X-Ray in-situ saturation monitoring, an aid to study relative permeability in water-wet carbonate rocks

The simultaneous flow of oil and water in porous media is described by relative permeability curves, mainly derived from laboratory experiments. Relative permeability is of paramount importance in predicting reservoir production performance and drive mechanisms and its value depends largely on the volume fraction of fluids present in the test samples. Nowadays X-ray scanners are one of the most accurate tools for non-destructive measurement of in-situ saturation. The mail purpose of this paper is to describe two-phase immiscible fluid flow behavior of low viscosity ratio oil/water through water-wet porous media interpreted by in-situ saturation profile data. Both steady state (SS) and unsteady state (USS) relative permeability measurement methods were applied and compared. The measured in-situ saturation profiles can confirm wettability character of studied rock samples and the yielded data are in good qualitative agreement with wettability characteristics of water-wet reservoir cores. In the USS experiments the saturation profile shapes characterize mainly production of oil before breakthrough and display front position. The flooding-rate dependency of the USS experiments was observed. In the SS experiments by imbibition process, water saturation in the samples was increased significantly even with flow of a very small fraction of water at the beginning of the test