Effect of Changing Injection Water Salinity on Oil Recovery from Oil-wet Carbonate Rocks

Open Access
Author:
Pakoz, Ugur
Graduate Program:
Petroleum and Natural Gas Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 11, 2015
Committee Members:
  • Zuleima T Karpyn, Thesis Advisor
Keywords:
  • Carbonate rocks
  • salinity
  • oil recovery
  • wettability
  • aging
  • core flooding
  • water flooding
Abstract:
Experimental studies and some field applications have shown that tuning the salinity of the injected water can affect oil recovery from water flooding. Most of the available literature has dedicated efforts to investigate the effect of low salinity water injection, especially for sandstone. Further studies on carbonate rocks also proved that low salinity effect might be observed for carbonate rocks as well. The main mechanism for the improved oil recovery from low salinity water flooding has been attributed to wettability alteration. The purpose of this work is to further investigate the effect of water salinity on oil recovery from oil-wet carbonate rocks. A series of core flood experiments were performed in the laboratory to measure and compare oil recovery from increasing and decreasing salinity floods at room temperature. Selected carbonate cores were aged with synthetic oil at 100 ºC for 12 days prior to core flooding. Contact angles were measured on pre-aged and post-aged core slices to validate aging procedure and oil-wet conditions. Both, increasing and decreasing salinity floods showed measurable recovery gains in the secondary and tertiary modes compared with initial floods. In case of increasing water salinity, 1.3% and 0.6% additional recoveries were obtained while in the case of decreasing water salinity, additional recoveries were 0.6% and 0.7%, all in terms of original oil in place in the core. Results suggest that the system disturbance caused by the change in injection water salinity may have a greater influence on oil recovery than wettability alteration under the laboratory conditions tested.