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- Volume 17, Issue 6, 1999
First Break - Volume 17, Issue 6, 1999
Volume 17, Issue 6, 1999
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Brazil prepares itself for an international invasion
By A. McBarnetBrazil is finally opening its doors to the international oil industry with major prospects in view for oil companies and their contractors. It has been a tortuous process but a new chapter in Brazilís remarkable oil and gas history is about to be written. Andrew McBarnet recounts the story so far. This month the identity of successful bidders for blocks in the Brazil Round 1 will be known. It will be a highly significant landmark in the opening up of Brazil's oil and gas industry to the international industry after over 40 years' reliance on the monopoly for the state oil company Petrobras. The story of Brazilís sudden change of heart over the virtue of a nationalized oil industry has been fuelled partly by a worldwide turning away from state control. More pertinently there has been growing concern over the country's oil import import bill and the need to increase home production as rapidly as possible, a task regarded as beyond Petrobras. The company was founded in 1953 as a state monopoly of the company's oil industry, upstream and downstream. It inherited from the former National Oil Council oil fields with a capacity to produce 2700 b/d as well as downstream interests in refineries, tankers and the like. Its recoverable reserves of oil were at that time put at 15 million barrels. The company's fortunes and stature in the world industry changed dramatically following the discovery of the Guaroupa field in the Campos Basin in 1974, which put Petrobras on the road to developing some of the most innovative offshore technological projects in the world, setting records for deep water production along the way. By 1981 the Guaroupa, Namorado, Anchova, Pampo and Badejo fields were in production producing over 50% of the countryís oil and gas. Today offshore production of oil and natural gas represents 73% of the total output of Brazil.
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Modelling and filtering of surface scattering in ground-penetrating radar waves
Authors M. Bano, F. Pivot and J.-M. MarthelotGround-penetrating radar (GPR) is a geophysical method based on the propagation, reflection and scattering of high-frequency (from 10 MHz to 1 GHz) electromagnetic (EM) waves in the subsurface (Daniels et al. 1988). This method is currently used to image the subsurface and has myriad applications; void detection; prediction of deterioration in railroads, airport runways and concrete; detection of archaeological objects; mapping of subsurface wastes and contaminants in environmental engineering (Owen et al. 1995); stratigraphic and bedrock mapping and hydrological applications (Beres & Haeni 1991; Van Overmeeren 1994); mapping faults hidden under vegetation cover (Meyers et al. 1996; Liner & Liner 1997). The depth of investigation depends on the frequency used and on the medium traversed by EM waves; for low-loss geological materials it does not exceed 50 m (Davis & Annan 1989). In some cases, GPR data show strong diffraction hyperbolae due to surface objects on the ground. EM waves propagate with little attenuation in air and conductive surface objects (power lines, metallic fences) and trees are strong reflectors, so reflections from above-ground features are often present in GPR data (Sun & Young 1995). Thus, it is very important to recognize and distinguish if the diffractions are from subsurface heterogeneities (Papziner & Nick 1998) or from surface scattering and not to confuse the latter with the subhorizontal geological reflections. A method of modelling and filtering such surface scattering is presented in this paper. Migration of radar data with the free-space velocity focuses the air diffractions producing large isolated amplitudes. Subsurface reflections are overmigrated (not focused) and random Gaussian noise is defocused and becomes more Gaussian (Harlan et al. 1984). After applying a filter in amplitude (treshold) to the migrated data, only the large amplitudes of the focused hyperbolae are preserved. Then the result is diffracted with the same velocity (free-space velocity) to produce synthetic air diffractions. Finally, a comparison of the synthetic air diffractions with the real data removes the surface scattering from the original data. The methodology described in this paper is tested and illustrated on two examples of GPR profiles which show strong surface scattering from objects on the ground.
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Improving the subsurface geological model while drilling
Authors L. Bertelli and F. di CesareThe revision of a well prognosis has, until comparatively recently, been possible only at the end of a drilling phase. As an inevitable consequence, the new data and the conclusions arising from the revised prognosis come too late to change the drilling or operational programme in any way. This paper discusses a technique whereby information gathered during drilling can influence the course of the drilling. These techniques are Seisbit or Seismic While Drilling (SWD) (Widrow 1990; Rector et al. 1991; Abramo et al. 1996; Miranda et al. 1996; Poletto et al. 1997), and Migration While Drilling Continuously (MWDC) (Aleotti et al. 1995). Both were pioneered by AGIP and are implemented using the software package Drilling and Real Time Migration (DREAM*), developed jointly by Agip and Western Geophysical (AGIP & Western Geophysical 1997).
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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)