avons-été amené d'une part à reprendre le levé de la carte géologique et d'autre àexaminer les dossiers et les nombreux sondages effectués par la Compagnie Nationale du Rhône. Le choix de Tournon et de La Voulte comme localités extrêmes au Nord et au Sud n'est pas arbitraire. Nous verrons en effet que cette région possède une certaine individualité tant au point de vue géographique que géologique. Nous avons limité notre levé dans sa partie occidentale aux formations paléozoïques du Plateau Central et, dans sa partie orientale aux formations alluviales de la vallée actuelle.

In 2007, the Barnett Shale in the Fort Worth basin of Texas produced 1.1 trillion cubic feet (Tcf) gas and ranked second in U.S gas production. Despite its importance, controls on Barnett Shale gas well performance are poorly understood. Regional and vertical variations of reservoir properties and their effects on well performances have not been assessed. Therefore, we conducted a study of Barnett Shale stratigraphy, petrophysics, and production, and we integrated these results to clarify the controls on well performance. Barnett Shale ranges from 50 to 1,100 ft thick; we divided the formation into 4 reservoir units that are significant to engineering decisions. All but Reservoir Unit 1 (the lower reservoir unit) are commonly perforated in gas wells. Reservoir Unit 1 appears to be clay-rich shale and ranges from 10 to 80 ft thick. Reservoir Unit 2 is laminated, siliceous mudstone and marly carbonate zone, 20 to 300 ft thick. Reservoir Unit 3 is composed of multiple, stacked, thin (~15-30 ft thick), upward coarsening sequences of brittle carbonate and siliceous units interbedded with ductile shales; thickness ranges from 0 to 500 ft. Reservoir Unit 4, the upper Barnett Shale is composed dominantly of shale interbedded with upward coarsening, laterally persistent, brittle/ductile sequences ranging from 0 to 100 ft thick. Gas production rates vary directly with Barnett Shale thermal maturity and structural setting. For the following five production regions that encompass most of the producing wells, Peak Monthly gas production from horizontal wells decreases as follows: Tier 1 (median production 60 MMcf) to Core Area to Parker County to Tier 2 West to Oil Zone-Montague County (median production 10 MMcf). The Peak Monthly oil production from horizontal wells is in the inverse order of gas production; median Peak Monthly oil production is 3,000 bbl in the Oil Zone-Montague County and zero in Tier 1. Generally, horizontal wells produce approximately twice as much oil and gas as vertical wells.This research clarifies regional variations of reservoir and geologic properties of the Barnett Shale. Result of these studies should assist operators with optimization of development strategies and gas recovery from the Barnett Shale.

Middle-Late Ordovician Mt. Wilson Quartzite, southern British Columbia, Canada, is a supermature quartz arenite deposited in shallow marine-marginal marine environments on the Early Paleozoic western Laurentian passive margin. Facies-stacking patterns indicate the Mt. Wilson Quartzite is an unconformity bounded, 2nd-order depositional sequence, containing two 3rd-order sequences, and numerous parasequences. Detrital zircon age spectra of six samples of the Mt. Wilson Quartzite have numerous peaks that are unique to Middle to Late Ordovician quartz arenites of western Laurentia. The main peaks, 1800-2000 Ma, 2000-2200 Ma, and 2300-2400 Ma are interpreted to have been derived from basement rocks that were exposed east of the study area: Trans-Hudson Orogeny (1800-2000 Ma), Taltson Orogen (1800-2000 Ma), Buffalo Head Terrane (2000-2400 Ma), Paleoproterozoic crust (2000-2400 Ma), and the Wopmay Terrane (2000-2400 Ma). It is likely that these areas were sourced by local rivers and tributaries draining the Transcontinental Arch and delivered sediment to the deposition location of the Mt. Wilson Quartzite. While longshore transport was a viable distribution method for sediment along the passive margin, it is unlikely that the Peace River Arch (located northwest of the Mt. Wilson Quartzite) was its sole point source; rather it is more likely that there were multiple sediment sources for these western Laurentian quartz arenites. Temporal changes in provenance indicate different areas of basement rock were exposed throughout the deposition of the Mt. Wilson Quartzite, most likely reflecting long-term flooding of North America. The potential for spatial changes in provenance remains unsolved.

High resolution sampling was performed along the &Uuml / z&uuml / ml&uuml / Formation exposed near the YeniceSihlar village of Mudurnu (Bolu). Field and thin-section analyses showed that the &Uuml / z&uuml / ml&uuml / Formation is composed of cm to m scale cycles of 4th and 5th order. The 4th order cycles are equivalencies of parasequences and have 0.4 Ma average duration. 5th order cycles are interpreted as episodic. Upper Albian (OAE1c or OAE1d) and Cenomanian/Turonian (OAE2) anoxic events are observed as black shale levels in the studied section. Position of black shale levels is interpreted using cyclostratigraphy and sequence stratigraphy. Four types of cycle are determined. A and B-type cycles are placed in transgressive and Highstand System Tract. C and D-type cycles are placed in Lowstand System Tract. Two type 3 and one type 1 sequence boundaries are recorded. The boundary between the Soguk&ccedil / am Limestone and the &Uuml / z&uuml / ml&uuml / Formation is interpreted as the first type 3 sequence boundary. The second one separates the &Uuml / z&uuml / ml&uuml / Formation and the Yenipazar Formation and is observed at the top of the section. Type 1 boundary is represented by a conglomeratic level in the middle of the succession. Provenance analysis of sandstones indicates that during the Cenomanian the source area changed from magmatic arc setting to continental setting.

The late Permian Queen Formation (115 m thick) is a succession of mixed clastics, carbonates and evaporites deposited in the northeastern margin of Central Basin Platform of the Permian Basin, west Texas, USA. Depositional facies, stacking patterns of cyclic facies associations and statistical correlation of rock property variations define geologic controls on reservoir rock properties. Textural, compositional, petrophysical and diagenetic variations within lithofacies exhibit systematic changes with stratigraphic position, which can be related to base level changes that were controlled by high-frequency, low-amplitude, sea level fluctuations during a greenhouse period. Ten lithofacies record variations in clastic input, shallow marine carbonate production, and evaporate precipitation in sabhkas and salinas. Four different types of lithofacies associations define: (1) transgressive deltaic deposits; (2) upward-shallowing evaporite and carbonate tidal-flat deposits; (3) transgressive beach ridge and sand flat deposits; and (4) upward-shallowing evaporite salina-sabhka deposits. Stacking patterns of lithofacies associations define sixteen depositional cycles that can be grouped into eight cycle sets. Cycle sets in turn are grouped to define two high-frequency sequences. Sequence 1 progresses from fluvial to carbonate tidal flat cycles. Sequence 2 consists of salina-dominated upward-shoaling cycles. Lateral continuity of cycles indicates restricted sedimentation on low-accommodation inner platform areas updip of prograding highstand platform-margin carbonate buildups, and a long-term trend of accommodation decrease. The Queen Formation contains two reservoir types; (1) siliciclastic reservoirs capped by evaporites and (2) layer-cake carbonate reservoirs. Of the four reservoir zones identified, R11 in lowstand fluvial-deltaic deposits has relatively little cement and the best reservoir characters.

This study uses a 1375 km2 3D seismic dataset located in the late Miocene to Pliocene Mississippi River Delta in order to investigate the external characteristics, lithology, and evolution of channelized deposits within the seismic survey. Fluvial thicknesses range from about 11 m to 90 m and widths range from about 100 m to 31 km. Channel fill can be generalized as sandy with low impedance and high porosity (~ 35%), though heterogeneity can be high. Three distinct fluvial styles were recognized: incised valleys, channel-belts, and distributive channel networks. Fluvial styles were interpreted as a result of changes in sea-level and a speculative late Miocene to Pliocene Mississippi River Delta sea-level curve constructed using these relationships. Additionally, a characteristic interval between the major changes in fluvial style was found. These fluvial systems interact with and are affected by other elements in the landscape. Growth faults in particular are common within the survey area; however, the dynamic between fluvial systems and growth fault related subsidence has been poorly understood and so was also a focus of this project. Previous work as well as this study found little evidence that growth faults are able to affect the course or geometry of the majority of small (with most < 500 m in width and < 20 m in depth) channels. However, the relationship between growth faults and larger scale channel-belt systems (between 1 km and 5 km in width and > 25 m in depth) has not been previously evaluated in this area. In contrast to the majority of small distributary channels found within the survey, channel-belts appear to be steered by growth faults. Fluvial response or insensitivity to fault induced subsidence is related to the relative timescales of avulsion and faulting. Channel-belts are longer lived features than more ephemeral small distributary channels. Channel-belts, due to their relatively low mobility compared to small channels, are more likely to experience punctuated faulting events which results in greater apparent sensitivity to faulting than seen in small channels. / text

The sequence stratigraphy, depositional systems and reservoir geology of the lower and middle Oligocene Frio Formation in the Red Fish Bay field, Nueces County, Texas, are examined based on 1,800 feet (548.6 m) of core, 28 wireline-logs and 30 mi2 of 3-D seismic data. The study interval is composed of an incomplete 3rd-order stratigraphic sequence with an incomplete lowstand systems tract (LST), a complete transgressive systems tract (TST) and an incomplete highstand system tract (HST). This 3rd-order succession is divided into 12 4th-order sequences with average thickness of 150 feet (45.7 m). The lowstand system tract (LST) from 4th-order sequence 1 to 4th-order sequence 7 displays an aggradational stacking pattern in cross-sections. The regressive part of each 4th-order sequence has an upward-coarsening trend that reflects a transition of depositional environments from offshore to lower, middle and upper shoreface. The transgressive part of each 4th-order sequence exhibits an upward-fining trend, commonly associated with backstepping cycles composed of shoreface, washover-fan, and back-barrier lagoonal deposits. Sandstone maps of 4th-order sequence and stratal-slice maps from 3-D seismic data within 3rd-order lowstand system tracts display a strike-elongate geometry, indicating wave-dominated depositional systems. The 3rd-order transgressive system tract (TST) displays a retrogradational stacking pattern in cross-sections. The overall upward-fining trend records water deepening during transgression, interpreted as a transition from lower-shoreface to shelf environments. The 3rd-order highstand system tract (HST) from 4th-order sequence 8 to 4th-order sequence 12 displays a progradational stacking pattern in cross-sections. It is upward-coarsening and upward-thickening, indicating a transition from to distal- to proximal-shoreline setting. The geometry of framework sandstone bodies, inferred from gross-sandstone and stratal-slice maps is relatively lobate, suggesting a wave-modified deltaic system. The sandstone body continuity is very good and heterogeneity is very low within shoreface or wave-dominated deltaic systems in LST and HST sequences in Redfish Bay. Sandstone thickness expands towards the growth fault, owing to structurally controlled accommodation, but is thicker in the southwest part of study area, where it is controlled by paleogeomorphology, related to the presence of a deltaic depocenter. The sandstone body thickness of each 4th-order sequence is as much as 240 ft (73.2 m) and commonly ~100 ft (30.5 m) in average. Sandstone development in the study succession is controlled by the sequence stratigraphic context, and modification by depositional processes. The average porosity and permeability of study interval are 19.4% and 33.6 md respectively. Lithology is the main control on porosity and permeability. Sedimentary and biogenic structures also modify grain-size sorting, indirectly affecting porosity and permeability. Reservoir quality in LST is higher than that in the HST, as the depositional environment in LST is within proximal-delta-front facies, whereas in the HST is within distal-delta-front facies. Reservoir quality varies greatly within each 4th-order sequence, owing to different levels of intensity in bioturbation per each sandstone bed. / text

There is evidence that a subset of fluvial deposits at Aeolis Dorsa, a basin on Mars, preserve incised valleys carved and filled during changes in base level, which was likely controlled by water surface elevation of a large lake or sea. Three low-albedo, channelized corridors, each several tens of kilometers long, contain relict point bars and scooped boundaries at their bases, indicating that the base and lateral extent of each corridor was defined by a migrating, net-erosional river. Above the basal deposits are stacks several tens of meters thick of “inverted sinuous ridges”, which are channel-filling deposits that have been exhumed and topographically inverted. Indicators of avulsions, channel re-occupations, an overall flattening of basal topography, and confinement of inverted sinuous ridges to the dark corridors are evidence of the gradual filling of a valley cut by the basal migrating river. Valley incision and fill are common responses to sea level change on Earth. Aeolis Dorsa is currently open to the northern lowlands of Mars, where an ocean has been hypothesized to have once existed, although a large lake could have also controlled base level. Cross-cutting valleys require at least two episodes of base level fall and rise. The magnitudes of the base level changes are estimated at about 80 meters, based on the thickness of the valley-filling stratigraphy. Meander asymmetry is consistent with a southeastern flow direction, and is supported by a set of branching fluvial deposits 40 km to the southeast which, qualitatively, appear to be deltaic in origin. / text

Campanian M1 Sandstone is one of the major prospective sandstone units in the Tarapoa field in Oriente Basin, Ecuador. The M1 Sandstone is always markedly sharp based, averages 25 m in thickness, shows upward increasing marine bioturbation and generally fines upward from coarse to very fine grained sandstone. In cores, the sandstones at base are amalgamated coarse to fine grained with prominent cross stratification (dm thick), sometimes clearly bi-directional and contains mud drapes. These suggest strong tidal or fluvial-tidal currents in estuary channels or delta distributary channels. The finer grained intervals in the middle are brackish-water intensely bioturbated and dominated by mud drapes, wavy and flaser bedding suggestive of intertidal flats. Associated overlying coals and coaly shales suggest supratidal conditions. The sandstones at top are cross stratified and contain mud drapes. These again suggest strong tidal or fluvial-tidal currents in estuary channels or delta distributary channels. The stacking pattern of facies in M1 Sandstone reveals the evolution of the M1 depositional system, as well as the sequence stratigraphy of M1 sandstone. The evolution includes four stages of deposition which indicates an initial sea level rise, a subsequent sea level fall, and another sea level rise. Lateral sand-mud heterogeneity exists in the study area, forming “shale barriers”, i.e. elongate shale-rich zones that are lateral barriers to hydrocarbon migration. They are interpreted to be abandoned tidal channels filled with muddy tidal flat deposits during the sea level fall. An alternative hypothesis was established to explain the stacking pattern of facies in M1 Sandstone. A tide-dominated delta with poor fluvial input experienced intense tidal erosion and produced a sharp base at the base of M1 Sandstone. Then subtidal sand bars, intertidal flats, and supratidal sediments were deposited in sequence during a continuous regression. The core and well logs in an extension of the study area in the northwest is interpreted as more distal open shelf deposits, beyond the mouth of the Tarapoa estuary system, where transgressive tidal shelf ridges were coeval with the Tarapoa estuary system. This interpretation allows us to predict the environment between the two areas as a transition zone between tide-dominated estuary and open shelf. / text

The San Andres and Grayburg Formations are important stratigraphic units for constructing correlation frameworks of the Guadalupe Mountains because these strata record the transition between the ramp profiles of the San Andres along the Algerita Escarpment and the reef-rimmed platforms of the Capitan Formation of the southern Guadalupe Mountains (Franseen et al. 1989). Sarg et al. (1999) and Kerans and Tinker (1999) have published significantly different models of shelf-to-basin correlations within this stratigraphic interval. Central to the debate is the correlation of mixed carbonate-siliciclastic strata exposed at Plowman Ridge in the Brokeoff Mountains to the better-constrained strata along the Shattuck Escarpment in the Guadalupe Mountains. This study applies high-resolution cyclostratigraphy, inorganic carbon isotope geochemistry, and sequence stratigraphic concepts to test the hypothesis that the strata exposed at Plowman Ridge are equivalent to Grayburg strata exposed at the Shattuck Escarpment in the southern Guadalupe Mountains (Kerans and Nance 1991, Kerans and Kempter 2002). The shelf-to-basin cyclostratigraphic framework of the Grayburg Formation used in this study was established at the Shattuck Escarpment with data compiled from nine detailed measured sections, high-resolution photopans, and petrographic analysis. Based on one- and two-dimensional cycle stacking analysis, the Grayburg Formation was divided into three high-frequency sequences (HFSs). The high-frequency sequences contain transgressive systems tracts separated by maximum flooding surfaces from the highstand systems tracts. The Grayburg high-frequency sequences are composed of between 6 and 20 high-frequency cycles (HFCs), which were identified and classified into vertical facies successions. The Grayburg succession at Shattuck section 7 (32.09ᵒ, -104.81ᵒ) was selected as the reference section from the Guadalupe Mountains for comparison with Plowman section PR1 (32.03ᵒ, -104.89ᵒ) in the Brokeoff Mountains. Correlation between sections is documented at the 3rd-order composite sequence, high-frequency sequence, and when feasible, high-frequency cycle scale. Three high-frequency sequences recognized at Plowman Ridge section PR1 are equivalent to the G10, G11, and G12 Grayburg sequences described at Shattuck section 7. Correlation of the Grayburg G10-G12 high-frequency sequences with the three sequences at Plowman Ridge is based on comparison of overall thicknesses, facies proportions, cycle number, vertical facies succession, stratigraphic position of diagnostic units, and excursions within the inorganic carbon isotope profiles taken from both sections. Establishing the links between Grayburg strata on the Shattuck wall with strata on Plowman Ridge corroborates the framework/correlation scheme of Kerans and Tinker (1999) in lieu of other published correlation frameworks. / text