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The AAPG/Datapages Combined Publications Database

Tulsa Geological Society


Tulsa Geological Society Digest
Vol. 28 (1960), Pages 43-58

Relationships Between Reservoir Petrography and Reservoir Behavior of Some Appalachian Oil Sands

J. C. Griffiths


Secondary recovery of oil from sandstones is largely predicated upon the mutual interactions between contained and introduced fluids and the reservoir rocks; if fluid movement were independent of the reservoir rock, prediction of behavior would be simple. In fact, relationships between behavioral characteristics such as porosity, permeability and fluid saturation and rock properties such as grain size, shape, packing etc. vary among different rocks. This article presents an organized plan for determining the roles of the petrographic variables in accounting for the reservoir properties.

Given a set of core samples, the reservoir properties of interest are determined and, by means of thin sections, the petrographic properties are determined on the same samples. Sampling procedures for different objectives are proposed. The resulting "matrix of observations" is a rectangular array of numbers comprising the jk properties in columns and the "m" samples in rows. This matrix is converted to the correlation matrix which is square and comprises jk rows and columns. The correlation matrix may then be manipulated to yield multiple regression equations relating reservoir behavior (permeability) to reservoir properties (grain size, shape, etc.) and the relative importance of each variable may be evaluated by analysis of variance.

Based on this evaluation, if "swelling clay" is playing an important role its variation in proportion will "account for" a significant proporton of variation in porosity, permeability, etc. It will then be necessary to adjust the input water to offset this effect. Similarly, if carbonate cement is accounting for an important part of the variation in porosity, acidising may be effective; if silica cement or other source of induration is related to porosity and permeability, then formation fracturing may be necessary.

These recommendations are based on relative roles or orders of magnitude, of the contributions made by reservoir (petrographic) properties to behavioral characteristics, and the analytical technique is of wide application to many problems of petroleum production and exploration.

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