An extended JBN method of determining unsteady-state two-phase relative permeability

Abstract

Relative permeability is the reduction of permeability of porous media when subjected to multiphase flow and a key parameter in subsurface hydrology. The JBN method is a well‐known method of obtaining relative permeability, which measures the overall pressure drop and the effluent phase ratio versus time during two‐phase displacements. By assuming no capillary pressure or gravity, the JBN method obtains the relative permeabilities to both phases at the core outlet. Since data across a range of saturations are acquired in a relatively short time, this method is widely used. This work extends the JBN method by having (1) section‐wise pressure drop measurements between the core inlet, four pressure taps on the core and the outlet, (2) local saturation measurements, and (3) local phase fluxes. With these data, the extended JBN method can determine relative permeabilities to both phases at each pressure tap of the core (not just at the core outlet). The JBN extension is shown using a data set where CO2 invades a brine‐filled core. From this it is found that the advantages of the extended JBN method over the regular JBN method are: (1) four times more data are obtained, and (2) data are more accurate because the capillary end effect is experimentally avoided. Avoiding the end effect results in tripling the saturation range, and obtaining relative permeabilities that are consistent with steady‐state measurements and roughly 40% higher than those from the regular JBN method.

Steady‐state supercritical CO2 and brine relative permeability in Berea sandstone at different temperature and pressure conditions

“…During CO 2 ‐brine two‐phase flows, CO 2 pressure differs from brine pressure by the capillary pressure. Previous studies [ Chen et al ., , ] have shown that CO 2 pressure is measured at each tap location since pressure taps are big openings and connected to the nonwetting phase (CO 2 ). Thus is equal to the measured pressure drop in center sections.…”

“…However, due to the non‐uniform saturation in the entrance, is not equal to in the entrance section. Previous studies [ Chen and DiCarlo , ; Chen et al ., , ] have shown that the exit section is dominated by the capillary end effect and we do not calculate relative permeability from the exit section. In summary, CO 2 and brine relative permeabilities are calculated in each of the center three sections and only CO 2 relative permeability is calculated in the entrance section.…”

“…This study used a similar experimental method to the previous measurements of CO 2 -brine relative permeability at 208C and 10.34 MPa [Chen et al, 2014[Chen et al, , 2016a[Chen et al, , 2016bChen and DiCarlo, 2016]. The difference is that this study used heaters and thermocouples to maintain the floods at elevated temperatures.…”

“…The porosity was calculated by dividing the CT number difference between the nonequilibrated brine saturated core and the dry core by the CT number difference between nonequilibrated brine (16) and air (-1000). The in situ water saturation was calculated by linear interpolation in CT number between the brine saturated core and the CO 2 saturated core measured at the particular experimental temperature and pressure [Chen et al, 2014[Chen et al, , 2016a[Chen et al, , 2016bChen and DiCarlo, 2016].…”

Measurements of CO2‐brine relative permeability in Berea sandstone using pressure taps and a long core

“…21,25,35,36 Bennion et al proposed to measure endpoint CO 2 relative permeability at different flow rates and fit the two parameters with an exponential function; then they corrected the endpoint CO 2 relative permeability by extrapolating this function to infinite flow rate. 10,12,21,25,33,35,36 On the other hand, Chen et al 37,38 and Kianinejad et al [39][40][41][42][43] introduced new unsteady-state methods that can locally measure pressure gradient, phase flux and saturation during two-phase and three-phase flows, which experimentally avoid the capillary end effect particularly for gas and supercritical phases and give more accurate CO 2 relative permeability data than conventional unsteady-state methods. They fit the flow rate versus overall pressure drop with a function; and by taking the derivative of this function, CO 2 relative permeability was determined at the inlet of the core.…”