ABSTRACT: Petroleum Source Rock Potential of Butte Valley, White Pine County, Nevada

HAZLETT, DOUGLAS P. AND JAMES B. HERSCH, Anadarko Petroleum Corporation, Houston, TX

An integrated exploration program in the eastern part of the Late Devonian Mississippian Antler foreland basin shows that the Chainman-Diamond Peak interval contains oil source rock in sparsely drilled Butte Valley. This interval is the source for the prolific oil production at Grant Canyon, Trap Springs, and Blackburn fields.

The Chainman-Diamond Peak package consists of an upward-coarsening and upward-shallowing 2900-3400-ft sequence of basinal to nearshore clastics that crop out in adjacent ranges. The middle Mississippian Chainman is dominated by black organic-rich shales

(TOC = 2-5%). The Upper Mississippian Diamond Peak is approximately 80% silty organic shales (TOC = 1-2%) and 20% fine-grained, sutured orthoquartzite. Rock-Eval data from outcrop samples exhibit low S1 + S2, high Tmax, and low hydrogen index and oxygen index values indicating a low-yield overmature oil source.

Subsurface data from the Anadarko Combs Creek Federal #6-21, combined with basin-modeling and soil-gas geochemistry, indicate the Mississippian interval should be actively generating in Butte Valley. Geochemical analysis of the saturate biomarkers, terpanes, and steranes of oil recovered in the well is consistent with a biodegraded crude oil derived from a mature marine shale. This combined with freshwater DST recovery and highly fractured Diamond Peak shales suggest oxidation of the source rock by pervasive contact with groundwater at the Combs Creek Federal #6-21 location. Such oxidation also may account for the apparently overmature outcrop samples.

AAPG Search and Discovery Article #91017©1992 AAPG Rocky Mountain Section Meeting, Casper, Wyoming, September 13-16, 1992 (2009)