TRAPPED NON-WETTING PHASE CLUSTERS: AN EXPERIMENTAL INVESTIGATION OF DYNAMIC EFFECTS AT THE PORE SCALE USING A MICRO-CT SCANNER

摘要

We used a state-of-the-art micro-CT scanner integrated with a two-phase core-flooding apparatus to perform flow experiments in a Bentheimer sandstone core sample in order to investigate the impact of dynamic effects on the trapping of non-wetting(oil) phase at the pore scale.We explore the size distribution of the trapped oil clusters at the pore level. The sample was 4.9 mm in diameter and 13 mm long.A new core holder was designed and built to allow flow experiments through small core samples(under confining pressure) while located inside the micro-CT scanner.An unsteady-state method was utilized to carry out three sets of experiments on the sample;each set included a drainage and imbibition cycle with identical initial brine saturation(i.e.,Swi=0.34) prior to each imbibition step.During imbibition,different brine flow rates were used to create flows with various capillary numbers,ranging from 10-6 to about 10-5 ,to cover both capillarydominated and viscous-dominated displacement regimes.The pressure and temperature of the experiments were 24 °C and 2.76 MPa,respectively.We mapped fluid occupancies at the end of each drainage and imbibition step for the entire sample.The Sor decreased significantly from 0.41 to 0.16 during the imbibition processes due to stronger viscous pressure drop at the end of the third imbibition compared to those of the first two imbibition tests.The contact area between oil and brine was considerably decreased at the end of the high imbibition brine flow rate compared to those of the first and second imbibition tests.