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- Volume 39, Issue 7, 2021
First Break - Volume 39, Issue 7, 2021
Volume 39, Issue 7, 2021
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Seismic response of gas-hydrate zones: a case study from the Oman Sea
Authors Oz Yilmaz, Ali Misaghi, Nasser Keshavarz and Mojtaba S. ArabaniAbstractAn offshore vintage 2D seismic dataset acquired in the Oman Sea recently has been reprocessed to achieve two objectives: mapping gas-hydrate zones and structural imaging beneath the bottom-simulating reflector (BSR). We present results of the analysis of the seismic data associated with three seismic lines in the project area. The sea-bottom water-saturated sediment column (WSZ) has an average thickness of 100 m and an interval velocity range of 1550–1700 m/s. The underlying gas-hydrate stability zone (GHSZ) has an average thickness of 180 m and an interval velocity range of 2000–2200 m/s. The BSR with its low-frequency, large-amplitude character is very prominent in the seismic images derived from prestack time migration (PSTM). The BSR defines the base of the GHSZ and thus is a crucial indicator of the presence of a gas-hydrate zone. Velocities close to the top of the GHSZ interval are slightly lower at some locations along the line traverses – indicative of a transitional boundary between the WSZ and GHSZ. The overthrust tectonics during the Mid-Miocene to Pliocene caused by the counterclockwise rotation of the Arabian Plate is evident in the seismic images. The resulting thrust faults may facilitate upward migration of fluids and gas, thus forming the free-gas zone beneath the BSRs.
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Viscoacoustic diffraction imaging to delineate karst features in a carbonate reservoir
Authors William A. Burnett, Craig Hyslop, Jaewoo Park, Alecia Wawrzynski, Arjun Srinivasan, Spyros Lazaratos, Gboyega Ayeni, Da Zhou, Debra Carlo, Mike Lahey, Patricia Montoya, William Espegren, Brandon M. Phillips, Trung Tâm Lê, Thanh Hà Mai, Văn Thanh Đỗ, Đúóng Trung Nguyễn, Thị Minh Huệ. Đặng and Duy Anh NguyễnAbstractWe demonstrate an attenuation-compensated diffraction imaging workflow to image complex carbonate reservoirs with overburden challenges including shallow gas accumulations. Diffraction separation is performed on pre-migration regularized common-offset gathers compatible with Kirchhoff migration, which allowed us to migrate the diffractions using our preferred viscoacoustic algorithm for the field. When carried out in parallel with conventional seismic data processing, diffraction analysis can help to constrain process parameters and decisions, ultimately leading to better results for both. We show that seismic attributes derived from such a workflow can help to better delineate karsts, fractures, and collapse features, which can be incorporated into the reservoir model and improve our confidence in well placement.
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Probabilistic forecasting for geosteering in fluvial successions using a generative adversarial network
Authors Sergey Alyaev, Jan Tveranger, Kristian Fossum and Ahmed H ElsheikhAbstractQuantitative workflows utilizing real-time data to constrain uncertainty have the potential to significantly improve geosteering. Fast updates based on real-time data are particularly important when drilling in complex reservoirs with high uncertainties in pre-drill models. However, practical assimilation of real-time data requires effective geological modelling and mathematically robust parameterization. We propose a generative adversarial deep neural network (GAN), which is trained to reproduce geologically consistent 2D sections of fluvial successions. Offline training produces a fast GAN-based approximation of complex geology parameterized as a 60-dimensional model vector with standard Gaussian distribution of each component. Probabilistic forecasts are generated using an ensemble of equiprobable model vector realizations. A forward-modelling sequence, including a GAN, converts the initial (prior) ensemble of realizations into EM log predictions. An ensemble smoother minimizes statistical misfits between predictions and real-time data, yielding an update of model vectors and reduced uncertainty around the well. Updates can then be translated to probabilistic predictions of facies and resistivities. This paper demonstrates a workflow for geosteering in an outcrop-based synthetic fluvial succession.
In our example, the method reduces uncertainty and correctly predicts most of the major geological features up to 500 m ahead of drill-bit.
The condensed summary is also submitted for presentation at the 3rd EAGE/SPE Geosteering Workshop to be held 2–4 November 2021, online.
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Cloud-computing approach for an environmental, social, and corporate governance focus in universities and businesses
Authors Nicholas T. Okita and Tiago A. CoimbraAbstractThere is an increasing demand for high-performance computing on geophysical exploration applications, which implies more carbon emissions due to higher energy consumption. Furthermore, there is increasing concern about the environmental and social impact that this can generate. We show how cloud computing can handle these challenges simultaneously and thereby assist business leaders in their decision-making. Cloud computing is a paradigm in which users rent computing capacity from providers on a pay-as-you-go basis, thereby reducing the carbon footprint by up to 88%. It can run software for years uninterrupted using the same capital required to acquire and run on-premises infrastructure, even if such infrastructure has over a thousand graphics processing units. However, the managers must consider that challenges arise from using the cloud, such as trusting their data in a third-party server and expenses throughout the years, especially with storage.
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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)