Geochemical characterization of the hydrous pyrolysis products from a recent cyanobacteria-dominated microbial mat

Authors

  • N. FRANCO Universidade Federal do Rio de Janeiro, Laboratório de Palinofácies e Facies Orgânica, IGEO. Ilha do Fundão, Av. Athos da Silveira, 274, 21941-909, Rio de Janeiro, Brazil
  • J.G. MENDONÇA FILHO Universidade Federal do Rio de Janeiro, Laboratório de Palinofácies e Facies Orgânica, IGEO. Ilha do Fundão, Av. Athos da Silveira, 274, 21941-909, Rio de Janeiro, Brazil
  • T.F. SILVA Universidade Federal do Rio de Janeiro, Laboratório de Palinofácies e Facies Orgânica, IGEO. Ilha do Fundão, Av. Athos da Silveira, 274, 21941-909, Rio de Janeiro, Brazil
  • K. STOJANOVIC University of Belgrade, Faculty of Chemistry. Studentski trg 12-16, 11000 Belgrade, Serbia
  • L.F. FONTANA Universidade Federal do Rio de Janeiro, Laboratório de Palinofácies e Facies Orgânica, IGEO. Ilha do Fundão, Av. Athos da Silveira, 274, 21941-909, Rio de Janeiro, Brazil
  • S.B.V. CARVALHAL-GOMES Universidade Federal do Rio de Janeiro, Laboratório de Palinofácies e Facies Orgânica, IGEO. Ilha do Fundão, Av. Athos da Silveira, 274, 21941-909, Rio de Janeiro, Brazil
  • F.S. SILVA Universidade Federal do Rio de Janeiro, Laboratório de Palinofácies e Facies Orgânica, IGEO. Ilha do Fundão, Av. Athos da Silveira, 274, 21941-909, Rio de Janeiro, Brazil
  • G.G. FURUKAWA Universidade Federal do Rio de Janeiro, Laboratório de Palinofácies e Facies Orgânica, IGEO. Ilha do Fundão, Av. Athos da Silveira, 274, 21941-909, Rio de Janeiro, Brazil

Keywords:

Microbial mat, Hydrous pyrolysis, Hydrocarbon potential, Biomarkers, Lagoa Vermelha

Abstract

Hydrous pyrolysis experiments were performed on a recent microbial mat sample from Lagoa Vermelha, Brazil, to determine whether crude oil can be generated and expelled during artificial maturation of the Organic Matter (OM). The experiments were conducted at 280ºC, 330ºC and 350ºC during 20h. Two types of liquid pyrolysis products, assigned as free oil and bitumen, were isolated and analyzed. Free oil represents free organic phase released by hydrous pyrolysis, whereas bitumen was obtained by extraction from the solid pyrolysis residue with dichloromethane. Changes in the OM maturity were determined using Rock-Eval parameters and biomarker maturity ratios of original sample and pyrolysis products. Biomarker compositions of original sample extract and liquid pyrolysates were used for determination of dominant bacterial source. The yields of free oil and bitumen showed that a microbial mat OM has a high liquid hydrocarbons generation potential. Rock-Eval maturity parameters, biopolymer and biomarker compositions indicate a significant increase of the OM maturity during hydrous pyrolysis. At 280ºC the release of free, adsorbed and occluded compounds was observed; however, without a cracking of the OM. At 330ºC the generation of bitumen and free oil is mostly related to the OM cracking. The highest yield of free oil was recorded at this temperature. Distribution of biomarkers in the extract of original sample and liquid pyrolysates confirms cyanobacteria-dominated microbial mats, whereas the identification of long chain n-alkane series, with maximum at C26, and prominent C30 hop-17(21)-ene additionally suggest the presence of sulfate reducing bacteria.

Author Biography

S.B.V. CARVALHAL-GOMES, Universidade Federal do Rio de Janeiro, Laboratório de Palinofácies e Facies Orgânica, IGEO. Ilha do Fundão, Av. Athos da Silveira, 274, 21941-909, Rio de Janeiro, Brazil

Laboratório de Palinofácies e Facies Orgânica (LAFO)

Geology department, IGEO

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Published

2016-10-11

Issue

Vol. 14 No. 4 (2016)

Section

Special Issues: Selected contributions from the XIV ALAGO Congress

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