GEOLOGIC AND ECONOMIC BACKGROUND 41 



random drilling. This list includes, such important producing fields as the 

 Midway-Sunset, Coalinga, and Kern River in California ; Glen, Burbank, 

 and Bristow-Slick in Oklahoma ; the East Texas in Texas ; the Smackover 

 in Arkansas; perhaps the New Delhi in Louisiana, the Bradford in Penn- 

 sylvania, and Mush Creek in Wyoming. In addition, we have many smaller 

 fields, such as the Cut Bank in Montana ; and the shoestring pools of Kan- 

 sas. Such a high frequency of blind discovery without the aid of geology 

 and geoph3'sics clearly indicates the importance of these stratigraphic 

 accumulations. Since present exploration methods are not generally applic- 

 able to the detecting and mapping of stratigraphic traps, it is to be 

 expected that unless some more efifective technique of prospecting for 

 them is developed very shortly, there will be a reversion to the wildcat drill- 

 ing cycle of exploration. If this happens, much exploratory drilling will be 

 done along stratigraphic trends, using less geology and geophysics, and 

 depending primarily on actual drilling luck for success. In the past, such 

 random drilling has been moderately successful in some areas and undoubt- 

 edly will find more oil in the future. Price increases for crude oil will 

 stimulate this type of exploration. Such wildcat drilling, however, will 

 not be as attractive as it was one or two decades ago, due to the greater 

 cost of drilling and the limitations imposed by present laws and taxes 

 on the financing of such operations.! 



Comparison of Wells Located with and without 

 Technical Evidence 



The effectiveness of geophysics in petroleum exploration has been 

 established by the past twenty-five years of intensive use. During 1947, 

 geophysical work was solely responsible for the locations of wells which 

 resulted in 165 producers and 615 dry holes. The combination of geo- 

 physics and geology together is credited with locating sites which yielded 

 134 producers and 405 dry holes. In this period there was a total of 6775 

 wells drilled. $ This means that geophysics played a vital role in the location 

 of about one-third of all the oil wells drilled in 1947, with a success record 

 of about one producing well to each four wells drilled. 



In the ten-year period from 1938 to 1947, inclusive, wells located by 

 geophysics had a success record of 21 per cent. During this same period, 

 the wells located on a non-technical basis had a success record of only 5.3 

 per cent. The technically-located wells were four times as successful as 

 those drilled without technical advice. Considering these trends, it is within 

 the bounds of realism to predict that probably fifty per cent of our new 

 well locations in the next ten-year period will be based on geophysical work. 



t J. J. Jakosky, "Whither Exploration," A.A.P.G. Bulletin, Vol. 31, No. 7, July, 1947. 

 t Frederic H. Lahee, "Exploratory Drilling in 1947," A.A.P.G. Bull., Vol. 32, June, 1948, No. 

 6, pp. 851-868. 



