bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of heterogeneities in a braided stream channel sandbody on the simulation of oil recovery: a case study from the Lower Jurassic Statfjord Formation, Snorre Field, North Sea
Authors: Høimyr Øistein , Kleppe Amund , Nystuen Johan P. 
Published: April 2008

Abstract

Three heterogeneous models of a channel sandbody of braided stream origin were constructed by combining reservoir data from the middle reservoir unit of the Lower Jurassic Statfjord Formation in the Snorre Field in the Norwegian Sector of the North Sea, with facies and geometry data from an exposed analogue channel sandbody in the Pennsylvanian-Permian Maroon Formation, Colorado. Permeability classes corresponding to those in the Statfjord Formation were distributed according to facies variation in the analogue sandbody and to the recorded vertical distribution in the Middle Statfjord sandbodies. Relative permeability and capillary pressure curves were made for individual permeability classes. Two-dimensional (
yz
-plane) reservoir simulation of waterflooding was carried out with injection at the down-dip end and production at the up-dip end of the models, which measured 104 m × 8.75 m and had a structural dip of 8°.

The results were compared with simulations on two reference models, one of a homogeneous sandbody and one with the permeability zonation organized in parallel layers with decreasing permeability from base to top. All models had the same volume-weighted arithmetic mean permeability. The 104 m long basic models were also compared with scaled-up versions measuring 312 m and 936 m, respectively.
The simulations show that variation in internal heterogeneity has considerable impact on recovery efficiency. Compared with the homogeneous reference model, the heterogeneous models had reduced recovery efficiencies at water breakthrough of 11% to 33%, depending on the type and degree of heterogeneity, and a corresponding reduction in mean effective permeability of 9% to 42%. This study also demonstrated the importance of using capillary pressure data in simulations of this type.
Capillary pressure allows imbibition into the low permeability rocks during waterflooding and explains the higher recovery efficiency on simulation runs on the scaled-up models compared to the short basic models. The effect of capillary pressure also results in higher recovery efficiency in runs with low flow rate than in runs with high rate. Similar simulation studies, also in 3-D, should be performed on various types of internal heterogeneities in complex fluvial reservoirs.
Geometry and facies of large-scale flow units in fluvial-dominated fan-delta-front sequences
Authors: Dreyer Tom 
Published: April 2008

Abstract
In heterogeneous reservoirs, an optimal number of large-scale flowunits (here termed building blocks) must be defined prior to detailed geological modelling. For the fluvial-dominated fan-deltaic parts of the Tilje Formation, Mid-Norwegian shelf, four fan-delta-front building blocks have been defined. Quantifications with regard to the geometry and spatial arrangement of these building blocks have been made based on outcrop studies of similar sediments in the Ridge Basin, California. The four building blocks are composite delta-front units (CDF), mouth-bar sandstones (MS), mouth-bar-related mudstones and carbonate-cemented zones (MMC), and distal delta-front mudstones (D). The main reservoir units in the Tilje Formation are the composite delta-front units. These have large lateral extents (tens of kilometres), and occur in three intervals separated by impermeable zones of building block D. Within the CDF units, the main heterogeneity is the alternation between permeable mouth-bar sandstones of building block MS and impermeable zones of building block MMC. The mouthbar sandbodies have width (W)/thickness (T) ratios of 220–525, and constitute a considerably larger percentage of the reservoir volume than the less widespread MMC flow-barriers. Hence, the internal communication within the CDF units is believed to be generally good.
Methods for improving the chronometric time-scale
Authors: Smith Alan G. 
Published: April 2008

Abstract
The problems of improving the chronometric time-scale are discussed with reference to the chronogram method for the estimation of the Cretaceous-Tertiary boundary. The need for better assessment of stratigraphic errors is emphasized. Suggestions are made on how the position of dated horizons relative to stratigraphic boundaries may be more precisely described. The assumption that stratigraphic thickness is linearly related to time is considered in relation to the likely gaps in the stratigraphic record from a variety of environments.
Magnetic polarity timescales: a new test
Authors: Mussett Alan E. , McCormack Alan G. 
Published: April 2008

Abstract
The magnetic polarity timescale, for times older than a few million years, is based upon sea-floor spreading magnetic anomalies, but the relative ages deduced from the anomalies must be calibrated to allow for non-uniform spreading rates. Calibration is carried out by using well-dated samples of known position in the magnetic timescale, but such samples are rare. This paper presents a method for testing the accuracy of a (portion of a) proposed magnetic timescale, using a body of polarity-plus-age data unconnected with sea-floor spreading anomalies. The method also suggests how a timescale could be improved by displacing or offsetting parts of it by a constant amount.

When this method is used with data for the British Tertiary Igneous Province, the timescale of Harland
et al.
(1989) is found to be superior to those of Harland
et al.
(1982) and Berggren
et al.
(1985) for part of the early Tertiary period (
c.
62–52 Ma). Over this interval the Harland
et al.
(1989) timescale is close to optimum for this data set, but it might be improved by subtracting about 0.25 Ma from the ages of all polarity boundaries.
Quantitative marine sediment core matching using a modified sequence-slotting algorithm
Authors: Thompson Roy , Clark R. M. 
Published: April 2008

Abstract
An automated core correlation procedure has been developed in order to match sequences, such as core logs, based on a mathematical sequence-slotting approach. The programme can be applied to univariate, multivariate or compositional data. In addition to finding the optimal slotting, the programme also quantifies the quality of match. It can also be used to detect sections of the sequences which are tightly constrained, by the match, or only fit together more loosely. An important aspect of any multivariate analysis is scaling. This topic is addressed through a simplex optimization method.
We have used the sequence-slotting method to analyse high quality oxygen-isotope data from ODP Site 658 on the continental slope, west of Cap Blanc, on the northwest African coast. Excellent agreement is found with the global oxygen-18 reference curve and this allows the sediments to be dated. By and large the resulting depth-age profile is very similar to that derived in previous studies. However, small changes in the age estimates between the original stratigraphy and our sequence-slotting lead to major differences in the pattern of sediment accumulation rate.
An hiatus spanning 24 500 SPECMAP years some 50 000 years ago has been proposed in the Site 658 sediments. However, as we find no compelling mathematical evidence for the hiatus, Site 658 may contain an even better stratigraphic record of palaeoclimatic change than previously thought.
Cretaceous foraminiferal events
Authors: Hart Malcolm B. 
Published: April 2008

Abstract
Bioevents range in importance from the first/last appearance of a single taxon, through zonal boundaries of local/regional/international significance, major non-sequences, to (at the highest level) global bioevents. The UK mid-Upper Cretaceous succession is now sampled at better than a 1 m spacing from many localities providing over 2000 samples for detailed analysis and development of high resolution stratigraphy. Examples of detailed correlation are provided for the Albian/Cenomanian boundary, the mid-Cenomanian and the uppermost Cenomanian, while consideration of the complete faunal succession provides information necessary for the monitoring of global environmental change in the Cretaceous.
Devonian goniatite biostratigraphy and timing of facies movements in the Frasnian of eastern North America
Authors: House Michael R. , Kirchgasser William T. 
Published: April 2008

Abstract

The conjunction of detailed goniatite and conodont biostratigraphy has enabled correlation of the Frasnian and adjacent strata of New York with the international standards. A regional goniatite zonation is proposed and as part of the documentation a new Frasnian goniatite assigned to the Triainoceratidae is described as
Wellsites tynani
n.gen. n. sp. The zonation has enabled documentation of the timing and extent of facies movements associated with the Catskill Delta and more easterly deposits in New York State. The broad pattern is one of westward progradation of shallower, more clastic facies. Pulses of deeper water sedimentation, represented by black shale facies indicating anoxic/hypoxic conditions, punctuate the succession and give marker levels. Typically, these black shales initiate shallowing upward cycles. The major pulses are represented by the Tully, Geneseo, Renwick, Genundewa, Middlesex, Rhinestreet, Pipe Creek and Dunkirk units. The cycles enable estimates to be made of deepening against a subsiding shelf; the Rhinestreet Shale represents the greatest. Evidence is given on the regional extent of some of these. International comparison suggests some of these cycles represent global, rather than local events. Microcycles at the Milankovitch Band level also show thin black shales suggesting that climatic control has a bearing on facies developments. General comment is made on the factors controlling local and eustatic changes.
Tectonics and seismic sequence stratigraphy: an introduction
Authors: Williams G. D. 
Published: April 2008

Abstract
The application of sequence stratigraphic models to seismic data is restricted by the vertical and spatial resolution of the data. The fundamental stratigraphic unit of the sequence stratigraphic technique is the seismically distinguished ‘sequence’ although the concept of tectonically related ‘megasequences’ is useful. Basin stratigraphy is controlled to varying degrees by eustatic sea-level change (or base level in lakes), subsidence/uplift (tectonics) and sediment supply. Three main basin types, rift-, wrench-, and thrust-related basins, have distinctive gross stratigraphic architectures. Localized, tectonically controlled subsidence and uplift has a significant control on three-dimensional stratigraphic patterns.
Wind-speed profiles over a reversing transverse dune
Authors: Burkinshaw Jennifer R. , Illenberger Werner K. , Rust Izak C. 
Published: April 2008

Abstract
Wind-speed profiles were measured within 1.5 m of the surface on the windward slope of a 7 m high transverse dune that reverses seasonally with respect to summer easterly and winter northwesterly winds. The profiles were measure along section lines normal to the dune trend at different stages of dune reversal. An independent weather station recorded relatively undisturbed flow at 6 m elevation above the surface.
Flow deceleration at the base of the windward slope and flow acceleration against the middle to upper slope generate non-logarithmic wind-speed profiles. The shape of the dune and the strength of the wind play a major role in determining the behaviour of the wind-speed profile. Airflow compression is enhanced by steeper slopes, resulting in high surface shear stress that causes rapid erosion of the windward slope.
The wind-speed profile can be divided into three zones: a surface shear stress layer, an amplification layer and a recovery layer. It seems that the shear stress that governs sand transport is developed within 5 cm of the surface, in the surface shear stress layer. Future work should concentrate on measurements within this zone.
Luminescence dating of aeolian sands: an overview
Authors: Wintle Ann G. 
Published: April 2008

AbstractAeolian sands are ideal materials for the application of luminescence techniques. Their primary mineral constituents, quartz and feldspars, exhibit a variety of luminescence properties and can be separated for mineral-specific measurements. Individual grains are usually well exposed to light prior to deposition thus enabling their signal to be zeroed at the time of interest.Luminescence is produced either by heating the grains to produce thermoluminescence (TL) or by stimulating at room temperature with wavelengths specific for each mineral component. Only light-sensitive signals are observed in measurements of optically stimulated luminescence (OSL). For feldspars, infra-red stimulated luminescence (IRSL) can be obtained using IR-emitting diodes.Luminescence dating techniques can be applied to inland sand seas, small dunefields, coastal dune systems or periglacial sand sheets. Natural variation in radioactive content in different geographical areas can be used to advantage — sands with a high radioactive content, as found in areas dominated by granitic rocks, are best suited for applications to Holocene dunefields (such as Kelso, California), whereas sands with a low radioactive content, as found in areas containing little feldspar-bearing rock and with much recycled sediment (e.g. Australia), are best suited to applications spanning the last 100 ka.
Entrada Sandstone: an example of a wet aeolian system
Authors: Crabaugh Mary , Kocurek Gary 
Published: April 2008

Abstract
Wet aeolian systems are those in which the water table is shallow and the floors of the interdune flats are within the capillary fringe. Accumulation within a wet aeolian system occurs because of a relative rise in the water table, and these accumulations are characterized by the presence of both dune and interdune-flat deposits. The Jurassic Entrada Sandstone, studied along a 2.7 km traverse in NE Utah, is interpreted as having been formed in a wet aeolian system because of a preponderance of features indicating a shallow water table throughout accumulation of the unit, and regional correlation to marine-sabkha units that vertically stack, then onlap the aeolian-dominated strata. Features indicating a shallow water table and/or evaporites include subaqueous ripple deposits, contorted strata, breccias, collapse features, wavy bedding, foundered sets, loaded set bases, corrugated surfaces, polygonal fractures, ball-and-pillow structures, and trains of small dunes ‘frozen’ in place. Along the traverse, oriented roughly parallel to the predicted palaeoflow from the NNE, sets of cross-strata, bounding surfaces and ‘flat’-bedded strata climb to the SW, while other surfaces and ‘flat’-bedded strata are horizontal. Climb is interpreted to result from the migration of dunes and interdune areas during periods of a rising water table, whereas horizontal surfaces represent super-bounding surfaces formed during periods of static or falling water table, and horizontal ‘flat’ strata represent vertical sabkha accretion. The cross-stratified units consist of compound sets with two scales of cyclicity. The larger, most prominent cyclicity is formed of scalloped bounding surfaces systematically truncating foresets to the SW, and results from superimposed dunes migrating NW and SE along-slope larger bedforms that migrated toward the SW. The smaller scale of cyclicity consists of packages of wind-ripple laminae and grainflow strata truncated by bounding surfaces, and these cycles are thought to represent annual variations in wind direction. Some cross-stratified units are co-sets in which the foresets of the main set can be traced downward into bottomsets consisting of small sets separated by corrugated surfaces. The basal sets are thought to represent small satellite dunes moving along the base of the larger bedforms and across damp interdune floors. The recognition of super surfaces within the Entrada allow the identification of four genetic packages that comprise the formation. Within genetic packages the available sand supply can be estimated, and is considered as a function of the rates of sediment supply and water table fluctuations. These relative rates, coupled with close proximity of the study area to the Jurassic palaeoshoreline and the regional stratigraphic relationships, suggest that fluctuation in relative sea-level controlled the facies architecture seen in the Entrada Sandstone of NE Utah.
Foredune morphology and sediment budget, Perdido Key, Florida, USA
Authors: Psuty Norbert P. 
Published: April 2008

Abstract

Along-shore foredune morphology on the eastern portion of Perdido Key is fitted to a model of foredune development related to sediment budget. The Perdido Key barrier island has a long history of shoreline erosion, up to 2 m a
−1
for over a century. Sediment availability was altered in 1985 because of beach nourishment. Subsequent re-working of the beach fill has transferred sediment in the along-shore direction as well as cross-shore. Over three years of survey data, including passage of three hurricanes, and aerial photo coverage portray the morphological changes in the foredune system and the displacement of the shoreline. Measurements of the changes in a spatial context record sediment redistribution from the nourishment area. Measurements of cross-sectional area changes support the model of foredune enhancement associated with negative sediment budget in the beach. Net along-shore changes of the foredune compare well with the barrier-island foredune development model.
Wind regime and sand transport on a coastal beach-dune complex, Tentsmuir, eastern Scotland
Authors: Wal Abhilasha , McManus John 
Published: April 2008

Abstract
Aeolian processes play a key role in the exchange of sediment between beaches and foredunes in coastal embayments. The present contribution examines the wind regimes characterizing one stretch of temperate coast (Tentsmuir, Scotland), the routing and volumes of the resultant aeolian sediment transport on the beaches and foredunes and presents a summary of wind-induced aeolian bedforms along the coast.
The wind regimes identified in the Tentsmuir area include high-energy seasonal ‘unimodal’ (offshore or onshore) and ‘bimodal’ (both offshore and onshore) patterns. Landward aeolian sand transport results in foredune accretion, whereas seaward and longshore components contribute to beach growth despite reworking by waves at high water. Under the influence of the prevalent wind regimes and the resultant aeolian sediment transport, foredune accretion at Tentsmuir leads to the burial of the landward margin of the beach face.
Genesis and sedimentary structures of late Holocene aeolian drift sands in northwest Europe
Authors: Koster Eduard A. , Castel Ilona I. Y. , Nap Ron L. 
Published: April 2008

Abstract

In northwest Europe local resedimentation of terrestrial deposits by wind from the Neolithic to the present has resulted in widespread accumulation of (aeolian) drift sands. These deposits consist mainly of fine, well-sorted and well-rounded unimodal sands; their mineralogical composition usually reflects local provenance. Palynological studies combined with radiocarbon analyses of the topmost part of buried peat sections reveal no distinct regional phases in drift sand accumulation: ages mainly vary from
ad
500 to 1700. Small remnants of current actively moving drift sands provide evidence of sub-recent deflation and accumulation processes in relation to relief, topsoil and aerodynamic conditions. These are reflected in the sedimentary structures. Principal structures show dune foreset cross-bedding as well as even or wavy sub-horizontal lamination, while occasional strings of granules or small pebbles represent deflation phases. Primary structures resulting from tractional deposition (mainly sub-critical climbing ripple migration) and grainfall deposition, secondary structures (mainly slump, scour-fill and adhesion structures) and non-aeolian structures (mainly caused by rain impact, convolution structures, wetted sand crusts, and foot- or hoof-imprints) have a distinct appearance in lacquer peels and in SEM micrographs. Transport and accumulation of these temperate aeolian sands appear to have occurred under dry, moist and wet conditions.
Tectonic controls upon drainage basin development, river channel migration and alluvial architecture: implications for hydrocarbon reservoir development and characterization
Authors: Leeder M. R. 
Published: April 2008

Abstract
Hydrocarbon reservoirs of fluviatile origin are the product of a number of geological processes acting on a variety of scales. Reservoir characterization must be approached holistically in order to understand these processes fully. Tectonic style produces the macro-architectural framework and influences the behaviour of rivers at a mesoarchitectural scale. Tectonics controls the magnitude, position and development of drainage basins and thus, with climate and local geology, controls the flux of sediment fed into any fluviatile system. Migration of normal faulting may lead to the initiation of drainage basins in previously depositional areas, erosion and reworking thus enhancing reservoir quality. Sediment may be introduced as axial or transverse fluxes. Deducing these contributions in ancient basins establishes basin geometry and the basis for reservoir characterization. Individual river channels are highly susceptible to gradient changes caused by tectonic tilting. This causes slow channel belt migration, incision or sudden diversion (avulsion), depending, in a poorly known way, upon the magnitude of the gradients involved. The alluvial architecture of both tilt-block and growth fold basins is discussed, the latter illustrated by recent studies in the Southern North Sea Basin.
Quantitative regime modelling of fluvial depositional sequences: application to Holocene stratigraphy of humid-glacial braid-plains (Icelandic sandurs)
Authors: Maizels Judith K. 
Published: April 2008

Abstract
This paper introduces a forward, 1–2 dimensional model that predicts fluvial depositional sequences in response to (a) variations in runoff and sediment supply regimes of the source catchment, as well as to (b) fluctuations in relative sea-level controlled by eustatic and isostatic changes. Variations in sedimentology and aggradational history are simulated from accommodation principles and unit power relations of flows of varying sediment concentration. The model is applied to the sandurs of Iceland, which have been subject to large-scale environmental changes over the past 10 ka, associated with deglaciation, isostatic uplift and fluctuations in runoff regimes. Flows include not only normal seasonal ablation runoff from glaciers, but also repeated glacier burst floods generated by sudden volcanic activity. Simulation of 100-year runoff events has allowed prediction of the stratigraphy, sedimentology and geomorphic history of the sandurs. The model has been successfully tested at the smaller Solheimasandur, and then applied to Skeidararsandur, the largest of the Icelandic outwash plains. In both deposits, the predicted stratigraphy and geomorphic history highlight the significance of extreme events for the development of the alluvial sequences. The results indicate that, since alluvial stratigraphy can be so highly dependent on fluctuations in runoff and sediment supply regimes, these factors should be essential components in development of quantitative models of alluvial sequences used for reservoir exploration.