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Shallow, Immobile Oil Resources of the Uinta Basin, Utah

Schamel, Steven 1
1 GeoX Consulting Inc, Salt Lake City, UT.

The shallow oil pools in the central portion of the Uinta Basin in northeast Utah present an immediate opportunity for development of a stranded, immobile oil resource. Here fluvial channel sandstones in the Uinta Formation and marginal lacustrine carbonates and sandstones in the upper Green River Formation (Eocene) reservoir both moderately biodegraded viscous heavy oil and normal high-wax oil having a pour point that is greater than the ambient reservoir temperature. The known pools of shallow, immobile oil generally overlie active oil and gas fields. Characteristically, the oils change down section from moderately degraded and/or immobile normal oil at depths less than 2,000 feet to mobile normal oil at current production depths below 4,000-5,000 feet. In terms of composition and viscosity, the deeper immobile oils are identical to the mobile oils currently produced. The full extent of these deposits within the central Uinta Basin has not been fully delineated and the total OOIP is unknown. However, the volumes of oil may be very large. In just an area of 7 square miles overlying the Wonsits Valley field there is an estimated 310 MMBO at depths less than 2,000 feet. Several factors indicate that geothermal hot-water flood could be successfully implemented in the shallow oil deposits overlying or near active oil and gas fields. First, there is a ready supply of hot, low salinity water recovered from normal field operations, hot water that otherwise would be discarded in disposal wells. Second, in at least some of the pools only a small increase in temperature (<10 F) is required to mobilize the now cold, immobile oil. Additionally, the shallow oil is of the same, or nearly the same, quality as the oil produced from the deeper Green River Formation. The gathering system is in place to handle this oil and it has a ready market. Alternative technologies for recovery of these relatively light oils (15-22 API) include CO2 injection, solvent vapor extraction, and small-scale cyclic steam stimulation. These shallow, immobile oil pools have received little attention in the past, yet they may constitute a large untapped oil resource accessible through thermal or alternative in situ recovery methods.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009