OS l 1-5 2 2-5 3 



DISTANCE ALONG TRAVERSE — KILOMETRES 



35 



Figure 28-1. Soil-gas methods show methane concentrations directly over the oil poo]. 

 This diagram is a simplified form of such an occurance (Taylor). 



Using a geodynamic method, Pirson ( 1941 ) , measured gaseous emanations 

 from the earth's surface. Recognizing the ethane content as the significant gas 

 fraction, he recorded microleakage in cubic milliliters of sample collected over 

 a 24-hour period. 



The fact that the Russians were dissatisfied with the results of their soil-gas 

 exploration methods was revealed recently (Kalinin, et al., 1955). Yet to be 

 explained satisfactorily were some of the following disturbing questions: (1) 

 Why had gas surveys in some areas failed to show positive anomalies over 

 known fields: and, (2) why had other areas that indicated positive hydro- 

 carbon anomalies failed to confirm the presence of gas or oil after drilling? 

 An equally disquieting fact was that many of their previously existing gas 

 anomalies had disappeared when supposedly improved pieces of apparatus (like 

 the chromathermograph and others) were used to check these fields. Obviously, 

 there is much more work to be done before gas surveys can be used with 

 confidence. 



GAS LOGGING Gas analysis for determining the hydrocarbon 



content of muds and cores in well cuttings 

 has had greater acceptance by the oil industry. This procedure (Mogilevski, 

 1938) has been found to reliably indicate favorable gas and oil accumulations 



624 



