bluuebunny/crossref_metadata_2025 huggingface dataset:
Methane hydrates: problems in unlocking their potential
Authors: LONG D. , JACKSON P. D. , LOVELL M. A. , ROCHELLE C. A. , FRANCIS T. J. G. , SCHULTHEISS P. J.
Published: April 2010

Methane hydrates have been recovered or postulated for virtually all continental margins around the world and a few areas onshore. Volumes of about 2 × 10
14
m
3
have been estimated for this potential resource. However, only a few sites have been suggested offshore northwest Europe, despite extensive hydrocarbon exploration and academic studies of the margin. Reasons for this anomaly are unclear. To aid the search a new hydrate stability zone map for the UK is presented. As well as identifying a resource, hydrate studies are also important in assessing geohazards to deep-water exploration and development. Stability, processes and distribution information contribute to the wider climate change debate as methane hydrates are estimated to hold a significant part of the global organic carbon budget.

To quantify reserve potential and to identify suitable methods of methane extraction, a full understanding of how hydrates are held within sediments is required. Although modelling (physical and theoretical) can contribute to an understanding, it is important to evaluate
in situ
conditions to ‘ground truth’ acoustic data and imagery. How hydrate is held and its control of dynamic geotechnical behaviour within the sedimentary system is still very poorly understood. Parameters such as pore size, fluid saturations, sediment mineralogy and cementation will affect hydrate morphology, distribution, behaviour (during dissociation) and potential recovery from porous media. Assessing physical parameters and processes under
in situ
conditions provides the next step along the route to exploiting methane hydrates as a resource. The requirement to recover samples under
in situ
pressures and temperature conditions provides a significant technological challenge that has been attempted over the last few years with some success. Currently, the European HYACINTH project is developing systems to recover, analyse and manipulate hydrate-bearing sediments under
in situ
pressures and temperatures. On Leg 204 of ODP this equipment was used for the first time to recover hydrate cores at
in situ
pressure, transfer them without loss of pressure into laboratory chambers and to log them geophysically. As the database of
in situ
properties grows, integrated laboratory studies of synthetic sediment-hosted hydrates can be developed to provide important benchmarking, which is crucial for the study of rare natural core samples.
The Atlantic Margin from Norway to Ireland: geological review of a frontier continental margin province
Authors: SHANNON P. M. , FALEIDE J. I. , SMALLWOOD J. R. , WALKER I. M.
Published: April 2010

The deep-water Atlantic Margin of NW Europe is a lightly explored frontier province. During the past six years there has been a modest level of exploration drilling with mixed results. However, a lot of new geological and geophysical data has helped in the understanding of the crustal structure and the tectonostratigraphic development of the region. The 27 papers in this thematic section illustrate a cross-section of the new information and ideas and highlight remaining questions regarding the geological development and petroleum prospectivity of the region. Geophysical data provide evidence for depth-dependent stretching across the continental/oceanic margin and in several of the deep-water basins. However, the associated thermal anomalies and volcanism are still poorly understood. New drilling results from the margins of the Rockall Basin prove the presence of Mesozoic and Cenozoic strata. Together with geophysical data, well results demonstrate that the Cenozoic evolution was accompanied by significant tectonism. Examples of new fields illustrate the petroleum potential and remaining risks in the region. A number of key uncertainties and remaining questions centre on the mechanisms of passive margin basin formation. These basins, characterized by significant crustal thinning, appear to differ in their formation and in their structural and sedimentary character, from low-extension, conventional intra-plate basins. The resultant thermal history and play types are also different.
A Middle to Late Miocene compression phase along the Norwegian passive margin
Authors: LØSETH H. , HENRIKSEN S.
Published: April 2010

A Middle to Late Miocene compression phase has been documented along the Norwegian margin from 62°N to 68°N. Reverse faults and inversion domes are numerous on the 300 to 450km wide central mid-Norwegian margin, but are only locally observed on the Møre and Lofoten margins. A major regression forced the coastline of the syn-tectonic Kai Formation 50–150km west of the present coastline and a genetic link between the regression and the smaller-scale contraction structures is observed. Long wavelength (200–300 km) lithospheric bulging is suggested to explain the coastline regression at the onset of the compression phase. The position of the regressed coastline suggests that the continent–shelf transition guides the lithospheric buckling such that the thicker crust segment is uplifted. Long wavelength folding may account for additional crustal shortening along the sharp crustal transitions on the Lofoten and Møre margins. It is suggested that the Norwegian onshore domes were formed during at least two independent stages – a Middle to late Miocene compression related uplift and later regional glacial isostatic uplift. The syn-tectonic Kai Formation fills in the depressions around the contraction-related structures and is dated as late Middle to Late Miocene. It is suggested that both the Utsira Formation and the assumed northern equivalent, the Molo Formation, were deposited after the compression event and, thus, are mainly early Pliocene in age. The Middle to Late Miocene compression phase is observed throughout the North Atlantic and the sea-level fall at the initiation and rise at the termination corresponds with significant shifts in climate.
Sedimentology and geochemistry of Late Jurassic organic-rich shelfal mudstones from East Greenland: regional and stratigraphic variations in source-rock quality
Authors: STROGEN D. P. , BURWOOD R. , WHITHAM A. G.
Published: April 2010

Late Jurassic (Late Oxfordian–Early Volgian) sediments exposed across a wide area of East Greenland are dominated by organic-rich mudstones and sandy mudstones and reach a maximum thickness of 500 m. The facies are characterized by parallel-laminated, generally unbioturbated mudstones, in some cases containing thin sandstone laminae. Deposition occurred in an offshore shelf environment, with water depths difficult to constrain. In the northern sections, heterolithic, sandier units occur at the base of the mudstone succession, marking a gradual transition from the underlying shallow-marine sandstones. Mudstones in the south (Milne Land–Jameson Land) are more oil prone, with greater dilution by terrestrially derived Type III/IV kerogen in the north (Wollaston Forland–Kuhn Ø). In both areas there is an improvement in source-rock quality and oil proneness from proximal to distal settings, with the geochemical data in agreement with the palaeogeographical interpretation. In the south, the Late Kimmeridgian to Early Volgian marks the maximum westward transgression of source-rock facies and also represents the richest source interval. In the north there is a decrease in sand content through the Late Oxfordian–Kimmeridgian, although trends in source-rock quality are less clear. Whilst the northern sections are predominantly gas prone, some marginally oil-prone mudstones do occur. The Vøring and Møre basins were situated immediately to the east of Greenland in the Late Jurassic. The presence of a continuous blanket of potential source rocks in East Greenland and the eastward improvement in source-rock properties implies that good quality oil-prone source rocks of Late Jurassic age are likely to be present in the Vøring and Møre basins.
Angola Block 18: a deep-water exploration success story
Authors: FRASER A. J. , HILKEWICH D. , SYMS R. , PENGE J. , RAPOSO A. , SIMON G.
Published: April 2010

Offshore Angola Block 18 was awarded to Amoco in October 1996 for an initial four-year exploration period with an associated four well commitment. This was subsequently extended in October 2000 for an additional three years and further two well commitment. Ownership is BP (operator) 50% and Shell 50%. The block covers an area of 4880 km
2
, the equivalent of some 35 UKCS blocks. Water depths range from 200m in the east to over 1600m in the west. Block 18 is almost entirely covered by over 5000 km
2
of high quality 3D seismic data.

Exploration activity has, to date, focused on the western part of the block lying in 1200–1600m of water on the southward extension of the successful Tertiary play from Blocks 15 and 17. Reservoir targets occur in Miocene and Oligocene submarine slope channel sands associated with the evolving Congo River cone. Charge is derived from Upper Cretaceous–Tertiary marine shales of the Iabe Formation. Dominant trap styles are combined structural and stratigraphic domes and turtles associated with movement of Aptian salt.

Since the BP–Amoco merger in January 1999, six exploration wells have been drilled to fulfil the first and second phase exploration commitments (Platina, Plutonio, Galio, Paladio, Cobalto & Cromio) all of which have been significant oil discoveries in turbidite channel and sheet sands of Miocene and Oligocene age. Given an unprecedented six discoveries out of six wells, it is clear that the working Tertiary fairway in Block 17 extends south into Block 18. Keys to success have been rapid integration of BP’s Block 15 and 17 experience with existing Amoco interpretation and technologies in Block 18.

The learnings from the successful exploration campaign in Block 18 Angola, specifically in the use of high quality 3D seismic attributes as a risk reduction tool, have application in deep-water plays elsewhere, such as the Tertiary and Upper Cretaceous of the North Sea and offshore mid Norway.
Deep-water plays of the Mauritanian continental margin
Authors: VEAR A.
Published: April 2010

The coastal basin of Mauritania is emerging as a potential major petroleum province as a result of renewed exploration activity over the past five years. Two significant discoveries of oil and gas have been made at Chinguetti and Banda, proving that an effective petroleum system exists in this passive margin basin. The successful play type comprises Miocene turbidite channel reservoirs, sealed by fine-grained channel abandonment facies or a hemipelagic shale drape. The most prospective structures are associated with diapiric salt, although a variety of other structural styles, including compressional toe thrusts and rotated extensional fault blocks, are also present. The only source rocks proven to be effective in the immediate area occur in Cenomanian to Turonian deep-marine mudstones. However, regional evidence suggests that other intervals, including the Albian and the Paleocene, may also contain source facies. Future drilling campaigns by Woodside and other operators in the region will focus on realizing the value of existing discoveries through appraisal and tie-back exploration, while at the same time targeting new plays, particularly Late Cretaceous turbidites. Some of the major challenges to would-be petroleum explorers and producers in this basin centre around operating in a remote location almost totally lacking in infrastructure, and conducting activities in an environmentally responsible and sustainable manner.
How wrong can it be? Understanding uncertainty in petroleum systems modelling
Authors: WENDEBOURG J. , TRABELSI K.
Published: April 2010

Petroleum systems modelling is used in industry to understand and predict the interplay between the main elements of a petroleum system. This is done using numerical modelling because it cannot possibly be done experimentally given the geological time- and space scales. Such models describe the geological processes forward in time and, therefore, generate a single unique solution for a given input dataset. The evidence from data is, in most cases, insufficient to remove any ambiguities. Therefore, it is more interesting to know how much this uncertainty can be reduced, or how wrong it still might be, rather than knowing the right answer. Given the uncertainty of model outcomes, the appropriate solution should, therefore, be probabilistic rather than deterministic, where the variance expresses the remaining uncertainty in the outcome covering all possible valid geological scenarios. This paper describes how experimental design and response surface analysis can be used to perform sensitivity and uncertainty analysis in petroleum generation and migration modelling, focusing on trapped volumes derived from its drainage area. Map properties are parameterized as end-member scenarios, either as discrete or linearly varying maps. Regression coefficients indicate a good representation of trapped hydrocarbon volume by the response surface. In the example presented, hydrocarbon volume is most sensitive to fault characteristics, total organic carbon content and, to a lesser degree, to thickness of the source rock and heat flow. Well data allow a significant reduction of uncertainties, which can be shown by the probability distribution that becomes narrower but remains similar in form. The volume probability distribution of the prospect is multimodal for a discrete parameter scenario and log-normal for both discrete or uniform input distributions. Volume distributions result directly from the deterministic modelling without any prior statistical assumption on the form of the distribution.
Quantitative hydrocarbon potential mapping and organofacies study in the Greater Balder Area, Norwegian North Sea
Authors: JUSTWAN H. , DAHL B.
Published: April 2010

Quantitative maps of the reconstructed oil and gas potential of the Draupne and Heather Formation in the South Viking Graben were produced in order to improve the understanding of lateral and vertical variations in the type of organic matter. For this purpose the Draupne Formation was subdivided into a lower synrift and an upper postrift part (Upper and Lower Draupne Formation, respectively). Both sections show large lateral variability in source rock quality and oil and gas potential. The total TOC distribution is strongly related to the depositional environment and also to the preservation of organic matter. The Upper Draupne Formation exhibits equally high amounts of oil- and gas-prone organic matter. The Lower Draupne Formation shows a considerably higher amount of land-derived Type III organic matter, which decreases upwards and towards the Utsira High. The marine Type II material in the synrift section is less abundant, because of dilution of the marine material by terrestrial material transported by mass flows from the surrounding highs. These findings are supported by environmental molecular data. The Heather Formation is a mixture of type-III and -II kerogen and shows moderate to good gas potential. The source rock sections were also correlated using the relative occurrence of bisnorhopane in the rock extracts.
Late Cenozoic depositional history of the Danish North Sea Basin: implications for the petroleum systems in the Kraka, Halfdan, Siri and Nini fields
Authors: RASMUSSEN E. S. , VEJBÆK O. V. , BIDSTRUP T. , PIASECKI S. , DYBKJÆR K.
Published: April 2010

The Central Graben area was filled with a thick pile of sediments during the Middle Miocene – Quaternary, corresponding to a period of 15Ma. As hydrocarbon expulsion from the most prolific source rock, the Upper Jurassic Bo Member, was initiated only 20 Ma BP and still occurs today, the Middle Miocene – Quaternary evolution is important. In the Middle Miocene, the Central Graben area was covered by a sea with water depth of 500–700 m. During the Late Miocene (Tortonian), the basin was successively filled by prograding slope and deltaic sediments from the northeast. The progradational infill resulted in local tilting of the substratum due to the loading effect of the deposits. In the latest Late Miocene (Messinian), the main input of sediments occurred from the south, as illustrated by a thick onlapping succession of upper Messinian sediments. Pliocene sedimentation was characterized by regular infill from the east within a shelf to shallow marine depositional environment. Following the Miocene and Pliocene, the North Sea Basin tilted due to strong uplift of the Fennoscandian shield and increased subsidence and sedimentation rates within the Central Graben area. This further complicated the maturation of the source rock, migration pathways and accumulation of hydrocarbons. The consequence of this complex burial history is exemplified by the Kraka and Halfdan fields. The Kraka Field has a large down-flank oil accumulation, which is the result of a porosity anomaly resulting from an early invasion of oil in this position before the late tilting of the North Sea Basin. The history of the non-structural accumulation of the Halfdan Field can be readily modelled; it constituted a simple four-way dip closure during the Late Miocene when peak oil migration occurred. The Quaternary tilting of the North Sea Basin due to uplift of the Fennoscandian Shield and strong subsidence of the Central Graben area resulted in a distinct gradient favouring long-distance migration of hydrocarbons. The occurrence of viable migration routes, especially within Paleocene sand layers, has resulted in long-distance migration of oil into the Siri submarine valley system. The most northern indication of hydrocarbons has been recognized as far as 75km from the source area. Long-distance migration of hydrocarbons is also indicated by direct hydrocarbon indications (DHIs) throughout the Cenozoic succession in the Danish North Sea. DHIs are particularly prominent above known hydrocarbon accumulations in the Central Graben. This indicates pronounced vertical migration, for instance along active faults, above these structures.
4D seismic quantification of a growing CO
2
plume at Sleipner, North Sea
Authors: CHADWICK R. A. , ARTS R. , EIKEN O.
Published: April 2010

CO
2
produced at the Sleipner natural gas field is being injected into the Utsira Sand, a major saline aquifer. Time-lapse seismic data were acquired in 1999 and 2001, with 2.35 and 4.26 million tonnes of CO
2
in the reservoir respectively. The CO
2
plume is imaged as a number of bright sub-horizontal reflections within the reservoir unit, growing with time, and underlain by a prominent velocity pushdown. No leakage has been detected from the repository reservoir. The reflections are interpreted as tuned responses from thin (<8 m thick) layers of CO
2
trapped beneath thin intra-reservoir mudstones and the reservoir caprock. However, these alone are unable to account for the amount of observed pushdown. A two-component 3D saturation model is therefore developed for the 1999 dataset, with high-saturation CO
2
forming the layers and a lesser component of low-saturation CO
2
between the layers. Saturations are calculated from the observed reflectivity and velocity pushdown and the resulting model contains 85% of the known injected mass of CO
2
. A 2D synthetic seismic section through the saturation model matches the observed seismic response well and the model is considered to provide an acceptable description of the CO
2
distribution. Signal attenuation is more pronounced within the 2001 plume and its effects are likely to become more significant with time, perhaps reducing the efficacy of seismic verification techniques as the plume grows further. Other geophysical methods, such as microgravimetry, may become increasingly useful at this stage.
Fluid and lithology identification using high-resolution 3D seismic data
Authors: CONNOLLY P. , WILKINS S. , ALLEN T. , SCHURTER G. , ROSE-INNES N.
Published: April 2010

BP acquired its first high-resolution 3D survey data in late 2000 over their Greater Plutonio development area in Block 18, offshore Angola. The seismic acquisition and processing parameters were designed to maximize temporal and spatial resolution of the reservoir sands. A compact and shallow source was used in conjunction with shallow cable deployment. The data were processed at 2 ms to a bin size of 6.25 m. AVO imaging and inversion technology were used to provide fluid and lithological impedance cubes. The survey was designed to aid development well drilling as well as providing a baseline 4D survey. The final datasets have significantly improved resolution compared to the previous conventional 3D survey. The new data show sharply defined fluid contacts, which allows the identification of potential pressure barriers within the reservoir.
Pre-stack depth migration and velocity model building for imaging in the North Sea
Authors: VAN DER BURGH J. , DOUMA J.
Published: April 2010

One of NAM’s Rotliegend prospects is situated at
c
. 2800 m below a major wrench-fault zone. Large lateral impedance contrasts across the faults are believed to be one of the main causes for the poor seismic imaging at the Rotliegend objective. Three-dimensional pre-stack depth migration (PSDM) seismic processing using hard-layer model updating was applied to the data in 2000. The results showed a significant improvement compared to previous post-stack depth migration (post-SDM) results and the original post-time migration processing. Despite these improvements in data quality, ambiguity still remained over the exact seismic pick of the top Rotliegend objective at the prospect. There was a clear case to optimize further the data quality at the prospect because only the high case interpretation proved to be economically viable.

A review of the 2000 PSDM processing concluded that there was still considerable scope for further improvement of the data by fine-tuning the velocity model near the complex re-activated fault systemas well as by detailed pre-stack data analysis. It was decided to embark on another 3D PSDM iteration to improve the structural definition of the prospect by using the latest available velocity modelling tools within Shell. The selected technique is based on non-layer constrained RMO measurements, followed by a velocity model inversion. This approach allows full and flexible interaction with the pre-stack data, a pre-requisite for proper velocity modelling in complicated wrench-fault systems.
Borehole seismic: what does it bring to the understanding of the reservoir?
Authors: BLANCO J.
Published: April 2010

When thinking about what we need for a more comprehensive approach to reservoir description and management, the range of information is large and various. The objective is always to improve our ‘vision’ of the geological setting, including a precise rock-type characterization and a good understanding of hydrocarbon flow paths. Each of these elements of the reservoir is determined with a varying level of uncertainty. Today, there is general agreement that integration of competences in business units is the optimal way to take the full benefit of technology breakthroughs in each individual discipline.

Borehole seismic is identified as being critical to increasing the quality and the reliability of processing and interpretation of surface seismic data. If until recently, borehole seismic applications were focused on seismic calibration using vertical seismic profiles (VSP) and sometimes on imaging when surface seismic defaulted, today the link to well data is growing stronger. Since not all disciplines involved in reservoir management can work at the same scale, this raises the problem of scale and model compatibility between the respective disciplines. Here again borehole seismic can play a key role. This is becoming possible because advances have been made in a variety of techniques and methods leading to applications such as multi-walkaway and 3D-VSP, 4C and 4D-VSP, single-well and crosswell acquisitions, amplitude variation with offset (AVO) calibration, and scale change. Moreover, improvements in technology make the acquisition and processing cost-effective. Multilevel, three- or four-component receiver strings and permanent seismic sensors are examples of a continued development of operationally efficient hardware. New borehole seismic techniques such as 4D-VSP or the improvement in more mature ones such as crosswell seismic, offer new images of the reservoir. Although these images may be spatially limited, they are usually of a higher resolution than surface seismic and can offer significant benefit for reservoir management and monitoring.

This paper illustrates the benefits of borehole seismic with three case studies, illustrating (1) how we can include uncertainties in the VSP imaging process and its impact on structural interpretation of a North Sea reservoir, (2) why AVO calibration using a walkaway technique is mandatory for a better prediction and interpretation of seismic attributes in terms of lithology and fluid content and (3) 4D walkaway and passive seismic surveys using fibre-optic seismic permanent sensors for monitoring an onshore gas storage.
A vision for 3D seismic technology and visualization
Authors: DAVIES R. J. , GRAS R. , PAYRE X.
Published: April 2010

Three-dimensional seismic data and visualization are the key elements of a rapid technological evolution in the remote sensing of the subsurface that has resulted in geoscientists moving from being data poor to data rich. The proliferation in subsurface data has profoundly affected the oil exploration and production industry in the last two decades. Most notably it has radically improved our ability to predict what lies beneath the Earth’s surface and, hence, reduce risk in exploration and production.

One-dimensional data (wells) were supplemented by 2D data (seismic sections and maps) in the 1950s and by 3D seismic data from the 1970s onwards. However, the evolution up to this point essentially dealt with a static Earth without the fourth dimension – time. More recently came the advent of recording changes in the subsurface due to hydrocarbon extraction over time, with the use of time-lapse 4D surveying.

There are also now more refined imaging techniques such as multi-component (4C) and single sensor recording. The resulting explosion of information has led to challenging questions as to how geoscientists can interact with the data to collaborate and communicate more effectively in this new data-rich world.

The breadth of influence of 3D seismic data and visualization in earth sciences is likely to be far wider than the oil and gas industry. Collaborative Visualization Environments (CVEs) are already being used in universities and 3D seismic data are also being used as a research tool in many unrelated earth science disciplines. The next step will be the establishment of CVEs at schools and colleges for teaching the next generation of earth scientists.

Supplementary material:
The movie referred to in the article is available at
https://doi.org/10.6084/m9.figshare.c.4812804
Applications of visualization in the Britannia Field, UK North Sea
Authors: COLLERAN J. , LOUTIT S. , KAISER K. , HAKES W. G. , SUMNER W. R. , ARCHER S. , CRIDDLE D.
Published: April 2010

Britannia is a large gas-condensate field located 140 miles NE of Aberdeen. The introduction of new tools and workflows has enabled the subsurface team on Britannia Field to increase their understanding of a complex turbidite reservoir whilst continually planning and drilling wells. In 2002, reprocessing of the existing 3D seismic data was completed, giving much improved data quality and a number of new data volumes for interpretation. These and further attribute volumes for reservoir prediction have increased the need for 3D visualization and volume interpretation. Revised, field–wide, top and near-base reservoir picks were made in two stages. 3D volume interpretation techniques were first used to rapidly pick events in good data areas. Then difficult areas were picked and final editing completed using sections and random lines (ribbons). These surfaces were used as the framework for a rebuild of the static geological field model. Fault picking and quality control of structural interpretation has been made easier providing a much improved understanding of faulting in the Britannia field. The new tools and techniques have enabled more of the overburden to be interpreted, giving a fuller understanding of the whole geological story. Flexible well planning is a significant advantage, and visualization tools have helped considerably in well design, especially with contingency planning and communication to management and partners. A number of examples are shown.

Britannia is a complex heterogenous turbidite reservoir, and visualization techniques allow greater integration of the seismic with geological models. Flattening and visualization of the results help to understand palaeobathymetry and potential sand distribution patterns. Various detailed cross sections, flattened on different events, build up a picture of sand infill history. Use of colour is particularly powerful here: detailed correlations between many wells can also be inspected more effectively.

A number of different pieces of software have been used in the visualization process – no interpreter can become expert in all, but in the subsurface team enough expertise can be gained to significantly impact workflows and productivity.

Supplementary material:
The movies referred to in the article are available at
https://doi.org/10.6084/m9.figshare.c.4812942
Using spectral decomposition as a hydrocarbon indicator tool in the Norwegian Sea
Authors: LEADHOLM R. H. , AUSTIN T. J. F. , OSTENDORF P. F.
Published: April 2010

Investigation of two deepwater gas accumulations in the Norwegian Sea indicate that phase and amplitude spectra derived using spectral decomposition can be used as hydrocarbon indicators. Specifically, this technique enhances the ability to evaluate phase and amplitude anomaly conformance to structure and complements the more traditional utilization of spectral decomposition for thin bed analysis.

The 6707/10-1 Luva well on the Nyk High encountered a 156 m thick column of dry thermogenic gas and was the first deepwater discovery in Norway. Despite the fact that the accumulation is characterized by a well developed flat event, examination of partial stack broadband 3D reflectivity data proved inconclusive in substantiating the presence of an amplitude anomaly conformant with structure at all offset ranges. Amplitude and phase tuning cubes were derived using spectral decomposition from near, far and full offset-stack 3D seismic data. Strong amplitude anomalies most notably at frequencies less than 10 Hz, structurally conformant with the observed gas/water contact, are observed at all offset ranges. Phase instability, associated with rock property differences between the gas charged and brine saturated portions of the reservoir, results in an anomaly in the phase tuning cube that is also most evident at low frequencies and is also conformant with the observed gas/water contact.

Similar spectral decomposition evaluation of seismic data over the Ormen Lange gas discovery gave equally dramatic results. Traditional amplitude extraction methodologies on the full stack broadband data set show an ambiguous amplitude anomaly with limited conformance to structure. Spectral decomposition of the same full stack data set show well defined anomalies at frequencies less than 12 Hz, in both amplitude and phase tuning cubes, conformant with the gas water contact proven by drilling.

3D forward models built using rock properties from the Luva and Ormen Lange wells have been processed with the same spectral decomposition software and substantiate observed results. Spectral decomposition analysis of untested prospects in other areas of the Norwegian Sea show both phase and amplitude anomalies at low frequencies that appear conformant with structure.
4D analogue models of extensional fault systems in asymmetric rifts: 3D visualizations and comparisons with natural examples
Authors: McCLAY K. R. , DOOLEY T. , WHITEHOUSE P. S. , ANADON-RUIZ S.
Published: April 2010

New three-dimensional analogue modelling experiments have been carried out to simulate the development of offset and segmented asymmetric rift systems. High-resolution digital photography, combined with animations and 3D reconstructions, has enabled the detailed study of the progressive 4D evolution of these complex rift fault systems. In particular, this paper focuses upon the growth of faults at the early stages of development and the formation of accommodation zones where the rift fault architectures change along-strike. These sandbox analogue models simulate the development of asymmetric oblique rifts where the extension direction was at an average angle of 60° to the rift axis, controlled by the underlying baseplate configuration. Segmented rifts were generated by discrete offsets in the baseplates of the sandbox models. In all models the rift border faults were controlled by the orientations (and offsets) of the baseplates beneath the models whereas the intra-rift faults generally initiated at high angles to the extension direction. With increased stretching, both the rift border faults and the intra-rift faults propagated along-strike, producing segmented fault systems separated by relay ramps that were breached as fault linkage occurred. Kinks along the fault traces indicate these linkage points. In all models the asymmetric extension produced a dominant border fault system on the static rift margin, whereas the moving rift margin was characterized by domino-style extensional fault systems dipping into the centre of the rift basins. In the segmented rift models, zones of offset were characterized by complex accommodation zones formed by arrays of oppositely dipping faults. In serial cross sections the accommodation zones consisted of complex conjugate fault systems formed by the overlapping tips of oppositely dipping faults. Three-dimensional visualizations of the completed models, together with fault displacement analyses using Traptester, allowed detailed analyses and geometric reconstructions of these accommodation zones. The asymmetric oblique and segmented rift models display many structural similarities to the segmented rifts of the Central and Northern North Sea rifts as well as to those in the Northern Ethiopian rift system, and in the Gulf of Suez, Egypt.
3D visualization of a rock sample, Rotliegend sandstone, Southern Permian Basin: applications for core analysis and petrophysics
Authors: KAYSER A. , KELLNER A. , HOLZAPFEL H.-W. , VAN DER BILT G. , WARNER S. , GRAS R.
Published: April 2010

A methodology has been developed to visualize and interpret the texture and pore system of rock samples using a virtual reality application. This technique is illustrated using an aeolian sandstone core sample of the Rotliegendes Dethlingen Formation from the Southern Permian basin of northwest Germany. The methodology involves digitizing a series of densely spaced microfocus computer tomography (μCT) images with an appropriate sampling and processing the individual images, which are based on density contrasts, into a volume definition similar to seismic data. Once the volume file has been created the data can be visualized and analysed using virtual reality software. Visualization of scanned core samples has benefits with regards to both the qualitative interpretation of the rock as well as to the quantitative evaluation of the intergranular volumes, cements and pore space. Further advantages exist in terms of the effective communication and collaboration within relevant communities in exploration and production. A key requirement for this technology to be beneficial is calibration of the input slices with rock properties.

In terms of the qualitative analysis of the rock, visualization offers the possibility to view slices of the rock samples in any direction. Consequently, bedding planes and fracture planes can be viewed orthogonally even if the physical sample has been cut oblique to these planes. Both slice and transparent volume views are possible, readily revealing the sedimentary and structural features of the rock. Provided that the scanning process has taken place with sufficient resolution, the views can separate grains from cement, matrix and pore space.

In addition to the qualitative aspect of visualization, the 3D interpretation capabilities of the software are very valuable. Voxel-based technology allows measurement of grain sizes, cement, matrix and pore space, both in terms of volume as well as geometry. This provides important information in addition, and complementary, to conventional core analysis. In most cases the volume measurements can be expected to be more precise than traditional 2D methods, such as point counting, because they account for the three-dimensional anisotropy of the rock. Stereo-viewing allows pore space to be ‘experienced’ in 3D, offering a better perception and analysis with a view towards hydrocarbon recovery and production strategies. Finally, visualization offers an optimal means to communicate and collaborate, creating a better shared understanding of the relevance of the rock properties within the overall exploration and production evaluation process.

Supplementary material:
The movie referred to in the article is available at
https://doi.org/10.6084/m9.figshare.c.4812969
Characterization of the inhibitory roles of RFRP3, the mammalian ortholog of GnIH, in the control of gonadotropin secretion in the rat: in vivo and in vitro studies
Authors: Pineda R. , Garcia-Galiano D. , Sanchez-Garrido M. A. , Romero M. , Ruiz-Pino F. , Aguilar E. , Dijcks F. A. , Blomenröhr M. , Pinilla L. , van Noort P. I. , Tena-Sempere M.
Published: April 2010

RF-amide related peptides (RFRP), as putative mammalian orthologs of the avian gonadotropin-inhibitory hormone (GnIH), have been proposed as key regulators of gonadotropin secretion in higher vertebrates. Yet considerable debate has arisen recently on their physiological relevance and potential mechanisms and sites of action. Present studies were undertaken to further characterize the effects of RFRP on LH and FSH secretion by a combination of in vivo and in vitro approaches in male and female rats. Initial screening via intracerebroventricular (icv) administration of different analogs of RFRP1 (RFRP1–12 and RFRP1–20) and RFRP3 (RFRP3–8 and RFRP3–17), as well as the related neuropeptide FF (NPFF8), to gonadectomized (GNX) female rats evidenced significant, albeit modest, inhibitory effects on LH secretion only for RFRP3–8 and RFRP3–17, which were detectable at the high dose rage (1 nmol for RFRP3–8, 5 nmol for RFRP3–17). This moderate inhibitory action was also documented after icv administration of RFRP3–8 to intact and GNX male rats. In addition, systemic (intravenous) administration of RFRP3–8 decreased the circulating levels of both gonadotropins in GNX male rats. Likewise, RFRP3–8 inhibited basal and GnRH-stimulated LH secretion by pituitaries from GNX males in vitro. This inhibitory effect was blocked by the antagonist of RFRP receptors, RF9. In summary, our results support a putative inhibitory role of RFRP3 as ortholog of GnIH in the regulation of gonadotropin secretion in mammals, which appears to involve direct pituitary actions as well as potential central (hypothalamic) effects.
MicroRNA-34a induces endothelial progenitor cell senescence and impedes its angiogenesis via suppressing silent information regulator 1
Authors: Zhao Ting , Li Jian , Chen Alex F.
Published: April 2010

Endothelial progenitor cells (EPCs) play an important role in angiogenesis, which is essential for numerous physiological processes as well as tumor growth. Several microRNAs (miRNAs) have been reported to be involved in angiogenesis. MiR-34a, recently reported as a tumor suppressor, has been found to target silent information regulator 1 (Sirt1), leading to cell cycle arrest or apoptosis. However, the role of miR-34a in EPC-mediated angiogenesis was unknown. The present study tested the hypothesis that miR-34a inhibits EPC-mediated angiogenesis by inducing senescence via suppressing Sirt1. Bone marrow-derived EPCs from adult male Spraque-Dawley rats were used. Results of flow cytometry showed that EPCs after 7 days of culture expressed both stem cell markers CD34 and CD133 and endothelial cell markers VEGFR-2 (flk-1) and VE-cadherin. MiR-34a was expressed in normal EPCs, and overexpression of miR-34a via its mimic transfection significantly increased its expression and impaired in vitro EPC angiogenesis. MiR-34a overexpression led to a significantly increased EPC senescence, paralleled with an ∼40% Sirt1 reduction. Furthermore, knockdown of Sirt1 by its siRNA resulted in diminished EPC angiogenesis and increased senescence. Finally, overexpression of miR-34a increased the level of Sirt1 effector-acetylated forkhead box O transcription factors 1 (FoxO1), an effect mimicked in EPCs following Sirt1 knockdown. In conclusion, miR-34a impairs EPC-mediated angiogenesis by induction of senescence via inhibiting Sirt1.
Pulsatile changes in free fatty acids augment hepatic glucose production and preserves peripheral glucose homeostasis
Authors: Hsu Isabel R. , Zuniga Edward , Bergman Richard N.
Published: April 2010

Recent studies in animal and human models have revealed that free fatty acid (FFA) release from adipose tissue is oscillatory. We have shown in our laboratory that these oscillations are controlled by the sympathetic nervous system (SNS). Although FFAs have been shown to directly stimulate glucose production [endogenous glucose production (EGP)] by the liver and to reduce peripheral glucose utilization, whether the specific pattern of FFA release affects glucose metabolism is unknown. The aim of this study was to examine the effects of pulsatile vs. constant infusion of FFA on glucose homeostasis in the canine model. Euglycemic clamps with basal insulin replacement (0.1 mU·kg−1·min−1 insulin) were performed in dogs ( n = 8) during infusion of saline (SAL) or the medium-chain fatty acid octanoate, which was given by either pulsatile infusion (PUL: 10 mmol over 2 min every 10 min) or continuous infusion (C-INF: 1 mmol/min) designed to achieve equivalent total FFA mass. Endogenous lipolytic pulses were suppressed with the β3-specific adrenergic receptor antagonist bupranolol. PUL infusion elicited a pulsatile pattern of FFA in circulation with average maximum pulse height of 0.82 ± 0.04 mM, whereas C-INF FFA levels reached 0.47 ± 0.03 mM (fasting levels) and were maintained throughout. Glucose uptake was not affected by PUL; however, C-INF significantly reduced glucose uptake compared with both SAL and PUL. Steady-state EGP increased by >90% from basal steady state during PUL but did not change during either SAL or C-INF. Thus, pulsatile FFA infusion led to an increase in EGP while preserving glucose disposal. These data suggest that the pattern of FFA may have a role in regulation of glucose homeostasis, which may have consequences in the obese or insulin-resistant state where the SNS is known to be altered.
Endonuclease G does not play an obligatory role in poly(ADP-ribose) polymerase-dependent cell death after transient focal cerebral ischemia
Authors: Xu Zhenfeng , Zhang Jian , David Karen K. , Yang Zeng-Jin , Li Xiaoling , Dawson Ted M. , Dawson Valina L. , Koehler Raymond C.
Published: April 2010

Activation of poly(ADP-ribose) polymerase (PARP) and subsequent translocation of apoptosis-inducing factor contribute to caspase-independent neuronal injury from N-methyl-d-aspartate, oxygen-glucose deprivation, and ischemic stroke. Some studies have implicated endonuclease G in the DNA fragmentation associated with caspase-independent cell death. Here, we compared wild-type and endonuclease G null mice to investigate whether endonuclease G plays a role in the PARP-dependent injury that results from transient focal cerebral ischemia. Latex casts did not reveal differences in the cerebral arterial distribution territory or posterior communicating arterial diameter, and the decrease in laser-Doppler flux during middle cerebral artery occlusion was similar in wild-type and endonuclease G null mice. After 90 min of occlusion and 1 day of reperfusion, similar degrees of nuclear translocation of apoptosis-inducing factor and DNA degradation were evident in male wild-type and null mice. At 3 days of reperfusion, infarct volume and neurological deficit scores were not different between male wild-type and endonuclease G null mice or between female wild-type and endonuclease G null mice. These data demonstrate that endonuclease G is not required for the pathogenesis of transient focal ischemia in either male or female mice. Treatment with a PARP inhibitor decreased infarct volume and deficit scores equivalently in male wild-type and endonuclease G null mice, indicating that the injury in endonuclease G null mice remains dependent on PARP. Thus endonuclease G is not obligatory for executing PARP-dependent injury during ischemic stroke.
Long-Term, Multisite, Parallel, In-Cell Recording and Stimulation by an Array of Extracellular Microelectrodes
Authors: Hai Aviad , Shappir Joseph , Spira Micha E.
Published: April 2010

Here we report on the development of a novel neuroelectronic interface consisting of an array of noninvasive gold-mushroom-shaped microelectrodes (gMμEs) that practically provide intracellular recordings and stimulation of many individual neurons, while the electrodes maintain an extracellular position. The development of this interface allows simultaneous, multisite, long-term recordings of action potentials and subthreshold potentials with matching quality and signal-to-noise ratio of conventional intracellular sharp glass microelectrodes or patch electrodes. We refer to the novel approach as “in-cell recording and stimulation by extracellular electrodes” to differentiate it from the classical intracellular recording and stimulation methods. This novel technique is expected to revolutionize the analysis of neuronal networks in relations to learning, information storage and can be used to develop novel drugs as well as high fidelity neural prosthetics and brain-machine systems.
The Time Course of Binaural Masking in the Inferior Colliculus of Guinea Pig Does Not Account for Binaural Sluggishness
Authors: Shackleton Trevor M. , Palmer Alan R.
Published: April 2010

Psychophysical studies show a slower response to changes in the specifically binaural input than to changes in the monaural input (binaural sluggishness). However, there is disagreement about the time course. Tracking changes in a target yields fast time constants, while detecting a constant target against a varying background yields the slowest. Changes in the binaural properties of a target are tracked up to high rates by cells in the midbrain. Indeed cells respond rapidly to a step change and then the firing rate slowly adapts. These experiments, though, are analogues of psychophysical experiments that give the faster time constants. Sluggishness should be more apparent physiologically in a binaural masking paradigm, detecting a short tone in a noise masker with a step change in masker correlation: the small change in firing rate due to the signal must be detected against the adapting firing rate change caused by the step change in the masker. However, in 40 inferior colliculus cells in the anesthetized guinea pig, in a direct analogue of the psychophysical masking paradigm, measuring thresholds for short tones across a transition in a binaural masker (e.g., from N0S0 to NπS0) provided little evidence of sluggishness within individual cells despite masking level differences in these cells comparable with previous data. Previous studies of physiological correlates of binaural masking level difference suggested that different psychophysical thresholds arise from different populations of cells. This suggests the hypothesis that sluggishness may result from a change in focus between the different populations of cells signaling threshold in different binaural configurations rather than within the intrinsic properties of the cells themselves.