This paper discusses processes for sustainable recovery of heavy oil from ultra-shallow reservoirs, using low cost, innovative horizontal drilling and completion methods, combined with regional reservoir mapping and reservoir characterization.
Heavy oil exists in the shallow Pennsylvanian sands in Southwestern Missouri and Southeastern Kansas. These sands occur over an area of about 8,000 sq. miles that extends for 250 miles along the Kansas-Missouri border. Reserves are significant, with approximately 2 billion barrels of oil in Missouri alone1 .
Recovery of the heavy oil in these shallow reservoirs has proven difficult. While the oil does flow into an open wellbore under natural conditions, flow rates are low due to the nature of the oil (18° API, 1000 cp.) and the low reservoir pressure due to shallow reservoir depth (< 200 ft or 61 m).
Historically, industry has examined or attempted a number of development schemes including steam injection, CO2 flooding, in-situ combustion, direct electrical heating, stimulation with borehole explosives, and the application of solvents in conjunction with subsurface explosives. The most recent, and perhaps most successful development scheme included cyclic steam injection enhanced with flue gas. This project operated successfully for a number of years and resulted in average flow rates of 12 bopd.
Economic recovery of the ultra-shallow heavy reserves requires a process that is both inexpensive and easily applied. Novel, water-jet horizontal drilling and horizontal fracturing coupled with microbial enhanced oil recovery provide such a low cost method of recovery. This paper details these completion processes, their sustainability, and their potential for regional application. The paper also discusses the application of geochemical and/or shallow geophysical methods for regional mapping of the heavy oil sands, and the reservoir characterization methods for the shallow reservoirs.