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- Volume 22, Issue 5, 2004
First Break - Volume 22, Issue 5, 2004
Volume 22, Issue 5, 2004
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Sticking to the 'six pillars' of behavioural safety may produce the best result
By T. MarshDr Tim Marsh of Ryder-Marsh Safety reflects on some issues in behavioural safety based on his company’s experience in behaviour-based safety and on the views of delegates to the European Behavioural Safety Users Conference which Ryder Marsh facilitates and hosts every 18 months. The company, which has a number of oil company clients, has also been involved in devising behavioural safety standards for the offshore oil and gas (North Sea) industry. As we have moved from a culture of guarding and legislative compliance to one of best practice and continuous improvement, it has become apparent that even large investments in managing and designing safety often deliver diminishing returns because the vast majority of accidents are now ‘behavioural’. The UK Health and Safety Executive and industry figures suggest between 70 to 95%. Initially, much effort was spent on trying to change behaviour by changing attitudes. Unfortunately, attitude change is notoriously difficult to achieve. Even very high impact events such as the Hillsborough football ground disaster and September 11 have had limited long term impact on people's day-to-day attitudes. Further, even if attitude change is achieved, behaviour may stay the same if the environment remains unchanged. One of the most important ‘laws’ of psychology is that the influence of the environment is greatly underestimated when understanding behaviour, particularly when there has been a negative consequence. As a result, the majority of UK companies have adopted an approach that focuses directly on ‘behaviour/conditions that are the direct consequence of behaviour’. There are any number of variations on the theme - some rather better than others - but collectively they are considered ‘behavioural safety’.
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How 3DVSP has become a practical proposition
By F. DohertyFran Doherty, director software development, VSFusion, explains how 3D vertical seismic profile technology has developed into an accessible tool for enhanced subsurface imaging and provides a case history to demonstrate its application. For the past 15 years, 3D surface seismic surveys have been the accepted standard mode of subsurface geophysical illumination. The change from acquiring and processing seismic data in single two-dimensional lines to massive 3D seismic surveys has come about due to large dollar amounts of R&D investments, as well as the dramatic drop in the computation power per dollar ratio. Today, more seismic data can be acquired, and the computer power exists that enables these large data volumes to be efficiently and economically processed. Subsequently, most of the earth’s sedimentary basins have been imaged by 3D seismic data. VSP (Vertical Seismic Profile) technology has likewise evolved significantly over the last decade. Perhaps the most important technological advance in the borehole seismic sector has been the development of the multi-level downhole array tool. Before this development, each desired VSP receiver position required that the tool be transported up or down the hole, locked to the borehole wall at some discrete depth, and after recording the data, unlocked and transported to the next desired location. This is a very time-consuming and hence expensive operation. The VSP multi-level array tool generally contains between five and 20 downhole receiver satellite assemblies. The spacing of these receiver satellites is variable, but in general they are spaced at approximately 15 m intervals. Each receiver satellite contains three orthogonally positioned geophones which are capable of recording the full downhole seismic vector waveform response. Compressional (P) and Shear (S) wave data can be recorded, and the waveforms identified and separated with careful VSP processing. Being able to deploy and record waveform data at multiple subsurface depths from a single source position has dramatically reduced VSP data acquisition cost, while dramatically increasing the amount of borehole seismic data that can be acquired.
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Clarion system calls for new approach to downhole seismic in reservoir management
By T. BostickSeismic technology traditionally has played a role in exploration, rather than production, of hydrocarbons. Weatherford, one of the big oil services companies, believes that its new optical seismic sensing system is changing the way the industry applies the technology. After four years of development and field testing, its permanent, in-well Clarion system is now being commercially deployed on a worldwide basis and integrated with other permanent optical sensing products and in-well flow controls for production optimization and reservoir management. Tad Bostick, vice president of business development for Weatherford's Intelligent Completions group, describes the background to the development. In the late 1970s and early 1980s, the industry began to recognize the potential of in-well seismic methods for improving exploration success, reducing drilling costs, controlling uncertainties and improving productivity. These years witnessed an explosive growth of interest in, and use of, vertical seismic profiling (VSP). The conventional seismic check shot survey was transformed to VSP when more well positions were occupied and the entire wavefield sampled by downhole geophones was processed. The acquired seismic signature of the earth was used for independently checking and correlating the surface seismic response. Placement of subsurface sensors, direct measurement of velocities and time versus depth, and the ability to link between the different scales of the various data, enabled comprehensive calibration of surface seismic with well information. Offsetting the source from the receiver (offset vertical seismic profiling, or OVSP) provided higher-resolution structural and stratigraphic images than did surface seismic profiling, despite a spatially limited investigation; but singlelevel tools were costly in terms of rig time, and rudimentary processing restricted widespread adoption of OVSP technology. The popularity of surveys using multi-source positions at surface with fewer well stations, together with the introduction of multilevel three-component (3C) tools, renewed interest in borehole seismic techniques in the late 1980s. In the following decade, the focus of research turned to further integration of surface seismic data, core data, and well logs. Borehole seismic profiling was the natural link; but the geophysical data extracted from this technique were not reliable enough, and acquisition costs were prohibitive. Unfortunately, the price of oil dropped at this time and oil companies restructured to meet increased pressure on nearterm financial targets, significantly curtailing further research. However, the perseverance of a few and some advances in acquisition and processing techniques ultimately made possible the provision of cost-effective borehole seismic data of the required quality. The most significant technical breakthrough was the introduction of more reliable, higher-capacity, multilevel 3C tools, which allowed rapid, simultaneous data acquisition from many levels. Better understanding of seismic wave theory yielded comprehensive 3C processing, resulting in more complete P- and S-wave images. Newer seismic techniques, such as hydraulic fracture mapping and micro-seismic monitoring, were also emerging as viable. By the end of the 1990s, improved desktop processing capability allowed rapid interpretation of borehole seismic data using optimized 3C processing sequences. Three-dimensional (3D) VSP became feasible and is now being vigorously pursued. The borehole seismic image was transformed again into even more useful volumetric information. The next step in the evolution of the technology is permanent sensing. Development of smaller, more rugged, fit-forpurpose optical sensors and state-of-the-art optical multichannel instrumentation has enabled the implementation of reliable seismic arrays for long-term deployment within the tight constraints found in well-bores.
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Pythagoras and the mystic Orient
By P. HubralWe welcome this opportunity to publish a further essay from Prof Peter Hubral, professor of applied geophysics at Karlsruhe University, whose personal intellectual quest extends well beyond geoscience to the evolution of modern scientific thought and the search for wisdom. This article is based on a talk delivered in March to the Emirate Society of Geoscientists (ESG) and the Society of Petroleum Engineers (SPE) in Abu Dhabi. Pythagoras (570-ca. 546 BCE) was a scientist and a sage. He was apparently born in Syria and travelled through the Middle East from where he brought knowledge and wisdom to the West. Though there is nothing written from Pythagoras himself, there are many references made about him and his teachings by philosophers and sages, who followed his footsteps. They allow us to reconstruct a personal profile about him and his doctrine. According to this, he accepted that humans, as part of their cultural evolution, suffer a certain loss of soul. This appears to result from an inner struggle between the mind dedicated to gaining knowledge and the soul required to gain wisdom. Pythagoras and his followers appear to have known what are today little understood ways of recovering the loss of soul in order to lead a harmonious life with oneself, others and nature. At a time like ours, where the relationship between the East and the West is tense, it is satisfying to know that there existed at one time people like Pythagoras, who not only have united the East with the West culturally, but have inspired soul searchers through the centuries from both parts of the world. Pythagoras had the reputation that he cultivated - with the help of Oriental mysticism - a harmonious relationship between mind and soul in himself and his students. The mind is for me that spiritual part in us, which is engaged with the outside world and the soul is that part related to our inner self. To the mind I count such functions as rationality, inductive thinking, will, control, study and demonstration. To the soul I count, for instance, reason, hope, love, emotion, intuition, creativity and tolerance.
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Integrated crosswell seismic: case histories in advanced technology to improve reservoir description
Authors M. Antonelli, F. Miranda, L. Terzi and G. ValentiM. Antonelli, F. Miranda, L. Terzi and G. Valenti, Eni E&P Division, provide an updated version of a paper first presented at the Offshore Mediterranean Conference and Exhibition in Ravenna, Italy, in March 2003 in which they illustrate the role of integrated crosswell seismic in reservoir management strategies with a number of case histories.
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Suppression of guided waves using the Karhunen-Loeve transform
Authors A. Bitri and G. GrandjeanGuided waves are the major source of coherent noise, either on terrestrial or on marine seismic data, because the signals they produce are much stronger in amplitude than the reflected ones. In marine contexts, these waves exhibit characteristics that depend on the water depth, on the geometry and on the material properties of the substrata. Guided waves – or ground roll – are dispersive, which constitutes their main property. This means that each frequency component of the wave travels at a different velocity, in the sense that smaller and larger wavelengths are respectively influenced by the seismic properties of the shallower and deeper parts of the media. Due to their linear moveout-versus-offset characteristics, it may be possible to suppress the guided waves by dip filtering techniques. Unfortunately, this kind of filtering causes serious distortion of the signal when the amplitude of guided waves is much stronger than that of reflection (Liu 1999). The method developed here consists of extracting the guided waves from common-shot gathers without disturbing the reflection signals. This operation is carried out on each shot gather in three steps: 1 Imaging the guided waves dispersion curve by a wavefield transform. 2 Applying a dynamic linear moveout (DLMO) in order to flatten the guided waves using the velocity functions estimated in the previous step. 3 Extracting the guided waves from the shot gather using a zero-lag Karhunen-Loève transform (K-L), and then subtracting these from the original data followed by inverse dynamic linear moveout. This procedure is described step-by-step in the following section and is applied to a real data set for illustration and discussion.
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LIFT: a new and practical approach to noise and multiple attenuation
Authors J. Choo, J. Downton and J. DewarThere is perhaps no greater frustration to the seismic interpreter than to have signal obscured by noise. This is a common occurrence and many noise attenuation algorithms have been developed to address it. Most methods attempt to separate the desirable signal from the undesired noise, usually by making use of some transform into a domain where the signal or noise is modelled mathematically, and signal and noise can be separated. Most historical noise suppression methods stop at separating noise and signal. That is, the signal model itself is the output of the noise attenuation program. Some methods go slightly further by adding back a percentage of the original input data. LIFT, Core Lab's new proprietary amplitudefriendly technique for attenuating noise and multiples, takes a new approach by adding back an estimate of the signal removed during the signal modelling, rather than adding back a percentage of the original data. This is a fundamental shift in noise suppression strategies. It is an approach that is very flexible in that it can incorporate a variety of application domains, filtering tools, and new technologies and ways of modelling data – including future technologies as they are developed. It is an approach that greatly improves signal preservation, making quantitative AVO and rock properties analyses much more reliable. Also it is a robust amplitudepreserving way to precondition data for prestack migration, avoiding migration artifacts and costly re-runs. The primary amplitudes after LIFT are trustworthy, making prestack migration with AVO now a realistic option.
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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)