Thermochemical sulfate reduction (TSR) involves a complex series of free radical and redox reactions that occurs in hot (>120�C) carbonate reservoirs whereby petroleum is oxidized by sulfate.  A suite of Smackover Fm. oils subjected to varying degrees of TSR was analyzed by ultrahigh resolution MS.  These analyses revealed systematic changes occur in the high molecular wt. PAH, sulfur, and oxygen compounds and the TSR process generates new species that are prone to precipitate as solid bitumen.  Evidence for oxidized intermediates and sulfur incorporation provides new insights to the reaction pathways.  The distribution of specific species appear to accurately reflect the extent of TSR and we have found these measurements to be particularly useful in deciphering the geohistory of reservoirs where H2S has migrated into formations from off-structure.

Evidence for sulfur incorporation and oxidation intermediate in crude oils subjected to thermal sulfate reduction

244th National Meeting (2012)

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