The Lower Silurian Whirlpool Sandstone is an important natural gas producing formation in western New York State. The Whirlpool outcrops in Niagara County, and is present in the subsurface in portions of Erie and Chautauqua Counties as well as adjacent areas in Pennsylvania.

In gas-productive areas of Chautauqua County, the Whirlpool usually ranges in thickness from 5 to 20 ft (2 to 6 m). Porosity as measured by the compensated formation density logging tool is typically 4 to 8%. Gas saturation is normally in the 20 to 65% range. The permeability of the rock is limited. Occasional localized areas of sharply greater porosity, permeability, and hydrocarbon saturation ("porosity pods") occur within the larger volume of tight, low permeability Whirlpool. The producing characteristics of the porosity pods are such that gas recovery may increase by a factor of 3 to 5 as compared with an average well. The economic benefits of drilling into these features are therefore substantial.

The presence of a porosity pod is sometimes indicated by an unusually large natural flow of gas from a well prior to stimulation. It can also be detected by certain characteristic indications on the density, resistivity, and neutron logs. Whirlpool porosity pods appear to be mappable and may be sufficiently large to provide 4 or 5 well locations. Recognition of their characteristics can be a significant aid to natural gas exploration in Chautauqua County, New York, and possibly elsewhere in western New York and northwestern Pennsylvania.

End_of_Article - Last_Page 1175------------