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- Volume 36, Issue 11, 2018
First Break - Volume 36, Issue 11, 2018
Volume 36, Issue 11, 2018
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High-resolution impedance estimation using refraction and reflection FWI constraints: the Fortuna region, offshore Equatorial Guinea
Authors Ian F. Jones, Jeet Singh, Stuart Greenwood, Johnny Chigbo, Phil Cox and Colin HawkeAbstractSeismic imaging and reservoir characterization in the Fortuna region, offshore Equatorial Guinea, is beset with various geophysical challenges related to the presence of extensive, but small-scale low-velocity gas pockets, which give rise to significant and cumulative image distortion at target level. This distortion had not been resolved in a vintage 2013 broadband pre-stack depth migration project, as the velocity model was not sufficiently well resolved, but was subsequently addressed successfully in a project conducted using high-resolution non-parametric tomography with improved broadband deghosted data. The primary objective of that subsequent project was to improve the understanding of the internal structure of the Viscata and Fortuna reservoirs, and this objective was met via clearer internal imaging of these reservoir intervals and the overlying gas-charged sediments. The follow-on work considered here deals with the use of full waveform inversion to further delineate small-scale velocity anomalies associated with the highly compartmentalized reservoir units, and also to use the full waveform inversion velocity model as a constraint during acoustic impedance inversion. We compare the results of impedance inversion using both a conventional approach (with the well-log velocities to build the background trend), with a new approach using a trend derived from high-resolution waveform inversion velocities.
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Multi-azimuth processing — the kinematics and dynamics of the azimuthal anisotropy, resolved by tilted orthorhombic tomography
Authors Chris Rudling, Abid Riaz and Jonathan SmithAbstractThis paper explains a qualitative and quantitative approach to identify and resolve P-wave TTI and HTI variations in the depth migration velocity model building process. The combination of these effects can be represented by an orthorhombic model with three mutually orthogonal planes of mirror symmetry; the P-waves in each symmetry plane can be described kinematically as an independent TTI model.
Orthorhombic velocity model building and imaging tools are required to address both HTI and TTI simultaneously in the subsurface. The orthorhombic anisotropy has been correctly identified and resolved, which has subsequently resulted in a high-resolution velocity model.
A combination of the accurate velocity model building and advancement in the pre-processing techniques has shown significant uplift in the image quality on the earlier processing. The reprocessed PreSDM has provided improved coherency, recovered improved bandwidth, enhanced character, and better fault plane definition.
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Source rock characterization in frontier basins — a global approach
Authors David Eastwell, Neil Hodgson and Karyna RodriguezAbstractExploring in frontier basins carries with it the challenge of identifying and derisking hydrocarbon play elements where well data and consequently, lithological and stratigraphic information is often sparse to absent. In this setting, seismic data will typically be the only source of information available to identify potential play fairways and derisk the corresponding petroleum system elements.
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The IOGP E&P Sound and Marine Life Joint Industry Programme — an international research programme to fill key data gaps
Authors K. Bröker, K. Speirs, D. Hedgeland, G. Wolinsky, B. Gisiner, G. Adams, M. Jenkerson, J. Weissenberger and J. CampbellAbstractThe potential impact of sound on marine life is one of the most important environmental issues faced by the oil and gas industry, which must be managed to avoid business impacts. Over recent years, there has been an expansion in regulatory and societal focus regarding sound sources, species of concern and categories of impacts of marine sound. Initially, the main concern was possible injury of marine mammals thought to be caused by seismic surveys. Now, impacts of other sound sources, such as drilling, vessel movement, pile driving, etc. are considered and are increasingly regulated. Additionally, there is growing concern over potential impacts on turtles, fish, fisheries, invertebrates (e.g. lobster and scallops), and more recently even fish eggs and plankton.
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Benefits of multi-sensor streamers for broadband acquisition
AbstractBroadband towed-streamer data has extended the usable seismic bandwidth at both ends of the frequency spectrum. As well as enriching the overall seismic image, improved low frequencies have delivered more reliable full-waveform inversion results and more quantitative elastic inversion, while improved high frequencies enable better interpretation of thin-layered structures. Various strategies have been developed to acquire broadband data, ranging from processing-only approaches using horizontal-tow hydrophone-only streamers, to combined acquisition and processing schemes using multi-level streamers (Posthumus, 1993), variable-depth streamers (Soubaras, 2010) or multi-sensor streamers (Carlson et al., 2007).
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Monitoring and mitigation of sound exposure from seismic surveys for a feeding whale population
Authors Roberto Racca and Koen BrökerAbstractSeismic surveys are an essential tool in the search for and periodic assessment of hydrocarbon deposits for oil and gas production. Airgun arrays, which are to date the overwhelmingly predominant sound source for these surveys, generate a high level of low-frequency pulses which can cause disturbance to marine life, particularly species with good low-frequency hearing such as baleen whales (Southall et al., 2007). Despite numerous studies (see Nowacek et al., 2007 for a review), substantial data gaps remain in terms of impacts of seismic surveys on cetacean physiology, behaviour and population dynamics. There is broad acceptance, however, of the need to mitigate the exposure of animals to noise from seismic surveys, especially for endangered populations or species (Nowacek et al., 2013).
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Multiple source acquisition for use in 4D marine seismic
More LessAbstractThroughout the lifecycle of an offshore oil or gas field seismic acquisition can be repeated a number of times. Within the O&G industry, seismic data enables E&P companies first to identify hydrocarbon reservoirs and then maximize the extraction of them.
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Latest field trial confirms potential of new seismic method based on continuous source and receiver wavefields
Authors Stian Hegna, Tilman Klüver, Jostein Lima and Endrias AsgedomAbstracteSeismic is a novel seismic methodology based on the emission and recording of continuous source and receiver wavefields. One of the motivations behind developing the methodology has been the increased focus on the potential environmental impact of marine seismic acquisition, which the new methodology seeks to reduce. A particular focus has been placed on the peak sound pressure levels emitted from seismic sources and their potential impact on marine mammals and fish with swim bladders. Consequently, authorities across the world have started to introduce stronger regulations concerning the use of seismic sources. The industry has responded by engaging in the development of marine vibrator systems that emit lower-amplitude transient signals and hence are expected to comply with stricter environmental regulations. Different marine vibrator systems are currently being developed or tested but none have reached full-scale commercial readiness.
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Reservoir delineation beneath a heterogeneous shallow gas overburden using ‘True-3D’ seismic imaging approaches
AbstractImaging through a heterogeneous shallow gas-charged overburden, such as a gas cloud, presents several imaging challenges and is a demanding problem to solve. Our preferred technical solution for imaging beneath gas clouds is to utilize converted wave imaging (Radzi et al., 2015), but this is not always available or cost effective and velocity model building is still difficult. Many previous case studies have been produced from Malaysia which demonstrate subsurface imaging techniques and improvements for fields affected by gas clouds, e.g., Akalin et al. (2010); El Kady et al. (2012); Abd Rahim et al. (2013); Ghazali et al. (2016) and Gudipati et al. (2018). In this paper, we describe a new comprehensive high-density experimental project to readdress these ever-challenging seismic issues by imaging the reservoir from both above and within existing boreholes. The integration of multiple technologies has significantly improved the subsurface images of the field including better-quality velocity models below gas clouds. The new data reveal a larger scale of near-surface heterogeneities than previously expected and future studies will selectively reprocess subsets of the acquired data in order to optimize the images; and, by extension to other similar fields, address a cost-effective imaging strategy.
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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)