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ABSTRACT: Ichnofabrics, sedimentary structures, architectural elements, and depositional processes from borehole images: an illustration of data acquisition methodology and interpretation from fluvial, shallow, and deep marine environments

Adriaan Bal, Peter Bright, Aaron Burt, Tariq Mahmood, Jeremy Prosser, and Jill Thompson
GEOScience, Baker Atlas, 2nd level, Sheraton Court, 207 Adelaide Tce, East Perth, Perth, WA 6004, Australia, phone: (618) 9268 2656, fax: (618) 9268 2623, [email protected]las.com

The application and development of ichnofabric, architectural elements, and depositional process concepts to core studies in the petroleum industry is relatively advanced, and has demonstrated its usefulness in correlation, sequence stratigraphy and determination of depositional environments. Furthermore, acquisition and development of image log technology is equally advanced but their value remains under utilised. This presentation presents case studies illustrating the sophisticated interpretations possible using image log data

The definition of the geometry of architectural elements in 3-D is crucial to interpretation of fluvial regimes. Elements identified from dip-azimuth vector plots are firstly assumed to be in-channel sandy bars (macroforms), and "upgraded" to higher-orders (e.g. 5th-order main channel or 6th-order channel belt) if they can be convincingly correlated between wells.

A shallow marine setting in the South China Sea, illustrates the use of image fabric index (IFI), akin to the bioindex, for understanding environmental controls at reservoir and exploration scale. The inverse of the IFI mirrors wave energy. When the wave energy index is displayed opposite sandstone intervals over hundreds of metres, specific packages reflecting high- and low-stand deposition are identified. These indices, when combined with other dipmeter/image log techniques, provide a robust database when integrated with log and core information.

Submarine fans provide challenging problems for image log interpretations. In this example, image logs are used to measure deformational structures developed within the submarine fan environment, often devoid of palaeocurrent indicators. A stereographic analysis of slump axial planes defines regional and local slope directions and differentiates fan subenvironments.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia