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| Format: | Artículo científico |
| Language: | en |
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Universitat de Barcelona
2007
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| Online Access: | https://www.redalyc.org/articulo.oa?id=50550107 |
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| author | A. Permanyer |
| author_facet | A. Permanyer |
| contents | The Impact of carbonate cements on the reservoir quality in the Napo Fm sandstones (Cretaceous Oriente Basin, Ecuador) A. Permanyer J. Estupiñan R. Marfil A. Delgado Ciencias de la Tierra Ecuador Geochemistry Oriente Basin Carbonate cement Sandstone reservoirs The Napo Formation of Lower-Middle Cretaceous age in the Oriente basin, Ecuador, is an important sandstonereservoir. The formation is buried at a depth of 1,500 m in the eastern part of the basin and down to 3,100 m inthe 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 mediumgrained 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 chloritehelped to retain porosity by supporting the sandstone framework against compaction. Dissolution of feldsparsand 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 contributorto porosity loss in the reservoir and that the precipitation of the carbonate cement occurred in early and latediagenetic stages. The stableisotope composition of the S1 siderite is consistent with precipitation from meteoricwaters in fluvial sandstones, and from mixed meteoric and marine waters in transitional sandstones. Thelow 18O values of some of these carbonate phases reflect the replacement and recristalization from S1 to S2siderite at deep burial and high temperature. Textural evidence, together with a low Sr content, also suggeststhat 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 tothis higher Mg content, siderite S2 could have precipitated as a result of the thermal descarboxilation of the Mgrich organic matter. The progressive decrease in 18O values in all carbonate cements could be related to thecontinued precipitation at different temperatures and burial depth. 2007 artículo científico 1695-6133 https://www.redalyc.org/articulo.oa?id=50550107 en http://www.redalyc.org/revista.oa?id=505 Geologica Acta: an international earth science journal application/pdf Universitat de Barcelona Geologica Acta: an international earth science journal (España) Num.1 Vol.5 |
| format | Artículo científico |
| id | redalyc_50550107 |
| language | en |
| publishDate | 2007 |
| publisher | Universitat de Barcelona |
| spellingShingle | The Impact of carbonate cements on the reservoir quality in the Napo Fm sandstones (Cretaceous Oriente Basin, Ecuador) A. Permanyer Ciencias de la Tierra Ecuador Geochemistry Oriente Basin Carbonate cement Sandstone reservoirs The Impact of carbonate cements on the reservoir quality in the Napo Fm sandstones (Cretaceous Oriente Basin, Ecuador) A. Permanyer J. Estupiñan R. Marfil A. Delgado Ciencias de la Tierra Ecuador Geochemistry Oriente Basin Carbonate cement Sandstone reservoirs The Napo Formation of Lower-Middle Cretaceous age in the Oriente basin, Ecuador, is an important sandstonereservoir. The formation is buried at a depth of 1,500 m in the eastern part of the basin and down to 3,100 m inthe 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 mediumgrained 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 chloritehelped to retain porosity by supporting the sandstone framework against compaction. Dissolution of feldsparsand 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 contributorto porosity loss in the reservoir and that the precipitation of the carbonate cement occurred in early and latediagenetic stages. The stableisotope composition of the S1 siderite is consistent with precipitation from meteoricwaters in fluvial sandstones, and from mixed meteoric and marine waters in transitional sandstones. Thelow 18O values of some of these carbonate phases reflect the replacement and recristalization from S1 to S2siderite at deep burial and high temperature. Textural evidence, together with a low Sr content, also suggeststhat 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 tothis higher Mg content, siderite S2 could have precipitated as a result of the thermal descarboxilation of the Mgrich organic matter. The progressive decrease in 18O values in all carbonate cements could be related to thecontinued precipitation at different temperatures and burial depth. 2007 artículo científico 1695-6133 https://www.redalyc.org/articulo.oa?id=50550107 en http://www.redalyc.org/revista.oa?id=505 Geologica Acta: an international earth science journal application/pdf Universitat de Barcelona Geologica Acta: an international earth science journal (España) Num.1 Vol.5 |
| title | The Impact of carbonate cements on the reservoir quality in the Napo Fm sandstones (Cretaceous Oriente Basin, Ecuador) |
| topic | Ciencias de la Tierra Ecuador Geochemistry Oriente Basin Carbonate cement Sandstone reservoirs |
| url | https://www.redalyc.org/articulo.oa?id=50550107 |