[First Hit]

Datapages, Inc.Print this page

Martin Schoell1, Karlis Muehlenbachs2, Dennis D. Coleman3, Steve Thibodeaux4, Lynn Walters5, Previous HitAnnaTop Martini6

(1) Chevron Research and Technology Company, San Ramon, CA
(2) University of Alberta, Edmonton
(3) Isotech Laboratories, Inc, Champaign, IL
(4) Burlington Resources, Farmington, NM
(5) University of Michigan, Ann Arbor, MI
(6) University of Massachusetts, Amherst, MA

ABSTRACT: Natural Sites of Bio-Conversion of CO2 and Hydrocarbons in the Subsurface: San Juan Basin and Michigan Basin

Natural gases in the San Juan Basin Fruitland Coal Fairway exhibit a large variation of C2+ hydrocarbons between 0.3 and 4.5%. Variations of carbon-13 concentrations of ethane (13C=-31 to -22 o/oo) and propane (13C=-27 to -6 o/oo) far exceed those in primary thermogenic gases. Ethane and propane isotopes and concentrations can be fit to a Raleigh distillation suggesting extensive bioconversion of ethane and propane through bacterial consortia in the coal seams. ). CO2 concentrations range from 8-18% with isotope values between +14.5 to +17.5 o/oo. Methane isotope values (13C=-43.8± 0.7o/oo) can be explained by extensive methanogenesis via the CO2 reduction pathway with a typical bacterial fractionation of ~1.060. We therefore can make a case for the subsurface conversion of CO2 to methane simultaneously with a bacterial oxidative removal of hydrocarbons. Very similar subsurface bioconversion processes can be observed in the Michigan Basin, where methanogenesis is very well documented to be related to freshwater influx. We add here new data which prove similar C2+ oxidative processes to be operative in the Michigan Basin. We conclude, therefore, that these sites contain all bacterial consortia for bioconversion of CO2 to methane and removal of C2+ hydrocarbons. Systematic studies of these bacterial consortia at these sites could possibly lead to insights for man-made sites of bioconversion for removal of greenhouse gases.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado