Subsurface Laboratory Methods 



303 



the mud weight and the formation pressure. While the core is being 

 brought to the surface, gas expansion takes place with the reduction in 

 pressure, thus driving out additional oil and gas; by the time the perme- 

 able cores reach the surface the pressure depletion is complete. 



The residual-condensate saturation is the result of the retrograde- 

 condensation mechanism that takes place as the pressure is reduced. 



The residual oil or condensate may be expressed in percentage by 



Figure 128. Gas- and water-permeability relationships for well B. The fresh-water- 

 salt-water permeability ratios are somewhat irregular. It is probable that this 

 sand would respond most readily to gas and salt-water injection. 



