Hydrogeophysical Log Analysis of Four Water-Supply Test Wells along an Appalachian Plateau Topographic Profile

Williams, John H.

Hydrogeophysical Log Analysis of Four Water-Supply Test Wells along an Appalachian Plateau Topographic Profile

Tuesday, April 25, 2017: 2:10 p.m.

John H. Williams , U.S. Geological Survey, Troy, NY

Dennis W. Risser , PA Water Science Center, U.S. Geological Survey, New Cumberland, PA

James A. Anderson , U. S. Geological Survey, Troy, NY

Hydrogeophysical logs from four 500-feet deep test wells drilled to extract freshwater for hydraulic fracturing of the Marcellus Shale were analyzed to determine the hydrogeologic framework along a topographic profile in southeastern McKean County, Pennsylvania. The wells were completed in sandstone and shale in a typical Appalachian Plateau setting along a 2.5-mile long profile having 400 feet of topographic relief. The hydrogeophysical logs collected from the wells included drill-cutting descriptions; caliper, gamma, and induction; acoustic and optical televiewer; and fluid-resistivity, temperature, and vertical flow under ambient and pumped conditions. The hydrogeophysical log analysis indicated that the test well at the highest elevation penetrated a transmissive fractured zone with high hydraulic head in sandstone of the Pottsville Formation at a depth of 175 feet below land surface. As indicated by aquifer-test results, this test well was hydraulically connected to the next test well downslope almost a mile away. The upper well and the downslope well both penetrated a transmissive fractured zone with low hydraulic head, which most likely provided the hydraulic connection between the wells, near the base of a thick sandstone bed at 330 and 240 feet below land surface, respectively, in the Waverly Group. The test well at the lowest elevation penetrated a high hydraulic-head fractured zone having minimal transmissivity that produced saline water near the base of a thick sandstone bed within the Catskill Formation at 475 feet below land surface. Borehole-wall breakouts were present in shale beds of the Catskill Formation penetrated by the well at 480 to 495 feet below land surface. Hydrogeologic framework characterization from analysis of hydrogeophysical logs, such as those used in this study, can provide important information for the design and installation of groundwater monitoring wells at shale-gas wellpads and for the evaluation of stray-gas migration and chemical spills.

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John H. Williams, U.S. Geological Survey, Troy, NY

John Williams has an M.S. in Geology from Penn State University and currently is the Groundwater Specialist for the U.S. Geological Survey Water Science Center in New York. He is an integral part of a Survey-wide training and technology transfer program in borehole geophysics. Williams also has provided technical assistance to the U.S. Environmental Protection Agency, the Army Corps of Engineers, the Nuclear Regulatory Commission, and state cooperators on borehole-geophysical applications in a wide range of groundwater investigations in fractured bedrock.

Dennis W. Risser, PA Water Science Center, U.S. Geological Survey, New Cumberland, PA

Dennis Risser is the USGS Pennsylvania Water Science Center Groundwater Specialist.

James A. Anderson, U. S. Geological Survey, Troy, NY

James Anderson is a hydrologist with the USGS in the New York Water Science Center. He started with the USGS as a student employee while attending the State University of New York at Albany where he received a B.S. in Geology in 1997. James provides support in geophysical log collection and analysis and helps oversee the cooperative, statewide observation well network. As part of the training and technology transfer program of the Office of Groundwater-Branch of Geophysics, he provides geophysical support to USGS offices nationwide.