IOWA ACADEMY OF SCIENCES. 



17 



This causes in the porous rock a movement of the water, oil and gas particles — a 

 free mechanical rearrangement. They accumulate in order of their specific gravity 

 — the water at the bottom, then the oil and then the gas at the top. The par- 

 ticular structure of the earth's crust must be ordinarily an arch or anticline. The 

 structure of the great oil belt at Findlay, Ohio, is as follows: 



Cross section of the Findlay region. (After Orton.) 

 It is readily seen that having arranged themselves according to their specific 

 gravities the gas occupies the central portion of the arch, the water the bottom 

 and the oil a space between. When the top of the dome is pierced gas 

 escapes; when the arch a little farther down is drilled into out flows oil; and if the 

 strata near the base of the bow are penetrated only water appears. The formation 

 of the arch is due to the same causes that elevates the mountains. A section ac- 

 cross the Appalachians to the Mississippi river shows sharp folds near the center 

 of the uplift. In passing westward the folds get lower, and lower until near the 

 great river the strata are almost horizontal. 



General section from the Appalachian to the Mississippi Kiver. 



In Pennsylvania and West Virginia some of the anticlines are so sharp that the 

 top of the arches are fractured. If ever any gas had accumulated there it escaped 

 long ago. In Ohio the folds are relatively low. They would not be impressed 

 in existing topography, for erosion obscures geological structure of this kind by 

 leveling the country — the elevations much more rapidly than the lowlands. 



The next condition to be considered is the presence of rock pressure, as the Penn- 

 sylvania drillers term it. It only needs to be stated that according to the best 

 evidence now at hand the pressure is artesian or hydrostatic and is measured by 

 height of the column of salt water that would rise in any well were water struck 

 instead of gas.* 



Such, then, are briefly the conditions, the fulfilment of which are necessary for 

 a successful flow of gas and oil of economic value. 



Now, which of these conditions are satisfied within the limits of Iowa? Which 

 are not, if any? What are the prospects of striking either substances under con- 

 sideration in the State? 



It has already been shown that large quantities of petroleum are doubtless dis- 

 semmated through Iowa's rocks, just as elsewhere — the direct evidence being the 

 actual presence of considerable amounts of hydrocarbons. 



There is httle doubt but that the porous strata or reservoirs and the shale cover- 

 ings are present. This is indicated by artesian wells already put down in the dif- 

 ferent parts of the State, as well as by the succession of the beds observable in the 

 northeastern part of the State. 



* The preceding remarl<s on the accumulatioa of the hydrocarbons are condensed 

 largely from Ortoa and White who have done more than any other persons to place 

 the oil and gas industry on a scientific basis. 

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