Saturation Prediction of Specific Tight Sandstone Reservoirs Based on Experimental Analysis of Oil-Water Relative Permeability

The isotonic point of the Chang-6 tight oil reservoir in the Qilicun Oilfield in the Ordos Basin cannot be determined from experimental data on the waterflooding permeability. Furthermore, there are missing data near the isotonic point. Previous research on phase permeability trends has uncovered significant uncertainties in the application of data normalization, standardization, and interpolation processing. In current research, there is a consensus on the existence of a relationship between the relative permeability and saturation indices. However, since measurements contain relative permeabilities of 0, coefficient indices cannot be directly derived. Researchers have theorized that the first data number in the wet phase relative permeability must be changed from a 0 to non-0 minimum in order to directly establish the relationship between the relative permeability and the water saturation index. The missing intervals after the first data point are not interpolated. Not only does this method incorporate the knowledge of the permeability indices obtained by researchers, but it also eliminates the processes of normalization, standardization, and interpolation of missing data intervals for permeability data in order to avoid errors introduced by these processes. Without introducing new parameters, interference with raw data was reduced and the accuracy was improved. The results indicate that the relative permeability is highly correlated with the water saturation indices. Furthermore, the relationships between the water content and relative permeability and between the water saturation and water content were analyzed using the Leverett displacement function and percolation theory. The water saturation corresponding to the water content of 17 samples was calculated under the condition of displacement, and the relationship between the critical water saturation and water content was further established. These results provide support for studies on the relationship between phase permeability and oil-water saturation within this area.