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The Trenton Formation is an Upper Ordovician sequence of interbedded limestones and limy shales that extends from the Hudson River valley in the east throughout the western part of New York state. It was one of the first gas-producing reservoirs in the area with most of the more than 300 test wells producing or indicating natural gas.
Subsurface information on the Trenton includes century-old reports, operators tops, sample logs, and geophysical logs. The logs, run over more than a 40-yr span, vary widely in type, lithology response, and depth scale. To aid interpretation, all available data were added to the New York state computer data base for map processing, and the geophysical logs were digitized for uniform evaluation and presentation. Individual log curves were corrected to a standard lithology response, combined, and played out as a series of standard control cross sections. Computer posted and contoured maps were constructed and compared to log sections for correction of errors. Finally, geologic interpretation was added to the maps and cross sections to produce a new evaluation of the Trenton Formation. >
The Trenton in the subsurface can be divided into three distinct members with a disconformity between the lower two. Depositional centers shifted from central New York for the lower member to the northern part of the state for the upper member. The formation is a fractured porosity reservoir with the main fracture zones located along basement-controlled tectonic structures. The main features trend northeast-southwest in the northern part of the state, whereas orthogonal, northwest-southeast trends dominate in the south.
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