--> ABSTRACT: Use of SHDT Data in Sedimentological Studies, by C. F. W. Hocker, J. C. Herweijer, K. M. Eastwood, and J. T. Adams; #91030 (2010)

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Use of SHDT Data in Sedimentological Studies

C. F. W. Hocker, J. C. Herweijer, K. M. Eastwood, J. T. Adams

In principle, resistivity curves from the eight measuring electrodes of the SHDT should be capable of being processed to give a detailed reservoir characterization inclusive of electrofacies and sedimentary dip data. The performance of SHDT processing to produce borehole images (STRATIM) and dips calculated from MSD, LOCDIP, CSB, and 4-SBS has been evaluated by comparison with information from over 3,000 ft of cores covering shallow marine, deltaic, lacustrine, fluvial, and eolian sedimentary environments. In practice, good results are achieved only if the chosen processing parameters are compatible with the scale of the sedimentary structures present.

The color-coded resistivity image of the borehole wall reveals, in some detail, bed thicknesses and patterns of resistivity variations within beds. Based on such data, a more detailed electrofacies scheme can be established and, in some cases, the internal sedimentary structures of beds can be identified.

The sedimentary structures on which sediment transport directions can be measured with some certainty are the foreset laminae of individual cross-bed sets. In our data set, 80% of fluvial and shallow marine cross-bed sets were less than 20 cm thick. Under these conditions, CSB and 4-SBS processings with a correlation interval of 10 cm and a step distance of 7.5 cm were found to give the best chance of identifying and quantifying foreset dips. However, a high degree of confidence cannot be placed in CSB dips alone. Meaningful sedimentary dips have been derived by further processing of CSB and 4-SBS output involving consistency constraints.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.