Water Permeability of Reservoir Sands

Abstract

Abstract For many years the permeability of reservoir sands has been measured by flowingair through a cleaned and dried core sample. This differs from the truereservoir permeability in one important respect: the rock particles in thereservoir are surrounded by interstitial water, not air, and their physicalshape and condition of hydration are greatly dependent thereon. Permeability asdefined must be measured with a single-phase fluid. Since no means exist forremoving the oil and gas from a core sample by simply flowing water through it, the sample must be cleaned and then resaturated with water before testing. Thepresent discussion attempts to show that after the cleaning process aconsiderably different permeability is determined with salt or fresh water thanis obtained with air. The postulate is made that the salt-water permeability isprobably closer to the true reservoir permeability than is the measurement withair. This is discussed in relation to both physically possible and economicallyfeasible measurements. Data on more than 1200 core samples are given to showthe nature of the effects observed, and a plea is made for others to considerwater permeability measurements as a routine necessity, eventually replacingair permeability in regions where the differences are great. Introduction Permeability is defined as "a measure of the capacity of a porous medium totransmit? fluids, when there is no interaction between the solids and thefluid." T.P. 1871