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- Volume 33, Issue 2, 2015
First Break - Volume 33, Issue 2, 2015
Volume 33, Issue 2, 2015
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Time-lapse multi-component seismic monitoring, Delhi Field, Louisiana
By Thomas DavisThomas L. Davis characterizes the Delhi Field in Louisiana by monitoring flow paths associated with immiscible carbon dioxide flooding. Time-lapse, multi-component seismic data were acquired during the start-up of the field rejuvenation effort at Delhi Field, Louisiana. The purpose of the study was to characterize the reservoir by monitoring flow paths associated with immiscible carbon dioxide flooding. Flow paths in the reservoir are associated with primary depositional facies involving fluvial deltaic deposition. These flow paths cannot be assessed by wells alone making seismic monitoring a valuable tool in the enhanced oil recovery project at Delhi.
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Fracture characterization of the Montney Formation using amplitude inversion of converted wave seismic
Authors Tyler MacFarlane and Thomas DavisTyler L. MacFarlane and Thomas L. Davis show that amplitude variation with angle (AVA) inversion of azimuthally sectored converted-wave (PS) seismic obtains proxy measurements of the fast and slow shear wave velocities, which enables a volume calculation of the shear wave splitting parameter. Natural fractures play an important role in defining the productive intervals of unconventional tight gas and oil formations due to the low permeability its matrix. Fractures can increase permeability by orders of magnitude, and strongly impact how a hydraulic stimulation interacts with the reservoir. Local variations in elastic properties and stress conditions lead to a heterogeneous distribution of fractures that need to be identified prior to field development in order to optimize well placement and completion design. Uniform completion and drilling strategies may result in lost profit as a consequence of not understanding the complexity within the reservoir.
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An integrated approach to unconventional resource play reservoir characterization, Thistleton-1 case study, NW England
Authors Scott Brindle, David O'Connor, Richard Windmill, Peter Wellsbury, Guy Oliver, Graham Spence and Chi V. LyScott Brindle, David O’Connor, Richard Windmill, Peter Wellsbury, Guy Oliver, Graham Spence and Chi V. Ly characterize a UK unconventional reservoir using integrated AM and TOC data to constrain and improve the accuracy of petrophysical modelling. In the past, the oil and gas industry considered hydrocarbon resources locked in tight, impermeable formations like shale uneconomical to produce. However, advances in well steering, drilling and reservoir stimulation techniques have dramatically changed this perspective. Unconventional shale reservoirs have low permeability and cannot produce economically without effective placement of horizontal laterals and effective hydraulic stimulation. To achieve this, it is critical to recognize brittle units responsive to hydraulic fracturing and rich in organic matter. Shale mineralogy impacts the effectiveness of stimulation. Heterogeneity in shale reservoirs expressed by mineral composition, richness of organic matter and brittleness significantly influences shale gas production. In these reservoirs, the occurrence of clays is a significant risk to production and it is a major challenge to be able to locate and quantify them. The industry reported $7bn of unnecessary costs due to unconventional wells not reaching their production targets (Welling and Company, 2012). Moreover, 15-20% of all fracture stages are reported as ineffective while 35-40% of perforation clusters do not contribute to production (Hodenfield, 2012) highlighting a need for more low-cost and low-risk data. This data could help to improve completion designs to achieve more consistent production from all stages and increase the overall profitability.
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Using predictive analytics to unlock unconventional plays
Authors Julie Vonnet and Gudmund HermansenJulie Vonnet and Gudmund Hermansen introduce a multi-disciplinary, integrated reservoir modelling workflow that gathers data of different natures, sources and scale in order to predict sweet spots locations. The dramatic expansion in computing power over the past two decades and the huge amount of data generated within organisations have led to a proliferation of new methods to identify patterns and trends among these large datasets. Data mining and predictive analytics are cross-disciplinary approaches that consist of advanced mathematical and statistical methods that retrace patterns from petabytes of data. Such methods and algorithms are able to extract information, correlations and interplays and turn them into structured sets of interactions for predicting the behaviour of a system – even under unknown conditions.
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Understanding production in unconventional wells using microseismic derived permeability
Authors Carl W. Neuhaus and Sudhendu KashikarCarl W. Neuhaus and Sudhendu Kashikar present two methods of estimating permeability using microseismic data. Over the past decade, microseismic monitoring has become an accepted industry practice and, for some operators, a standard when fracking in unconventional reservoirs. Fractures that are created during hydraulic stimulation in unconventional plays can be extremely complex. Accurate imaging of these fractures is necessary to understand the formation and enable completions optimization, maximize asset value and increase recoverable reserves.
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Shale gas formation research: from well logs to outcrop – and back again
Authors Mart Zijp, Johan ten Veen, Roel Verreussel, Jan ter Heege, Dario Ventra and John MartinMart Zijp, Johan ten Veen, Roel Verreussel, Jan ter Heege, Dario Ventra and John Martin show the added value of outcrop analogue studies to understand and characterize the heterogeneity of gas shale formations. Intense exploration activities over the past 75 years have resulted in an impressive amount of publically available subsurface data for the Netherlands. About 100 exploration wells penetrate the Early Jurassic Posidonia Shale Formation (PSF) in the Netherlands, which is considered the most important oil source rock in the Netherlands. More recently, this approximately 30m-thick black shale has attracted attention as a possible target for shale gas. Since outcrops and tangible subsurface data are virtually absent, Dutch geoscientists face the reality that shale-gas research typically takes place on a work station. For instance, petrophysical analysis shows that the PSF stands out from the surrounding shales by conspicuous patterns on wire-line logs: high gamma ray, high sonic, low density and high resistivity. Higher order trends in the well logs can be traced across large distances and are thought to represent a remarkable variation in lithology that is important for the characterization of potential shale gas targets. Ideally this reservoir characterization should be carried out at different scales: from an analysis of fault networks and responses to local stress regimes at reservoir scale, to analyses of hydro-mechanical properties and fracture networks at bed scale, finishing at a characterization of compositional and sedimentological heterogeneity at the scale of laminae. Thus, the common practice of lithology deduction via petrophysical methods is incomplete and requires ground truthing, which can be best provided by outcrop studies.
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Reservoir surveillance opportunities – A view of the potential in frontier and mature basins
By Sean DunnShaun Dunn, global business manager for exploration and surveillance at Sonardyne, presents innovations in reservoir monitoring. Offshore exploration is heading into ever deeper water as many shallow reservoirs gradually move towards the end of their useful production lifecycles. The majority of geographical regions and sedimentary basins have now been explored with reducing volumes of untapped conventional resources available to be discovered, most notably for giant and super giant fields in excess of 500 Mmbbls (million barrels) reserves. There are a few exceptions in places such as the Arctic and the very deep water regions of the Gulf of Mexico and the South Atlantic margin but accessing these reserves is fraught with technical uncertainty, risk and high cost-per-barrel extraction; these regions are increasingly commercially challenged and are currently rendered unappealing. Many deep water reservoirs are also geologically complex and require an increasing number of high-quality seismic surveys to provide information on the changing structure and, ultimately, to maximise productivity.
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Is curvature overrated? No, it depends on the geology
Authors Satinder Chopra and Kurt J. MarfurtIn an article that appeared in the June 2014 issue of First Break, it was suggested that seismic curvature attribute is an overrated attribute and that the coherence attribute was better for carrying out interpretation of discontinuity features such as channels and faults. We believe that coherence and curvature are complimentary attributes that define tectonic deformation including faulting and folding as well as incisement, collapse, and differential compaction of stratigraphic horizons, and add additional insight to the same geologic features being interpreted. Instead of searching for the best attribute or getting into a debate of an attribute being overrated or not, we recommend the complimentary application of these attributes for interpretation of the features of interest, and strongly contend that this aspect not be overlooked.
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Ambient noise to estimate depth to basement: case studies from East Africa basins
Authors F. Martini, R. Davi, J. Doherty and J. MonganPassive recording of background noise have been successfully used to retrieve information about the large-scale structure of a sedimentary basin. Ambient noise can be used to retrieve velocity profiles in order to investigate the velocity structure and the depth of a sedimentary basin, in an unexplored area and/or when additional constraints on the basement depth may be needed for interpretation of active seismic or non-seismic data. We exploit techniques usually used in geotechnical or earthquake hazard/engineering studies. Surface wave dispersion analysis can be used to obtain 1D velocity-depth profiles below an array of seismic stations which record passive ambient noise. Analogously, the horizontal-to-vertical spectral ratio of both the surface and body waves can provide 1D velocity-depth profiles below standalone seismic stations which record passively ambient noise. We successfully applied this technique in Uganda, Ethiopia and Kenya, where field surveys were carried out to recover the depth to basement. With this work we present and discuss the results we obtained in those areas, the accuracy of which was validated by comparing with depth values obtained by other seismic and non-seismic datasets (independently acquired and processed).
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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)