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Abstract: Blackburn Oil Field, Pine Valley, Nevada - a Case History Update

BORTZ, LOUIS C., Advantage Resources, Inc. Denver, CO

Two wells drilled by Petroleum Corporation of Nevada since 1992 have dramatically increased the oil production and recoverable reserves in the Blackburn Field:

1. Unit No. 18 was completed in 1992 and averaged 1,367 BOPD for the first year of production. Cumulative production through July, 1997 for this well is 1,050,832 BO.

2. Unit No. 19 was completed in 1994 and averaged 1,146 BOPD for the first year of production. Cumulative production through July, 1997 for the No. 19 is 760,369 BO.

Field cumulative through July, 1997 totals 4,525,297 BO for the six producing wells.

The Blackburn discovery well (Unit No. 3) was drilled in 1982 based on gravity, magnetic and seismic surveys. The No. 3 was completed for 346 BO + 767 BWPD from Mississippian and Oligocene reservoirs.

Blackburn field is a faulted horst block located four miles west of the Sulphur Spring Range near the basin axis. The main producing area has about 500 feet of fault closure with an areal extent of 120 to 150 acres. A productive northeast fault closure covering about 20 acres is structurally low to the main area. Faults within the main productive area form compartments with distinctly different oil columns and bottom-water levels. These fault blocks are difficult to accurately map with seismic data because of a thick basalt 2500 feet above the reservoirs. Several development locations exist which could add significant recoverable oil reserves

Field reservoirs consist of: 1) the Oligocene Indian Well formation (tuffs and tuffaceous siltstones and standstones) which has poor reservoir quality and has produced a minor amount of oil commingled with other reservoirs in three wells; 2) Mississippian Chainman sandstones are thin and discontinuous with good reservoir quality in three wells; 3) the main reservoir, the Devonian Nevada group brecciated and fractured dolomite, has produced approximately 80% of the field's oil from four wells The gross oil column is at least 1500 feet, however the oil column in the Devonian reservoir in the main producing area is about 450 feet.

Favorable geological attributes of Pine Valley include a deep Tertiary basin overlying Paleozoic source and reservoir rocks, high-relief structures and thick oil columns.

Many of the future field discoveries in the Tertiary basins in Nevada and western Utah will be located in the deeper, non-flank portions of these basins Blackburn is a model for these prospects.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah