PROBLEM OF THE GREAT AUSTRALIAN ARTESIAN BASIN. 187 



excessive flows could not be throttled by finishing the last 

 few hundred feet with a smaller bit, and employing at the 

 same time a smaller-sized and less costly string of deep 

 casing. 



The calculated casing losses are lower than the static 

 pressures by amounts representing those due to friction in 

 the pores of the sandstone forming the bore-walls, for the 

 velocity in the capillaries increases progressively on 

 approaching the borehole. 



When, after eliminating the loss in head due to the casing, 

 the residuals are compared, the great differences even in 

 bores possessing similar depths and yields become apparent, 

 and in this direction there is scope for considerable invest- 

 igation. Examining only a few instances, we find in the 

 deeper bores of New South Wales high values in comparison 

 with their outputs in Finger Post, Goondablui No. 4, and 

 Mullawa, and the reverse entirely in Boomi, Euraba, 

 Ooubal and Tyreel. 



Among Queensland bores an interesting point is the high 

 static pressure of many of the shallow wells regarded from 

 this standpoint, e.g., on the Corinda Leases, Manfred 

 Downs, Saxby Downs, Warenda Lease and the deep Ero- 

 manga bore. 



Slichter's formula for the yield of a well is unsatisfactory 

 to apply, in that the most important quantity — the limiting 

 distance of interference of wells — is given the arbitrary 

 value 600 feet, this being undoubtedly too low. It is clear 

 anyway that the " permeability " of the strata vary much 

 from point to point. 



In order to determine whether this variation takes place 

 according to any definite or orderly plan, the assumption 

 was tentatively made that the porosity of the strata does 

 not change abruptly from point to point, but in a gradual 

 manner. The volume of water passing across a unit strip 



