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



On the other hand, in the Oklahoma and Kansas fields, on a great 

 monocline between the Ozark Mountains and the Great Plains geosyn- 

 cline, there are numerous domes and anticlines, dne to some sort of pres- 

 sure forces aside from those which elevated the mountains on the east or 

 west of the fields. 



Substance of a geological Examination 



Considering the last few pages, we must, in closing, call attention to 

 the fact that while geological structure is the most important factor in 

 any examination for finding oil or gas, all the other factors must be given 

 due weight in forming our conclusions; and, above all, we must use our 

 judgment in digesting the field data. It is important, after finding the 

 structure, to proceed in the following manner : 



1. Make as accurate a structure-contour map as available data will 

 permit. 



2. With the help of '^^convergence maps,'^ make a separate geological 

 and well map for every individual sand. 



3. Before making any recommendations, consider carefully the ques- 

 tion of local peculiarities of the structures — water conditions, number, 

 character, parallelism and continuity of the sands, character of overlying 

 beds, possible source of supply, metamorphism, and "structural habits" 

 for the particular group of fields. 



By such an appraisal of the characteristics of the region, it will not be 

 difficult to form some conclusion of the probabilities of the prospective 

 field. 



Conclusion 



In a scientific study of any oil field for the purpose of determining its 

 possibilities, it is necessary for the expert to distinguish the features 

 which it has in common with other fields from those in which it differs 

 from them, and by a process of comparison and inference, based on the 

 detailed observations and calculations, to draw his conclusions as to 

 whether or not the locality is favorable for petroleum. 



It is probable that oil will continue to be discovered in types of struc- 

 tures not enumerated here, and from time to time further additions and 

 subdivisions of the classification must be made. "We can record in the 

 present classification only what is now actually known or inferred. 



