Facies delineation by using a multivariate statistical model from

Article
Z. Dt. Ges. Geowiss. (German J. Geol.), 166 (4), p. 375–390, 10 figs., 3 tables
Stuttgart, December 2015
Facies delineation by using a multivariate statistical model from onshore wells
in the Nile Delta
Dieter Krott1,2,3, Christoph Hilgers1 & Christian Bücker2*
Krott, D., Hilgers, C. & Bücker, C.(2015): Facies delineation by using a multivariate statistical model from onshore wells in
the Nile Delta. [Anwendung multivariater statistischer Methoden zur Gewinnung von Elektrofaciesmodellen aus OnshoreBohrungen im Nildelta.] – Z. Dt. Ges. Geowiss., 166: 375–390, Stuttgart.
Abstract: Geological information is derived from geophysical well logs from seven onshore wells in the Nile Delta using
gamma ray-, resistivity-, sonic velocity- and density logs. Caliper logs are used for quality control. The Tertiary siliciclastics
and carbonates can be delineated from electrofacies models, which are based on multivariate statistical methods applied to
well log data. The electrofacies models are based on principle component and cluster analysis and were validated with core
data. The decimetre-resolution of the log data were successfully applied to correlate the wells with special emphasis on the
reservoir units of the Miocene Abu Madi Formation and the superimposed strata of the Pliocene Kafr el Sheikh Formation.
The electrofacies analysis is a quick and powerful tool for objective identification and subdivision of lithological patterns
and offers an additional, often neglected dataset on a subseismic scale.
Kurzfassung: Geologische Information werden aus Bohrlochmessungen von sieben Bohrungen auf dem Festland des Nildeltas gewonnen: Gammastrahlen-, Widerstands-, akustische Geschwindigkeits- und Dichte-Logs. Das Kaliberlog wird
dabei zur Qualitätskontrolle genutzt. Die tertiären Siliziklastika und Karbonate können aus den Elektrofaziesmodellen abgeleitet werden, die durch Anwendung multivariater statistischer Methoden auf Bohrlochdaten gewonnen wurden. Das Elektrofaziesmodell beruht auf einer Hauptkomponenten- und einer Cluster-Analyse, die anhand von Kerndaten validiert werden. Die Dezimeter-Auflösung der Log-Daten wurde erfolgreich genutzt, um die Bohrungen mit besonderem Fokus auf die
Reservoireinheiten der miozänen Abu-Madi-Formation und den hangenden Schichten der pliozänen Kafr-el-Sheikh-Formation zu korrelieren. Die Elektrofaziesanalyse ist ein schnelles und leistungsfähiges Werkzeug für eine objektive Identifikation und Unterteilung von lithologischen Einheiten und bietet damit eine zusätzliche, oft vernachlässigte Datengrundlage im
subseismischen Maßstab.
Keywords: electrofacies model, facies delineation, reservoir characterisation, geophysical well logs, Nile Delta
Schlüsselwörter: Elektrofaziesmodell, Fazies-Erkennung, Reservoir-Charakterisierung, geophysikalische Bohrlochmessungen, Nildelta
1. Introduction
Log analysis is a powerful tool in reservoir characterisation,
using open borehole and core data (e.g. Collett 2001, Ellis &
Singer 2008). The resolution of such analysis is much higher
than in seismic surveys, which are commonly used as an exploration subsurface tool. Petrophysical analysis in combination with seismic data thus enables efficient quantitative
geological interpretation (Gregory 1977). Log analysis can
be used as a supportive tool, which verifies interpreted seismic data and provides additional high-resolution information. It also provides data in areas where no seismic survey
or core data is available.
Electrofacies models using well logs delineate lithological facies based on their physical properties and identify different sedimentary provenances (Lee et al. 2002). However,
it is not a very common interpretation method and only described in some publications (e.g. Gupta & Johnson 2001,
Perez et al. 2005, Torghabeh et al. 2014). Lee et al. (2002)
pointed out that electrofacies classification does not require
any manual artificial subdivision of the data population. For
this reason, the compilation of an electrofacies follows welllog measurements reflecting petrophysical properties of
minerals and lithofacies within the logged interval. The analysis of the lithology is free of interpretational issues, which
minimize errors. Bücker et al. (2001) applied this technique
*Addresses of the authors: 1EMR – Institute of Reservoir-Petrology, RWTH Aachen University, Wüllnerstr. 2, 52062 Aachen,
Germany; 2DEA Deutsche Erdoel AG, Überseering 40, 22297 Hamburg, Germany; 3now at Martrick GmbH, Doha, Qatar / dieter.
[email protected]; [email protected]; [email protected] (corresponding author).
© 2015 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany
DOI: 10.1127/zdgg/2015/0040
www.schweizerbart.de
1860-1804/0040
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