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Hydrogen (H) Isotope Composition of Type II Kerogen Extracted by Pyrolysis-GC-MS-IRMS: Terrestrial Shale Deposits as Martian AnalogsDescribed here is a technique for H isotope analysis of organic compounds pyrolyzed from kerogens isolated from gas‐ and liquids‐rich shales. Application of this technique will progress the understanding of the use of H isotopes not only in potential kerogen occurrences on Mars, but also in terrestrial oil and gas resource plays. H isotope extraction and analyses were carried out utilizing a CDS 5000 Pyroprobe connected to a Thermo Trace GC interfaced with a Thermo MAT 253 IRMS. Also, a split of GC‐separated products was sent to a DSQ II quadrupole MS to make qualitative and semi‐quantitative compositional measurements of these products. Kerogen samples from five different basins (type II and II‐S) were dehydrated (heated to 80 C overnight under vacuum) and analyzed for their H isotope compositions by Pyrolysis‐GC‐MS‐TC‐IRMS. This technique takes pyrolysis products separated via GC and reacts them in a high temperature conversion furnace (1450 C), which quantitatively forms H2. Samples ranging from ~0.5 to 1.0mg in size, were pyrolyzed at 800 C for 30s. and separated on a Poraplot Q GC column. H isotope data from all kerogen samples typically show enrichment in D from low to high molecular weight. H2O average delta D = ‐215.2 per mille (V‐SMOW), ranging from ‐ 271.8 per mille for the Marcellus Shale to ‐51.9 per mille for a Polish shale. Higher molecular weight compounds like toluene (C7H8) have an average delta D of ‐89.7 per mille, ranging from ‐156.0 per mille for the Barnett Shale to ‐50.0 per mille for the Monterey Shale. We interpret these data as representative of potential H isotope exchange between hydrocarbons and sediment pore water during basin formation. Since hydrocarbon H isotopes readily exchange with water, these data may provide some useful information on gas‐water or oil‐water interaction in resource plays, and further as a possible indicator of paleoenvironmental conditions. Alternatively, our data may be an indication of H isotope exchange with water and/or acid during the kerogen isolation process. Either of these interpretations will prove useful when deciphering H isotope data derived from kerogen analyses. Understanding the role that these H‐bearing compounds play in terrestrial shale paleo‐environmental reconstruction may also prove useful as analogs for understanding the interactions of water and potential kerogen/organic compounds on the planet Mars.
Document ID
20140016926
Acquisition Source
Johnson Space Center
Document Type
Abstract
Authors
Socki, Richard A.
(Jacobs Technology, Inc. Houston, TX, United States)
Pernia, Denet
(Houston Univ. Houston, TX, United States)
Evans, Michael
(Texas A&M Univ. College Station, TX, United States)
Fu, Qi
(Houston Univ. Houston, TX, United States)
Bissada, Kadry K.
(Houston Univ. Houston, TX, United States)
Curiale, Joseph A.
(Chevron Corp. San Ramon, CA, United States)
Niles, Paul B.
(NASA Johnson Space Center Houston, TX, United States)
Date Acquired
December 3, 2014
Publication Date
December 15, 2014
Subject Category
Geosciences (General)
Report/Patent Number
JSC-CN-32093
Report Number: JSC-CN-32093
Meeting Information
Meeting: 2014 American Geophysical Union Fall Meeting
Location: San Francisco, CA
Country: United States
Start Date: December 15, 2014
End Date: December 19, 2014
Sponsors: American Geophysical Union
Distribution Limits
Public
Copyright
Public Use Permitted.
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