Chapter 32 



POROSITY, PERMEABILITY, AND CAPILLARY PROPERTIES 

 OF PETROLEUM RESERVOIRS 



Charles D. Russell and Parke A. Dickey 



Research Chemist and Head of Geological Research, Respectively 



The Carter Oil Company Research Laboratory 



Tulsa, Oklahoma 



The production of oil involves the flow of oil, gas, and water through 

 porous rocks. To obtain the most complete and efficient recovery the 

 flow must be controlled. Intelligent operations thus require an under- 

 standing of the behavior of fluids in porous media. The search for new 

 pools requires a better understanding of the mechanisms that control 

 the migration and accumulation of oil. The capillary behavior of 

 the three separate fluids, oil, gas, and water, in the porous medium de- 

 pends partly on the physical and chemical properties of the medium. 

 Some of the important properties of the medium are porosity, perme- 

 ability, and pore pattern, all of which are controlled by the petro- 

 graphic texture of the rock. 



Porosity, permeability, and capillary properties are measurable, 

 and they serve to characterize the porous medium. Porosity controls 

 the amount of space available for fluids. Capillary properties con- 

 trol the amount of interstitial water and therefore the amount of pore 

 space available for oil. Permeability controls the rate at which the 

 fluids will move under a given pressure differential. The effective 

 permeability to any one fluid, however, depends on the amount of pore 

 volume occupied by that fluid. As flow continues, the relative amounts 

 of the different fluids change, and therefore their effective permeabilities 

 change also. The ratio of the permeability of the rock to oil to its 

 permeability to gas or water determines the efficiency of the recovery 

 mechanism, and this ratio continually changes. The determination and 

 prediction of these permeabilities and their ratios not only require a 

 more complete knowledge of the physical properties of the substances 

 than we now have, but also involve difficult unsteady-state flow prob- 

 lems. Satisfactory formulas describing and predicting the production 

 of oil, gas, and water have never been solved, although they are needed 



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