Permeability Continuity of Laminae in the Calvin Sandstone

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Abstract
Laboratory tests that were conducted to determine the continuity of laminae in a sandstone outcrop in Oklahoma revealed that such laminae would probably have adverse effects on miscible displacement operations in a sandstone reservoir. Introduction The existence of thin, horizontal strata in sandstone rocks has long been recognized by geologists. These same permeable layers of consolidated sand grains have recently been identified in sandstones that appeared outwardly to be homogeneous. The existence of the microstrata seems to be accepted even though a detailed study of their areal extent has not been attempted. One reason for this neglect may be that the thin strata have in the past been considered relatively insignificant in relation to the larger strata in the formation. It is now thought, however, that these thin layers may be very important in the way they affect some of the processes used to recover petroleum from the sandstone reservoir. Holden and petroleum from the sandstone reservoir. Holden and Sprinkle found the laminae to exist in several water-deposited sandstone formations along the Gulf Coast and inland to Oklahoma. The laminae examined by Holden and Sprinkle were found to differ radically in permeability, with adjacent ones having ratios as high permeability, with adjacent ones having ratios as high as 10:1. If the laminae are continuous over a long distance, the extreme permeability differences would most probably affect the recovery of petroleum obtained probably affect the recovery of petroleum obtained by the replacement of one fluid with another. This would include miscible secondary recovery operations and also primary operations in which the energy source is solution gas drive. Holden, in his investigation, found the laminae to exist in the Calvin sandstone of Oklahoma. The Calvin is a highly permeable, well consolidated sandstone, and because of this, we selected it for this study of the continuity of microstrata. The laminae in question are about 1 mm and larger in thickness. A Calvin sandstone thin-section is shown in Fig. 1, which indicates the relative dimensions involved. Dye was injected into the sample before the thin-section was taken. JPT P. 661

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