Core Analysis Techniques, Case Histories and Interpretation of Data For the Rocky Mountain Region

Abstract

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the Improved Oil Recovery Symposium of the Society of Petroleum Engineers of AIME, to be held in Tulsa, Okla., March 22–24, 1976. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and with the paper, may be considered for publication in one of the two SPE magazines. Abstract Reasons are presented for securing core analysis data that furnish porosity, permeability, residual fluid saturations and lithology. Types of core analysis are briefly reviewed. Changes in in-situ fluid saturations resulting from flushing during coring and fluid expansion during transport of the core to the surface are discussed. Precautions in core sampling, handling, packaging and preservation are briefly reviewed. Interpretation of data, using actual case histories of formations in the Rocky Mountain Region, are presented to illustrate gas-oil contacts, transition zones, oil-water contacts and coning of gas and water. Also, a comparative example of conventional (plug type) versus whole core (full diameter) analysis is presented to illustrate the importance of whole core analysis in assessing productivity of fractured reservoirs. Introduction Cores are taken and analyzed to permit direct examination of samples of the section so that lithologic changes can be correlated and evaluated with the subsequent core analysis data and down hole logs. Cores are analyzed to permit a direct determination of the petrophysical characteristics of the formation. These characteristics include porosity, permeability, residual fluid saturations, lithology, grain density, cation exchange capacity, electrical and elastic properties, capillarity and relative permeability. All other methods of evaluating these properties are indirect. Table No. 1 summarizes routine core analysis data and its use. TYPES OF CORE ANALYSIS Core analysis has evolved into two major types related to the size and portions of the core analyzed, as various formations require different analytical techniques to obtain valid data.