bluuebunny/crossref_metadata_2025_split huggingface dataset:
Paleo-landslides in the Tyee Formation and highway construction, central Oregon Coast Range
Authors: Hammond Charles M. , Meier Dan , Beckstrand Darren 
Published: April 2010

ABSTRACT
Investigation and design-build construction of the Highway 20 realignment through the Oregon Coast Range provides new insight into paleo-landslides of the Tyee Formation and their slope stability. They are widespread, often extending outside of current drainage basins, and much of their morphology has been almost completely hidden by surficial processes. Radiocarbon tests indicate that some of the slide features are older than the testing limits, while other results range from approximately 18,000 to 40,000 yr B.P. The depth of erosion suggests that the paleo-slides may be as old as Pliocene.
Geotechnical models of the paleo-slides, needed to analyze potential construction impacts, are developed from subsurface explorations, construction outcrops, radiocarbon testing, monitoring of geotechnical instruments, and geomorphology revealed by light detection and ranging (LIDAR). The process of predicting landslide boundaries (head scarps, toes, lateral and basal shear zones, etc.) for stability analysis of specific landslides has revealed details of their geologic evolution. This field trip provides background on (a) the investigations that have exposed numerous giant paleo-landslides, (b) findings and interpretations of the age of the landslides and (c) methods that are being employed to mitigate landslide reactivation.
The geology of the Gryphon Oil Field
Authors: NEWMAN M. St. J. , REEDER M. L. , WOODRUFF A. H. W. , HATTON I. R. 
Published: April 2010

The Gryphon Oil Field is located 320 km northeast of Aberdeen in UK Ninth Round Block 9/18b. The field was discovered by Well 9/18b-7 in 1987. This well proved the prognosed Eocene/Paleocene submarine fan system.
To date, Kerr-McGee has drilled 13 wells and 10 sidetracks on the field. In 1990 a 3D seismic survey was acquired over the whole trend, in Blocks 9/18a, 9/18b, 9/23a and 9/23b.
The field is a complex combination structural/stratigraphic trap formed on the northerly plunging nose of the Crawford Ridge. The principal reservoir sands are of the Balder Formation (latest Paleocene-earliest Eocene) and consist of thick, massive, well-sorted, high porosity sands deposited from high-density gravity flows. Water-escape and soft sediment deformation features are common and no primary sedimentary structures are preserved. These sands formed a 'Lowstand Fan' complex within a lowstand systems tract. Areas of sand deposition were determined by the sea floor topography, which was controlled by basement structure, soft sediment deformation and the disposition of older sandbodies.
In order to establish accurate time lines, it is important to identify the relative ages of these sands correctly. This was achieved using detailed biostratigraphy combined with the innovative techniques of 'desanding' and petrophysical analysis of the Balder Tuff.
Overlying the Balder sequence is the earliest Eocene interbedded claystone, silt and sand sequence of the Frigg Formation. These sediments were deposited within the 'Lowstand Wedge' channel/levee complex which built out across the previously deposited Balder Fan.
Oil and gas migrated into the structure via the ridge fault system from the mature Kimmeridge Clay source in the deep graben to the north and east.
Physical modelling of North Sea salt diapirism
Authors: WESTON P. J. , DAVISON I. , INSLEY M. W. 
Published: April 2010

Scaled analogue models provide a powerful tool for investigating progressive deformation. By varying experimental parameters it is possible to produce a wide variety of diapir morphologies and overburden responses.
This paper describes the results of one of a series of experiments which investigates the geometry of overburden sediments around diapirs. The roles of basement faulting and differential sediment loading in the growth of diapirs are assessed. The template for this experiment is provided by analysis of a regional seismic line across the Central Graben of the North Sea.
The model produced two diapir types which formed in different ways. Type 1 diapirs are initiated by a large fault smearing the salt along the fault plane which creates a path for later upward migration of salt to produce small diapiric walls. Type 2 diapirs can be triggered by either tectonic or sedimentary differential loading. They are predicted to be longer lived and more voluminous than Type 1 diapirs and will tend to form isolated circular structures.
F15-A: a Triassic gas field on the eastern limit of the Dutch Central Graben
Authors: FONTAINE J. M. , GUASTELLA G. , JOUAULT P. , de la VEGA P. 
Published: April 2010

The F15-A gas field lies at the eastern margin of the Dutch Central Graben, the reservoirs being found within the overpressured Triassic Main Buntsandstein Formation. The discovery well, F15-4, was drilled in 1985 and was subsequently followed by the two appraisal wells, F15-5 and F15-7. Structurally speaking, the F15 area is located in an intermediate structural compartment between the Central Graben, to the west and the Schill Grund High, to the east. The structure consists of a NNE–SSW-trending turtle back anticline, plunging to the south, with gently dipping flanks to the east and west. Northwards, closure is provided by a NW–SE-oriented erosional trough which cuts deeply into the Lower Triassic and is filled by Upper Triassic/Jurassic sediments.
The primary reservoir is the Volpriehausen Sandstone Member, which is very fine to coarse grained and irregularly cemented by dolomite, anhydrite and halite. Four lithofacies have been recognized: dunal, interdunal, ephemeral fluviatile (distal wadi) and playa-lake related. These facies show a coarsening-upward profile, caused by the successive depositional environments becoming increasingly arid as they grade from playa lake to dunes. A seismic amplitude study was carried out, based on the links between porosity and seismic response at the reservoir level, to identify the areas with the best potential reservoir development.
The field was originally identified and discovered on the basis of two-dimensional seismic data; however, a three-dimensional survey was subsequently shot and has increased the confidence in the structural interpretation. Based on this, one horizontal production well will be drilled in order to put the field on stream in June 1993.
A review of the Triassic play in the Roer Valley Graben, SE onshore Netherlands
Authors: WINSTANLEY A. M. 
Published: April 2010

The Roer Valley Graben is a NW-trending fault-bounded graben marking the eastern limit of the Sole Pit/West Netherlands basins. Sedimentation is composed of four megasequences. The first is a broadly regressive Carboniferous (Visean to Stephanian) sequence which is terminated by the Saalian Unconformity. This is followed by a Zechstein to Middle Jurassic megasequence comprising marine fringe facies and alluvial clastics which grade upwards into open marine sediments of Middle Jurassic age. Megasequence three is composed of syn-rift Upper Jurassic deltaics and is very sparsely preserved due to inversion-related erosion. The final megasequence is composed of post-rift Upper Cretaceous chalk and Tertiary clastics. A major inversion occurred during the Maastrichtian and subsequent erosion removed all the chalk (up to 1000 m) from the graben area but left the sequence on the flanks largely unaffected.
Tectonic development of the basin is dominated by the Late Jurassic rifting phase. This was largely extensional; however, a component of oblique-slip motion is evident and is responsible for the intersecting pattern of N–S- and more NW–SE-trending faults. This structural fabric was subsequently overprinted by NW-trending Cretaceous inversion structures.
Alluvial fan sandstones within the Main Buntsandstein and Röt formations are the primary reservoir target. Repeated rejuvenation of early faults caused renewed influxes of sediments and stacking of the fan sequences. Subsequent diagenesis, primarily associated with the rifting phase, has reduced porosities and permeabilities.
The source rocks for this play are the Westphalian and Namurian coals and shales. These are gently folded and subcrop to the Zechstein-Upper Jurassic sequence across the graben. Peak generation is estimated to have occurred in Early to Late Cretaceous times, prior to the main period of inversion which effectively shut off hydrocarbon generation over much of the basin.
Trap development was initiated during the Early Jurassic and developed further throughout the Late Jurassic rifting phase. However, substantial modifications occurred as a result of the Cretaceous inversion and, more locally, relaxation of the graben during the Tertiary.
The two discoveries at Waalwijk are early rift (Early Jurassic) tilted fault block structures, which were modified during the Cretaceous inversions. Oil and gas charges followed each other into the reservoirs, with gas probably displacing the oil. Other tested trap types include both pure inversion and inverted rift structures. The latter trap type has met with some success, whereas all wells on the former have been dry to date.
The overall success rate for the area is good but not as high as that achieved in the offshore extension of the play fairway. This is primarily a function of the Cretaceous inversion of the Roer Valley Graben which not only downgraded trap integrity and reservoir quality but also shut off hydrocarbon generation.
Permo-Carboniferous and older plays, their historical development and future potential
Authors: GÉRARD J. , WHEATLEY T. J. , RITCHIE J. S. , SULLIVAN M. , BASSETT M. G. 
Published: April 2010

The plays reviewed in this paper are those developed where Permian and older organic-rich rocks have been preserved. These have sourced approximately 60 × 109 barrels of oil equivalent in the area under consideration, in oil, gas and oil shale developments, and range in age from the Cambrian to Permian. They were deposited in marine to terrestrial environments, and their development was controlled by the evolution of life forms, changes of relative sea-level and the plate tectonic configuration of the depocentres. Clastic and carbonate reservoir distribution was controlled by tectonic phases and relative sea-level variations. Trapping is by both structural and stratigraphic mechanisms. Preservation of source and reservoir potential is dependent on a lack of intense orogenic activity and should, therefore, be sought away from zones of intense tectonism that post-date potential source rocks.
Proven play types are extrapolated to under-explored areas where similar potential may exist, and the potential of methane extraction from coal beds is suggested.
The late Carboniferous ‘Barren Red Bed’ play of the Silver Pit area, Southern North Sea
Authors: BESLY B. M. , BURLEY S. D. , TURNER P. 
Published: April 2010

A multidisciplinary study of the gas-bearing Westphalian red bed sequence of the Southern North Sea is presented. Comparison with analogous fades in Carboniferous sequences in the UK onshore and the eastern Netherlands suggests that two distinct alluvial red bed units are present, one of Westphalian C and one of Westphalian D age. Development of red pigment in these units was largely the result of contemporaneous pedogenesis. Interpretation of the stratigraphy is complicated by the widespread occurrence of reddening caused by penetrative weathering, both during the Carboniferous and related to the formation of the sub-Permian unconformity.
Gas reservoirs are present in sandstones in the Westphalian C red bed unit. This unit has higher net:gross ratios and better poroperm characteristics than the underlying Coal Measures. The better reservoir quality in the red bed unit is largely influenced by late diagenetic alteration related to hydrocarbon migration.
A sedimentological and diagenetic model for the formation of the Westphalian C red bed unit implies that this unit is likely to have a distinctive reservoir architecture, which, together with better reservoir qualities, distinguishes it from the hydrocarbon play in the underlying Coal Measures.
The Bruce Field
Authors: BECKLY A. , DODD C. , LOS A. 
Published: April 2010

The Bruce Field is a giant gas condensate accumulation which lies on the western side of the Viking Graben at the northern end of the Beryl Embayment. Although discovered in 1974, the Annex B was not approved until 1990 by which time the field had been shown to extend across three exploration licence blocks (9/8a, 9/9b and 9/9a) and to be extremely complex. There are three main elements to the complexity: structure, reservoir distribution and hydrocarbon charge.
The major structural elements are the Western Flank (a rotated fault block) and the Eastern High with a central low between, the Central Panel; however, relatively poor seismic data quality makes detailed structural interpretation difficult. Each of these structural elements has a different hydrocarbon–water contact, with a proven range of nearly 500 m. The shallowest contact is found on the Eastern High and though the contact in the central low is nearly 350 m deeper, pressure data indicate that the gas leg is in communication with that in the Eastern High. The distribution of the main reservoir, the Middle Jurassic Beryl Group, and the magnitude of the unconformity that underlies it, appear to be controlled by earlier faults which are cross-cut by the present structure. The result of these complexities is that long hydrocarbon columns can be found in the structural lows, and thick reservoir successions can occur on the structural highs.
Geological aspects of horizontal drilling in chalks from the Danish sector of the North Sea
Authors: FINE S. , YUSAS M. R. , JØRGENSEN L. N. 
Published: April 2010

Field development in the Danish chalk fields using horizontal wells has increased productivity in low-permeability reservoirs, maximized fracture intersection with the wellbore and optimized oil rim development.
Horizontal drilling requires extraordinary planning in order to achieve proper well placement. Unfortunately, the available data from logs, shows and field mapping does not always give consistent results and adjustments to the planned well trajectory must be made. A review from Mærsk Oil experience indicates that despite uncertainties related to such factors as structural dip, fluid levels and faults, objectives can nevertheless be satisfactorily attained.
Several techniques incorporating 3D seismic, pilot holes, wellsite biostratigraphy, wellsite geology and logging while drilling are utilized. They have proven crucial for recognizing and implementing rapid changes in the prognosed well trajectory where necessary. Our experience further emphasizes the absolute necessity of ongoing communication between qualified wellsite and office personnel during both the planning and operational phases of drilling a well.
The first deepwater well in Norway and its implications for the Upper Cretaceous Play, Vøring Basin
Authors: KITTILSEN J. E. , OLSEN R. R. , MARTEN R. F. , HANSEN E. K. , HOLLINGSWORTH R. R. 
Published: April 2010

Well 6707/10-1 in the Nyk High licence PL218 was the first exploration well to be drilled in the deepwater Vøring Basin. It targetted a prominent tilted fault block trap with a pronounced flatspot conforming to structure. The pre-drill evaluation highlighted gas-over-water, with the gas–water contact (GWC) at the flatspot, as the most likely case. Given the water depth of 1274 m and the remote location of PL218 this case was not commercially attractive. However, seismic attributes indicated the possibility of an oil leg below the flatspot and this gave the necessary encouragement for drilling the well. The presence of an oil-prone source rock, and more importantly, its maturation relative to trap formation, were seen as the main pre-drill risks.
The well found an excellent quality Santonian to Early Campanian age reservoir of more than 1000 m thickness and a 156 m thick column of dry thermogenic gas. Poor oil shows were recorded on core chips and small amounts of heavier hydrocarbons were extracted from the core. This is seen as an important finding of the well, although the concern over the timing of maturation and migration relative to trap formation still remains.
Reservoir presence is considered low risk for future wells in areas where the distinct seismic character can be tied to the Nyk High well. The sandy nature of the Santonian to Lower Campanian section does, however, also mean that traps relying on fault seal (e.g. hanging wall traps) are high risk and that the possibility for stacked pools is reduced compared to the pre-drill view.
The flatspot does not match the current free-water level and is interpreted to represent an earlier, deeper gas–water contact. The reason why the contact moved up is not yet fully understood and may be a result of either late fault reactivations or gas compression during the Plio-Pleistocene burial. Late fault movement is a general concern in the Vøring Basin, with faults in some areas cutting up to seabed. If the contact moved up because of gas compression, it has the implication that gas charge to the trap, and Nyk High area, had ceased in the Plio-Pleistocene.
Evidence for pre-Cretaceous rifting in the Rockall Trough: an analysis using quantitative plate tectonic modelling
Authors: COLE J. E. , PEACHEY J. 
Published: April 2010

Plate tectonic reconstructions of the North Atlantic Margin, west of Britain and Ireland have been generated using computer modelling software. A particular emphasis has been placed on the timing of rift phases within the Rockall Trough as this has significant implications for the distribution of Mesozoic hydrocarbon source rocks. A variety of geophysical and bathymetric data have been integrated to update existing plate boundary definitions, which has improved the resolution of the modelling. Forward and reverse modelling studies were then employed to quantify the amount of rifting in the Rockall Trough. Present-day plate outlines were contracted to discover the amount of intra-plate deformation required for a geometric fit. These results were then compared with the effects of contracting plate outlines by specified amounts usingβfactors from independent datasets from the Rockall Trough and adjacent areas.The reconstructions suggest that the majority of rifting occurred in the mid to Late Cretaceous and continued into the Eocene. They also indicate the occurrence of at least one episode of pre-Cretaceous rifting corresponding to a β factor of 1.6. The results of this study are corroborated by an independent structural and stratigraphic basin modelling project that examined the crustal evolution of the Rockall Trough. This produced a range of model solutions which, when constrained by data from this study and elsewhere, suggests a best-fit solution which requires a substantially thinned pre-rift crust, best explained by a pre-Cretaceous basin. The implications of the presence of an older rift system are favourable for hydrocarbon exploration in the area. Regionally there are important petroliferous Triassic to Jurassic rift systems and it is likely that an older rift system in the Rockall Trough would be of a similar age with significant potential to be hydrocarbon bearing.
Structural evolution of the Slyne Trough
Authors: DANCER P. N. , ALGAR S. T. , WILSON I. R. 
Published: April 2010

The Slyne Trough is a Mesozoic half-graben which lies approximately 60 km offshore west of Ireland, in water depths of 200–400 m. It is part of a Mesozoic basin system which stretches from the West of Shetland basins in the north to the Porcupine Basin in the south. The Slyne Trough can be divided into three asymmetric half-graben, containing a thick section of Permo-Triassic and Jurassic sediments, which are unconformably overlain by a thin Tertiary/Quaternary section. This subdivision of the basin is controlled by the presence of a number of complex transfer zones which show strike-slip movement and post-Miocene reactivation, and are often characterized by zones of poor quality seismic data.
The major rifting episode in the Slyne Trough occurred during the Middle Jurassic. Up to 2.5 km of Aalenian to Bathonian sediments are preserved in a number of NNE–SSW trending half-graben sub-basins. These reverse their dip directions (polarity) from east to west at transfer zones, which cut across the Slyne Trough. This main rifting episode is interpreted to have been linked to the proto-North Atlantic rifting process, the episodes of rifting being related to the relative motion of the Rockall Plateau with respect to Eurasia.
’NW European Gas Atlas’ – new implications for the Carboniferous gas plays in the western part of the Southern Permian Basin
Authors: GERLING P. , GELUK M. C. , KOCKEL F. , LOKHORST A. , LOTT G. K. , NICHOLSON R. A. 
Published: April 2010

The ‘Northwest European Gas Atlas’ comprises maps on characteristics (e.g. molecular and isotopic compositions) of natural gases in northwest European gas fields, on the distribution and facies of source and reservoir rocks, on maturities, and other relevant geological information. The mapped area includes the entire Southern Permian Basin from the Southern North Sea to central Poland. Palaeozoic source rocks in the Dinantian, Namurian and Westphalian have been identified in the western part of the Southern Permian Basin. They contain kerogens of marine (Type I and II) and continental origin with TOC contents as high as 12%.
There are two Carboniferous production provinces in this area: C1 in the Southern North Sea and C2 in the area along the border between The Netherlands and Germany. The natural gas in most of the C1 production province has methane contents of more than 80%; in most of the C2 province even more than 85%. Nitrogen is the second most abundant constituent in both provinces. Carbon dioxide plays a significant role only locally in the areas of intrusive rocks. Isotope data show that the source of the natural gases in the C2 province is a terrestrial rock (Westphalian). In the C1 province, the gases are of mixed origin: a low maturity terrestrial source rock (Westphalian) and a more mature marine source rock (?Namurian).