"Closing the Flood Gates" - History of the South Belridge Field Steam Drive Aquifer Project
Authors: Fram J.H. , Palermo R.M. 
Published: December 2007

Abstract
The eastern flank of the South Belridge Field heavy oil reservoir is bounded by an active aquifer. Millions of barrels of heavy oil are in direct contact with this aquifer. To improve the recovery efficiency a project was installed in the mid-1980's to lower the reservoir pressure at the Oil-Water- Contact (OWC). This paper will discuss the reservoir simulation, wellbore and artificial lift design that has resulted in the successful implementation of this project. Data showing the impact of the Aquifer Project on water influx and Oil-Steam ratio is also presented.

Introduction
This paper discusses the justification, installation, operation, and results-to-date of the Aquifer Project in the Tulare Formation of the South Belridge field in Kern County, California. It discusses the design and implementation work performed in the mid-1980's and summarizes the progress and results of the project to-date.
The South Belridge field is located about 40 miles west of Bakersfield in the San Joaquin Valley of California. The Tulare sands produce 13 degree API gravity crude in response to steamflood operations at depths ranging from 400 to 1300 feet. Many of the steamflood target sands are attached to very active aquifers. These aquifers impact the steamflood operations negatively resulting in higher than desired steam chest pressures and large volumes of aquifer water being produced in the oil field production wells.
The large dependence of steam drive efficiency on steam chest pressure has been well documented in a number of previous publications. The higher the steam chest pressure, the poorer the steam drive efficiency. Therefore, reducing steam chest pressure will improve the efficiency of a steam drive. This is the fundamental challenge tackled by the Aquifer Project - reducing the relatively high steam chest pressures maintained by the active aquifers.
Through much simulation work, it was observed that steam chest pressures could be reduced, and therefore steam drive efficiencies improved, by producing water through dedicated aquifer lift wells located below the oil-water contact. Installing a series of wells downdip of the oil-water contact and producing large volumes of water would do two things. would decrease the pressure at the oil-water contact and subsequently reduce the amount of water influx into the oil field. The benefits of these impacts are threefold:Improve Steam Drive Efficiency. Reducing the reservoir pressure would reduce the steam zone temperature and therefore improve the steam drive efficiency.Increase Ultimate Recovery. Decreasing the pressure will allow the steam zone to expand down to the oil-water contact enabling the extreme downdip oil reserves to be heated and produced.Reduce Operating Costs. Lift costs will by reduced by reducing the amount of water influx into the oil field. Lifting and disposing of aquifer water is less expensive than lifting, treating, and disposing of oil field produced water.
The simulation work performed justified the installation of a field pilot in 1985. The pilot performance was encouraging and full scale development took place in 1987.

Geology/Reservoir Description
The Tulare Formation is Pleistocene in age and represents the final basin fill of the San Joaquin Valley. The Tulare was deposited over much of the San Joaquin Valley extending as far north as Modesto and as far South as the Yowlumne area.
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