Exploration and Production Technologies

Cooperative Agreement on Energy Technologies: Characterization and Alteration of Wettability States of Alaskan Reservoirs to Improve Oil Recovery Efficiency

DE-FC26-01NT41248 (Task 3.03.1)

Goal
The overall goals of this project are to:

  • Develop a new method for rapid, non-destructive wettability characterization.
  • Experimentally ascertain the influence of wettability on oil recovery efficiency in representative Alaskan cores.
  • Demonstrate how influencing the wettability through injection of fluids with different salinity and altered composition can be used to improve recovery efficiency in typical enhanced oil recovery (EOR) processes of interest to Alaska North Slope (ANS) oil producers.

Performers
University of Alaska, Fairbanks, AK.
Pacific Northwest National Laboratory, Richland, WA.
BP Exploration (Alaska) Inc. (BPXA), Anchorage, AK

Results
Project highlights to date include the following:

  • Experiments on ANS BPXA core samples have been conducted from January 2006 to the present.
  • Both high- and low-salinity waterfloods were performed on ANS core samples at partial reservoir conditions (reservoir temperature, reservoir brine). Experiments showed a reduction in residual oil saturation (Sor) and improvement in the oil recovery efficiency with a decrease in brine salinity.
  • The injection of low-salinity brine resulted in an increase in the water-wetness of the core samples.
  • Low-salinity waterfloods have the potential for improved oil recovery in secondary oil recovery processes.
  • Both high- and low-salinity waterfloods were performed on ANS BPXA oil-aged cores.
  • Due to oil aging, the wettability of core is decreased compared with its previous wettability (i.e., wettability when cores were unaged).
  • Increases were seen in Sor value compared with Sor value when cores were unaged; however, with low-salinity brine injection, Sor values were reduced.

Benefits
The expected benefits of this project to Alaska include increased oil production from existing reservoirs and facilities, additional petroleum industry employment, and development of licensable technologies. The results from this work will be the first of their kind and directly useful to oilfield operators. There is strong evidence that changing the wettability conditions of ANS reservoirs by means of injected brine composition and salinity may be a viable, economical means to achieve significant improvements in EOR efficiency in Alaskan reservoirs.

Background
Several EOR methods currently used in Alaska include thermal methods, gas flooding, chemical methods for medium to light oils (surfactant and polymer methods), and microbial methods. However, in a typical reservoir more than half of the original oil still remains in place after completion of EOR operations. Recent studies indicate that changing wettability can improve recovery with no additional costs. Results from this work can help design more-efficient EOR floods. In a 10-20 billion-barrel reservoir, recovery of only an additional 10 percent of the residual oil would be significant.

Summary
In this project, new methods for a rapid, non-destructive wettability characterization will be developed. The new techniques will be used to experimentally ascertain the influence of wettability on recovery efficiency in representative Alaskan cores and demonstrate how influencing wettability through injection of fluids with different salinity and composition can be used to improve recovery efficiency.

Current Status: (March 2007) 
The project, which began August 30, 2004, is in its third and final year. The project was scheduled to be completed September 2006, but the completion date has been extended 12 months to September 30, 2007.

Funding
This project was selected in response to DOE’s Arctic Energy Office solicitation DE-FC26-01NT41248, January 2004.

Project Start: August 30, 2004
Project End: September 30, 2007

Anticipated DOE Contribution: $301,757
Performer Contribution: $168,813 (36% of total)

Contact Information
NETL – James Hemsath (james.hemsath@netl.doe.gov or 907-452-2672) 
University of Alaska Fairbanks – Abhijit Dandekar (ffayd@uaf.edu or 907-474-6427)

Publications
Agbalaka, C.C., Dandekar, A.Y., Patil, S.L., and Hemsath, J.R., “The Effect of Wettability on Oil Recovery: A Review,” currently undergoing review by the Journal of Petroleum Science and Engineering, for possible publication in September 2007.

Schematic representation of the core flooding setup (Agbalaka, 2006).

Temperature and salinity effects on wettability, Core Sample No. 1 (DNR Cores/Decane System)

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