Abstract

Many basic rock properties—such as lithology, bedding, grain size, sorting, and porosity—are expressed in geologic cores by changes in color, brightness, and texture. Quantitative descriptive rock properties can thus be derived from digital core images. Despite the widespread availability of high-resolution core images and image analysis software, these data are underutilized by geoscientists tasked with describing core.

This paper demonstrates the application of image analysis for quantitative core description using examples from three different carbonate reservoirs: (1) evaporite-rich dolostone from the First Eocene, Kuwait–Saudi Arabia Partitioned Zone, (2) vuggy dolostone from the Cretaceous Toca Formation, offshore Angola, (3) thin-bedded limestone and mudrock from the Ordovician Utica Formation, Ohio, USA. In each example, quantitative data are extracted from core images using ImageJ or WellCAD software. The image-derived descriptive parameters are consistent with petrophysical log and core data, supporting the validity of this approach to core description.

Image-analysis-guided core description offers many advantages over traditional hand-drawn core description: 1) hand-drawn core descriptions tend to be qualitative and core-log integration is difficult and imprecise, whereas image analysis generates quantitative descriptive data that are directly comparable with petrophysical datasets; 2) image analysis can characterize fine-scale geologic heterogeneity that is difficult or impossible to resolve using log and core plug data and hand-drawn core descriptions; 3) image analysis allows geologists to generate preliminary descriptions prior to actual core viewing, a more efficient workflow that minimizes time expended in offsite core viewing, perhaps in remote locations with limited time available; 4) integration of image-derived core data with petrophysical log and core data allows rigorous evaluation of core data quality—before, during, and after the process of core description.

Image analysis thus provides a valuable tool for geoscientists to efficiently generate quantitative, petrophysically significant core descriptions.