Organic and mineral matter changes due to oil generation, saturation and expulsion processes based on artificial maturation experiments

Authors

  • I.V.A.F. SOUZA PETROBRAS, CENPES, Av. Horácio Macedo 950, Cidade Universitária, Ilha do Fundão, CEP: 21941-915, Rio de Janeiro, Brazil.
  • C.V. ARAÚJO PETROBRAS, CENPES, Av. Horácio Macedo 950, Cidade Universitária, Ilha do Fundão, CEP: 21941-915, Rio de Janeiro, Brazil.
  • T.R. MENEZES PETROBRAS, CENPES, Av. Horácio Macedo 950, Cidade Universitária, Ilha do Fundão, CEP: 21941-915, Rio de Janeiro, Brazil.
  • L.F.C. COUTINHO PETROBRAS, CENPES, Av. Horácio Macedo 950, Cidade Universitária, Ilha do Fundão, CEP: 21941-915, Rio de Janeiro, Brazil.
  • R. BINNOTTO PETROBRAS, CENPES, Av. Horácio Macedo 950, Cidade Universitária, Ilha do Fundão, CEP: 21941-915, Rio de Janeiro, Brazil.
  • A.L.D. SPIGOLON PETROBRAS, CENPES, Av. Horácio Macedo 950, Cidade Universitária, Ilha do Fundão, CEP: 21941-915, Rio de Janeiro, Brazil.
  • R.A. FONTES PETROBRAS, CENPES, Av. Horácio Macedo 950, Cidade Universitária, Ilha do Fundão, CEP: 21941-915, Rio de Janeiro, Brazil.
  • E.V. SANTOS NETO PETROBRAS, CENPES, Av. Horácio Macedo 950, Cidade Universitária, Ilha do Fundão, CEP: 21941-915, Rio de Janeiro, Brazil.
  • N.D.V.F. RONDON Instituto de Geociências, Universidade Federal do Rio de Janeiro. Av. Athos da Silveira 274, Ilha do Fundão, CEP 21.949-900, Rio de Janeiro, Brazil.
  • J.G. MENDOÇA FILHO Instituto de Geociências, Universidade Federal do Rio de Janeiro. Av. Athos da Silveira 274, Ilha do Fundão, CEP 21.949-900, Rio de Janeiro, Brazil.

Keywords:

Hydrous Pyrolysis, Oil Generation, Primary Migration, Suppressed-vitrinite, Organic Petrography, Oil Expulsion

Abstract

Hydrous pyrolysis experiments were conducted on immature organic-rich rock with type-I kerogen to evaluate petroleum generation, saturation and expulsion processes. The experiments were carried out under isothermal conditions at ten different temperatures (280° through 360°C) for nine different time spans between 18 and 144h. Rock samples recovered from the experiments were analyzed for total organic carbon (TOC–weight%), Rock-Eval pyrolysis, vitrinite reflectance (Ro%), spectral fluorescence and visual characterization of organic matter under the microscopy. TOC, S2 and HI tend to decrease with increasing temperature and duration of the experiments as expected. The Ro% values reach up to 1.14% in the most severe experiment (i.e. 360°C/96h). The Ro% is believed to be suppressed due to hydrogen incorporation from bitumen. The bitumen production was observed with the increase of transformation index (TI) and two types of bitumen were differentiated by fluorescence color. The bitumen with yellow fluorescence was mainly composed of saturate and aromatic hydrocarbons that were probably generated earlier than the bitumen with brown fluorescence which is rich in NSO compounds. The greatest bitumen saturation occurs at TI around of 41% to 45%, when the S1 reaches its highest values. The decrease of bitumen saturation and consequent oil expulsion is marked by a reduction in S1 values and fluorescence color. This phenomenon occurs simultaneously with the development of fractures and voids in the mineral matrix which reduces the oil retention capability and facilitates the expulsion process. These observations enhanced the understanding of oil generation and saturation processes, as well as primary migration, expulsion and type of generated bitumen.

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Published

2014-11-10