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Onondaga-Bass Island Trend--Salt Detachment Structure in Western New York

Michael W. Patenaude, Richard W. Beardsley, Richard C. Campbell

Oil and gas production has been established in the Devonian Onondaga-Silurian Bass Islands stratigraphic section in Chautauqua County, New York. The known productive trend is approximately 1.5 mi wide and 30 mi long and strikes northeast-southwest across central Chautauqua County, encompassing over 30,000 ac.

This structural feature has been coined the "Bass Islands trend." The trend is a complex, multiple horst-graben feature, characterized by high-angle reverse faults associated with a Salina B salt decollement. Over 200 mi of seismic records have been used to delineate the trend.

The high-angle reverse fault or fracture zones within the Onondaga-Bass Islands stratigraphic section are the exclusive reservoirs. The productive section is capped by the Devonian Hamilton shales and sealed at the base by the Salina G anhydrite. Nearly 300 wells have been drilled on the structure with 38% having producible capabilities. Some producible wells have been encountered with natural flows and others have been stimulated with varying results.

Completion attempts and production efforts have been complicated by the very high oil-paraffin content and the high dissolved solids content of the formation brine.

Present development activity in the Onondaga-Bass Islands trend has lessened due to the present market conditions and newly proposed drilling and production regulations by New York State, specifically for the "Bass Island trend." Operators are using this slowdown to collect reservoir and production data, evaluate completion and production techniques, observe stimulation effects, and plan future development.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.