Control diagenético sobre la porosidad y permeabilidad en areniscas-almacén cretácicas (área Salam, Western Desert, Egipto).

Zusammenfassung

Pelrographic analysis of core samples of reservoir sandstones from the Sa/am Field show that porosity and permeability are strongly influenced by diagenesis. The studied sandstones can be subdivided into two populations that reflect major differences In the origin of porosity and in the diagenetic evolution: (1) Sandstones with dominance of primary intergranular porosity in which porosity reduction is mainly due to compaction and quartz overgrowths, This category includes the shallow marine glauconitic quartzarenites to subarkoses of the Bahariya Fm and of the upper part of Alam El Bueib Fm (unit 3A). Modal porosities range 10-17% and permeabilities do not exceed 300 md. Compactional porosity loss (usually around 20% of initial volume) increases with increasing ductile grain content and decreases with the presence of early siderite cement fwhich acts as a framework-strengthening agent). (2) Sandstones with dominance of intergranular secondary porosity generated after leaching of pore-filling/grain-replacing ferroan dolomite cement. This category includes the fluvial quartzarenites of the lower part of Alam El Bueib (units 5A and 3E) and of the middle part of Lower Bahariya. Reservoir quality is optimum in this group, as porosities are usually around 20% and permeabilities are commonly very high (over WOO md)