640 m. l. fuller appalachian oil field 



Eelations of Appalachian Oils to Structure 

 : ■ principal factors 



The distribution of oil in the pools in which it is now found is depend- 

 ent upon its origin, migration, and method of segregation on the one hand, 

 and upon the composition, texture, stratigraphic form, dynamic struc- 

 ture, and confining agents of the reservoirs on the other. The former 

 have been briefly referred to under ^'Origin of appalachian oils/' 



In the past, most geologists, while recognizing the existence of other 

 factors of importance, have given by far the greatest weight to dynamic 

 structure. A reaction has been under Avay for some time, however, and 

 there has been a growing tendency on the part of some to minimize the 

 value of structure. It has been pointed out^^ that in Pennsylvania and 

 West Virginia about 75 per cent of the oil pools fail to cross the axes of 

 the folds on which they lie. This, however, is hardly an argument against 

 the importance of structure, siiice it is not to be expected that oil pools 

 will cross the axes except at the terminations of folds or local bulges, 

 their normal position being on the sides. The partial condemnation of 

 structural terraces^^ is apparently based mainly on theoretical consider- 

 ations and does not seem to be warranted by the observed field relations. 



It is probably true that many have given too little consideration to com- 

 position, cementation, stratigraphic form, and other factors pertaining to 

 reservoirs ; but, as in all reactions, there is danger of the pendulum swing- 

 ing too far. It must not be forgotten that, aside from stratigraphy, 

 structure is the only factor that may be predetermined in advance of 

 drilling in new territory, and that operations based on anticlines and 

 structural terraces have been essentially successful in almost every field. 

 Unquestionably, however, more attention should be paid to other factors 

 than has been customary in the past, especially on the part of corporation 

 geologists having access to records and other development data. Many - 

 sands have individualities and trends that may be made use of to advan- 

 tage in new fields. 



STRUCTURES 



The principal structures afi'ecting the collection of oil in pools are 

 given below. Practically all of them are represented in the Appalachian 

 field. 



i*W. E. Bernard: Thesis, University of Pittsburgh, "Relations of folds to the oil 

 pools of Pennsylvania and West Virginia," pp. 27-2.S. Quoted hy .Tohnson & Huntley, 

 "Principles of Oil and Gas Production." .John Wiley & Sons, 1016, p. 71. 



i"' .Tohnson & Huntley : Ibid., p. 72. 



