NIELSON, DENNIS L., Univ. of Utah Research Institute, Salt Lake City, UT; DAVID THORNE, Schlumberger Well Services, Aurora, CO; and SUSAN LUTZ, Univ. of Utah Research Institute, Salt Lake City, UT

ABSTRACT: Formation Microscanner Imagery in Coreholes in the Fluvial-Deltaic Ferron Sandstone, Utah

Two large diameter coreholes have been drilled through the fluvial-deltaic Ferron Sandstone Member of the Mancos Formation in Emery County, Utah, to develop interpretation techniques for borehole imaging logs. Formation Microscanner images were collected in the holes, and bedding orientations were determined on a workstation using standard methods and then evaluated using the Statistical Curvature Analysis Technique (SCAT). It was concluded that borehole imaging can be extremely valuable in understanding reservoir heterogeneity by accurately imaging the character and orientations of sedimentary features. Forward-stepping deltaic architecture exhibits highly directed bedding orientations while vertical-stepping architecture has more diffuse orientations resulting from decreases in acco modation space relative to sediment supply. However, in general, SCAT and the concept of bulk curvature are not applicable to stratigraphic interpretation. Bulk curvature assumes that the bedding features reflect the geometry of the parasequence level environment. However, bed orientation does not uniquely reflect position within the body or, at the present state of knowledge, the geometry of the parasequence. In contrast to structural analysis of imaging data, stratigraphic applications should emphasize azimuth rather than dip. In our wells, conventional analysis schemes of increasing or decreasing dip with depth do not provide consistent paleoenvironmental insight, often due to the influences of erosion. Data on stratigraphic orientations with respect to position in a sedimentary facie are not abundant in the literature, but would greatly improve the usefulness of imaging logs.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.