bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analogue and numerical modelling of accretionary prisms with a décollement in sediments
Authors: Yamada Yasuhiro , Baba Kei , Matsuoka Toshifumi 
Published: April 2008

Abstract
Active accretionary prisms at subduction margins generally include a horizontal detachment, décollement, within the sedimentary pile. The décollement, and its extension to undeformed regions (i.e., proto-décollement), corresponds to a layer of high fluid pressure. The deformation of the prisms, including such an anomalous layer, can be modelled and examined using analogue experiments and numerical simulations. Both these methods approximate the material under deformation as an assembly of particles (grains). The décollement layer is found to be best modelled by intercalating a layer with smaller internal frictional coefficient than the surrounding materials corresponding to the sediments. Our analogue experiments with dry sand and microglass beads reproduce structural geometry similar to that of interpreted seismic profiles at the toe of the prisms. Thrust faults originate from the horizontal beads layer and propagate upward with a constant angle of about 30°. Each of the fault bends produces a series of minor back thrusts. A particle image velocimetry (PIV) analysis revealed that the fault activity is characterized by intermittent reactivation and segmentation. The numerical simulations based on the distinct element method (DEM) were performed with similar kinematic settings and material properties as the analogue experiments. The numerical simulation results not only reproduce similar geometries as in the analogue experiments, but also show that the particle assembly experiences temporal variations in the deformation velocity and stress field as deformation propagates. This might be related to stick-slip motion of the frictional fault surfaces, which is a common feature of faulting during accretionary processes at subduction margins.
Integrated four-dimensional modelling of sedimentary basin architecture and hydrocarbon migration
Authors: Clarke S. M. , Burley S. D. , Williams G. D. , Richards A. J. , Meredith D. J. , Egan S. S. 
Published: April 2008

Abstract
Structural geometries, faults and their movement histories, together with the petrophysical properties of flow units, are some of the major controls on hydrocarbon migration pathways within sedimentary basins. Currently, structural restoration, fault-seal analysis and hydrocarbon migration are treated as separate approaches to investigating basin geohistory and petroleum systems. Each of these separate modelling approaches in their own fields is advanced and sophisticated but they are not compatible with each other. Lack of integration produces incorrect palaeogeometries in basin models and inaccurate migration pathways.
A combined structural restoration and fault-seal analysis technique, integrated with fast hydrocarbon migration pathway modelling code based on invasion percolation (IP) methods, is described. These modelling methods are used to develop a 4D basin modelling workflow in which evolving basin geohistories and geometries form an integral part of the analysis of hydrocarbon migration and trapping. By combining structural restoration and 3D fault-seal analysis it is possible to investigate the evolution of structurally complex traps through time. Integration of these techniques with a numerically fast migration pathway modelling technique allows hydrocarbon migration pathways and accumulations to be modelled through the evolution of the basin with time. Additionally, the effects of uncertainties in structural geometry, fault seal or any of the model input parameters can be explored using a risk-driven approach to modelling.
These methods are demonstrated using synthetic, computer generated, 3D models and a well-constrained model of the Moab Fault, Utah, USA. Comparison of modelled structural geometries, fault-seal properties and predicted trapped hydrocarbons with outcrop data is used to validate the integrated modelling approach. The validated techniques are then applied to a seismically derived, 3D model from the southern North Sea, UK, to demonstrate how an integrated, risk-driven approach to modelling allows the effects of uncertainties in the distribution of hydrocarbon accumulations to be investigated.
3D modelling of rifting through a pre-existing stack of nappes in the Gulf of Corinth (Greece): a mixed analogue/numerical approach
Authors: Le Pourhiet L. , Mattioni L. , Moretti I. 
Published: April 2008

Abstract
The Gulf of Corinth is a young (1 Ma) active rift currently extending N00, which displays significant contrasts in structural style along strike. A possible explanation for these variations is the presence of the Phyllades nappe in the basement of the western part of the Gulf. Previous 2D thermo-mechanical models have shown that a strong strength contrast between this metamorphic unit and the rest of the basement can explain the kinematics and the spacing of the faults in the western part. The rift, however, displays a wide variety of 3D features (e.g., en echelon faulting, N30 transverse normal faults) that cannot be taken into account using 2D modelling. To obtain 3D insights into the role of an inherited dipping weakness zone, analogue (sand and PDMS) experiments based on the results of the 2D numerical thermo-mechanical model have been performed. The analogue models show that a 30° discrepancy between the dipping direction of the weak nappe and the direction of extension leads to the formation of en echelon and N30 striking normal faults as observed in the Gulf of Corinth. However, fault spacing and graben width completely misfit both the data and the results of the thermo-mechanical models on which the analogue experiments were based. In order to understand those differences, numerical mechanical benchmarks of the analogue experiments have been run to test different factors (3D lateral displacements, values of the elastic parameters and bottom boundary conditions) that could have affected the dynamics of the analogue model. This approach highlights, for our case study, that the misfits are mostly related to the lack of isostatic compensation at the base of the analogue experiments.
Lower crustal rheological expression in inverted basins
Authors: Sandiford Mike , Hansen David L. , McLaren Sandra N. 
Published: April 2008

Abstract
Although lithospheric modelling has provided extraordinary insights into the processes that shape the continental crust, considerable uncertainty surrounds the basic rheology that governs behaviour at geological timescales. In part, this is because it has proved difficult to identify the geological observations that might discriminate, or unify, models of lithospheric rheology. In particular, the relative strength of lower crust and upper mantle remains a contentious aspect of continental lithospheric rheology. We show that various models for lower crustal rheology may produce distinct patterns of inversion in extensional sedimentary basins, consistent with some of the observed natural variability of inversion styles. Inversion of basin interiors, as is common in European Mesozoic basins, is favoured by a lithospheric rheology more sensitive to lateral thermal structure than to changes in the depth of the Moho, consistent with there being little strength contrast between the lower crust and upper mantle in these settings. In contrast, inversion of basin margins, particularly involving basinward verging structures, is consistent with a rheological sensitivity to the depth of Moho as would apply for a lower crust much weaker than the upper mantle. We use an example from central Australia to demonstrate this latter response, together with thermochronologic data that suggests that a relatively weak lower crust in this setting may reflect abnormally high geothermal gradients.
Using an elastic dislocation model to investigate static Coulomb stress change scenarios for earthquake ruptures in the eastern Marmara Sea region, Turkey
Authors: Muller Jordan R. , Aydin Atilla , Wright Tim J. 
Published: April 2008

Abstract
Using an elastic dislocation model, we incorporate a historical earthquake catalog, mapped Marmara Sea fault traces, and fault slip distributions for the 1999 Izmit earthquake inferred from InSAR and GPS data to determine various stress change scenarios crucial for evaluating future earthquake potential in the eastern Marmara Sea. We have tested six plausible past rupture configurations arising from the uncertainty in the location of the western termination of 1999 Izmit earthquake rupture and the location of the 1963 Yalova earthquake rupture. Coulomb stresses calculated are increased on the Princes’ Islands, Çinarcik, and Armutlu fault segments in each case. In four of the six plausible configurations of previous ruptures, the Çinarcik fault receives the greatest average stress change. In one other configuration, the average stress increase on the Princes’ Islands fault is greatest. In another, the stress changes on the Çinarcik and Princes’ Islands faults are comparable. Moreover, we show that rupture initiating on either the Princes’ Islands or Armutlu faults would be favoured to propagate onto the Central Marmara, or Imrali fault, respectively, based on the favourable geometries of the respective fault intersections. Rupture initiating on the Çinarcik fault, however would be limited to a much shorter length based on its mapped western termination. Therefore, while the earthquake-induced stress changes may, in most cases, be greatest on the Çinarcik fault, an earthquake initiating on this fault segment may produce a shorter cumulative rupture compared to rupture initiated on the two other major eastern Marmara Sea fault segments. These results are encouraging for the use of geomechanical modelling tools in addressing uncertainties inherent in most geological and geophysical data applied to earthquake-related problems.
Oil reservoirs in foreland basins charged by thrustbelt source rocks: insights from numerical stress modelling and geometric balancing in the West Carpathians
Authors: Nemčok Michal , Henk Andreas 
Published: April 2008

AbstractThe West Carpathian thrustbelt advanced northeastwards over the European Platform. Its thrust sheets comprise sediments of the Early Cretaceous rifts that evolved on a passive margin of the European Platform, the Late Cretaceous-Paleocene basins formed by rift inversion, and the Eocene-Oligocene flexural basin. Geochemical analyses established a clear link between pooled oils in the foreland and the Oligocene Menilite Formation inside the thrustbelt. In order to understand the driving forces for this oil migration scenario, finite-element models of fault-propagation and fold-bend folds are used to study the mean stress distribution in the thrust sheets and the foreland. Mean stress has a profound control on the pore fluid pressure through the relationship affected by sediment porosity, and sediment skeleton and fluid compressibilities. Modelling results suggest that only fault-propagation folds are capable of generating foreland-directed mean stress gradients as they are characterized by a large foreland area of decreased mean stress, by coupled increased/decreased mean stress areas on advancing/receding sides of the ramp tip, and an overall mean stress decrease inside the thrust sheet in the direction towards the foreland. This interpretation is in accordance with the dominant fold-and-thrust style in the Western Carpathians inferred from balanced cross-section restoration. It shows that frontal fault-propagation folding was active during the late Oligocene-Early Miocene, providing an effective tectonic driving force for hydrocarbon migration from source rocks inside the thrustbelt towards reservoirs in the foreland.
Relation between effective friction and fault slip rate across the Northern San Andreas fault system
Authors: Provost Ann-Sophie , Chéry Jean 
Published: April 2008

Abstract
The San Andreas Fault system is a complex tectonic ensemble that accommodates most of the relative plate motion between the Pacific and the North American plates. The structure and rheological properties of the faults vary along the plate boundary and lead to the distribution of deformation that we observe today. In order to learn more about the mechanical behaviour of such a fault system, a model of the northern California fault system is built, constrained by heat flow data, GPS and palaeoseismological measurements of slip rates (on the San Andreas, the Maacama and Bartlett Springfaults), and stress orientations. Our basic assumption is that the upper crust has a high frictional strength and that major faults represent weak zones with a lower effective friction. Several combinations of effective fault frictions on the three major faults of the system in the model are tested. We find that slight variations of the effective friction angle on one of the three active strands lead to an important redistribution of slip rates through the system. If present in nature, this fault behaviour could explain why fault slip rates vary in time, as suggested by slip rate variations over geological scales in intracontinental fault systems.
Stratigraphic traps in the Tertiary rift basins of Indonesia: case studies and future potential
Authors: Atkinson Christopher , Renolds Michael , Hutapea Oskar 
Published: April 2008

Abstract
Stratigraphic traps are often regarded as one of the most risky exploration targets and are frequently the most difficult trap type to secure management support for drilling. This is despite their frequent occurrence in many basins, in particular the mature onshore basins of North America. The critical factors required for the development of stratigraphic traps are the presence of a fully charged petroleum system, favourable basin and reservoir architectures, low dips in the accumulation zone and good seal integrity. These factors commonly occur in the Palaeogene rift basins of Indonesia and consequently, since the early 1990s stratigraphic traps have often accounted for the majority of recently discovered fields.
The Palaeogene rifts of Indonesia are prone to the stratigraphic trapping of hydrocarbons simply because they possess an almost perfect petroleum system in which traps of this type can form. Every rift has a similar history beginning with a syn-rift phase, which primarily provides source rocks of various types as well as reservoir sandstones. This is followed by a thermal sag phase (‘early post-rift’) where better quality reservoir sandstones and sometimes reef carbonates are found. The ensuing transgressive phase (‘late post rift’) guarantees a marine shale regional seal. This seal is most impressive at the Minas Field in Central Sumatra where 6 billion barrels of oil are trapped at only 600 metres depth with no surface oil seeps. The various late Tertiary ‘orogenic’ phases trigger migration of hydrocarbons generally up the flanks of the rifts as well as creating structures at shallower levels. Sometimes this structural activity is so intense that the regional seal is breached causing hydrocarbons to migrate into these shallower structures where major accumulations have been found. However, where the seal is not breached the hydrocarbons must still be trapped below it on the flanks of the rift. The giant Widuri and Kaji Semoga fields are perfect case history examples.
There is no doubt that in Indonesia the ‘easy oil’ has already been found in large 4-way dip closures or classic Sunda Fold inversion structures. However, it is contended that there is still a huge potential for finding large reserves in stratigraphic traps in basins with the right characteristics. In this context, two largely unexplored basins within the Asahan Offshore PSC, North Sumatra and the Biliton PSC, West Java are discussed. Both these areas exhibit all the ingredients required for successful stratigraphic trap discoveries but both remain at the present day undrilled for this play type.
The importance of stratigraphic plays in the undiscovered resources of the UK Continental Shelf
Authors: Stoker S. J. , Gray J. C. , Haile P. , Andrews I. J. , Cameron T. D. J. 
Published: April 2008

Abstract

This paper analyses the statistics of existing United Kingdom Continental Shelf (UKCS) fields and discoveries as a means of assessing which plays are likely to contain the greatest untapped potential for stratigraphic traps. Current Department of Trade and Industry (DTI) estimates put the maximum discovered ultimate recovery of the UK at 50 billion (× 10
9
) barrels of oil equivalent (BBOE); estimated technically recoverable undiscovered resources are between 4.1 to 21.3 BBOE, based on a prospect mapping approach.

As of end 2003, 82% of the oil and gas fields and discoveries on the UKCS have been found in structural traps; 12% have been found in combination structural/stratigraphic traps and only 6% in stratigraphic traps. The majority of stratigraphic traps and combination traps occur in association with syn-rift (Upper Jurassic) and post-rift deep-water plays. There has been relatively little direct exploration for stratigraphic traps until recently, and a number of the major discoveries in stratigraphic traps were found by chance. Few substantial untested structural traps remain in the UK North Sea except at considerable depth with associated risks. We estimate that perhaps 50% of the UKCS undiscovered resources are located in stratigraphic or combination traps, principally within syn- and post-rift deep-water sandstone plays.
Lower Cretaceous deep-water sandstone plays in the UK Central Graben
Authors: Milton-Worssell R. J. , Stoker S. J. , Cavill J. E. 
Published: April 2008

Abstract
Up to the present, exploration of the UK Lower Cretaceous deep-water sandstone play has been confined largely to the Moray Firth basins. The Lower Cretaceous of the Central Graben area has been modelled previously as predominantly shale-prone, and hence unattractive to exploration. There is a growing realization that this may not be the case. Since seismic imaging of Lower Cretaceous sandstones is known to be poor whether hydrocarbon-bearing or water-wet, a robust depositional model must be constructed from well and regional geological data in order to predict sandstone distribution and geometry, and hence to aid identification of potential hydrocarbon traps. Of the hundreds of wells drilled in the Central Graben area that targeted deeper Jurassic-Triassic reservoirs, virtually all have been located on the flanks of the graben, or on intra-graben highs. However, 71 of these wells have proved sandstones or traces of sandstone within the Lower Cretaceous, giving grounds for optimism that more substantial deep-water sandstone developments may be present within the graben depocentres. Twenty-six leads have been identified within these depocentres; most of these are located within stratigraphic traps in interpreted detached basin floor fans.
Extrusive sandstones (extrudites): a new class of stratigraphic trap?
Authors: Hurst Andrew , Cartwright Joseph A. , Huuse Mads , Duranti Davide 
Published: April 2008

Abstract
Extrusive sandstone bodies are identified as entirely stratigraphic traps associated with sand injectites. They may be difficult to recognize but have four-way dip closure and are invariably connected through underlying lower permeability strata to parent sandbodies by sandstone dykes or transgressive sills that belong to sand injectite complexes. Extrusive sandstones (extrudites) constitute an immature exploration target, which is largely untested by deliberate exploration wells. Using seismic data alone, the distinction between extrudites and intrusive sills, and between extrudites and depositional sands, may be problematic. Sedimentological criteria may make differentiation possible when core is available. Extrudites are likely to have been drilled and misinterpreted as conventional deep-water turbidites within deep-water systems affected by sand injection.
Rhodalgal/bryomol assemblages in temperate-type carbonate, channelized depositional systems: the Early Miocene of the Sarcidano area (Sardinia, Italy)
Authors: Bassi Davide , Carannante Gabriele , Murru Marco , Simone Lucia , Toscano Francesco 
Published: April 2008

Abstract
During Aquitanian-Burdigalian times, temperate-type carbonate-siliciclastic successions were deposited in basins located on the graben and half-graben along the Oligo-Miocene Sardinia Rift Basin (Sardinia, Italy). In one of these basins, the Isili Basin, rhodalgal/bryomol limestone was deposited in a temperate-type carbonate depositional system in which a shallow carbonate factory, a marginal tributary belt and a main channel were identified. In this paper, the Isili Limestone is described in terms of biogenic components and taphonomic characterization. To understand the palaeoecology of the depositional settings and the related palaeoceanographic controls, the coralline algal assemblages were differentiated according to coralline growth forms, rhodolith shapes, rhodolith inner structure and taxonomic composition. In addition, a first analysis was carried out in order to discriminate among the different bryozoan and mollusc assemblages present in different localities corresponding to different palaeoecological settings. The results obtained provide fundamental support for palaeoenvironmental reconstruction that combines palaeobiological analyses (i.e. rhodolith characteristics, bryozoan growth forms, taphonomic features) with previous physical (sedimentological and geometrical) observations. This allows a more detailed reconstruction of the complex relationships between the different sectors of the sedimentary system: the carbonate factory, the smaller erosive tributary channels and the deeper main channel.
Models of temperate carbonate deposition in Neogene basins in SE Spain: a synthesis
Authors: Braga Juan C. , Martín José M. , Betzler Christian , Aguirre Julio 
Published: April 2008

Abstract
Upper Miocene (Tortonian-Messinian) to Lower Pliocene (Zanclean) temperate bioclastic limestones occur in the Betic intermontane basins mixed with diverse proportions of siliciclastics. Components are mostly originally calcitic skeletons of invertebrates (especially bryozoans and bivalves) and coralline algae. Carbonate mud content is usually low and cementation is generally weak. These temperate carbonates formed in ramps. The depositional surface profile and local hydrodynamic conditions in each example controlled the occurrence of diverse facies at similar positions within the ramp. Shallow-water facies are well represented and formed in beaches and backshore lagoons, spits, rocky shores and submarine cliffs. Shoals developed seawards of shore deposits; the relatively quiet environments basinwards of the shaosl were the areas of maximal carbonate production (factory facies). The lack of early lithification favoured mobilization of skeletal particles. Waves and currents during storms transported carbonate grains landwards from the factory areas to shoals, spits and beaches. Skeletal grains were also transported downslope along the ramp. Re-deposited carbonates occur within basinal marls in submarine lobes and channels fed by channels cross-cutting and excavating the platform sediments. The absence of hermatypic corals and calcareous green algae in shallow-water deposits suggests cool surface water temperatures during carbonate formation. Large benthic foraminifers and oxygen stable isotope values indicate winter surface water temperatures of 16–17°C.