Detalhes da historia geologica de Campo de Albacora - Bacia de Campos a partir de biomarcadores acidos

AUTOR(ES)
DATA DE PUBLICAÇÃO

1996

RESUMO

The GC/MS biomarker analyses of eight oils from Albacora Field - Campos Basin(RJ), revealed that the acidic fossil molecules are sensitive to geological phenomena connected with the formations of the reservoirs. It was sugggested some years ago that the reservoirs in Albacora Field were mixtures of two oil pulses of different thermal evolution. This hypothesis was based on the study of hydrocarbon biomarkers. In our study we have first reinvestigated the neutral biomarkers to retrace the former hypothesis and then searched for more detaiIs through the study of other fossiI molecules, neutral and acidic. The analysis of the resconstructed ion chromatograms of the hopanoic acid methyl esters and their corresponding hydrocarbons (RIC m/z 191 e m/z 219) revealed different thermal evolution among the samples under analysis. Fatty acids were particularly helpful to detect a geochromatographical variation between well A and B. The fatty acids present in oil F had an even predominance which was taken as the first oil pulse characteristics. Coinjection of standard 2,2,6 - trimethyl - (3 ,7 - dimethyl-nonanyl)cyclohexane with oil D (acidic fraction derivatized to hydrocarbon) revealed the presence of these monocyclic acids (beta-carotene has been suggested as their precursors) as a minor homologous series and that the predominant homologous series of monocyclic acids are very similar to the standard but possessing a nonbranched lateral chain. We have detected 16 different classes of biomarkers in the hydrocarbon fractions obtained from the reduction of the acidic fossil molecules in the studied oils. A 8a(H) drimane synthetic standard was coinjected to oil H neutral fraction) thus confirming its presence in this oil. The presence in other oils was also inferred trom this experiment by comparison MS spectra and RI. Classes of compounds detected in the neutral fractions: linear hydrocarbons (C11 a C33), isoprenoid hidrocarbons (C19 a C22), n-alkyl cyclohexanes (C11 a C25) , methyl-n-alkyl-cyclohexanes (C12 a C25), bicyclic terpanes (drimanes) (C14 a C19), bicyclic terpanes (rearranjed drimanes, C14 a C16), tricyclic terpanes (queilantanes, C19 a C29), tetracyclic terpanes (C24), hopanes (C27 a C34), moretanes (C30), 25 nor-hopanos (C27 a C33), gammacerane (C30), esteranes (C27 a C29), diasteranes (C27 a C28). pregnanes (C21 a C22), metil pregnanos (C22). aromatic pregnanes (C19 a C20). Classes of compounds detected in the acidic fractions ( Ex, EHx, Edx): linear acids (C11 a C34), branched linear acids (C10 a C23), pristanoic and fitanoic acid, bicyclic acids (C16), labdanoic acids (C19 a C21), w-cyclohexyl alkanoic acids (C16 a C19)*, n-alkyl-cyclohexanoic acids (C16 a C20)*, n-alkyl-methyl-cyclohexanoic acids (C15 a C23)*, n-akyl-dimethyl-cyclohexanoic acids (C16 a C24)*, tricyclic terpanoic acids (queilantanes, C21 -C24 - C26 ), 3,4-seco-lupanoic acid (C30), 3,4-seco-friedelanoic acid (C30), hopanoic acids ( ab ) (C30 a C33), hopanoic acids (ba ) (C30 a C33) hopanoic acids bb (C30 a C33), 25-nor-hopanoic acids (C29 a C32). (* unpublished serie of compounds)

ASSUNTO(S)

petroleo - campos bacia de (rj) acidos naftenicos acidos carboxilicos

ACESSO AO ARTIGO

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