Mineralogical and Maturation Considerations of the Coqueiros Formation (Campos Basin, Brazil): Insights from Multi-Technique Analyses of Source Rocks
Gabriel A. Barberes,
Flávia C. Marques,
Dalva A. L. Almeida,
Linus Pauling F. Peixoto,
Lenize F. Maia,
Antonio Carlos Sant’Ana,
Gustavo F. S. Andrade,
Celly M. S. Izumi,
Victor Salgado-Campos,
Thiago Feital,
Luiz Fernando C. de Oliveira,
Ana Luiza Albuquerque
Affiliations
Gabriel A. Barberes
Departamento de Geologia e Geofísica, Universidade Federal Fluminense, Av. Gen. Milton Tavares de Souza s/nº—Gragoatá—Campus da Praia Vermelha, Niterói 24210-346, RJ, Brazil
Flávia C. Marques
Núcleo de Espectroscopia e Estrutura Molecular, Centro de Estudos de Materiais, Departamento de Química, Universidade Federal de Juiz de Fora, R. José Lourenço Kelmer s/n, Martelos, Juiz de Fora 36036-900, MG, Brazil
Dalva A. L. Almeida
Núcleo de Espectroscopia e Estrutura Molecular, Centro de Estudos de Materiais, Departamento de Química, Universidade Federal de Juiz de Fora, R. José Lourenço Kelmer s/n, Martelos, Juiz de Fora 36036-900, MG, Brazil
Linus Pauling F. Peixoto
Núcleo de Espectroscopia e Estrutura Molecular, Centro de Estudos de Materiais, Departamento de Química, Universidade Federal de Juiz de Fora, R. José Lourenço Kelmer s/n, Martelos, Juiz de Fora 36036-900, MG, Brazil
Lenize F. Maia
Núcleo de Espectroscopia e Estrutura Molecular, Centro de Estudos de Materiais, Departamento de Química, Universidade Federal de Juiz de Fora, R. José Lourenço Kelmer s/n, Martelos, Juiz de Fora 36036-900, MG, Brazil
Antonio Carlos Sant’Ana
Núcleo de Espectroscopia e Estrutura Molecular, Centro de Estudos de Materiais, Departamento de Química, Universidade Federal de Juiz de Fora, R. José Lourenço Kelmer s/n, Martelos, Juiz de Fora 36036-900, MG, Brazil
Gustavo F. S. Andrade
Núcleo de Espectroscopia e Estrutura Molecular, Centro de Estudos de Materiais, Departamento de Química, Universidade Federal de Juiz de Fora, R. José Lourenço Kelmer s/n, Martelos, Juiz de Fora 36036-900, MG, Brazil
Celly M. S. Izumi
Núcleo de Espectroscopia e Estrutura Molecular, Centro de Estudos de Materiais, Departamento de Química, Universidade Federal de Juiz de Fora, R. José Lourenço Kelmer s/n, Martelos, Juiz de Fora 36036-900, MG, Brazil
Victor Salgado-Campos
Departamento de Geologia e Geofísica, Universidade Federal Fluminense, Av. Gen. Milton Tavares de Souza s/nº—Gragoatá—Campus da Praia Vermelha, Niterói 24210-346, RJ, Brazil
Thiago Feital
OPTIMATECH Ltd.a., Rio de Janeiro 22410-905, RJ, Brazil
Luiz Fernando C. de Oliveira
Núcleo de Espectroscopia e Estrutura Molecular, Centro de Estudos de Materiais, Departamento de Química, Universidade Federal de Juiz de Fora, R. José Lourenço Kelmer s/n, Martelos, Juiz de Fora 36036-900, MG, Brazil
Ana Luiza Albuquerque
Departamento de Geologia e Geofísica, Universidade Federal Fluminense, Av. Gen. Milton Tavares de Souza s/nº—Gragoatá—Campus da Praia Vermelha, Niterói 24210-346, RJ, Brazil
The Coqueiros Formation, a strategic stratigraphic unit within the Lagoa Feia Group (LFG) in the Campos Basin offshore Brazil, is known for its lacustrine carbonate deposits, which include both organic-rich shales and economically important “coquina” reservoirs. While coquina facies are widely recognized as reservoirs, the source-rock potential of the intercalated shales remains relatively underexplored. This study aims to characterize the mineralogy and thermal maturity of the Coqueiros Formation to assess its potential as a source rock, using a multi-technique approach integrating X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Raman spectroscopy analyses of shale samples from two wells: 3-BP-11-RJS and 6-DEV-18P-RJS. XRD analyses revealed a heterogeneous mineralogy dominated by carbonates (calcite and dolomite) and quartz, with significant contributions from clay minerals and trace minerals such as pyrite and barite. SEM imaging revealed a heterogeneous fabric with grain size, morphology, and porosity variations, reflecting a dynamic lacustrine depositional setting influenced by storm events and fluctuations in terrigenous input. The presence of authigenic minerals, as reported in other studies, such as saddle dolomite, mega-quartz, and various sulfides, provides evidence for hydrothermal alteration, likely related to Late Cretaceous magmatic activity in the Campos Basin. Raman spectroscopy yielded equivalent vitrinite reflectance (Ro%) values consistently exceeding 1.00, ranging from 1.03 to 1.40, indicating that the organic matter in the Coqueiros Formation shales has attained a high thermal maturity level, surpassing the oil window and reaching the condensate wet gas zone. The mineralogical and equivalent maturation data presented herein provide a valuable foundation for future studies, highlighting the complexity and heterogeneity of the Coqueiros Formation and its potential significance as a source rock within the Campos Basin petroleum system.
