bluuebunny/crossref_metadata_2025 huggingface dataset:
ASYMPTOTIC PROFILES FOR A TRAVELING FRONT SOLUTION OF A BIOLOGICAL EQUATION
Authors: CHAPUISAT GUILLEMETTE , JOLY ROMAIN
Published: May 2011

We are interested in the existence of depolarization waves in the human brain. These waves propagate in the grey matter and are absorbed in the white matter. We consider a two-dimensional model ut = Δ u + f(u)𝟙|y|≤R − αu𝟙|y|>R, with f a bistable nonlinearity taking effect only on the domain ℝ × [−R, R], which represents the grey matter layer. We study the existence, the stability and the energy of nontrivial asymptotic profiles of the possible traveling fronts. For this purpose, we present dynamical systems techniques and graphic criteria based on Sturm–Liouville theory and apply them to the above equation. This yields three different types of behavior for the solution u after stimulation, depending on the thickness R of the grey matter. This may partly explain the difficulties to observe depolarization waves in the human brain.
ANOMALOUS DIFFUSION LIMIT FOR KINETIC EQUATIONS WITH DEGENERATE COLLISION FREQUENCY
Authors: BEN ABDALLAH NAOUFEL , MELLET ANTOINE , PUEL MARJOLAINE
Published: May 2011

This paper is devoted to hydrodynamic limits for collisional linear kinetic equations. It is a classical result that under certain conditions on the collision operator, the long time/small mean free path asymptotic behavior of the density of particles can be described by diffusion-type equations. We are interested in situations in which the degeneracy of the collision frequency for small velocities causes this limit to break down. We show that the appropriate asymptotic analysis leads to an anomalous diffusion regime.
SUM OF ELEMENT ORDERS ON FINITE GROUPS OF THE SAME ORDER
Authors: AMIRI H. , JAFARIAN AMIRI S. M.
Published: May 2011

For a finite group G, let ψ(G) denote the sum of element orders of G. It is known that the maximum value of ψ on the set of groups of order n, where n is a positive integer, will occur at the cyclic group Cn. In this paper, we investigate the minimum value of ψ on the set of groups of the same order.
Europe overview
Authors: Goffey G.
Published: May 2011

Over 35 years, the Petroleum Geology Conference series has been the leading UK conference dedicated to making public the scientific advances and findings of some four decades of NW European hydrocarbon exploration and production. Leading edge issues in the NW European province after four decades include small pool and high pressure high temperature (HPHT) exploration, late-stage field exploitation and field redevelopment. The rich subsurface datasets and pioneering of emerging technologies provide a stream of valuable models, lessons, techniques and ideas which have both local and international applicability. Papers grouped under the exploration theme contain regional, local and detailed studies which illustrate the nature of current exploration activity for small, deep and complex structural and stratigraphic prospects. Closer and more comprehensive integration of seismic-derived understanding of structural evolution and seismic, well and analogue-derived depositional and sequence stratigraphic constraints are probably the most fruitful approaches and are shown by a number of papers. Papers on field development and production themes describe the industry's response to challenges such as low permeability and reservoir prediction through the use of multiple 3D and 4D seismic datasets and the exploitation of advances in drilling, well logging and completion technologies to drain progressively smaller per well reserves. Again, integration is the watchword, here between interpretations and analyses of subsurface data with well planning and construction. Finally, a number of papers describe current techniques in petrophysics, 3D and 4D seismic applications and remote sensing approaches.
Channel structures formed by contour currents and fluid expulsion: significance for Late Neogene development of the central North Sea basin
Authors: Knutz P. C.
Published: May 2011

Channel horizons, delimiting a major Pliocene sedimentary prism in the central North Sea basin, have been investigated in the context of oceanographic, climatic and tectonic controls, using 3D seismic and well data from the UK and Norwegian sector. Aggrading channel structures, forming 700–2500 m wide and 75–150 m deep linear to arcuate troughs, superimpose the truncated distal part of the prism in the northern Central Graben. The origin of the aggradational channel and prism complex is related to differential deposition and erosion by contour currents that intensified as tectonic subsidence formed a deep marine basin (>600 m) with open connections to the Atlantic and Norwegian Sea. The largest channel troughs appear to be filled with consolidated sediments and emerge from areas where the Neogene strata is pierced by salt diapir chimneys. From Early Pleistocene (
c
. 2.5 Ma) the channels were subject to progressive burial by rapid clinoform progradation. Based on the seismic observations, a depositional model is proposed that relates contourite channel development to fluid expulsion from salt diapir structures and fracture zones extending from lower Miocene strata. The sedimentary prism accumulated over a Late Miocene/Early Pliocene Unconformity marked by incised channels that are reminiscent of a northward diverging drainage system. This erosive low-stand development is probably related to late Alpine compression, which promoted uplift in the British Isles and the Channel region. The ensuing subsidence of the central North Sea, associated with concomitant uplift of the Norwegian–Danish Basin, generated the present southwestward dip of 0.5–0.8° of the basal unconformity. The Late Miocene compressional phase followed by rapid basin depending during Pliocene to early Pleistocene suggests that present concepts of North Sea basin development have to be re-evaluated.
The Ensign enigma: improving well deliverability in a tight gas reservoir
Authors: Purvis K. , Overshott K. E. , Madgett J. C. , Niven T.
Published: May 2011

The Ensign Gas Field is located in the Sole Pit basin in the Southern North Sea. The reservoir is the Rotliegend Group Leman Sandstone Formation of Lower Permian age and comprises sediments deposited in an arid continental environment. The main gas-bearing interval in the field consists of sabkha, waterlain and minor aeolian sands, reflecting deposition in an erg margin/lake margin setting. The poor primary reservoir quality of these sands has been severely reduced by extensive illite cementation resulting in average air permeabilities of <1 mD. Attempts to develop the field economically utilizing fracture‐stimulated vertical wells has met with mixed results, with flow rates of 14 MMscf per day and lower being measured during testing. The most recent appraisal well drilled on the field was a long horizontal well that was stimulated with five hydraulic fractures resulting in an economic flow rate of 44 MMscf per day. Analysis of the core and log data acquired during the appraisal of the field has shown that the reservoir contains a heterogeneous distribution of fractures, faults and micro-faults. The fracture population is dominated by conductive north–south striking fractures, with subordinate NNW–SSE resistive fractures and NE–SW mixed fractures that are arranged in clusters, with zones of high and low fracture density. Well results to date suggest that the NE–SW open and partially open fractures observed in core do not improve reservoir productivity, but those orientated north–south that are conductive appear to improve well deliverability.
Sedimentology and unexpected pressure decline: the HP/HT Kristin Field
Authors: Quin J. G. , Zweigel P. , Eldholm E. , Hansen O. R. , Christoffersen K. R. , Zaostrovski A.
Published: May 2011

Since production began in the HP/HT Kristin Field off mid-Norway, reservoir pressure in each of the three mid to late Jurassic reservoir units (the Garn, Ile and Tofte formations) has declined significantly more rapidly than was initially predicted. In the Garn Formation, the Tofte Formation and to some extent also the Ile Formation, this has occurred at least partly because an unusual distribution of reservoir properties led to bias in the four-well appraisal dataset and this in turn resulted in an overestimation of reservoir properties. Of particular importance to this bias was the fact that very good but unrepresentative reservoir properties were encountered in all three reservoir zones in the discovery well located in the centre of the field. These, it is now realized, are not even typical of most of the central part of the field but are, instead, restricted within one, small, anomalous area. Study of cores and thin sections indicates that in each reservoir unit this directly reflects a concentration of more energetic depositional facies in the area while less energetic facies are present on three sides. This pattern was not predictable from the original dataset and seems to have arisen because there was structural control upon facies positioning during accumulation of the reservoir section. This influenced the distribution of cleaner, coarser grained, more proximal depositional facies and, ultimately, reservoir quality distribution and pressure development. What is interesting about Kristin Field is that the structural influence upon sedimentation is observed within the footwall stratigraphy of a major relay structure where the primary provenance direction was on the hanging-wall side. This pattern is the reverse of what is normally reported in tectono-stratigraphic studies.
A road map for the identification and recovery of by-passed pay
Authors: Worthington P. F.
Published: May 2011

By-passed pay can occur at or between wells. Either way, it constitutes a lower risk prospect than hydrocarbon accumulations in unappraised areas. Beyond this, there are three contemporary drivers for its exploitation. First, new technology in the form of sharper reservoir imaging allows insights that were not achievable previously. Second, an evolving understanding of how reservoirs work has led to improved procedures for maximizing the exploitation of even the most problematic accumulations. Third, market forces amid global post-peak production fears are giving the incremental development of by-passed pay an even greater commercial impetus today. An examination of case histories that illustrate the role of these drivers has led to a six-fold type classification of by-passed pay. Type 1 can be produced using an existing identified well. Type 2 requires a side track or a new well in order to capture the reserves. Each type is further subdivided into three classes. The classification scheme has provided the context for an emerging
modus operandi
to maximize commercially recoverable hydrocarbons in developed assets. Thus, the approach takes the form of a road map for practical application. By corollary, the type classification demonstrably accommodates a wide range of reported exploitations of by-passed pay from diverse reservoirs. Therefore, this classification constitutes a potential foundation for further systemic refinements to the identification and recovery of by-passed pay.
A holostratigraphic approach to the chalk of the North Sea Eldfisk Field, Norway
Authors: Hampton M. J. , Bailey H. W. , Jones A. D.
Published: May 2011

A biostratigraphic review, conducted on 34 wells from the chalk of the Eldfisk Field, Norwegian Central Graben, has been integrated with petrophysical, geophysical and sedimentological information resulting in a revised lithostratigraphic framework for the chalk on this structure. Chalk of Danian to Turonian age is divided into five formations: the established Ekofisk Formation of Danian age and Tor Formation of Maastrichtian age, together with a new three-fold division of the Hod Formation, namely the Magne Formation of Campanian age, the Thud Formation of Santonian age and Narve Formation of Coniacian to Turonian age. This work demonstrates the application of this three-fold division of the Hod Formation. Internal field specific subdivisions of all formations are also presented for the Eldfisk Field. This lithostratigraphic framework is applied across the Eldfisk Field, together with the recognition of erosional features, unconformities, areas of non‐deposition, reworking and lateral changes in biofacies. The results have also allowed recognition of the following regionally synchronous tectonic phases for the first time on a Norwegian chalk structure: Stille's Ilsede phase (Late Turonian–Coniacian) and Wernigerode phase (Late Santonian–‘earliest’ Campanian), Mittel–Santon phase (Middle Santonian) of Niebuhr
et al.
and Reidel's Peine phase (‘latest’ Early Campanian), together with un-named phases of ‘latest’ Campanian, intra Mid Maastrichtian and (previously unrecognized?) intra Danian age. Evidence for these tectonic phases is compared with work from Denmark, Germany and the Anglo-Paris Basin. An innovative approach to mapping lateral biofacies (principally water depth) variations has been applied using the microfaunal database. This enhances understanding of the timing of structural phases when integrated with time lines generated by nanoplankton data. Biofacies proxies for silica content in the sediment may also correlate with changes in reservoir quality. Biofacies interpretations have also facilitated the identification and mapping of allochthonous bioclastic rich debris flow deposits. The fully calibrated biostratigraphic, lithostratigraphic and tectonostratigraphic frameworks presented can be applied to chalk structures regionally.
Assessment of undiscovered petroleum resources of the north and east margins of the Siberian craton north of the Arctic Circle
Authors: Klett T. R. , Wandrey C. J. , Pitman J. K.
Published: May 2011

The Siberian craton consists of crystalline rocks and superimposed Precambrian sedimentary rocks deposited in rift basins. Palaeozoic rocks, mainly carbonates, were deposited along the margins of the craton to form an outwardly younger concentric pattern that underlies an outward-thickening Mesozoic sedimentary section. The north and east margins of the Siberian craton subsequently became foreland basins created by compressional deformation during collision with other tectonic plates. The Tunguska Basin developed as a Palaeozoic rift/sag basin over Proterozoic rifts.

The geological provinces along the north and east margins of the Siberian craton are immature with respect to exploration, so exploration-history analysis alone cannot be used for assessing undiscovered petroleum resources. Therefore, other areas from around the world having greater petroleum exploration maturity and similar geological characteristics, and which have been previously assessed, were used as analogues to aid in this assessment. The analogues included those of foreland basins and rift/sag basins that were later subjected to compression. The US Geological Survey estimated the mean undiscovered, technically recoverable conventional petroleum resources to be
c.
28 billion barrels of oil equivalent, including
c.
8 billion barrels of crude oil, 103 trillion cubic feet of natural gas, and 3 billion barrels of natural gas liquids.
From Neoproterozoic to Early Cenozoic: exploring the potential of older and deeper hydrocarbon plays across North Africa and the Middle East
Authors: Craig J. , Grigo D. , Rebora A. , Serafini G. , Tebaldi E.
Published: May 2011

As the traditional exploration plays in the main productive basins of North Africa and the Middle East become more ‘mature’, attention is increasingly focusing on more challenging, older and deeper plays in the main producing basins and on high-risk, but more conventional, plays in under-explored frontier areas. This shift brings with it a range of technical and commercial challenges that must be addressed, if exploration in the region is to remain an attractive proposition. Exploration in North Africa and the Middle East has traditionally focused on the prolific Mesozoic- and Cenozoic-sourced petroleum systems of the Nile Delta, the Sirte Basin, the Pelagian Shelf, and the Arabian Plate and on the Palaeozoic-sourced petroleum systems of the Berkine, Ghadames, Illizi, Ahnet and Murzuq basins, the Central Arabian Basin, the Qatar Arch and the Rub Al Khali Basin. Together these form one of the most prolific petroleum provinces in the world and, as a consequence, there has been little commercial incentive to invest in exploring more challenging and riskier plays in these areas. However, as the need to find new reserves becomes imperative, attempts are increasingly being made to test new play concepts and to extend already proven plays into new areas. Key recent developments in this regard include the recognition of the hydrocarbon potential of the Neoproterozoic to Early Cambrian (‘Infracambrian’) sedimentary section lying below the traditionally explored Palaeozoic succession in many basins in North Africa. In some areas, particularly the Berkine Basin in Algeria, the Nile Delta in Egypt and the Rub Al Khali Basin in Saudi Arabia, attention is also increasingly being focused on developing deeper gas plays, both in new areas and beneath existing producing fields. The technical challenges associated with these deeper gas plays are immense and include difficult seismic imaging of deep prospects, low porosity and permeability, high temperature and pressure and a critical need to identify ‘sweet spots’ where either locally preserved primary reservoir characteristics or secondary enhancement of reservoir quality through palaeo-weathering and/or fracturing allow commercial rates of gas production to be achieved. Despite these challenges, it is clear that the future for exploration in many of the more mature basins of North Africa and the Middle East will increasingly lie in evaluating such older and more deeply-buried plays.
Palaeohighs: their influence on the North African Palaeozoic petroleum systems
Authors: Eschard R. , Braik F. , Bekkouche D. , Rahuma M. Ben , Desaubliaux G. , Deschamps R. , Proust J. N.
Published: May 2011

We present new insights for the characterization of the petroleum system evolution in North Africa based on a review of the stratigraphic architecture description of some selected North African Palaeozoic basins. During Palaeozoic time, the Gondwana platform was divided into sub-basins bounded by structural highs. Most of the highs were inherited from north–south and SW–NE Pan-African crustal faults which were reactivated during the Palaeozoic and later, in the Austrian and Alpine tectonic phases. We studied the stratigraphic architecture of the Palaeozoic succession around four main highs showing a clear tectonic activity during the Palaeozoic sedimentation. The Gargaff Arch, in Libya, is a major SW–NE broad anticline which slowly grew up during the Cambrian and Ordovician and stopped rising during the Silurian. The activity resumed during Late Silurian and early Devonian and during the Late Devonian. The Tihemboka High is a north–south anticline in between Libya and Algeria. The uplift started during the Cambro-Ordovician then stopped during most of the Silurian. The activity resumed during the Late Silurian and continued until the Lower Carboniferous. The Ahara High, separating the Illizi and Berkine basins in Algeria, has continuously grown during the Cambro-Ordovician, stopped rising during the Silurian, and grew again continuously during the Devonian. The Bled El-Mass High is a part of the Azzel-Matti Ridge separating the Ahnet and Reggane basins in Algeria. The high mostly rose during the Cambro-Ordovician then subsided relatively less quickly than the surrounding basins during the Silurian and Devonian. The uplift timing and chronology of each palaeohigh partly controlled the petroleum systems of the surrounding basins. Topographic lows favoured the occurrence of anoxic conditions and the preservation of Lower Silurian and Frasnian source rocks. Complex progressive unconformities developed around the palaeohighs form potential complex tectonostratigraphic traps. Finally, hydrocarbons could have been trapped around the highs during pre-Hercynian times, preserving reservoir porosity from early silicification. Mixed stratigraphic–structural plays could then be present today around the highs.
Stratigraphic trapping potential in the Carboniferous of North Africa: developing new play concepts based on integrated outcrop sedimentology and regional sequence stratigraphy (Morocco, Algeria, Libya)
Authors: Lubeseder S. , Redfern J. , Petitpierre L. , Fröhlich S.
Published: May 2011

The lower Carboniferous (Tournaisian to Visean) of North Africa is characterized by cycle-stacks of predominantly shelfal to marginal marine sandstones and limestones, thick shelfal mudstones and less common but important interbedded fluvio-deltaic sandstones. The cyclic sedimentation pattern continues into the Mid Carboniferous (Serpukhovian to Bashkirian), when mixed siliciclastic–carbonate sequences give way to tropical carbonates, before an abrupt return to continental deposits in the upper Carboniferous (Bashkirian to Gzhelian). The alternation of widespread shallow marine and more discrete fluvial reservoirs with interbedded offshore mudstone seals is interpreted to result from high-frequency, high-amplitude Carboniferous glacio-eustatic sea-level changes. The large base-level changes during that time, combined with climatic conditions that produced high amounts of terrigenous mud, provided favourable conditions for the development of stratigraphic traps in the clastic-prone lower Carboniferous, while the advent of tropical carbonates produced reefal buildups in the Mid Carboniferous. Four stratigraphic trapping types are recognized: (1) truncation traps in which reservoir units were eroded on subaerially exposed proximal palaeohighs and thick underlying transgressive and highstand systems tract (TST and HST) mudstones form the bottom-seal and the rapid transgression of the offshore facies forms the top-seal; (2) pinchout traps of lowstand wedges on the flanks of distal palaeohighs, which were only affected by subaqueous reworking of previous TST–HST mudstones and were buried during the subsequent transgression; (3) incised valleys of the lowstand systems tract (LST), filled with thick fluvial and tidal sandstones, cutting either into TST–HST mudstones in the lower Carboniferous, or into exposed carbonate platforms in the Mid Carboniferous; (4) Waulsortian-type reefal buildups of the Mid Carboniferous. The four trapping types are discussed using selected outcrop examples, and are placed into regional sequence stratigraphic context of the Carboniferous depositional systems and sequence development of North Africa. These concepts can be readily applied to the subsurface and offer significant potential for new plays across North Africa.
Biostratigraphy, chemostratigraphy and thermal maturity of the A1-NC198 exploration well in the Kufra Basin, SE Libya
Authors: Lüning S. , Miles N. , Pearce T. , Brooker E. , Barnard P. , Johannson G. , Schäfer S.
Published: May 2011

The A1-NC198 exploration well was drilled in the Kufra Basin in 2007 by RWE Dea and represented only the third well in a large, 400 000 km
2
frontier basin. Despite being dry and lacking any hydrocarbon shows, the well provides important data to improve the understanding of the regional petroleum play. In the 1980s and 1990s the basin's prospectivity was questioned largely because of supposed (1) lack of structuration, (2) lack of source rock and (3) thermal immaturity at Silurian level. Following a series of academic and industry studies over the past 10 years, these assertions can no longer be upheld. The analysis of available seismic has proven the existence of Murzuq-style fault blocks as well as late Ordovician glacial erosional relict buried hills, potentially forming suitable structural and stratigraphic traps. The presence of hot shale in the Kufra Basin is evidenced by typical seismic onlaps of strong amplitude reflectors at base Silurian levels, shallow drilling results and outcrop spectral gamma-ray evidence. A spore colouration study of A1-NC198 cuttings indicates a deep oil window maturity for the Silurian, implying potential oil generation in the basin if suitable Silurian source rocks exist. The stratigraphy of the A1-NC198 succession was analysed by means of biostratigraphy and chemostratigraphy, which form the basis for improved well correlations within the basin.
Exploring subtle exploration plays in the Gulf of Suez
Authors: Dancer P. N. , Collins J. , Beckly A. , Johnson K. , Campbell G. , Mumaw G. , Hepworth B.
Published: May 2011

The Gulf of Suez Basin is a classic extensional rift basin of Miocene age, with a number of syn- and pre-rift hydrocarbon plays. Exploration started in 1886, targeting areas around documented oil seeps, and was highly successful. During the boom in offshore exploration in the 1950s and 1960s, a combination of diligent geology and serendipity resulted in the discovery of a number of giant fields whose reserves form a major part of some 10 billion barrels discovered to date. However, the pursuit of smaller fields, both structural and stratigraphic, has been hampered by the poor quality seismic data characteristic of the basin. The poor quality of the seismic data is due to the interbedded shales and evaporites of shallow post-rift Zeit and South Gharib formations that create massive reverberation and severe attenuation of the seismic signal. Incremental progress in imaging the deeper horizons, including the key pre-rift Nubia Sandstone reservoir, has been achieved through low frequency enhancement and 3D seismic data acquisition. However it is still common for exploration and development wells to miss the Nubia objective due to the poor imaging and consequent misinterpretation of the seismic data. Exploration is now directed towards the smaller targets and subtle plays of the Gulf of Suez. To improve seismic imaging the focus has been on improved acquisition, with 3D ocean-bottom cable seismic data. This has the advantages of reduced multiple energy, higher fold and a broader bandwidth over streamer 3D data. Combined with detailed models of the tectonically controlled sedimentation that characterizes the syn-rift section, this has allowed the development of a re-invigorated exploration programme.
Appraisal and development of the Taq Taq field, Kurdistan region, Iraq
Authors: Garland C. R. , Abalioglu I. , Akca L. , Cassidy A. , Chiffoleau Y. , Godail L. , Grace M. A. S. , Kader H. J. , Khalek F. , Legarre H. , Nazhat H. B. , Sallier B.
Published: May 2011

The Taq Taq Field is located within an anticline in the gently folded zone of the Zagros mountains, northeastern Iraq, approximately 50 km ESE of Erbil. The main reservoirs are fractured limestones and dolomites of Late Cretaceous age, with an oil column exceeding 500 m in thickness. Eocene limestones and dolomites at shallow depth form a subsidiary reservoir. The structure is a gentle thrust-related fold which has also been affected by dextral transpression. A pervasive fracture system is present within the reservoirs, giving good connectivity and deliverability. Initial discovery and appraisal was made in 1978 when three wells were drilled. The recent appraisal programme started in 2005 and by the end of 2008 two seismic surveys had been acquired and eight additional wells had been drilled. Mapping has incorporated a seismic principal component analysis for horizon and lithology identification. Modelling of the fractures has utilized a comprehensive data set derived from core and image logs. Special core analysis has been directed towards the understanding of the pore system and its interaction with the fractures. Synthesis of all these elements is performed in a dual-media dynamic model which is currently in use for development planning.
Sedimentology, geochemistry and hydrocarbon potential of the Late Cretaceous Shiranish Formation in the Euphrates Graben (Syria)
Authors: Ismail S. , Schulz H.-M. , Wilkes H. , Horsfield B. , di Primo R. , Dransfield M. , Nederlof P. , Tomeh R.
Published: May 2011

The Shiranish Formation consists of mudstones and wackestones in the central Euphrates Graben which are rich in organic carbon. Here the Shiranish Formation is more than 700 m thick with a minor increase in organic maturity with depth. The Shiranish Formation sediments are characterized by a continuously increasing hydrogen index to the top whereas the oxygen index is markedly lower in the Upper Shiranish Formation (USF). The Lower Shiranish Formation (LSF) is characterized by lower hydrogen indices and higher oxygen indices relative to the USF. These organic geochemical characteristics enable a rough subdivision into a lower and an upper part of the Shiranish Formation. Furthermore, mineralogical results enable a subdivision of the USF into two parts (USF-1, lower part; USF-2, upper part) each with individual mineralogical signatures due to a modified depositional environment and differing diagenetic history. The LSF resembles mineralogically the USF-2. Ankerite, together with higher pyrite contents in the LSF and USF-2, reflect similar diagenetic pathways which were controlled by higher clay contents. During early diagenesis, a traceable conversion of metabolizable organic matter led to mineral assemblages due to significant methanogenesis. Intervals in the USF with total organic carbon (TOC) contents up to around 4% and hydrogen indexes up to 500 mg HC/g TOC indicate the presence of very good potential source rock intervals for oil generation. Additionally, intervals of the LSF also contain gas-prone organic material. Bulk kinetic investigations show a broad activation energy of the LSF and a narrow activation energy pattern for the USF for hydrocarbon generation. Furthermore, the predicted petroleum formation temperatures are 136°C for the USF and 144°C for the LSF, respectively. This corresponds to
c
. 630 m difference in burial depth for petroleum formation. These differences in activation energies and corresponding depth to reach oil window maturity are controlled by facies, and less by maturity.
Passive margins: overview
Authors: Levell B. , Argent J. , Doré A. G. , Fraser S.
Published: May 2011

Passive margins have been the reliable, accessible mainstay of exploration success worldwide for the last 25 years, and have hosted the spectacularly fast exploitation of deepwater resources (Angola, Nigeria, Brazil, Trinidad, USA Gulf of Mexico, Egypt, Australia and India). Despite, or perhaps because of this, there is still much to learn about the variety of hydrocarbon habitats they present.

For example: (1) deep seismic observations and deep sea drilling have revealed more of the diversity of passive margins geodynamics. This liberates explorationists from simple geodynamic models, with consequences not only for new views of thermal history but also for the whole tectonic and stratigraphic evolution. For example, the time significance assigned to the geometries traditionally labelled ‘pre-rift, syn-rift and sag’ may be misleading. This has implications for correlations, the significance assigned to unconformities and sequence boundaries, heat flow and structural history. (2) New deep imaging of the sedimentary sections has revealed mistaken assumptions about the importance of ‘mobile substrate’ in major deltas and allowed the detailed unravelling of salt and shale movement and its implications for reservoir and trap. (3) Depositional models for deepwater reservoirs have increased in predictive capability and modern seismic imaging supports new models for shallow water sequences. (4) Discoveries of very large amounts of dry bacterial methane in stratigraphic traps have challenged old assumptions about prospectivity based on thermally matured source rocks. (5) New engineering and development technologies are opening up the commercialization of remote frontiers. As a consequence there is legitimate scope to re-visit old ‘dogmas’ and to propose that each passive margin segment is best regarded as unique, with analysis and interpretation rooted in observation rather than models (at least while the newly proposed models evolve to stability). Many of these themes were visited in the Passive Margins session of the Seventh Petroleum Geology Conference, held in London in 2009. This paper outlines some of these ideas, and considers how exploration along passive margins in the next decade can use new geoscience thinking.
Structural architecture and nature of the continent-ocean transitional domain at the Camamu and Almada Basins (NE Brazil) within a conjugate margin setting
Authors: Blaich O. A. , Faleide J. I. , Tsikalas F. , Lilletveit R. , Chiossi D. , Brockbank P. , Cobbold P.
Published: May 2011

Regional seismic reflection profiles and potential field data across the conjugate magma-poor Camamu/Almada–Gabon margins, complemented by crustal-scale gravity modelling and plate reconstructions, are used to reveal and illustrate the relationship of crustal structure to along-margin variation of potential field anomalies, to refine and constrain the continent–ocean boundary, as well as to study the structural architecture and nature of the continent–ocean transitional domain. The analysis reveals that the prominent conjugate Salvador–N'Komi transfer system appears to be a first-order structural element, governing the margin segmentation and evolution, and may have acted as an intraplate decoupling zone. The continent–ocean transitional domain, offshore northeastern Brazil, is characterized by rotated fault-blocks and wedge-shaped syn-rift sedimentary sequences overlying a prominent and undulated reflector (‘M-reflector’), which in turn characterizes the boundary between an extremely thinned, possibly magmatically intruded, continental crust and normal lithospheric mantle. The ‘M-reflector’ in the northeastern Brazilian margin shows remarkable similarities to the S-reflector at the West Iberia margin. In the same way, the ‘M-reflector’ is interpreted as a detachment surface that was active during rifting. Unlike the well studied central and northern segments of the West Iberia margin, however, the present study of the northeastern Brazilian margin does not clearly reveal evidence of an exhumation phase. The latter predicts exhumation of middle and lower crust followed by mantle exhumation. Increase in volcanic activity during the late stages of rifting may have ‘interrupted’ the extensional system, implying a failed exhumation phase. In this setting, the break-up and drift phase may have replaced the exhumation phase. Nevertheless, the available observations cannot discount the possibility that the ‘M-reflector’ is underlain by partially serpentinized mantle. Our study further leads to the development of a detailed conceptual model, accounting for the complex tectonomagmatic evolution of the conjugate northeastern Brazilian–Gabon margins. This model substantiates a polyphase rifting evolution mode, which is associated with a complex time-dependent thermal structure of the lithosphere. In the conjugate margin setting, asymmetrical lithospheric extension resulted in the formation of the thinned continental crust domain prior to the formation of the approximately symmetrical transitional domain.
Some emerging concepts in salt tectonics in the deepwater Gulf of Mexico: intrusive plumes, canopy-margin thrusts, minibasin triggers and allochthonous fragments
Authors: Jackson M. P. A. , Hudec M. R. , Dooley T. P.
Published: May 2011

We summarize four emerging concepts in salt tectonics in the deepwater Gulf of Mexico, selected from a longer list of concepts that have advanced significantly in the last decade. Squeezed salt stocks are common in orogenic forelands, in inverted basins and at the toe of salt-bearing passive margins. Modelling suggests that during early shortening, an inward salt plume from the source layer inflates the diapir and arches its roof. After further shortening, diapiric salt is expelled as an outward plume back into the source layer. Salt canopies are conventionally thought to advance by glacial extrusion. However, almost all modern salt canopies are now buried and can only advance by frontal thrusting. Thrusting allows the salt canopy and its protective roof to advance together, minimizing salt dissolution. Advance is by a roof-edge thrust rooted in the leading tip of salt or by thrust imbricates forming accretionary wedges. Minibasins can sink into salt if the average density of the overburden exceeds that of salt. This requires 2–3 km of burial of siliciclastic fill, yet most minibasins first sink when much thinner. Three alternative mechanisms to negative buoyancy in the deepwater Gulf of Mexico address this paradox of initiation. First, squeezed diapirs inflate, leaving the intervening minibasins as depressions. Second, when a diapir's salt supply wanes, the overlying dynamic salt bulge subsides, allowing a minibasin to form. Third, differential loading causes the thick end of a sedimentary wedge to sink faster into the salt, creating a sag. Spreading salt canopies can transport their dismembered roof fragments tens of kilometres basinward. These exotic fragments are up to 25 km in breadth and comprise anomalously old Mesozoic through Miocene sequences. Strata of the same age underlie the salt canopy or its welded equivalent, signalling lateral transport by thick salt.
Unconventional oil and gas resources and the geological storage of carbon dioxide: overview
Authors: Johnson H. , Doré A. G.
Published: May 2011

The ‘Unconventional oil and gas resources and the geological storage of carbon dioxide’ section of the
Proceedings
is designed to provide new insights from recent research and exploitation within these major growth areas in applied geology. Research and innovation on unconventional oil and gas have been driven by market needs – specifically concerns over oil and gas supply – as well as technological development. A cross-section of this work is highlighted in the current set of papers, covering ultra-heavy oil, shale oil, shale gas, basin-centred gas, tight gas and clathrates. Unsurprisingly, much of this research has been pioneered in North America. This work is complemented herein by some initial studies from Europe. Similarly, the geological storage of CO
2
is not simply a story of technological advance but also a response to an urgent societal imperative. Carbon dioxide sequestration is recognized as an important method for reducing greenhouse gas emissions in the near future, and is expected to have growing relevance to the oil and gas industry and the energy sector. Recent findings from current commercial carbon capture and storage projects in the North Sea and North Africa are presented and are complemented by an overview of major research programmes established in North America.
Tight gas exploration in the Pannonian Basin
Authors: Király A. , Milota K. , Magyar I. , Kiss K.
Published: May 2011

The Pannonian Basin is a mature exploration area where most of the obvious structural features have been tested and the largest conventional accumulations probably have been found. The history of hydrocarbon exploration and production in the central Pannonian Basin, Hungary, is more than 90 years old. The evaluation of unconventional hydrocarbon reserves offers an opportunity to rejuvenate exploration in this young and hot basin.
History-matching flow simulations and time-lapse seismic data from the Sleipner CO
2
plume
Authors: Chadwick R. A. , Noy D. J.
Published: May 2011

Since its inception in 1996, the CO
2
injection operation at Sleipner has been monitored by 3D time-lapse seismic surveys. Striking images of the CO
2
plume have been obtained showing a multi-tier feature of high reflectivity. In the medium to longer term, the topmost layer of CO
2
, accumulating and migrating directly beneath the topseal, is the main determinant of storage site performance. Fortunately it is this topmost layer that can be most accurately characterized, its rate of growth quantified, and CO
2
flux arriving at the reservoir top estimated. The latter is mostly controlled by pathway flow through thin intra-reservoir mudstones. This has increased steadily with time, suggesting either that pathway transmissivities are increasing with time and/or the pathways are becoming more numerous. Detailed 3D history-matching of the topmost layer cannot easily match the observed rate of spreading. Isotropic permeabilities result in a stronger radial component than observed and a degree of anisotropic permeability, higher in a north–south direction, is possible. The main contributor to the mismatch, however, is likely to be small but significant uncertainty in the depth conversion. Irrespective of uncertainty, the observed rate of lateral migration seems to require very high permeabilities, and is, moreover, suggestive of a topseal which behaves like a ‘hard’ impermeable flow barrier. Detailed studies such as this will provide important constraints on longer term predictive models of plume evolution and storage performance which are key regulatory requirements.
An autonomic-oriented framework based IEEE 802.21 for mobility management in 4G networks
Authors: Yahiya Tara Ali , Pujolle Guy , Beylot André-Luc
Published: May 2011

The main challenge in the development of future wireless communication systems is to provide users with a wide range of services across different radio access technologies through a single mobile terminal, while maintaining the quality of service requirements. Thus, the need for seamless interworking between heterogeneous wireless communication systems consisting of multiple radio access technologies and overlapping networks emerges. In this article, we address the main issues that arise while implementing the interworking mechanisms between different radio access networks. An interworking mechanism based on IEEE 802.21 framework is proposed and described in detail. We combine concepts of autonomic networking in the design of the framework in order to use intelligence to provide flexibility, accessibility and transparency to the mobile users.
A cooperative approach to collusion in auctions
Authors: Bachrach Yoram , Zadimoghaddam Morteza , Key Peter
Published: May 2011

The elegant Vickrey Clarke Groves (VCG) mechanism is well-known for the strong properties it offers: dominant truth-revealing strategies, efficiency and weak budget-balance in quite general settings. Despite this, it suffers from several drawbacks, prominently susceptibility to collusion. By jointly setting their bids, colluders may increase their utility by achieving lower prices for their items. The colluders can use monetary transfers to share this utility, but they must reach an agreement regarding their actions. We analyze the agreements that are likely to arise through a cooperative game theoretic approach, transforming the auction setting into a cooperative game. We examine both the setting of a multi-unit auction as well as path procurement auctions.
GUARDS and PROTECT
Authors: An Bo , Pita James , Shieh Eric , Tambe Milind , Kiekintveld Chris , Marecki Janusz
Published: May 2011

We provide an overview of two recent applications of security games. We describe new features and challenges introduced in the new applications.
The lemonade stand game competition
Authors: Zinkevich Martin A. , Bowling Michael , Wunder Michael
Published: May 2011

In December 2009 and November 2010, the first and second Lemonade Stand game competitions were held. In each competition, 9 teams competed, from University of Southampton, University College London, Yahoo!, Rutgers, Carnegie Mellon, Brown, Princeton, et cetera. The competition, in the spirit of Axelrod's iterated prisoner's dilemma competition, which addressed whether or not you should cooperate, asks the questions, "how should you cooperate, and with whom?" The third competition (whose results will be announced at IJCAI 2011) is open for submissions until July 1st, 2011.
Solution to Exchanges 8.2 puzzle
Authors: Romm Assaf
Published: May 2011

This is a solution to the editor's puzzle from issue 8.2 of SIGecom Exchanges. The puzzle is about finding a Bayesian equilibrium for a Dutch auction which can end according to a stochastic price schedule. The full puzzle [Conitzer 2009] can be found online at: http://www.sigecom.org/exchanges/volume_8/2/puzzle.pdf.
Why specialized disks for composite operations may be unnecessary
Authors: Thomasian Alexander
Published: May 2011

Disk arrays with erasure coding such as RAID5 and RAID6 incur four and six disk accesses respectively for updating data and check blocks. The small write penalty can be reduced by the Read-Modify-Write (RMW) composite operations to update data and associated check blocks. The Disk Architecture with Composite Operation (DACO) is a proposal to eliminate the disk rotation associated with RMWs, by using a complex read/write head, which allows the writing of a block immediately after reading and modifying it without needing an extra disk rotation. We argue that the extra cost associated with DACO may not be justifiable, because it is not expected to have a significant impact on RAID performance. Furthermore an XOR capability is still required at the disk array controller for reconstructing missing data blocks. A duplexed Nonvolatile Storage (NVS) cache at the disk array controller provides the same reliability as magnetic disks and allows fast writes, i.e., writing to disk is considered completed as soon as data is written onto NVS. Deferring the destaging of data blocks from NVS allows these blocks to be be overwritten, obviating unnecessary disk writes. This also allows neighboring dirty blocks to be destaged in batches, so that a higher disk access efficiency is attained. Disks with multiple arms can also be used to make the processing of RMW requests more efficient, while disks with multiple R/W heads on one arm have little effect on RMW requests. In addition there are alternative methods to update check blocks, such as floating parities, parity logging, the reconstruct write method, log structured arrays, and variable scope parity protection.
3D Interactions between Virtual Worlds and Real Life in an E-Learning Community
Authors: Lucke Ulrike , Zender Raphael
Published: May 2011

Virtual worlds became an appealing and fascinating component of today's internet. In particular, the number of educational providers that see a potential for E-Learning in such new platforms increases. Unfortunately, most of the environments and processes implemented up to now do not exceed a virtual modelling of real-world scenarios. In particular, this paper shows that Second Life can be more than just another learning platform. A flexible and bidirectional link between the reality and the virtual world enables synchronous and seamless interaction between users and devices across both worlds. The primary advantages of this interconnection are a spatial extension of face-to-face and online learning scenarios and a closer relationship between virtual learners and the real world.
A Dual-Band Band-Pass Filter with Overlap Step-Impedance and Capacitively Loaded Hairpin Resonators for Wireless LAN Systems
Authors: Chomtong P. , Mahatthanajatuphat C. , Akkaraekthalin P.
Published: May 2011

This paper presents a dual-band band-pass filter using modified cross-coupled step-impedance and capacitively loaded hairpin resonators for WLAN systems. The proposed filter has been designed to operate at a fundamental frequency of 2.4 GHz and the first harmonics frequency of 5.2 GHz. The techniques of step impedance and load capacitor are combined in the design of the proposed filter. In particular, the techniques of modified cross-coupling and overlap resonators are applied to improve the response of insertion losses at the first harmonic frequency of 5.2 GHz. The simulated and experimental results of insertion losses and return losses are better than 3 dB and 20 dB, respectively, at the operating frequencies.