RESISTIVITY INDEX AND CAPILLARY PRESSURE CHARACTERISTICS OF RESERVOIR SANDSTONES IN DIFFERENT WETTABILITY CONDITIONS

摘要

This research focuses on resistivity index and capillary pressure saturation relationships measured on reservoir sandstones using refined oil and synthetic formation brine.The experiments mimic different displacement processes that could occur during the history of the reservoir: for example,the displacement of water by oil during the initial hydrocarbon migration,the displacement of oil by mud filtrate around the wellbore during drilling,the displacement processes during the formation of transition zones under gravity/capillary forces and during waterflooding.The resistivity index and capillary pressure experiments were performed on UKCS reservoir samples in both”preserved”and cleaned states.Measurements of the same samples in the”preserved”and cleaned states allowed us to study the effect of surface wettability on capillary pressure and resistivity index.Based on the results from special core analysis and geochemical analysis of reservoir and core-extracted fluids,we found that oil wet surfaces in the”preserved”cores were very pervasive and hard to remove even by cleaning with strong solvents.Variations in the capillary pressure and resistivity indices have been observed for the reservoir samples when they were in different states.This has a profound effect on the use of core data for log calibration and reservoir engineering studies.