Chapter 31 



SUBSURFACE TECHNIQUES 



Daniel A. Busch 



Senior Research Geologist 



The Carter Oil Company 



Tulsa, Oklahoma 



In subsurface studies of oil-bearing formations the geologist is con- 

 stantly in search of new techniques and combinations of techniques 

 which may be of value in discovering new oil pools or extensions of 

 known accumulations. In the earlier history of oil finding the prime 

 technique consisted in locating structures exposed at the surface. This 

 was accomplished by determining the elevations on a key bed, or 

 various key horizons, exposed on the surface and contouring these 

 numerical values on a map. It was not long before the oil man began 

 to compare the subsurface elevations of key beds in the sequence of 

 strata penetrated in neighboring wells. Many drillers and operators 

 kept penciled notes on the depths to the top of some of the sandstone, 

 shale, and limestone layers and sometimes attempted to describe them. 

 J. F. Carll (1875, pp. 23-31, 35) was the first man to plot and correlate 

 formations logged by the driller into what he termed "vertical sec- 

 tions." Considerable advances have been made since Carll's time in 

 the techniques of logging wells and in the manner of interpreting well 

 logs. 



Within the past several decades the geophysicist has developed 

 several techniques for subsurface probing which require neither surface 

 outcrops nor well-log information. He is able to locate deeply buried 

 structures by means of gravimetric, seismic, magnetic, or electric data. 

 By a combination of geological and geophysical methods it is believed 

 that most of the major structures in sedimentary rocks in this country 

 have been mapped. Many of them have been drilled and proved 

 productive, whereas others have been proved barren. Many pools such 

 as the Burbank, Bartlesville, Cheyraha, Wewoka Lake, Southwest 

 Antioch, Elmore, and Katie pools of Oklahoma, the shoe-string sand 

 pools of Kansas, the east Texas pool, and numerous others that are not 



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