A New Method to Optimize and Interpret Lab Measurement of Tight Gas Saturation Exponents from Equilibrium Capillary Pressure Resistivity Index Pc-RI

摘要

Equilibrium Pc-RI measurements on low permeability core plugs present the SCAL laboratory with some difficult challenges regarding the duration of measurements and the attainment of truly equilibrated resistance readings. A new empirical method is described that allows estimation of fully equilibrated resistance by application of a simple transient data linearizing transform and plot slope analysis. A small set of plugs from a conventional tight gas field in the Sultanate of Oman is used to demonstrate the method. The method may also be used by the lab to monitor and shorten the Pc-RI measurement duration without compromising the interpretation of saturation exponents or capillary curves. Transform plot transients and macro capillary number are examined to estimate a boundary where the plugs transition from shock front rapid desaturation to slow percolation desaturation behavior.