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The objectives of this program are essentially four-fold: (1) the data gathering process leads to a quantitative
petrography and thence, via a model, to petrogenesis; (2) the data analysis leads to specification of the relationships between reservoir behavior and variation in the petrographic properties; (3) the analysis, suitably extended, leads to a measure of relationship between logging responses and variation in the petrographic properties; and (4) the analysis may be used to identify reservoir rocks and differentiate them from similar appearing barren rocks. Such objectives encompass an interpretative petrology, a means for predicting and controlling reservoir behavior, a means for selecting the important logging parameters and a possible interpretation of their role in reflecting variation in rock properties and, by identifying the reservoir rock, may form the basis for an exploration pro ram.
This program has been used for the analysis of eleven sands either actual or potential reservoir rocks from the Appalachian Province; they include representatives of the Devonian (Chipmunk, Bradford, Lewis Run, and First Venango sandstones), Mississippian (Berea, Weir, and Maxton sandstones), Pennsylvanian (two Cow Run sandstones, and a middle Kittaning sandstone), and Permian (the Waynesburg sandstone) systems.
The most important properties in each case are grain size, size-sorting, and the cementitious constituents, carbonate and silica cement. There are two dominant types of sandstone, the one in which grain size and (or) size-sorting act as the main controls and the other in which the size and size-sorting is subordinate in importance to the cementitious materials. When the dominant properties are size and size-sorting, channeling is the most important problem in production and secondary recovery. When the dominant features are the cements, then combinations of acidizing and hydraulic fracturing are likely to be important palliatives.
Those sandstones in which the cements are most important are sporadic in occurrence and, under present conditions, would be difficult to impracticable to locate, whereas, in those sandstones in which grain size and size-sorting are the dominant characteristics, it should be possible to detect gradients which could form exploration guides.
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