Practical Use of Modern Well Test Analysis

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 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. 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 Analysis of short time well test data by loglog type curve was introduced in 1970. The first type curve concerned the wellbore storage effect with damaged permeability in an annular shaped region adjacent to the s face. Later type curves for vertical and horizontal fractures were added. Practical experience with these curves now indicates a great deal of useful information may be extracted from complete matching of both log-log and conventional semi-log curves. Examples include almost certain detection of the correct semi-log straight line, and the detection and correction of errors in data. the other hand, some early claims for log-log type curves appear to be incorrect. The purpose of this paper is to summarize useful purpose of this paper is to summarize useful findings to date with field case illustrations. Introduction Based upon fundamental studies of transient flow of fluids through porous media by Hurst in 1934 van Everdingen and Hurst in 1949, Muskat, the two pressure buildup studies by Horner in 1950, and by Miller, Dyes and Hutchinson in 1951, there began an intensive study of pressure transient (well test). analysis which continues vigorously to this day. Both Refs. 4 and 5 demonstrated that it was possible to determine the effective permeability to the flowing fluid phase by permeability to the flowing fluid phase by means of an appropriate graph of pressures measured vs. time after shut-in of a well previously produced at a constant rate. previously produced at a constant rate. However, both studies contained ideas sufficiently different to cause a great deal of confusion. Figure 1 is a schematic of a Horner pressure buildup graph which demonstrates some of the problems. Horner taught that a graph of problems. Horner taught that a graph of buildup pressures vs. a logarithm of a time ratio involving the sum of the producing and shut-in time to the shut-in time should yield a straight line whose slope was inversely proportional to the permeability. The correct proportional to the permeability. The correct Horner straight line for permeability determination is represented by the straight segment on Fig. 1 indicated by the letter B. Horner also showed that for wells in closed boundary drainage systems, eventually the pressure would stop rising, become static pressure would stop rising, become static and provide a measure of a mean pressure within the drainage boundary of the well.