tology, especially micropaleontology, have been perfected as tools for the petro- 

 leum geologist. In the Gulf Coast, in California, and in Indonesia, species 

 of foraminifera are used in structural contouring and in detailed local corre- 

 lation. During the past 10 years, considerable advances have been made in 

 the usage of fossils for determining sedimentary environments that are, in turn, 

 related to the study of source beds for petroleum and to the more complete un- 

 derstanding of reservoir rocks. 



Structural Geology 



Probably the most important facet of the geologic science used by the pe- 

 troleum geologist is structural geology. A student must be versed thoroughly 

 in the classification of folds and faults and in the types of local and regional 

 forces that account for their development. The student also must be well acquaint- 

 ed with the methods of construction of maps and cross sections that are used to 

 depict structural configuration in three dimensions. The part played by various 

 logging and geophysical techniques in assembling structural data should be a 

 part of the training of the petroleum geologist, either in school or in the early 

 years of professional work. 



Stratigraphy and Sedimentation 



The increasing importance of petroleum accumulations that are controlled 

 in large part by stratigraphic factors has brought into greater focus the neces- 

 sity for an understanding of the basic principles of stratigraphy and sedimenta- 

 tion. Here again, the methods of collecting data in the field and in the subsur- 

 face and the manner in which these data may be depicted on maps, as well as 

 the significance of the data, should be made a part of every geologist's knowl- 

 edge. An effort also should be made to acquaint the student with regional and 

 systematic stratigraphy in order to instill a clearer understanding of the inter- 

 relationships between historical geology, structural geology, and stratigraphy. 

 Petroleum exploration, from a strictly geological viewpoint, is primarily the ap- 

 plication of the principles of stratigraphy and structural geology. 



Mineralogy and Petrology 



The mineralogy of the grains, interstitial matter, and cement of detrital 

 rocks can play a direct part in the migration and entrapment of petroleum. 

 There is often a correlation between the mineralogy of chemically precipitated 

 rocks and areas of high porosity and permeability. A knowledge of source areas 

 and diagenesis is necessary to the complete understanding of the stratigraphy of 

 sedimentary rocks; this knowledge then may be used in the delineation of areas 

 and formations that are more favorable for the entrapment of petroleum. The 



