556 F. G. CLAPP CLASSIFICATION OF PETROLEUM AND GAS FIELDS 



13 



Doctor White's theory was applied strictl}^ to saturated rocks. Orton 

 deserves great credit for deciphering the detailed structure of structural 

 terraces along similar lines of research. The various theories for the 

 accumulation of oil have been ably summarized by Campbell.^* In fact, 

 the anticlinal theory has been advocated by so eminent nuthorities as to 

 be apparently accepted for many years. 



.L1HUTATIO.N8 OF THE .ANTICLINAL ThEOEY 



In practice, however, the anticlinal theory frequently lias not met ex- 

 pectations. After making careful locations of wells based on this theory, 

 operators sometimes were rewarded only by dry holes. The successes, 

 overshadowed by the fancied failure of the theory, were lost sight of by 

 practical oil men, and thus the theory fell largely into disrepute for a 

 time. The reports of the United States Geological Survey and the vari- 

 ous State geological surveys throughout the country contained references 

 to the anticlinal theory, and every writer on the subject tried to show 

 the geological relation of fields in the particular territory covered. In 

 many cases the geologists were successful in finding some relation, and 

 in most instances the major axes of pools were discovered to correspond 

 in a general way with the main anticlinal and synclinal . axes. Many 

 ])ools correspond closely with the crests of anticlines and seemed to prove 

 the theory. Other cases prevail, howeve]-, in which the relation was less 

 striking, and some exist in which no relation could be determined. 



To explain the apparent defects of the theory various so-called "limita- 

 tions" were formulated. The limitations, like the original theory, were 

 incomplete in their application. They, too, h^ve been added to and 

 reviewed by various geologists, until now little seems to be left of the 

 original ^'anticlinal theory." Great advances have been made, however, 

 consequent on detailed mapping of geological structure by Government 

 surveys and private geologists. While we have not yet reached, and may 

 never reach, the knowledge by which a production can be infallibly lo- 

 cated, we may truthfully assert that geology can now save a large propor- 

 tion of dry holes, as well as bonuses and rentals on prospective oil 

 territory. 



Statement of the structural Theory 



The improvement in the value of geology to oil development was largely 

 due to the evolution of the "structural theory." This term seems prefer- 



13 Edward Orton : Geol. Survey Ohio. vol. 6, 1886, pp. 21 and 94. 

 --i*M R. Campbell : Historical review of tbeorie.s advanced by American geologists to 

 account foi* the origin and accumulation of oil. Ucon. Geol., vol. 6, no. 4, 1911, pp. 

 3(32-386. 



