Prasad Saripalli, PNNL (PI) B. Peter McGrail, PNNL(Co-PI) CHARACTERIZATION AND ALTERATION OF WETTABILITY STATES OF ALASKAN RESERVOIRS TO IMPROVE OIL RECOVERY EFFICIENCY Oil 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.

PRESSURE DROP PROFILE for kabs.

PKS DATA – ANS CORES

PKS DATA – ANS CORES

New i.e. clean core sample EXPERIMENT DETAILS Experiment 1 Experiment 2 Oil aged core sample New i.e. clean core sample Water flooding Rates of 30 cc/hr. Overburden Pressure of 500 psi is used in all floods. Flood temperature - Reservoir temperature.

Preparation for Experiment 1 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

RESULTS…continued Quarter: Nov-Jan

RESULTS…continued Quarter: Nov-Jan

RESULTS…continued Quarter: Nov-Jan

RESULTS…continued Quarter: Nov-Jan

RESULTS…continued

RESULTS…continued

RESULTS…continued

RESULTS…continued

RESULTS…continued

RESULTS…continued

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.

No cost extension upto 9/30/2007 PROGRESS No cost extension upto 9/30/2007

THANK YOU!