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- Volume 40, Issue 1, 2022
First Break - Volume 40, Issue 1, 2022
Volume 40, Issue 1, 2022
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Multispectral Dip for Improved Geometric Attribute Computations
Authors Satinder Chopra and Kurt J. MarfurtAbstractAccurate estimates of volumetric dip serve as input for curvature, aberrancy, reflector convergence attributes, guide the application of structure-oriented filters and the computation of coherence, amplitude gradient, as well as GLCM texture attributes. Different frequency components can exhibit slightly different dips, due to the differences in their resolution and sensitivity to noise. Research during the last few years has shown that multispectral coherence computed by summing the covariance matrices of individual spectral voice components can provide significant improvement over coherence computed from the covariance matrix computed from the original broadband data. A similar workflow can be constructed by computing multispectral dip by summing the gradient structure tensors computed from the individual spectral voice components. We apply this workflow to two different seismic datasets from the Taranaki and Canterbury Basins of New Zealand and find that the resulting multispectral dip estimates exhibit sharper images than those computed from the original broadband data. Images from the Taranaki dataset show improvements on the definition of a fault system, whereas those from the Canterbury dataset exhibit enhanced definition of faults and associated fractures as seen on the dip estimates, as well as both structural and amplitude curvature displays
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Advances in Vibroseis Technology
More LessAbstractThe development of vibroseis technology in the 1950s ushered in a new era in seismic data acquisition. The vibroseis gave control of the source wavelet and frequency range to the user. In addition, the vibroseis is a surface-mobile source, which does not require substantial site preparation. Combined, the technical advantages of the vibroseis and its operation benefits make the vibroseis source the primary method for acquiring seismic data on land today.
Vibroseis technology has advanced dramatically since the early days. The most recent innovations in vibroseis span areas ranging from mechanical engineering to software and controller development. This article will discuss the latest innovations in vibroseis technology and explain the benefits expected to be derived by contractors and explorationists.
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Evaluating an Unconventional Shale Completion with Repeat Crosswell Tomography
Authors David Rampton and Mitch SmallAbstractEvaluation of hydraulic fracturing relies on indirect inference from measurements that are distorted by distance and noise of various kinds, so reservoir monitoring technology that places the measurement as close to the completion as possible is important. Crosswell tomography is just such a technology, placing source and sensor in the plane of the feature to be analysed, and is an excellent technology for making in situ estimates of subsurface properties in simple geologic settings when source-receiver separation is small and when noise levels are low. Since these conditions are not typical in-field scale surveys of unconventional shales, this study overcomes these deficits by incorporating vertically transverse isotropy in raytracing and applying a strong source effort to increase signal-to-noise. The survey used Schlumberger’s Ztrac source and multicomponent geophones to both generate and record compressional and shear wave energy, matching baseline and repeat surveys within a few days of hydraulic fracturing to detect subtle timelapse changes prior to flowback and fluid diffusion. The result is a unique characterization of fracture creation due to hydraulic fracturing, highlighting an out of zone response and subsequent impact on the bounding limestone layers.
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The Diminishing Returns of Low-Frequency Vibroseis and How Only Physics Will Get Us out of the Rut
Authors Spencer L. Rowse and Bob HeathAbstractAll land seismic sources are inefficient in the conversion of their energy/force, generated at the surface, into useful seismic signals. It is not commonly known that less than 5% of the source’s energy is converted into energy of the propagating wave. Until now, one of the objectives of the designers of land seismic sources has been to increase the maximum force (or energy) output at the surface to increase the amplitude of the seismic signal. Today’s vibroseis sources, at about 40 tonnes, are at their maximum size and weight limits for many road infrastructures limiting their areas of use, as well as being beyond the budget of most seismic operators. As force output is related to vehicle weight (hold down force), the vibroseis source is effectively at its maximum output (and therefore maximum seismic signal) under its current configuration. For this reason, to achieve further increases in the amplitude and frequency content of the propagating seismic signals, the emphasis in future research and development must be in understanding the many factors that are involved in the conversion of the force/energy generated by the surface source into useful seismic signals. This has been missing in the past; it is where only physicists can play a role.
In this article, we discuss the physics of impulsive and vibroseis sources and their interactions with the ground to show that improving the amplitude/frequency content and efficiency of the vibrator, especially at low frequencies, cannot be fixed by ‘mere engineering’.
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Mastering the Highest Vibroseis Productivity While Preserving Seismic Data Quality
Authors Nicolas Tellier, Gilles Ollivrin, Stéphane Laroche and Christophe DonvalAbstractIncreasing the productivity of seismic acquisition projects has been a key goal for contractors and operators for decades now. It remains topical, mainly in respect of efforts to increase a given project’s trace density for a cost in line with the resulting reservoir quality uplift.
The Middle East and North Africa have traditionally pioneered the development and introduction of advanced productivity techniques, given the presence of large hydrocarbon deposits located beneath open terrain with limited anthropogenic activity. After the successful introduction of several high-productivity methods in the region, two of them – DS4 and Unconstrained Vibrators – have won recognition and are now standard on most projects. While the level of productivity these methods enable is unprecedented, they still show some scope for improvement: the productivity of DS4 is not the highest achievable, whereas the aggressive blending associated with unconstrained vibrators acquisitions can affect the overall imaging quality.
In this paper, we introduce a new high-productivity methodology, at the confluence of the two aforementioned methods while addressing their limitations. xDSS makes it possible to reach the ultra-high productivity enabled by unconstrained vibrators, while preserving the blended acquisition golden rules ‘randomness in time and space’ and ‘sparseness in the frequency – wavenumber domain’. The automated observance of these two rules makes it possible to get as close as possible to the maximum achievable source productivity, while delivering to the processors a deblending-friendly dataset.
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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)