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Scientific Investigations Report 2010–5224

Evaluation of Well Logs for Determining the Presence of Freshwater, Saltwater, and Gas above the Marcellus Shale in Chemung, Tioga, and Broome Counties, New York

By John H. Williams

ABSTRACT

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Recent technological advances in horizontal drilling and high-volume hydraulic fracturing have made the Marcellus Shale the newest gas-development target or play in the northern Appalachian basin. Protection of freshwater aquifers from contamination by saltwater and gas during the development of the Marcellus Shale play is an issue of concern. Chemung, Tioga, and Broome Counties are in the southwestern part of the Marcellus Shale play in New York and likely will be the focus of drilling early in development of the play in the State. As a preliminary step in understanding and protecting the groundwater resource in the three-county area, logs of water wells in the U.S. Geological Survey National Water Information System and gas wells in the New York State Museum Empire State Oil and Gas Information System were evaluated for the determination of the presence of freshwater, saltwater, and gas above the Marcellus Shale.

Results of the evaluation of the water- and gas-well logs indicate that freshwater aquifer zones are log normally distributed with depth in the three-county study area and that freshwater circulates to a greater depth in the uplands than in the valleys. The base of the freshwater aquifer appears to be about 800 feet below land surface in upland settings but only about 200 feet below land surface in valley settings. At depths greater than 200 feet in valley settings, groundwater in the Upper Devonian bedrock, and in a few areas in the glacial drift, is salty. Gas is present locally in the glacial drift, Upper Devonian bedrock, Tully Limestone, and Hamilton Group above the Marcellus Shale. The highest rates of gas flow above the Marcellus Shale may be associated with the Tully Limestone. The frequency of gas zones generally increases with depth in the Upper Devonian bedrock with pockets of gas locally present above the base of the freshwater aquifer.

Consistent and complete reporting of freshwater, saltwater, and gas during the drilling of future Marcellus shale-gas wells would greatly improve existing information. Field measurement of specific conductance of water produced during drilling and specific-conductance and temperature wireline geophysical logging of open boreholes prior to surface-casing installation would enhance the value of the gas-well logs. Compilation and integration of information from water wells that are inventoried and sampled for water quality during gas development with data from ongoing county-wide and regional programs would provide an important database for understanding and protecting the freshwater aquifers.

First posted February 4, 2011

For additional information contact:
Director
U.S. Geological Survey
New York Water Science Center
425 Jordan Road
Troy, NY 12180
(518)285-5600

http://ny.water.usgs.gov

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Suggested citation:

Williams, J.H., 2010, Evaluation of well logs for determining the presence of freshwater, saltwater, and gas above the Marcellus Shale in Chemung, Tioga, and Broome Counties, New York: U.S. Geological Survey Scientific Investigations Report 2010–5224, 27 p., at http://pubs.usgs.gov/sir/2010/5224/.


Contents

Abstract

Introduction

Descriptions of the Well Databases and Methods

Description of the Geologic Formations

Description of the Wells

Freshwater, Saltwater, and Gas above the Marcellus Shale

Preliminary Conclusions

Considerations for Future Water and Gas Logging

References Cited

Appendix 1. Log Summary for Water Wells in the National Water Information System that Penetrated Saltwater and (or) Gas in Cheming, Tioga, and Broome Counties, New York, 2010

Appendix 2. Log Summary for Gas Wells in the Empire State Oil and Gas System that Penetrated Freshwater, Saltwater, and (or) Gas above the Marcellus Shale in Chemung, Tioga, and Broome Counties, New York, 2010


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