Origin and Timing of Carbonate Cementation of the Namorado Sandstone (Cretaceous), Albacora Field, Brazil: Implications for Oil Recovery

  1. Sadoon Morad
  1. R. S. de Souza and
  2. C. M. de Assis Silva

Published Online: 17 APR 2009

DOI: 10.1002/9781444304893.ch14

Carbonate Cementation in Sandstones: Distribution Patterns and Geochemical Evolution

Carbonate Cementation in Sandstones: Distribution Patterns and Geochemical Evolution

How to Cite

de Souza, R. S. and de Assis Silva, C. M. (1998) Origin and Timing of Carbonate Cementation of the Namorado Sandstone (Cretaceous), Albacora Field, Brazil: Implications for Oil Recovery, in Carbonate Cementation in Sandstones: Distribution Patterns and Geochemical Evolution (ed S. Morad), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304893.ch14

Author Information

  1. Petrobras Research and Development Center, Cidade Universitária, Quadra 7, Ilha do Fundão, CEP 21949-900, Rio de Janeiro, RJ, Brazil

Publication History

  1. Published Online: 17 APR 2009
  2. Published Print: 29 MAY 1998

ISBN Information

Print ISBN: 9780632047772

Online ISBN: 9781444304893

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Keywords:

  • carbonate cementation of Namarado Sandstone, Albacora Field, Brazil;
  • feldspathic turbide sandstones – main oil reservoirs in Campos basin;
  • sandstone petrography;
  • burial history of Namarado basin;
  • oil emplacement – influence on carbonate cement;
  • Albian-Turronian carbonate rocks

Summary

The Namorado Sandstone is one of the main oil reservoirs of the Campos basin, offshore Brazil, and consists of a thick turbiditic sequence deposited during the Albian–Cenomanian. Calcite cement is volumetrically the most important diagenetic parameter controlling reservoir quality in the sandstones.

Three types of calcite cement were detected: (i) blocky mosaic with an oscillatory cathodoluminescence (CL) zonation pattern, formed by the replacement of bioclasts in response to meteoric water invasion during eodiagenesis; (ii) very fine mosaic, showing thin CL zonation, formed by nucleation around bioclasts and precipitating relatively early during diagenesis at an estimated temperature of about 25°C, prior to oil emplacement; (iii) coarse mosaic with a poikilotopic texture, formed after oil charging into the reservoir at a precipitation temperature of approximately 40°C, in the water-saturated sandstones. Cement supply was from the underlying carbonate sediments (the Albian–Turonian Macaé Formation). Oil emplacement inhibited both calcite cementation and mechanical compaction within the reservoir, and thus explain the higher porosity and permeability in the oil zone than in the water zone.