Abstract

Evaluation and interpretation of the hydrogeologic and hydrodynamic characteristics at the Kern River field, a four billion barrel (OOIP) giant oil field, suggests a “non-trapping” oil emplacement mechanism for the highly productive sands of the Kern River Formation. The 12 - 14 degree API gravity crude is produced from stacked fluvial/alluvial sands of the Kern River Formation. These shallow deposits are part of a homoclinal structure, dipping 4 to 6 to the southwest, that overlie the Bakersfield Arch, a basement high. Migrating hydrocarbons lost buoyancy at the top of the regional groundwater table and became subordinate to gravitational forces. In effect, a floating oil pool was established whose laterally dispersive tendencies were inhibited by a combination of the reservoir rock’s low relative permeability to the biodegraded, viscous, heavy crude oil, to heterogeneities of the host rocks, and to local structure. The geometry of this floating oil accumulation is also influenced by the hydrodynamic regime imposed by groundwater recharge from the Kern River and from drawdown brought on by production increases using thermal EOR techniques.