PROSSER, D. JEREMY, and B. P. J. WILLIAMS, Department of Geology and Petroleum Geology, Kings College, Aberdeen Univ., Aberdeen, Scotland, UK

ABSTRACT: Permeability Heterogeneity within Aeolian Sandstones

The geologists perception of permeability heterogeneity within aeolian reservoir sandstones is colored by the scale at which permeability has been sampled. In particular, fine scale permeability variation is not always evident using conventional 1 ft (30 cm) core-plug sampling strategies. In recent years however, the advent of the nitrogen probe-permeameter has enabled rapid gathering of permeability data at a variety of operator-determined scales, and improved understanding of the many and varied scales at which permeability heterogeneity may occur. Use of the probe permeameter to precisely sample permeability at a laminar scale has allowed comparison of permeability with a variety of petrographic data for individual sample points, and evaluation of microscopic-scale diagenetic contr ls upon permeability. Data used for laminar scale comparison of permeability with petrographic phenomena can be gathered simply and easily using standard petrographic point count techniques, or using an SEM based image analysis system.

Comparison of subsurface permeability data sets from North Sea fields with data gathered at surface outcrop has allowed quantification of the frequency and magnitude of some of the permeability heterogeneities that arise in aeolian depo-systems. Geostatistical analyses of data gathered from outcrop analogues in the U. K. suggest that although surface weathering and leaching result in their yielding permeability values an order of magnitude higher than those typically encountered in the offshore subsurface, basic permeability correlation structures arising as a result of sedimentological variation (laminar or set boundaries) can still be detected and occur at similar scales.

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