Unitizing and Waterflooding the California Yowlumne Oil Field
- A.A. Burzlaff (Tenneco Oil Exploration and Production)
- Document ID
- Society of Petroleum Engineers
- SPE California Regional Meeting, 23-25 March, Ventura, California
- Publication Date
- Document Type
- Conference Paper
- 1983. Society of Petroleum Engineers
- 4.1.9 Tanks and storage systems, 6.5.2 Water use, produced water discharge and disposal, 2.2.2 Perforating, 4.3.4 Scale, 5.4.1 Waterflooding, 1.6 Drilling Operations, 4.2 Pipelines, Flowlines and Risers, 2.4.3 Sand/Solids Control, 5.6.5 Tracers, 4.6 Natural Gas, 4.1.5 Processing Equipment, 4.5 Offshore Facilities and Subsea Systems, 5.2.1 Phase Behavior and PVT Measurements
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The Yowlumne field, located at the southern end of the San Joaquin Valley of California, is one of the largest new onshore oilfields discovered in California in the past twenty years. The field, at an average depth of 12,200', has produced over 42 million barrels of oil since its discovery in 1974.
In May, 1982, a portion of the Yowlumne field was unitized and called Yowlumne Unit "B". Nine operators and about 160 royalty owners cooperated to form this unit. A two phase unitization formula based on 1) remaining primary and 2) initial hydrocarbon pore volume was used to form Unit "B". A secondary waterflood project is being implemented which is project is being implemented which is estimated will increase oil recovery by some 25 million barrels.
The Yowlumne field, located about 20 miles southwest of Bakersfield, California, was discovered in January, 1974 (see Figure 1). Production is primarily from Upper Miocene sands which are 11,000'-13,000' deep. Original oil in place (OOIP) for the field was 290 million stock tank barrels.
The Yowlumne reservoir is an undersaturated dissolved gas system with a saturation pressure of 2770 psia. Initial reservoir pressure in the discovery well was 5660 psia @ -10,500' datum. Rapid pressure declines were observed throughout pressure declines were observed throughout the development of the field. This decline and the operators' concern for maximum recovery led to their efforts to unitize for the purpose of waterflooding.
The field has been unitized in two stages. The first unit, Yowlumne Sand Unit "A" , was formed in February, 1978, four years after the field was discovered and while it was still being developed. Only four operators were involved in this first unit. They were anxious to start a water injection pressure maintenance project and did not want to wait for complete field development while the Unit "A" area reservoir pressure declined. A crestal line drive water injection project was initiated in January, 1979.
The formation of the second unit, Yowlumne Unit "B", took place under much different circumstances. The productive limits of the field were known and several producing zones had been encountered in the producing zones had been encountered in the "B" area. The "B" area had well spacing variations (25-40 acres per well), two different windfall profit tax tiers (Tiers 1 and 3), and portions which were at significantly different stages of depletion.
Despite these complexities, Yowlumne Unit "B" was formed because the operators desired to waterflood the "B" area, and they agreed on a two phase unitization formula which maintained current income for both operators and royalty owners, and recognized the waterflood potential of each lease.
This paper will summarize the Yowlumne field geology, history and reservoir characteristics, describe how the two phase formula for Unit "B" participations was determined, and discuss the waterflood project being implemented in Unit "B". project being implemented in Unit "B". FIELD GEOLOGY
The main producing horizon in the Yowlumne field is the Yowlumne sand, an Upper Stevens (Miocene) sandstone.
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