The Utica Shale holds an estimated 38 Tcf of undiscovered, technically recoverable natural gas, or less than half that of the Marcellus Shale, according to the first assessment of the Appalachian Basin play by the U.S. Geological Survey (USGS). An estimated 940 million bbl of unconventional oil resources and 9 million bbl of natural gas liquids (NGL) also are trapped in Utica rock, said scientists Thursday.
Undiscovered natural gas in the Utica Shale ranges from 21 Tcf (95% chance) to 61 Tcf (5% chance), while oil estimates were put at 590 million bbl (95%) to 139 billion bbl (5%). Undiscovered NGL amounts range from 4 million bbl (95%) to 16 million bbl (5%), the assessment said.
By comparison, the Marcellus Shale contains an estimated 84 Tcf of undiscovered, technically recoverable gas and 3.4 billion bbl of undiscovered NGLs, the USGS reported last year (see Daily GPI, Aug. 24, 2011). The Greater Green River Basin in southwestern Wyoming also is estimated to contain about 84 Tcf of undiscovered natural gas, of which 82 Tcf is tight gas, said the Department of Interior agency.
“Understanding our domestic oil and gas resource potential is important, which is why we assess emerging plays like the Utica, as well as areas that have been in production for some time” said USGS’s Brenda Pierce, who coordinates the energy resources program. “Publicly available information about undiscovered oil and gas resources can aid policymakers and resource managers, and inform the debate about resource development.”
Technically recoverable resources are considered to be quantities of oil and gas producible using currently available technology and industry practices, regardless of economic or accessibility considerations.
The new Utica assessment covers a 15 million-acre swath of shale rock that extends across Maryland, New York, Ohio, Pennsylvania, Virginia and West Virginia, with the shales “mostly present” in New York, Ohio, Pennsylvania and West Virginia. The play, which lies beneath the Marcellus Shale in the Appalachian Basin, is the “longest producing petroleum province” in the country, USGS said. The assessment is an estimate of continuous oil, gas and NGL accumulations in the Upper Ordovician Utica Shale of the Appalachian Basin.
“The Utica has little history of production, therefore production data were supplemented with analog data from the Devonian Marcellus Shale, Cretaceous Eagle Ford Shale and Cretaceous Niobrara Formation,” the assessment said. “The Marcellus is an analog mainly for its proximity and similar geologic setting, and the Cretaceous units for their facies similarity. Analog data include estimated ultimate recoveries (EUR), mean drainage areas of wells, and ranges of well success ratios.” The Utica was found to contain both “sweet” and “nonsweet” spots.
“Because of the limited amount of existing production from the Utica to date, EUR distributions for the sweet and nonsweet spots were estimated from distributions of other shale oil assessments. Based on these input parameters, recovery of the resource would require at the mean about 7,000 wells to be drilled within the sweet spot and an additional 10,500 wells at the mean to be drilled in the nonsweet spot to extract this potential.”
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