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- Volume 40, Issue 6, 2022
First Break - Volume 40, Issue 6, 2022
Volume 40, Issue 6, 2022
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Phase Decomposition and Its Applications
AbstractWe discuss the recently introduced phase decomposition analysis, which entails amplitude variation with time for a specific seismic phase. Assuming a zero-phase wavelet embedded in the seismic data, while flat spots or unresolved water contacts may be seen on the zero-phase component, thin-bed and impedance changes will show up on phase components that are 90° out of phase with the wavelet. Similar bright spots caused by thin hydrocarbon reservoirs are associated with low impedance and show up on the phase component that is −90° out of phase with the embedded wavelet. In all cases the interpretation of bright spots is found to be convenient, and easier with the use of −90° seismic phase component. In this paper, application of phase decomposition to a few instances are first demonstrated through synthetic data examples, followed by a couple of real seismic data case studies. In particular, the case study from a gas storage reservoir in Denmark exhibits how phase decomposition can aid interpretation efforts. Some of the typical issues that seismic interpreters might come across, including the one where the input seismic data might have a phase different from zero phase are elaborated in the ‘Discussion’ section.
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Quaternary and Neogene Reservoirs of the Norwegian Continental Shelf and the Faroe-Shetland Basin
AbstractGlaciogenic reservoirs host important hydrocarbon resources across the globe. Examples such as the Peon and Aviat discoveries in the North Sea show that Quaternary and Neogene reservoirs can be prospective in the region. In this study, we interpret 2D and 3D reflection seismic data combined with borehole information to document unconventional play models from the shallow subsurface of the Norwegian Continental Shelf and the Faroe-Shetland Basin. These plays include (i) glacial sands in ice-marginal outwash fans, sealed by stiff subglacial tills (the Peon discovery), (ii) meltwater turbidites, (iii) contouritic fine-grained glacimarine sands sealed by gas hydrates, (iv) remobilized oozes above large evacuation craters which are sealed by megaslides and glacial muds, and (v) Neogene sand injectites. The hydrocarbon reservoirs are characterized by negative-polarity reflections with anomalously high amplitudes in the reflection seismic data as well as density and velocity decreases in the borehole data. Extensive new 3D reflection seismic data are crucial to correctly interpret glacial processes and distinguish shallow reservoirs from shallow seals. These data document a variety of play models with the potential for gas in large quantities and enable the identification of optimal drilling targets at stratigraphic levels which have so far been overlooked.
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Diffraction Imaging of the Fractured Crystalline Basement, Lancaster Field, UK
Authors Roger White, Hannah Kearns, Artem Kashubin, Evgeny Landa and Konstantin SmirnovAbstractIn this paper, we demonstrate the application of seismic diffraction imaging technology to map the distribution of faults within Hurricane Energy’s operated, fractured basement fields, offshore West of Shetland. After the reprocessing of legacy 3D seismic data in 2018, it became apparent that the reflection seismic image had limited ability to image the intra-basement structure. Intra-basement imaging is crucial for understanding the distribution, frequency and geometry of intra-basement structures which directly influence production trends in fractured basement reservoirs. Diffraction imaging is a novel seismic processing technique that can produce high-resolution images of small-scale scattering subsurface events by extracting and focusing the diffractive component of the total wavefield to its subsurface origin. Analysis of the diffraction imaging seismic volume alongside well data and other seismic products can complement conventional seismic attributes and enhance the interpretational value of the seismic data. This paper shows how the intensity of the diffraction image varies from location to location across the Rona Ridge and is seen to have a strong, positive correlation with observed well productivity. As such, the application of this technology shows great promise to provide additional information for detailed analysis of Hurricane Energy’s fractured basement reservoirs and can facilitate new well placement and trajectory design.
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Energy Transition or Energy Mix?
By Garry KolafaAbstractIn light of the enormous tension that has been generated by different views on energy policy, a discussion is offered of the general problematics associated with the provision of various energy solutions. The primary objective is to look at how to manage these problems, beginning with attitudes, progressing to understanding solution constraints and enablers, and followed by a baseline for evaluation and comparisons to aid decision-making processes. The discussion hopes to bring some clarity in tackling our current and future energy problems in the light of mixing energy options and working towards a realistic energy transition that suits our future.
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Early Detection of Non-Conformance in Monitoring of CO2 Storage Reservoirs Using Auto-Encoder Neural Networks
Authors Eduardo Barros and Boris BoullengerSummaryPlanning and managing operations of subsurface reservoir assets in terms of conformance is crucial for responsible CO2 storage. One important component of conformance management is the monitoring of the reservoir dynamics in response to the implemented operational strategies, particularly for early detection of deviations from intended behaviour (i.e., non-conformance). In recent work, we have introduced a model-based quantitative workflow to objectively assess the usefulness of monitoring for conformance verification in CO2 storage and shown how to use state-of-the-art supervised learning techniques to achieve a more practical workflow. In the present work, we investigate the use of a semi-supervised anomaly detection approach based on auto-encoder neural networks as an alternative to circumvent limitations of the supervised classification approaches explored so far. The results of our case study of a real storage aquifer show that auto-encoders trained on simulated time-lapse seismic data from (only) conformance scenarios can be used to accurately detect scenarios where the migration of CO2 deviates from the desired range of behaviours. These promising results confirm that the proposed approach can be used to derive efficient conformance classification workflows without an explicit finite dataset representing non-conformance to be defined in advance.
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Cover Mapping with Passive Seismics at the Boulia Prospect, Mount Isa Province, Queensland, Australia
Authors Charles D. Beard, Nicholas Arndt, Richard Lynch and Jamin CristallAbstractTo determine the thickness of sedimentary cover overlying Proterozoic basement, an ambient-noise surface-wave tomo-graphic (ANSWT) survey was conducted in the Boulia region of the Mt Isa Province in Queensland, Australia. An array of 100 three-component seismic nodes was deployed along a 30 km section and ambient seismic noise was recorded for 19 days. In the resultant seismic model, the top-basement contact is resolved as a sharp, subhorizontal interface at a depth of about 700 m, where seismic velocity (Vs) increases downward from about 2500 to 3500 m/s. The accuracy of the retrieved top-basement contact was confirmed by comparison with drill hole intersections and with results from active seismic and magnetotelluric surveys. This study demonstrates that the ANSWT method can accurately and inexpensively map the thickness of sedimentary cover that obscures potentially mineralised regions globally.
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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)