--> Abstract: Establishing Fluvial Reservoir Architectural Elemements Through Petrophysical Motifs: Example—Upper Tertiary Fluvial Sandstones, Gondong Oil Field, Onshore Bohai Bay, PRC, by Rui Zhai, Shenghe Wu, and John D. Pigott; #90078 (2008)

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Establishing Fluvial Reservoir Architectural Elemements Through Petrophysical Motifs: Example—Upper Tertiary Fluvial Sandstones, Gondong Oil Field, Onshore Bohai Bay, PRC

Rui Zhai1, Shenghe Wu1, and John D. Pigott2
1Department of Geosciences, China University of Petroleum, Beijing, China
2ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Norman, OK

In the Bohai Bay basin, PRC, meandering river systems are ubiquitous in the Upper Tertiary sandstones and mudstones in the Huanghua depression of onshore Bohai Bay. We attempted to employ a sedimentological characterization of the “Miall” architectural element analysis to the sandstones of the Gangdong Oil Field through petrophysical motif delineation. Four principal architecture elements are identified as petrophysical motifs: channel (CH), levee (LV), crevasse splay (CS) and floodplain fines (FF). The petrophysical characterization of these architectural elements was conducted by comparison of SP, GR and resistivity logs and compared to available cores.

The motifs are: CH which consists of thick sandstone composite bodies (2-15m). If it is an abruptly abandoned meander, the SP and GR present box-shape (CHbox); and if it’s a normal deposit meander, the SP and GR motifs reveal a bell-shaped curve (CHbell). CS units are comprised of thin sandstone bodies (1-3 m), interbedded sandstone, siltstone, silty lutite and pelitic and siltstone bodies. The thin sandstone bodies (< 2 m) comprised of interstratified siltstone, silty shale, and pelitic siltstone, and overly the CH sandstones are interpreted as LV elements. Although the CS log character is similar to LV, they can be differentiated by their thickness and geometries. . The mudstone-dominated bodies comprised of mudstone, thin sheet-like or lenticular silty sand beds (< 1m) are interpreted as FF where sand is frequently deposited as thin sand sheets .

The petrophysical characterization of fluvial sandbody motifs may provide an effective way to predict reservoir quality geometries, and, if seismic resolution is permissive, allow the geovalidated extrapolation of reservoir qualities stratigraphically.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas