Whole Core Analysis - Experience and Challenges

Abstract

Abstract Whole core analysis is critical for characterizing porosity and directional permeability in heterogeneous, fractured, and/ or anisotropic rocks. Whole core measurements are essential for heterogeneous reservoirs because small-scale heterogeneity may not be appropriately represented in plug measurements. For characterization of multi-phase flow properties (special core analysis) in heterogeneous rocks, whole core analysis is also required. Few commercial laboratories are equipped to conduct routine measurements on whole cores up to 5 inch in diameter and up to 8 inches long, and importantly, under simulated reservoir net confining stress (NCS). Special whole core analyses are rarely conducted because of difficulties associated with establishing a representative water saturation in drainage capillary pressure experiments and measuring directional effective permeability. Electrical properties are also measured occasionally to determine saturation exponents for situations where resistivity tools are utilized in horizontal or highly deviated wells. In this paper we provide an overview of routine and special core analysis measurements on whole cores. Results from selected heterogeneous sandstone and carbonate rocks will be discussed. We will also show how the results relate to data obtained from plug analysis at the same depth, with particular emphasis on directional absolute permeability, directional effective permeabilities, trapped fluid saturation, and the effect of net confining stress. Finally, we will describe a novel whole core apparatus and provide examples of capabilities of the system. In this paper, we will present: Recommended techniques for the determination of directional absolute, effective permeability and establishing initial water saturation in whole cores;Improved understanding of the effect of scale (sample size) on the measured properties;Description of a novel whole core apparatus with measurement of fluid saturation distribution using in-situ saturation monitoring.