Methanogenic archaea in marcellus shale: a possible mechanism for enhanced gas recovery in unconventional shale resources.
Marcellus Shale occurs at depths of 1.5-2.5 km (5000 to 8000 feet) where most geologists generally assume that thermogenic processes are the only source of natural gas. However, methanogens in produced fluids and isotopic signatures of biogenic methane in this deep shale have recently been discovered. This study explores whether those methanogens are indigenous to the shale or are introduced during drilling and hydraulic fracturing. DNA was extracted from Marcellus Shale core samples, preinjected fluids, and produced fluids and was analyzed using Miseq sequencing of 16s rRNA genes. Methanogens present in shale cores were similar to methanogens in produced fluids. No methanogens were detected in injected fluids, suggesting that this is an unlikely source and that they may be native to the shale itself. Bench-top methane production tests of shale core and produced fluids suggest that these organisms are alive and active under simulated reservoir conditions. Growth conditions designed to simulate the hydrofracture processes indicated somewhat increased methane production; however, fluids alone produced relatively little methane. Together, these results suggest that some biogenic methane may be produced in these wells and that hydrofracture fluids currently used to stimulate gas recovery could stimulate methanogens and their rate of producing methane.
†National Energy Technology Laboratory, United States Department of Energy, 3610 Collins Ferry Road, Post Office Box 880, Morgantown, West Virginia 26505, United States.|‡Division of Plant and Soil Sciences, West Virginia University, Morgantown, West Virginia 26505, United States.
Yael Tarlovsky
YT
Tucker
‡Division of Plant and Soil Sciences, West Virginia University, Morgantown, West Virginia 26505, United States.
James
J
Kotcon
†National Energy Technology Laboratory, United States Department of Energy, 3610 Collins Ferry Road, Post Office Box 880, Morgantown, West Virginia 26505, United States.
Thomas
T
Mroz
D001105:Archaea / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D019015:Geologic Sediments / Q000382:microbiology*; D056186:Metagenomics; D008697:Methane / Q000378:metabolism*; D059206:Natural Gas / Q000032:analysis*; D061329:Oil and Gas Fields; D011786:Quality Control; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA
D059206:Natural Gas; D012336:RNA, Ribosomal, 16S; D008697:Methane