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- Volume 20, Issue 12, 2002
First Break - Volume 20, Issue 12, 2002
Volume 20, Issue 12, 2002
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iSIMM pushes frontiers of marine seismic acquisition OBS
Authors R.S. White, P.A.F. Christie, N.J. Kusznir, A. Roberts, A. Davies, N. Hurst, Z. Lunnon and C.J. ParkinLast summer (2002) the iSIMM (integrated Seismic Imaging and Modelling of Margins) project successfully completed a seismic programme on the northwest European Atlantic margin with OBS acquisition by the NERC vessel Discovery and Q-Marine acquisition by WesternGeco’s Geco Topaz. This project is pushing the frontiers of technology in seismic acquisition targeted at subbasalt and deep crustal imaging. These data will constrain new theoretical models which address the development of rifted continental margins, including the effects of dynamic support by mantle plumes and the production and intrusion of igneous melt.
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Q-Marine seismic acquisition results: report from WesternGeco
By L. LarsenQ-Marine is the outcome of a 10-year programme that began with a Schlumberger research project to identify the most significant sources of noise in seismic data. This was followed by the development of new seismic technology to suppress or minimize that noise. The resulting system particularly addresses variations in source characteristics and receiver sensitivity, swell noise from wave action, and positioning errors associated with receiver groups. In addition to improved resolution and bandwidth, the system delivers properly calibrated data for 4D time-lapse analysis of reservoir fluid movement.
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How PGS created a new image for the Varg field
Authors P.A. Reksnes, E. Haugane and S. HegnaHistory of Southern North Sea Licence 038 Production Licence 038 (see Fig. 1 for location) is today owned by Pertra (70%), and the Norwegian state through Petoro (30%). Pertra is a wholly owned subsidiary of Petroleum Geo-Services (PGS). Licence 038 includes both the Varg oil-field and the Varg South structure (previously called Rev). Oil and gas was found on Varg South in 2001, but this structure needs further appraisal before decisions about its development can be taken. Norwegian authorities approved the plan for field development and operations for the Varg field in 1996. It was decided to use an FPSO (Floating Production Storage and Offloading) vessel to produce the oil. The licence group at that time sold the FPSO to PGS in 1999, and leased it back for a three year period. Through this transaction PGS came one step closer to its goal of becoming one of the world’s largest and most reliable operators of advanced FPSO vessels in harsh weather conditions. In December 2001, Norsk Hydro offered its share of Licence 038 to PGS and subsequently Statoil did the same. PGS accepted both offers, and hence currently owns 70% of Licence 038. This is the first time a service company has owned and operated an oil field in the North Sea, representing a new and interesting business model for the oil industry. Why did PGS want to go into the role as operator? The FPSO rental agreement between PGS and the previous license group was approaching a decision point and PGS had to evaluate other missions for the vessel. As licence owner it would be simpler for PGS to find the optimal time for transferring the FPSO vessel to other fields. In addition, PGS felt there was a commercial upside in applying its knowledge and technology to increase and extend the oil production of the Varg field and also in developing unrealised prospects in licence 038.
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Self-landing and ascending OBS: opportunity for commercial seismics in the ultra deep sea
Authors T. Buettgenbach and K. SchleisiekOffshore seismic exploration focuses more and more on water depths below 1000 m Nowadays, tenders for seismic surveys down to 3000 m water depths are on the increase. As the water gets deeper, so the resolution of measurements made by surface streamer tends to decrease. To obtain enhanced resolution and an indication of the fluid content of a hydrocarbon reservoir, the acquisition of shear waves is becoming of interest. This requires the data to be acquired on the seabed. To date, such surveys have predominantly been conducted using OBCs (ocean bottom cables). But there are a number of shortcomings with this type of survey: • The cable itself substantially distorts the horizontal shear wave components. • In rugged terrain, several 3C geophones may not be coupled to the ground at all. • In jagged areas, the cable may be damaged or even cut. • In rough sea, the vessel may run into trouble. • Below 2000 m the weight/strain relation of the feeder cable itself becomes uneconomical. This is why self-landing and ascending ocean bottom seismic (SLA-OBS) systems, which have been used by the scientific community for the past 20 years, offer a promising alternative, especially in the ultra-deep sea environment.
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Options for multi-component seismic data acquisition in deep water
Authors E.R. Flueh, D. Klaeschen and J. BialasIntroduction Since the discovery of ‘bright spots’ associated with hydrocarbon deposits, ever increasing interest in determining lithological subsurface parameters has been a driving force for technological development in the hydrocarbon exploration industry. Quantification of lithological parameters is of utmost importance for reservoir prediction and monitoring. Amongst various attempts to determine these, attribute analysis of pwave data and the direct observation of shear wave data are the most visible and successful methods applied. The direct observation of shear waves in the marine environment has been attempted by several means, mainly using ocean bottom cables (OBC) that have three-component geophones (3C) and a hydrophone in addition (thus 4C in total). Some manufacturers offer two component geophones with only one horizontal component. These cables are laid out on the seafloor, sometimes even buried using specialized tools like ROVs (remotely operated vehicles). Data transfer is through the cables as in streamers or land operations, recording is made on a boat or platform where the cable terminates. Geophones are housed in tubes with a self-levelling gimballed mounting system, damped by a viscous fluid. This technique is regarded as proven technology and has been widely accepted. Especially in production areas with many man-made obstacles, this technique also offers a safe operation, and is especially suitable for monitoring purposes (4D–4C seismic). Any desired geometry and density of receivers can be laid out. Direct shear wave observations have been made by several academic institutions, both for active seismic exploration as well as for passive seismological monitoring of earthquakes. These institutions have built ocean bottom seismometers (OBS), which are also four component, two sensor instruments. Unlike OBC, they are autonomously lowered to the seafloor, record within specified time windows, and are later brought back to the surface. Amongst the various instruments designed over the past decades is the OBS range built at GEOMAR, which – due to its modular design – has been used for a wide range of applications.
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Point bar geometry, connectivity and well test
Authors M. De Rooij, P.W.M. Corbett and L. BarensIntroduction Many hydrocarbon accumulations are found in fluvial deposits. This has triggered several studies into the morphology of present day and preserved fluvial systems (Carling & Dawson 1996; Martinius 1996). Ideally, these studies require detailed data in three dimensions (Miall & Tyler 1991), which are often not available. A diverse, shallow data set from the Gulf of Thailand, including high resolution 3D seismic, has made it possible to investigate the morphology of several well preserved, recently buried, meandering fluvial systems (Feng 2000; Miall 2002). The shape and internal architecture of three neighbouring point bars found in the Gulf of Thailand data have been interpreted. From these data, a numerical flow simulation model was built. Petrophysical properties were assigned from analogues. The resulting modelled well test signatures of these specific point bars are investigated. Zheng (1997) and Corbett et al. (1998) have previously discussed well testing in isolated meander loop sandstones. Here, the focus will be on lateral connectivity between the point bars.
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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)