From Bureau of Economic Geology, The
University of Texas at Austin (www.beg.utexas.edu).
For more information, please contact the author.
Bureau Seminar, October 22, 2010
Geochemical Characterization of Gases from the Mississippian Barnett Shale, Fort Worth Basin, Texas
Link to streaming video TBA: available 10.22.2010 at 8:55am
Chevron, Energy Technology Company and R. Paul Philp
Chevron, Energy Technology Company, Exploration and New Ventures
Molecular and isotopic composition of 51 gas and 7 condensate samples produced from the Barnett Shale were determined by gas chromatography isotope ratio mass spectrometry in order to investigate their origin and maturity at the time of generation. Additionally, two hydrous pyrolysis experiments were performed to calibrate maturity values predicted for gas generation.
Molecular carbon and hydrogen isotopic compositions of the gases indicate that gas produced from the Barnett is thermogenic. In order to estimate generation maturity, additional analyses were performed on the condensates and available core samples.
Diamondoid indices combined with vitrinite reflectance measurements, isotopic and molecular composition, and hydrous pyrolysis experiments suggest gas produced from the Barnett Shale was generated within the condensate/wet gas window (1.3 - 2.0 %Ro) at a later stage than hydrocarbons accumulated in shallower reservoirs. The origin of the gas is thermogenic, probably derived from both kerogen cracking and secondary cracking of previously generated non migrated hydrocarbons. Additionally, the occurrence of an ethane isotope reversal in group 1 gases corroborates that in situ oil or gas cracking is taking place in the easternmost part of the study area.