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Blackburn Field, Eureka County, Nevada: A Case History

Cheryl Scott, Alan K. Chamberlain

The Blackburn field lies along a late Mesozoic thrust-fault trend in east-central Nevada. All Nevada production is located along this thrust system, although traps are mostly Tertiary block-fault related. The thrust places porous Devonian carbonates reservoir rock over organic-rich Mississippian source rock.

A Devonian fractured dolomitic limestone provides major production in the Blackburn field. Good intercrystalline shows are also evident. Some production comes from fractured and intercrystalline porosity developed in Mississippian/Devonian arkosic sandstones. Another producing horizon, the Tertiary Indian Wells formation, produces from porous, poorly consolidated tuffaceous sandstones and nonwelded tuffs.

Gamma-ray signatures of the Mississippian-Devonian in Blackburn wells can be correlated along strike with surface gamma-ray signatures of measured sections in the Diamond Range. These gamma-ray correlations, in addition to detailed cuttings description and interpretation of well-log data, have prompted correlation of limestone and sandstone units in the lower part of the Blackburn field.

Adequate seals are a major concern in eastern Nevada. Mississippian/Devonian shales provide seal for Paleozoic limestone and sandstone reservoirs, while welded tuff traps oil in poorly consolidated tuffaceous sandstones of the Tertiary Indian Wells formation.

The apparent simple structure of the Blackburn field is interrupted by a fault on the western edge of the field. This fault can be seen on magnetic lines across the field and in wells adjacent to it. Other minor faults also cut the field. The Blackburn field shows as a positive gravity anomaly, suggesting an intervalley horst block.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.