The Performance Of Heterogeneous Reservoirs
Authors: Warren J.E. 
Published: December 2007

This paper is to be presented at the 39th Annual Fall Meeting of the Society of Petroleum Engineers on Oct. 11–14, 1964, in Houston, Tex., and is considered the property of the Society of Petroleum Engineers. Permission to publish is hereby restricted to an abstract of not more than 300 words, with no illustrations, unless the paper is specifically released to the press by the Editor of JOURNAL OF PETROLEUM TECHNOLOGY or the Executive Secretary. Such abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in JOURNAL OF PETROLEUM TECHNOLOGY or SOCIETY OF PETROLEUM ENGINEERS JOURNAL is granted on request, providing proper credit is given that publication and the original presentation of the paper.
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Abstract
Core-analysis data, pressure build-up test flow tests and production histories were to determine the effects of permeability heterogeneities. Data from eight formations were statistically analyzes-carbonates, consolidated sands and unconsolidated sands were considered in the investigation. From this study, it was concluded that the flow capacities of the individual wells within a reservoir tended to be log-normally distributed and that lateral permeability variations were actually as significant as vertical permeability variations. It was shown that the observed relationships were useful in the treatment of field-development problems.

Introduction
Although it has long been recognized that permeability variations significantly affect the performance of a reservoir, there are only a few cases reported in the literature in which attempts have been made to determine the nature of the heterogeneities that actually, occur in specific reservoirs. Kruger, Nelson, Warren, Skiba, and Price, Johnson and Greenkorn, Testerman, and Dupuy and Pottier have applied various analytical techniques to field data. The paper by Dupuy and Pottier also provides an excellent discussion of the general problem.
In this study, field evidence concerning the effects of heterogeneous permeabilities on reservoir performance is of primary interest. Only information that is available on a relatively routine basis is considered; i.e., data obtained from core analysis, build-up tests, productivity and injectivity measurements and the evaluation of the production-decline curves.
The objectives of this investigation are the following:
To present field measurements which characterize the performance of heterogeneous reservoirs. To examine these data in order to infer the gross pattern of the permeability variations that are present. To indicate the practical implications which follow from the qualitative nature of the variations in the permeability of a reservoir.
While this study is exploratory in nature, it is hoped that it will suggest areas for further investigation. It is important that information of this type be published whenever it is possible; only in this way can sound reservoir-characterization techniques be evolved.