PROBLEM OF THE GREAT AUSTRALIAN ARTESIAN BASIN. 173 



p. 671, etc.). Let v — velocity of flow produced by gas rising 

 freely from the bottom of a bore in which water would 

 stand normally flush with the top of the casing, a = ratio 

 "volume of gas at atmospheric pressure to volume of water 

 issuing at surface owing to levitation of the column, ,, d= 

 diameter of bore in feet, ft=deptli of bore in feet, and f = 

 constant for frictional resistance, which in the case of fairly 

 clean wrought-iron or steel pipe may be taken as '00575. 



From Table A 1, it is seen that even an extremely small 

 amount of gas can give quite an appreciable flow, a l/100th% 

 of gas in a 6-inch bore 1000 feet deep, inducing a yield of 

 13,300 gallons per day; the total volume of gas set free in 

 that time will be only 2*1 cubic feet. 



A marked instance of a shallow bore — in which this effect 

 would be most pronounced and recognisable — is Fort Con- 

 stantine No. 1, Queensland, 620 feet to the water-bearing 

 beds (1 § 269), giving off 40 cubic feet of methane per day. 

 This quantity would account for 74,000 gallons out of a 

 total of 111,620, or two-thirds of the actual flow. A special 

 example is Westlands No. 2, Queensland, with the water- 

 bearing beds at about 3,300 feet in depth; the gas set free, 

 40 cb. ft. per hour, is enough to give an outflow of 163,800 

 gallons, whereas the actual flow is only about 30,000. In 

 view of the high static pressure (42 — 80 lbs.) the supply 

 below must be restricted. 



Considering some actual cases in New South Wales as 

 given by Symmonds, the effects in Wangrawally, Polly 

 Brewon No. 2, Kensington, Walgett and Wapweelah No. 4 

 are negligible. In Yarraldool only 20,000 gallons per day 

 and in Wirrah, Four Posts and New Yarrawa from 100,000 

 to 150,000 can be accounted for out of over a million. The 

 only one in which gas can play an important part is Pera 

 No. 1, where its effect (as based upon a statement of Sym- 

 monds) can be estimated roughly at one-sixth of the yield. 



