YENANGYOUNG. 71 



However that may be, it is beyond doubt that the oil flows more 

 freely during certain months of the year, and this can only be ex- 

 plained by the assumption of certain currents existing in the oil 

 sand. 



(b) The continuity of production of the drilled wells. — It is most 

 remarkable that although some of the drilled wells are over six 

 years of age, their production has not become less. If these wells 

 derived their supplies from only a limited area they would have 

 already shown signs of exhaustion. The steady production of the 

 wells seems to indicate that the oil which is taken out is immediately 

 replaced, and this involves the assumption of the existence of a 

 current of oil which is moving towards the deep wells. 



(c) Relations between the occurrence of water and petroleum. — 

 With regard to the general relations between the occurrence of water 

 and that of oil within the area of the Yenangyoung oil field, the 

 deep wells have revealed some facts, which do not seem to be quite 

 compatible with the theory that we should have gas at the highest 

 points of the anticlinal, oil in the centre, and water below. Whatever 

 may be the value of this theory for localities, it does not seem to hold 

 good for the Yenangyoung oil field, where there is apparently an 

 irregular distribution of the above named three substances through- 

 out the series. I must, however, put stress on the words throughout 

 the series, as it is quite possible that the theory holds good withia 

 the compass of one and the same bed. It seems certain that 

 within the same bed the oil always seeks to rise to the highest points 

 because the most prolific wells are unquestionably situated at such 

 points where the petroliferous beds have risen highest above the sea 

 level, and it is also certain that whenever petroleum and water are 

 associated in one and the same bed, the former always rises above 

 the water, with the exceptions of wells No. 48, No. 61 and No. 54, 

 where it has been stated that water sand was found on the top of 

 the oil sand without being separated from it by an argillaceous 

 parting as it is generally the case. 



( "7 ) 



