Main Fairway Research Articles

The arrival of the paleo–Orinoco Delta at Trinidad: The Cruse Formation delta lobes and delivery to deepwater Atlantic

ABSTRACT Icehouse continental-shelf-margin accretion is typically driven by high-sediment-supply deltas and repeated glacio-eustatic, climate-driven sea-level changes on a ca. 100 ky time scale. The paleo–Orinoco margin is no exception to this, as the paleo–Orinoco River Delta with its high sediment load prograded across Venezuela, then into the Southern and Columbus basins of Trinidad since the late Miocene, depositing a continental-margin sedimentary prism that is > 12 km thick, 200 km wide, and 500 km along dip. The Cruse Formation (> 800 m thick; 3 My duration) records the first arrival of the paleo–Orinoco Delta into the Trinidad area. It then accreted eastwards, outwards onto the Atlantic margin, by shallow to deepwater clinoform increments since the late Miocene and is capped by a major, thick flooding interval (the Lower Forest Clay). Previous research has provided an understanding of the paleo–Orinoco Delta depositional system at seismic and outcrop scales, but a clinoform framework detailing proximal to distal reaches through the main fairway of the Southern Basin has never been built. We integrate data from 58 wells and outcrop observations to present a 3-D illustration of 15 mapped Cruse clinoforms, in order to understand the changing character of the first Orinoco clastic wedge on Trinidad. The clinoforms have an undecompacted average height of 550 m, estimated continental slope of 2.5° tapering to 1°, and a distance from shelf edge to near-base of slope of > 10 km. The clinoform framework shows trajectory changes from strong shelf-margin progradation (C10–C13) to aggradation (C14–C20) and to renewed progradation (C21–24). Cruse margin progradational phases illustrate oblique clinothem geometries that lack well-developed topsets but contain up to 70 m (200 ft) thick, deepwater slope channels. This suggests a high supply of sediment during periods of repeated icehouse rise and fall of eustatic sea level, with fall outpacing subsidence rates at times, and delivery of sand to the deepwater region of the embryonic Columbus channel region. Also, evidence of wholesale shelf-edge collapse and canyon features seen in outcrop strongly suggest that deepwater conduits for sediment dispersal and bypass surfaces for Cruse basin-floor fans do exist. The change to a topset aggradational pattern with a rising shelf trajectory may be linked to increased subsidence associated with eastward migration of the Caribbean plate. The Cruse-margin topsets were dominated by mixed fluvial–wave delta lobes that were effective in delivery of sands to the basin floor. The preservation of a fluvial regime of the delta may have been impacted by basin geometry which partly sheltered the area from the open Atlantic wave energy at the shelf edge. Ultimately, understanding shelf-edge migration style as well as process-regime changes during cross-shelf transits of the delta will help to predict the location of bypassed sands and their delivery to deepwater areas.

Petroleum Plays of the Bowen and Surat basins

The plays of the Bowen and Surat basins consist of conventional structural plays along major regional structures and depositional platforms, most of which have some stratigraphic component. These can be subdivided into three main regions: the eastern and western flanks of the Taroom Trough, and the Denison Trough. Coal seam gas is found in fairway zones within the Permian coals of the Bowen Basin, which can be subdivided into two main fairways: structurally associated plays in the southern Bowen Basin, and a tighter play in the northern Bowen Basin. Coal seam gas is also found along a broad fairway in the Walloon Coal Measures of the Surat Basin. Recent exploration for new targets has highlighted potential for tight gas in the deeper sections of the Bowen Basin, though further evaluation is required. More speculative plays within the region include tight gas within potential, but untested targets in the deeper sections of the Denison Trough.

Controls on submarine canyon head evolution: Monterey Canyon, offshore central California

The Monterey submarine canyon, incised across the continental shelf in Monterey Bay, California, provides a record of the link between onshore tectonism, fluvial transport, and deep-marine deposition. High-resolution seismic-reflection imaging in Monterey Bay reveals an extensive paleocanyon unit buried below the seafloor of the continental shelf around Monterey and Soquel canyon heads. Paleocanyons shifted position through numerous phases of cut-and-fill in response to Salinas, Pajaro, and San Lorenzo river extensions and avulsions across the continental shelf during high-frequency Pleistocene sea-level and climatic variations. Five seismic facies within the Monterey paleocanyon unit and below the modern canyon are defined to interpret canyon evolution during the Pleistocene. Repeated sea-level oscillations appear to have switched the main fairway(s) of sediment transport. Large-scale erosion and fill occurred in marine environments. Paleocanyon fill is characterized by paleo-axial channel deposits and mass transport deposits, followed by canyon head abandonment and marine sedimentation. The upper portion of the paleocanyon unit contains relatively small channels that were likely incised by erosion in the paleo-Salinas and Pajaro rivers and filled with a mix of nonmarine and marine deposits. Shifting position of submarine canyons over time is characteristic of Monterey Bay, east of the Monterey Bay Fault Zone, and is likely unidentified in other submarine canyon head regions that lack dense high-resolution seismic-reflection subbottom images. We show that canyon heads can be areas of sediment accumulation linked to sea-level oscillations, providing new insights into submarine canyon evolution and sequence stratigraphy.

Lower Triassic reservoir development in the northern Dutch offshore

Abstract Sandstones of the Main Buntsandstein Subgroup represent a key element of the well-established Lower Triassic hydrocarbon play in the southern North Sea area. Mixed aeolian and fluvial sediments of the Lower Volpriehausen and Detfurth Sandstone members form the main reservoir rock, sealed by the Solling Claystone and/or Röt Salt. It is generally perceived that reservoir presence and quality decrease towards the north and that the prospectivity of the Main Buntsandstein play in the northern Dutch offshore is therefore limited. Lack of access to hydrocarbon charge from the underlying Carboniferous sediments as a result of the thick Zechstein salt is often identified as an additional risk for this play. Consequently, only a few wells have tested Triassic reservoir and therefore this part of the basin remains under-explored. Seismic interpretation of the Lower Volpriehausen Sandstone Member was conducted and several untested Triassic structures are identified. A comprehensive, regional well analysis suggests the presence of reservoir sands north of the main fairway. The lithologic character and stratigraphic extent of these northern Triassic deposits may suggest an alternative reservoir provenance in the marginal Step Graben system. Fluvial sands with (local) northern provenance may have been preserved in the NW area of the Step Graben system, as seismic interpretation indicates the development of a local depocentre during the Early Triassic. These insights help to improve the chance of finding Lower Buntsandstein reservoir rocks in the northern Dutch offshore.

Fairway Traffic Capacity in Indonesia

Problems of congestion and road damage due to traffic density and excessive vehicle loads can be solved by shifting the traffic load of the highway to river transport. For regional areas in Indonesia, which are traversed by rivers with water levels and width navigable by various types of vessels, river transport can be the main alternative transportation of goods other than highways. South Sumatra is one of the provinces in Indonesia which has a network of rivers that can be traversed by large cargo vessels. Musi River with its tributaries network is the main fairway in South Sumatra where water levels of the river are affected by the environment, especially tides, seasons and sedimentations. This environmental influences have led to vessels being unable to sail safely and smoothly all the time. Therefore, it is deemed necessary to determine the fairway capacity as a riverway performance indicator that takes into account environmental influences, especially tides. Various research on capacity of inland waterways previously conducted have not specifically considered the effect of tides.

Quantifying Resources for the Surmont Lease with 2D Mapping and Multivariate Statistics

Summary The McMurray formation consists of heterogeneous Cretaceous-bitumen-saturated sands. The reservoirs are thick and laterally extensive in the main fairways. Many commercial projects are in the early stages of development. Resources too deep to mine are considering steam assisted gravity drainage (SAGD) (Butler 1991). Detailed high-resolution 3D geostatistical modeling is useful for individual well-pair or pad flow simulation, but is neither practical nor necessary for resource assessment across large areas. A methodology for resource assessment is developed from a geostatistical study on the Surmont lease. The uncertainty in more than 30 correlated variables is calculated on a dense 2D grid using all available information including wells, seismic, and geologic trends. The correlation structure between the variables is modeled under a multivariate Gaussian model. The local distributions of uncertainty have been checked with cross validation and with more than 100 new wells drilled during the last two drilling seasons. Resource uncertainty across the entire lease area and a number of arbitrary development areas is derived from the 2D maps of uncertainty. A combined P -field/LU simulation approach is used; the global uncertainty is consistent with the local uncertainty.

The hydrocarbon systems of North Africa

North Africa's hydrocarbon reserves are spread over a wide range of reservoirs and play types but derive from only a few key source rock intervals, particularly those in the Silurian, Late Cretacous and Eocene. Source rock maturity, together with the timing of the generation relative to trap forming and destructive events, seem to be the key controlling factors on success or failure at a basin level. In most cases, generation clearly post-dates trap formation, although a more complex relationship is evident in various parts of Algeria, where some traps did not form until gas was being generated. Source rock deposition and maturation can be tied to two main extensional tectonic cycles which ended in the compressional and destructive events of the Hercynian and Alpine orogenies. Remaining exploration potential in mature provinces may be tied largely to subtle and stratigraphic traps. In addition, significant frontier potential can be identified in two main fairways, corresponding to regions where Silurian/Devonian and Cretaceous/Eocene sources respectively are likely to have generated petroleum. Critical factors in these areas are timing of generation and preservation. The gas discoveries in the Ahnet Basin provide analogues for Palaeozoic generation/preservation models in the interior Silurian/Devonian source fairway. Similarly, the key to success for the Mesozoic basins of the Atlas region lies in demonstrating a favourable relationship between trap formation/destruction and generation from Late Cretaceous and Eocene source rocks.

SHORE PROTECTION OF KAOHSIUNG HARBOR OUTER BREAKWATER

As shown in Fig.l the main fairway of Port of Kaohsiung is running from north to south with a length of 12 kilometers. To the west, there is a sand bar served as a natural breakwater, the so called outer Breakwater, to provide the port and resident's property the necessary safety and security. Recently, due to rapid growth of container traffic and bulk cargo transportation, Port of Kaohsiung has developed some parts of the outer breakwater near the 2nd Harbor Entrance as Container Terminal No.4 with seven 14-meter-deep, 320-meter-long container berths and about 100 hectares container yard on northern side, and coal Terminal with 16-meter-deep, 320-meter-long berth and a huge storage yard on southern side. Therefore, the shore protection along the area become more and more important year by year. So far, some 6-kilometer seawall and 20 groynes have built successively, and already played a very important role for the shore protection there.

Presence and Control of Evaporite Top Seals on Occurrence and Distribution of Hydrocarbon Traps: Main Fairway, Central Overthrust Belt, Wyoming and Utah: ABSTRACT

In the Central Overthrust belt fairway, there are 18 known productive formations ranging from Cambrian to Cretaceous in age. Four units - the Ordovician Big Horn formation, Mississippian Mission Canyon formation, Jurassic Nugget formation, and Jurassic Twin Creek Formation - account for 99% of a reported 1.4 billion bbl of oil estimated recoverable reserves discovered to date. A critical factor necessary for significant hydrocarbon accumulations is the presence of effective evaporite seals above these reservoirs. Major accumulations exist in anticlines associated with Paleozoic or Jurassic cutoffs in the hanging wall of the Absaroka thrust with recognized source rocks occurring in the Cretaceous footwall section. Vertical migration is required to source the overlying reservoirs. Migration pathways are via hanging wall cutoffs of these reservoirs or through fractures in the cores of the structures. Hanging wall reservoirs either lacking top seals or having top seals disrupted by extensive fracturing due to folding or faulting, permit vertical migration into higher, more effectively sealed reservoirs. In the Overthrust producing fairway, anhydrites of the Mission Canyon formation and Gypsum Spring Member of the Twin Creek formation as well as the Jurassic Preuss salt are the three effective seal units. Analysis of Overthrust belt traps suggestsmore » that the presence and ductile nature of these evaporite seals are important controlling factors for the significant hydrocarbon accumulations in this highly deformed terrain.« less