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Oil. Oil. CHARACTERIZATION AND ALTERATION OF WETTABILITY STATES OF ALASKAN RESERVOIRS TO IMPROVE OIL RECOVERY EFFICIENCY. Abhijit Y. Dandekar, UAF (PI) Shirish L. Patil, UAF (Co-PI) Santanu Khataniar, UAF (Co-PI) Shivkumar Patil (Graduate Student). Prasad Saripalli, PNNL (PI)
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Oil Oil CHARACTERIZATION AND ALTERATION OF WETTABILITY STATES OF ALASKAN RESERVOIRS TO IMPROVE OIL RECOVERY EFFICIENCY Abhijit Y. Dandekar, UAF (PI) Shirish L. Patil, UAF (Co-PI) Santanu Khataniar, UAF (Co-PI) Shivkumar Patil (Graduate Student) Prasad Saripalli, PNNL (PI) B. Peter McGrail, PNNL(Co-PI) Patrick L. McGuire
OUTLINE • Focus on wettability • Experiment Details • PKS Data of Cores • Results • Conclusion/Summary • Future work • Progress
FOCUS ON WETTABILITY • Relative distribution of fluids within the pore space of a reservoir rock is controlled by wettability, i.e., influence on Sor or oil recovery • Residual oil saturation is controlled by a complex, poorly understood interaction involving water, oil, and mineral chemistry • Oil/Brine/Rock system Wettability is a function of numerous variables; prominent ones being fluid chemistry and rock type • USBM and Amott considered as industry standards; however they characterize average wettability and are inadequate for mixed wettability characterization
EXPERIMENT DETAILS • Experiments are being carried out to determine the secondary oil recovery potential of low salinity brine injection and the effect of wettability variation on Sor • Two sets of experiments were carried out • Experiment 1 Observing the effect of oil aging on wettability and consequently on Sor value of ANS cores.
EXPERIMENT DETAILS • Experiment 2 Determine the secondary oil recovery potential of low salinity brine injection and the effect of wettability variation on Sor. • Test Materials for Experiment- Cores- 1.5” diameter, 0.8” length, Clean and Oil Aged Alaska North Slope cores. Crude Oil- Alaska North Slope crude oil.
EXPERIMENT DETAILS • All brines were reconstituted in the lab using NaCl, NaHCO3, Na2SO4, KCl, CaCl2, SrCl2, MgCl2 and distilled water. High salinity brine = 22,000 TDS. Low salinity brine = 11,000 TDS and 5,500 TDS salinities respectively.
EXPERIMENT DETAILS • Preparation for Experiment 1 • Connate water saturation (Swc) was established in the cores on which already high and low salinity waterflood tests had been carried out. (Core A, Core C, Core D) • Cores were oil aged for 21 days in an autoclave. • Reason behind aging - To observe the role of crude oil constituents on the salinity dependence of wettability and oil recovery
RESULTS Quarter: Nov-Jan
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CONCLUSIONS/SUMMARY • Low salinity waterfloods performed on core A, B, C, D, E showed reduction in Sor with reduction in salinity. • The injection of low salinity brine resulted in slight increase in the water-wetness of the core samples.
CONCLUSIONS/SUMMARY • Effect of oil aging: (Core A, C & D) • Because of oil aging the wettability of core is decreased (in water wetting) compared to its previous wettability (wettability when cores were unaged) • Increase in Sor value; however, with low salinity brine injection Sor value reduced. • The wettability of original mineral surfaces can be altered by the adsorption of polar compounds and/or the deposition of organic matter that was originally in the crude oil.
FUTURE WORK • Conducting coreflood experiments on oil aged core samples. • Core flooding studies at complete reservoir conditions with live oil are to be conducted.
PROGRESS No cost extension upto 9/30/2007