THE GEOCHEMICAL FINGERPRINT OF PRODUCED WATERS AND NATURAL GAS FROM HYDRAULICALLY FRACTURED BLACK SHALES: A NOBLE GAS PERSPECTIVE
Here, we present a method to determine the genetic fingerprint of hydrocarbon gases and produced fluids using the atmospheric and radiogenic noble gas composition of these geofluids. Although the stable isotopes of carbon are a staple of gas geochemistry and traditionally have been applied for these purposes, these proxies can be altered by microbial activity and fluid migration. By comparison, the elemental and isotopic composition of noble gases provide inert geochemical tracers that are unaffected by chemical reactions or microbial activity. Their inert behavior eliminates the need to make assumptions regarding the sources, original concentration, and/or isotopic compositions of C1, C2, C3+ hydrocarbons. The atmospheric, mantle, and/or crustal components are characterized by unique noble gas elemental and isotopic signatures and preserve information about the source, migrational process, and residence time of crustal fluids. Thus, noble gas geochemistry provides a novel, unique, and externally defined variable capable of distinguishing the genetic fingerprint of hydrocarbon fluids and formational brines sourced from fractured black shales in the Earth’s crust.