Miscellaneous Subsurface Methods 



697 



rigorous sense, the term "viscous-flow" is applied to this necessary condi- 

 tion. Likewise by similar analogy, the conditions under which Darcy's 

 law does not hold is designated "turbulent flow." The change in flow from 

 one type of flow to the other can be correlated with the familar Reynold's 

 number.^** 



Equation (8), which properly applies to one pore in a rock, must 

 be integrated for the particular geometry of many pores, which is deter- 

 mined by the boundary conditions that prevail in a given situation and 

 for the physical properties of the fluids. For example, in the radial 



Figure 375. Sand model for radial flow 

 of fluids to central well bore. 



isothermal flow of an homogenous fluid from a circular boundary to a 

 central well bore (fig. 375), upon integration, equation (8) becomes 



Q 



6 



27rktipe — Pw) 



ixln — 



(10) 



in which the symbols undefined so far have the following meaning: 

 t is the thickness of the producing zone, centimeters 

 In is the natural, or Naperian logarithim 

 r is the radius of the sample, any units 



Fancher, G. H., and Lewis, J, A., Ind. and Eng. Chem., vol. 25, pp. 11391147, 1933. 



