241 research outputs found
Investigation of the origin of shallow gas in outer Moray Firth open blocks 15/20c and 15/25d
This report briefly describes the evidence for the origin of shallow gas in Outer Moray Firth
open blocks 15/20c and 15/25d. Sea floor pockmarks are known to occur within these blocks,
and they indicate the seepage of gas from shallow levels into the local water column. An
environmental concern is that any industry activity in these blocks must not plumb into any
component of the system that is sustaining the gas seepages at sea bed. The conclusions of this
study are:
1. Interpretation of the available BGS shallow seismic data and commercial site
investigation data shows that gas is seeping from sea bed in three large active
pockmark complexes in approximately 150 m or more water depth: the Challenger
Pockmark Complex in the north of block 15/25d, the Scanner Pockmark Complex in
the south of block 15/25d and the Scotia Pockmark which is adjacent to the north-east
of the Scanner Pockmark Complex.
2. A review of the peer-reviewed scientific publications indicates that the majority of the
arguments based on isotope analyses of gas and authigenic carbonate are for a
predominantly biological origin for the gas seeping from the active pockmarks.
However, biogenic isotopic signatures in the Gulf of Mexico and the North Sea are
thought to have been generated when thermogenic hydrocarbons in shallow sediments
were re-cycled by bacteria to produce ‘secondary’ methane with an identical isotopic
signature to biogenic methane. Thus, the isotopic data derived from the Scanner
Pockmark Complex do not provide a secure basis for determining whether the gas
escaping from the pockmarks in block 15/25 is primarily biogenic or thermogenic in
origin.
3. Interpretations completed during this project indicate that gas seeping to sea bed in the
largest pockmarks is reservoired within the uppermost part of the Aberdeen Ground
Formation, where it is preserved between buried sub-glacial channels. The gas
seepages at sea bed are fed from an almost continuous blanket of buried gas-charged
sediments situated between the sub-glacial channel margins at approximately 280-300
ms two-way time (around 120 m below sea bed) in the northern part of block 15/25d.
4. An empirical conclusion from distribution patterns observed in the interval between
sea bed and 400 ms two-way time is that loss of shallow gas from the gas-charged
interval at approximately 280-300ms two-way time will cut off the supply of shallow
gas to the active pockmarks. Dry well 15/25b-1A, located immediately to the north of
the Scanner Pockmark Complex, appears to have been drilled on the margin of the
shallow gas reservoir. A recommendation is that future development operations should
not disturb the shallow gas reservoir.
5. All of the hydrocarbon discoveries made within and around the study area are oil. The
nearest Upper Jurassic Kimmeridge Clay Formation principal thermogenic gas kitchen
lies some 30 km to the south-east, in the Fisher Bank Basin. Gas has been proved to
have migrated up into Mid-Eocene sandstones (e.g. Alba Field) in that basin. Although
it is possible that further vertical migration might have been achieved through minor
faults and fractures in the Late Eocene to Pliocene, no evidence was observed in the
3D data to connect the location of the active pockmarks with supply from the
thermogenic gas kitchen. For example, no gas chimneys have been observed within
the Tertiary section on 3D seismic data across the study area.. Although no major
faults have been found in 3D seismic data that transect the entire Eocene to Pliocene
interval, minor polygonal faulting has been observed within the upper part of the
Hordaland Group
The importance of stratigraphic plays in the undiscovered resources of the UKCS
This paper analyses the demographics of existing Un
ited Kingdom Continental
Shelf (UKCS) fields
and discoveries as a means of
assessing which plays are likely to offer the greatest untapped
potential for stratigraphic traps. The talk is illustrated with examples of proven and untested
stratigraphic traps
The remaining hydrocarbon potential of the UK Continental Shelf
The United Kingdom Continental Shelf (UKCS) has been a very successful exploration province in the last 38 years, with an average technical success rate of 31% from its 2150 exploration wells. Although the peak of exploration activity on the UKCS occurred during the 1980s and 1990s, there have been 41 technical successes from 82 wells in the last four years, representing an improved recent success rate of 50%.
Estimates of undiscovered (yet-to-find) hydrocarbon volumes have been made from a database of prospects compiled over 20 years by the UK Government. This ‘bottom-up’ method provided an estimate of the yet-to-find resources at the end of 2002 of between 3.6 and 22.9 × 109 BOE recoverable. Methodology utilizing an inverse timescale to plot cumulative discovered volumes per year provides minimum estimates of between 4.5 and 9.5 × 109 BOE in place (c. 2.5 to 4.4 × 109 BOE recoverable). Pool size distribution methodology predicts that 11.5 × 109 BOE of in-place (c. 5.8 × 109 BOE recoverable) resources remain to be found on the entire UKCS. Geographically, the UK Central North Sea and Moray Firth area is predicted to contain the largest proportion of undiscovered resources (42%). Thirty-three per cent of the yet-to-find resources are judged to lie within the Atlantic Margin region.
Eighty-three per cent of existing UKCS fields and discoveries are located within structural traps. The majority of stratigraphic and combination traps occur in association with syn-rift (Upper Jurassic) and post-rift plays. Many of the major discoveries in these traps were found serendipitously, and there has been relatively little direct exploration for stratigraphic plays. In the UK North Sea, there are few substantial remaining structural traps, except at considerable depth with attendant reservoir quality, high-pressure and high-temperature risks. The future of exploration is believed to lie with the search for subtle stratigraphic traps. Deep-water sandstone stratigraphic plays within the syn- and post-rift sequences offer the greatest potential for substantial new resources
Reconstruction and regional significance of the Coire Breac palaeoglacier, Glen Esk, eastern Grampian Highlands, Scotland
Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV
We report the results of a study of color coherence effects in ppbar
collisions based on data collected by the D0 detector during the 1994-1995 run
of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8
TeV. Initial-to-final state color interference effects are studied by examining
particle distribution patterns in events with a W boson and at least one jet.
The data are compared to Monte Carlo simulations with different color coherence
implementations and to an analytic modified-leading-logarithm perturbative
calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters
Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events
The - oscillation frequency has been measured with a sample of
23 million \B\bar B pairs collected with the BABAR detector at the PEP-II
asymmetric B Factory at SLAC. In this sample, we select events in which both B
mesons decay semileptonically and use the charge of the leptons to identify the
flavor of each B meson. A simultaneous fit to the decay time difference
distributions for opposite- and same-sign dilepton events gives ps.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
Were New Labour’s cultural policies neo-liberal?
This article assesses the cultural policies of ‘New Labour’, the UK Labour government of 1997–2010. It takes neo-liberalism as its starting point, asking to what extent Labour’s cultural policies can be validly and usefully characterised as neo-liberal. It explores this issue across three dimensions: corporate sponsorship and cuts in public subsidy; the running of public sector cultural institutions as though they were private businesses; and a shift in prevailing rationales for cultural policy, away from cultural justifications, and towards economic and social goals. Neo-liberalism is shown to be a significant but rather crude tool for evaluating and explaining New Labour’s cultural policies. At worse, it falsely implies that New Labour did not differ from Conservative approaches to cultural policy, downplays the effect of sociocultural factors on policy-making, and fails to differentiate varying periods and directions of policy. It does, however, usefully draw attention to the public policy environment in which Labour operated, in particular the damaging effects of focusing, to an excessive degree, on economic conceptions of the good in a way that does not recognise the limitations of markets as a way of organising production, circulation and consumption
Helicity of the W Boson in Lepton+Jets ttbar Events
We examine properties of ttbar candidates events in lepton+jets final states
to establish the helicities of the W bosons in t->W+b decays. Our analysis is
based on a direct calculation of a probability that each event corresponds to a
ttbar final state, as a function of the helicity of the W boson. We use the 125
events/pb sample of data collected by the DO experiment during Run I of the
Fermilab Tevatron collider at sqrt{s}=1.8 TeV, and obtain a longitudinal
helicity fraction of F_0=0.56+/-0.31, which is consistent with the prediction
of F_0=0.70 from the standard model
Search for electroweak production of single top quarks in collisions.
We present a search for electroweak production of single top quarks in the electron+jets and muon+jets decay channels. The measurements use ~90 pb^-1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DZero detector between 1992 and 1995. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process ppbar->tb+X of 39 pb. The upper limit for the t-channel process ppbar->tqb+X is 58 pb. (arXiv
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