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Fault Play Wells In A 115 Year Old Heavy Oil Field, Kern River Field, Bakersfield, California, USA


In the middle of the Kern River Field, three small faults (< 30′ offset) block heavy oil migrating down-dip to pool in the up-thrown block. Identifying unique situations to improve oil production in a 115 year old oil field enables us to keep the production decline to a minimum and improve ultimate recovery. Kern River Field is located in the southern San Joaquin Basin, California, USA. The field has produced over 2,200 MMBO of 10-13 API gravity heavy oil since discovery in 1899, with the greatest production coming in the past 45 years with the initiation of steam flooding. The field produces from vertically stacked, continuous, unconsolidated sands that are separated by laterally discontinuous low-perm siltstones of the Upper Miocene-Pleistocene Kern River Formation. Despite the close well spacing, correlating oil zones can be challenging due to the rapid facies changes that exist in a braided fluvial system. The porosity and permeability of the sands are in the 28-32% and 1-5 Darcy ranges. Hydrocarbon migration is due to gravity drainage in a homoclinal structure dipping 3.5 – 6∞ to the southwest. Hydrocarbon entrapment is caused by potentiometric surfaces, including localized up-dip biodegration and deasphalting of oil where reservoir sands crop out at surface. Field bounding faults have offsets of greater than 100′. The internal faults have normal offsets in the 10′ to 30′ range that seal and bank oil. Fault mapping has been almost exclusively done from careful log correlation by Jim Eacmen (Chevron retired); these interpretations are held valid and are still used to identify opportunities along this fault play. Drilling in this play includes atypical wellbore paths for this field. Deviated wells (∼20-30∞ inclination, 6-8∞ dogleg) closely parallel the fault plane on the up-thrown side of the fault intersecting all nine oil sands as close to the fault as mechanically possible. To date, there are 19 fault play wells that have been drilled since 2005.