CONDITIONS AFFECTING OIL ACCUMULATION. 201 



sylvania, since at the very time the famous Mevey well number 1 was 

 gushing oil at the rate of 15,000 barrels daily, another well was drilled 

 through the same " Fifth sand," only 300 feet distant, and proved to be 

 practically dry — the character of the producing rock having undergone 

 a great change and become so close-grained within such a short distance 

 that it could not hold oil in paying quantity. If such changes as this 

 can happen in the character of an oil rock reservoir within a few feet, 

 much more would we expect such changes within a few miles ; and thus 

 it happens that although there appears to be a continuous deposit of oil 

 in the Mount Morris sand, from the Pennsylvania line southward to 

 Mannington, and for at least six miles beyond, yet the productiveness of 

 the rock is not everywhere the same, because the character of the sand 

 (reservoir) is not constant. This condition of affairs tends to concentrate 

 the richest territory into pools of greater or less extent which are sep- 

 arated from each other by territory that is "spotted" or less productive. 



When this tendency to change in the character of the sand or reservoir 

 is carried so far as to render the rock impermeable to gas, oil or water 

 for a considerable distance, then any oil belt must come to an end, and 

 we need not expect it to set in again on the same strike of the rocks 

 (though that is possible), but rather when the same stratum become- 

 again productive it will be found at a lower or higher level and on a 

 different strike line, so that in this way we may have several parallel 

 belts of oil in the same stratum, and occupying different levels with 

 reference to their tidal elevation. Thus, there are numerous productive 

 belts of the old Third Venango oil sand from Titusville, where it lies 

 several hundred feet above tide, down to the southwestern corner of 

 Pennsylvania, where it is 2,000 feet Inline tide. Hence the principles 

 illustrated in this paper have a local as well as a general application — 

 local, to enable the operator to follow the course of the oil belt when 

 discovered; and general, to enable him to limit his search for oil terri- 

 tory to the localities where the geological structure is favorable. 



An effort has been made to find oil on the Mount Morris-Mannington 

 belt in Harrison, Doddridge and Gilmer counties southwest of Marion: 

 but the oil rock has changed its character completely along the strike of 

 this helt, becoming slaty and changing to Limestone; so that although some 

 oil and gas have keen found in this stratum in both Doddridge and <lil- 

 mer counties, 50 miles from Mannington, the rock is too close-grained to 

 hold oil in merchantable quantity. Nevertheless, its presence in small 

 quantity at the righl geological and tidal elevation at distances along the 

 Btrike so far away from Mannington as Big Isaac in Doddridge county 

 and Tannersville in Gilmer demonstrates the correctness of the structural 

 theory. 



