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- Volume 16, Issue 1, 1998
First Break - Volume 16, Issue 1, 1998
Volume 16, Issue 1, 1998
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Study stresses value of UK technical reserves
Britain's most valuable remaining hydrocarbons lie with 'technical reserves' awaiting the right economic and technological conditions to be exploited. First Break reports on a new study by energy analyst Wood McKenzie. Is the opening up of the Atlantic Margin such a good deal? That is the question asked by energy analyst company Wood Mackenzie. In a new study it says that the development of the UK Continental Shelfís (UKCS) technical reserves provides 'a serious alternative to tackling the technological requirements of exploring new reserves, particularly in the frontier areas such as the Atlantic Margin. According to Wood Mackenzie technical reserves make up 22% of the remaining recoverable reserves in the UKCS. This amounts to some 4.8 billion barrels of oil equivalent (boe) out of the total remaining reserves figure of 21.6 billion boe. The technical reserves are thought to be split between some 2850 million barrels of recoverable liquids and 11.2 trillion ft3 of recoverable gas reserves.
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'The truth is in there' for geoscientists exploring new visualization technology
By A. McBarnetWalk-in 3D effects are about to join the panoply of techniques available to multi-disciplinary teams searching for a better picture of the subsurface. Andrew McBarnet reports on two pioneering projects. The way we look at petroleum data may well be about to change for ever. That's the impression you get listening to scientists enthusing about the latest 'virtual reality' visualization technology being pioneered notably by Norsk Hydro and Texaco with other oil companies expected to follow suit. Norsk Hydro last month became the world's first oil company to install a CAVE facility. Housed at its research centre in Bergen, CAVE uses sight, spatial awareness and sound to present information in an immersive, experiential environment which is impossible to create with the flat-screen keyboard and mouse interfaces of ordinary workstations. To experience the CAVE users have to wear lightweight stereo glasses. They can then walk into the three dimensional nine feet square space where they can visualize and manipulate different types of geological and reservoir data and models. In effect, the user can walk around and discuss the reservoir with colleagues. For example, by using a 3D pointer, a new production oil well can be planned from inside the reservoir and the effects of any changes can be immediately experienced.
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Offshore elephants are awaiting South Atlantic hydrocarbon hunters
South Atlantic abyssal plain is the emerging new exploration frontier, according to a new study by Petroconsultants of the deep water between Africa and Brazil. The report makes use of previously unworked seismic data in predicting big finds in the area. Elephant hunting is back in fashion, not just in Africa but across to Brazil. That's how Petroconsultants whimsically refers to the essence of its important new study of the deepwaters of the southern Atlantic which predicts a crop of giant 'elephant' size oil field discoveries over the next few years. The new finds will not, however, confirm to the classical concepts shaped from shallower exploration. Shelf concepts cannot be extrapolated to the slope, and the slope will not reflect the ultimate challenge of the abyssal plain. But Petroconsultants asserts with some authority that a major new oil province is emerging between the Girassol and Dalia 'elephants' on the African side and Marlim, Albacora and Albacora-Leste offshore Brazil. The South Atlantic African Basins study foresees exploration extending from water depths of 500-2000 m to ultra deep water depths of 2000-4000 m. The target will be giant turbiditc sandstone bodies on the plain of the ocean abyss. It will mean massive investments, high risk but hopefully rich rewards.
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Modelling in thrusted areas - sensitivity analysis and application
Authors P. Svara, A. De Poli, K. Leischner, F. Mosca and C. TurriniCompressional areas frequently provide potential exploration targets and therefore an understanding of the effects of overthrusting and structural evolution on rock thermo/physical history and, consequently, on hydrocarbon generation and expulsion processes, can effectively contribute to reducing exploration risks. As many uncertainties in the available information occur in this geological scenario (seismic resolution, structural interpretation, source rock evidence, lack of well measurements, etc.), this paper demonstrates the potential for an integrated approach which improves the quality of the final interpretation, which attempts to predict the petroleum system. We will verify how it may be possible to make use of numerical simulations, both in the structural and geochemical fields, to define the factors which have most impact on the relationship between the timing of hydrocarbon expulsion (primary migration from potential source rocks) and the age of trap formation. The significance of some uncertainties in the available data and the model can also be estimated through `sensitivity analysis' techniques. This allows the investigation of the effects of pressure/temperature linked to successive phases of thrusting, erosion and deposition on potential source rocks, emphasizing the strong tectonic controls not only on the hydrocarbon generation but also on the more crucial expulsion process. In a case history, it will be demonstrated how the use of non standard thermochronology analysis as AFTA (Apatite Fission Track Analysis) and fluid inclusions can better constrain the thermal and burial history of thrust belts, with respect to traditional methods based only on vitrinite reflectance data. This approach is very useful particularly when erosional events, which may cause cooling episodes, heavily control the period in which maximum temperatures are reached. For instance, measured maturity data may not be representative of the present day thermal regime in a basin, especially in the belt's inner part where uplift is more common, and therefore an estimate of the age of erosion and the thickness of the missing sediments has to be determined.
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Deformation bands and their significance in porous sandstone reservoirs
Authors H. Fossen and J. HesthammerGeologists and engineers in the oil industry are becoming increasingly aware of the importance of small-scale (sub seismic) faults and fractures in many reservoirs, but modelling of such structures is currently hampered by our limited understanding of these structures. The many fault parameters that, directly or indirectly, should be input to advanced reservoir simulation models include the number, distribution, orientation, geometry, displacement, length, and petrophysical properties of small-scale faults and deformation bands. In porous sandstone reservoirs, which are the focus of the current contribution, deformation bands with displacements less than a few tens of centimetres are generally developed instead of slickenlined fault surfaces typical for less porous lithologies. Deformation bands may show reduction in permeability by up to three orders of magnitude (Antonellini & Aydin 1994). This parameter needs to be estimated for each field or reservoir level, as it will depend on degree of lithification during deformation (for example, increasing depth during faulting implies increased influence of cataclasis and therefore stronger reduction of permeability across the deformation bands). Although of less importance at the exploration stage (Harper & Lundin 1997), deformation bands that significantly reduce permeability may be very important with respect to production from sandstone reservoirs. Displacement, as an isolated parameter, is of less importance, as it generally is too small for deformation bands to cause sealing by juxtaposition of sand and shale layers. Field studies have shown that deformation bands generally can be modelled as straight structures that are particularly numerous around larger faults, but may also occur as scattered structures between seismically resolvable faults (e.g. Antonellini & Aydin 1995). Much work is left to explore the relation between the distribution of micro faults and larger structures. However, the question of distribution must always be addressed in each case, for example by use of attribute maps and core data (e.g. Hesthammer & Fossen 1997). In this work we will discuss the length vs. displacement of small-scale structures (deformation bands) in porous sandstones. It has been suggested that length and displacement can be scaled down from the size range covered by seismic data to the sub seismic domain (e.g. Yielding et al. 1992). The underlying assumption is that displacement and length are related through a power law and thus are fractal by nature. Down-scaling of fault length and displacement has already been applied as input to sandstone reservoir simulation models (e.g. Gauthier & Lake 1993). We here present new results from a population of deformation bands and discuss why properties of the seismically mappable part of a fault population cannot necessarily be extrapolated far into the sub seismic domain.
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Volumes & issues
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Volume 42 (2024)
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Volume 41 (2023)
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Volume 40 (2022)
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Volume 39 (2021)
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Volume 38 (2020)
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Volume 37 (2019)
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Volume 36 (2018)
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Volume 35 (2017)
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Volume 34 (2016)
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Volume 33 (2015)
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Volume 32 (2014)
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Volume 31 (2013)
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Volume 30 (2012)
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Volume 29 (2011)
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Volume 28 (2010)
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Volume 27 (2009)
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Volume 26 (2008)
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Volume 25 (2007)
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Volume 24 (2006)
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Volume 23 (2005)
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Volume 22 (2004)
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Volume 21 (2003)
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Volume 20 (2002)
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Volume 19 (2001)
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Volume 18 (2000)
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Volume 17 (1999)
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Volume 16 (1998)
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Volume 15 (1997)
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Volume 14 (1996)
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Volume 13 (1995)
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Volume 12 (1994)
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Volume 11 (1993)
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Volume 10 (1992)
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Volume 9 (1991)
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Volume 8 (1990)
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Volume 7 (1989)
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Volume 6 (1988)
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Volume 5 (1987)
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Volume 4 (1986)
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Volume 3 (1985)
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Volume 2 (1984)
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Volume 1 (1983)