Effect of Positive Rate Sensitivity and Inertia on Gas Condensate Relative Permeability at High Velocity

The authors have previously reported that gas condensate relative permeability will increase with increasing velocity when conducting steady-state measurements. The increase in relative permeability was referred to as "positive rate sensitivity" or the "positive coupling effect", with the initial studies having been conducted using a single core sample at two values of interfacial tension (IFT). A systematic series of core tests have since been completed which generated data for values of IFT ranging from 0.015 to 0.78 mN/m, using core types ranging in permeability from 11 to 350 md. The results confirmed that the positive coupling effect existed in low permeability cores and different lithologies at low and high IFT. The maximum tested velocity was in the region of 75 m/day, which was estimated to be at the boundary above which inertia would be significant.