The goal of this three-year research project is to develop methods using water soluble polymers to recover viscous oil from unconventional reservoirs (e.g., on Alaska’s North Slope).
New Mexico Institute of Mining & Technology, Socorro, NM 87801
Alaska’s North Slope contains a very large unconventional oil resource—over 20 billion barrels of heavy/viscous oil. Conventional wisdom argues that thermal recovery methods are most appropriate for recovering viscous oils. However, for viscous oil reservoirs at Alaska’s North Slope, a number of factors complicate this thinking. The formations that hold vast viscous oil reserves— Ugnu, West Sak, and Schrader Bluff—are relatively shallow and therefore close to permafrost. Steam generation is prohibitive here due to severe cold weather on the surface, heat losses while pumping steam down through 700 to 2,200 ft of permafrost, heat losses when contacting the cold formation, and environmental considerations.
Miscible gas injection and water-alternating-gas have been proposed and attempted, with some success, as ways to reduce the viscosity and enhance displacement in some North Slope reservoirs. However, this displacement is characterized by a remarkably unfavorable mobility ratio. Therefore, the current technology is confined to the least viscous of the North Slope’s heavy oils. The availability of natural gas for miscible EOR purposes may be restricted by the potential construction of a gas pipeline to the lower 48 states.
This project will identify a wider range of conditions (especially regarding the limits of oil viscosity) for application of polymer flooding. It should specifically open opportunities for increased oil recovery in North Slope viscous oil reservoirs. New methods will be developed to improve injectivity during polymer injection for fractures/horizontal wells without compromising sweep efficiency. In fact, opportunities for enhancing sweep efficiency may be realized. The studies of polymer properties versus permeability will identify the most suitable polymer(s) for cost-effectively improving sweep in North Slope viscous oil reservoirs. The project will establish whether a newly identified mechanism using viscoelastic polymers can be useful for reducing residual oil saturations in North Slope reservoirs below the values possible from waterflooding. If induced fracturing or formation parting proves to be detrimental, the project will develop a means to correct these problems using gel treatments. This project will also compare the viability of a “Bright Water” type of process with that of normal polymer flooding when applied to North Slope reservoirs with viscous oils. All of the above information will be valuable in establishing the most cost-effective path forward to develop Alaska heavy oil resources.
The project has been completed and the final report is available below under "Additional Information".
Final Project Report [PDF-1.82MB]