Per citar aquest document:
The Impact of carbonate cements on the reservoir quality in the Napo Fm sandstones (Cretaceous Oriente Basin, Ecuador)
Marfil, R. (Universidad Complutense de Madrid. Departamento. de Petrología y Geoquímica)
Estupiñan, J. (Universidad Complutense de Madrid. Departamento. de Petrología y Geoquímica)
Delgado Huertas, Antonio (Centro Superior de Investigaciones Científicas. Estación Experimental del Zaidín. Laboratorio de isótopos estables)
Permanyer, A. (Universitat de Barcelona. Departamento de Geoquímica, Petrologia i Prospecció Geològica)

Data: 2007
Resum: The Napo Formation of Lower-Middle Cretaceous age in the Oriente basin, Ecuador, is an important sandstone reservoir. The formation is buried at a depth of 1,500 m in the eastern part of the basin and down to 3,100 m in the western part. The sandstones display higher porosity values (av. 20%) than other reservoirs in the region. These sandstones were deposited in fluvial, transitional and marine environments, and they are fine to medium grained quartzarenites and subarkoses. The principal cements are carbonates, quartz overgrowth and kaolin, with scarce amounts of pyrite-pyrrhotite and chlorite. Carbonate cements include: Eogenetic siderite (S1), mesogenetic and post-compactional calcite, Fe-dolomite, ankerite and siderite (S2). Early siderite and chlorite helped to retain porosity by supporting the sandstone framework against compaction. Dissolution of feldspars and carbonate cements are the main mechanism for secondary porosity development during mesodiagenesis. The high intergranular volume (IGV) of the sandstones indicates that cementation is the predominant contributor to porosity loss in the reservoir and that the precipitation of the carbonate cement occurred in early and late diagenetic stages. The stable–isotope composition of the S1 siderite is consistent with precipitation from meteoric waters in fluvial sandstones, and from mixed meteoric and marine waters in transitional sandstones. The low δ18O‰ values of some of these carbonate phases reflect the replacement and recristalization from S1 to S2 siderite at deep burial and high temperature. Textural evidence, together with a low Sr content, also suggests that siderite (S1) in fluvial environment is an early cement that precipitated from meteoric waters, near the sediment/ water interphase, followed by the generation of calcite with a higher Fe and Mg content. However, due to this higher Mg content, siderite S2 could have precipitated as a result of the thermal descarboxilation of the Mg rich organic matter. The progressive decrease in δ18O values in all carbonate cements could be related to the continued precipitation at different temperatures and burial depth.
Drets: Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l’obra i la creació d’obres derivades, fins i tot amb finalitats comercials, sempre i quan aquestes es distribueixin sota la mateixa llicència que regula l’obra original i es reconegui l’autoria de l’obra original. Creative Commons
Llengua: Anglès.
Document: article ; recerca ; publishedVersion
Matèria: Carbonate cement ; Geochemistry ; Sandstone reservoirs ; Oriente Basin ; Ecuador
Publicat a: Geologica acta, Vol. 5, Núm. 1 (2007) , p. 89-107, ISSN 1696-5728

Adreça alternativa:
DOI: 10.1344/105.000000312

19 p, 1.9 MB

El registre apareix a les col·leccions:
Articles > Articles publicats > Geologica acta
Articles > Articles de recerca

 Registre creat el 2012-01-30, darrera modificació el 2016-10-14

   Favorit i Compartir