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Volume 43, Issue 5, 2025
- Technical Article
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Reservoir characterisation of compacted sandstones in the Osmancık Formation, Thrace Basin, Türkiye
Authors Taner Arpaci, İsmail Ömer Yilmaz, Serhat Akin and Emin U. UlugergerliAbstractThe Thrace Basin houses the main gas-producing fields of Türkiye. The gas reservoirs in the basin are mostly located in deltaic sediments of the Oligocene Osmancık Formation where the hydrocarbon-bearing sandstone reservoirs generally reflect class 3 type of amplitude-versus-offset (AVO) anomalies. Our results indicate that AVO behaviour changes from Class 3 to Class 2 response due to the ascending compaction trend of the lithology with increasing depth. Acoustic impedances (AI) show an abrupt increase, because of higher compaction of the sandstones of the Osmancık Formation. Bright spots are the distinctive characteristics of gas sands encased in shale lithology in seismic stack sections. However, at higher depths of the Osmancık Formation, sweet spots tend to disappear due to lower porosity and permeability at the producing reservoir intervals. We propose a workflow to integrate pre-stack seismic analysis and lithology prediction of the field to characterise the gas-producing reservoirs. Spatial distribution of gamma ray values obtained with neural network prediction indicates highly lateral variation of shaliness, which is directly related to reservoir quality in the deeper Osmancık Formation. Therefore, diagenesis in sandstones and increase in shaliness play a crucial role in terms of evaluation of petrophysical properties of the reservoir, such as porosity and permeability.
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- Special Topic: Global Exploration
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The Pelotas Basin: A Rising Global Exploration Hotspot
Authors Sindre Bull-Jansen, Javier Martin, Christian Strand, Karen Purcell and Mustafa Al-WailyAbstractThe Pelotas Basin in south east Brazil is rapidly emerging as one of the world’s most promising regions for hydrocarbon exploration. This paper examines the impact of the recent exploration successes in its geological conjugate, the Namibian Orange Basin, where multi-billion-barrel discoveries have been made over the past four years. The success in the Orange Basin is particularly significant in addressing key uncertainties related to source rock presence and maturation, as well as reservoirs in the Pelotas Basin. Shearwater, in collaboration with Searcher Seismic, is leveraging critical insights from the Orange Basin to unlock the exploration potential of the Pelotas Basin. Seismic analysis clearly identifies striking similarities between the two basins within the Early Cretaceous target interval, helping to derisk key uncertainties related to source rock and reservoir presence. Similar to the Orange Basin, quantitative interpretation techniques have shown potential AVO anomalies, providing valuable guidance for prospect identification.
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Volumes & issues
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Volume 43 (2025)
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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)
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