YENANGYAT. 1 35 



must be left undecided for the moment, but to me it seems highly pro- 

 bable, that the petroliferous beds are subject to irregular changes in 

 every direction. For the above mentioned reasons the identification 

 and correlation of each single bed has been a little difficult, although 

 much less so than at Yenangyoung. 



It will be seen from the sections that the various levels in which 

 one and the same bed was found in the different wells are due to the 

 dip of the strata. The lesson taught by the deep wells might have 

 been a /^w/'z'deducted from the structural features at the surface : any 

 well situated east of the crest of the anticlinal is sure to be a failure 

 from a commercial point of view, as, even if not too far off, the 

 high dip will cause the petroliferous beds to be found at such a depth 

 that they are practically inaccessible. Boring operations will therefore 

 have to be more or less to the western side of the anticline, but in 

 this case we see that there are almost insurmountable natural difficul- 

 ties in the way of reaching a given petroliferous bed, say the first 

 oil sand, at a given distance west of the crest of the anticlinal. As 

 already stated the ravines on the eastern side of the Tangyi range 

 are very short, the crest of the range being close to the river. A well 

 sunk at a spot too far west from the crest of the anticline would 

 therefore have to pass through a large thickness of younger strata 

 before reaching a given bed ; the length of the ravines being very 

 short, and the eastern slope of the main ridge being very steep* 

 suitable sites for wells would be very difficult to find. The range 

 would probably have to be crossed and the well drilled on the western 

 side. In either case, a large series of younger strata would have to be 

 drilled through before the petroliferous sands were reached. Further 

 test wells should therefore be sunk where streams have eroded longer 

 ravines on the eastern slope than at Yenangyat in order to avoid the 

 unnecessary drilling through the unpetroliferous younger beds. 



The possibility that wells sunk in more westerly localities will prove 

 unprofitable must, however, not be quite disregarded. It is quite possi- 

 ble that the petroleum rises towards the highest parts of the anticline at 

 Yenangyat and that the lower parts of the petroliferous sands contain 



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