Belridge Giant Oil Field - Learnings from an Unusual Marine Reservoir in an Old Field

Malcolm E. Allan, Mahmood Rahman, and Barbara A. Rycerski
Aera Energy LLC, Bakersfield, CA

The Belridge giant oil field in the San Joaquin Valley, California, has produced more then 1.5 billion BO & 1.2 billion CFG from multiple reservoirs since being discovered in 1911. Aera Energy LLC (a company owned jointly by Shell & ExxonMobil) currently produces 65 thousand (10,300 cu m) BO and 50 million (1.4 million cu m) CFG daily from a sequence of deep marine diatomite layers in the Miocene Monterey Formation. The diatomite sequence is vertically continuous for over 2,000' (600 m) and covers about 3,100 acres (1,250 ha) inside Aera's field limits. The field has over 3,500 producers and 1,100 water injectors actively maintaining oil production from the diatomite. Wells are very closely spaced, less than 50 ft (15m) apart in better areas, and hydraulic fracturing is essential for production from a reservoir that would be considered an excellent seal elsewhere.

Learnings from this field that can be readily applied elsewhere:

• Why we need another log when we have a 5-year old one 50 ft (15m) away
• Formation pressure logs can be used to fine-tune water injection
• Orientations of induced fractures can be measured, and control infill drilling locations
• Horizontal wells can tap thin pay zones more profitably than vertical wells
• Limits of economic production are still expanding

Reservoir management continues to be a challenge because of the size and complexity of the reservoir, and because of the 700-800 new wells being drilled annually to maintain production.