IMPACTS OF THE DIAGENETIC HISTORY ON THE PETROPHYSICAL FEATURES OF THE JURASSIC MARINE FACIES IN GEBEL EL MAGHARA MASSIF, NORTH SINAI, EGYPT | ||
| Journal of Egyptian Geophysical Society | ||
| Volume 5, Issue 1, 2007, Pages 9-24 PDF (1.71 M) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/jegs.2000.380806 | ||
| Author | ||
| B.S. Nabawy | ||
| Department of Geophysical Sciences, National Research Centre, Cairo | ||
| Abstract | ||
| Routine and special core analyses were conducted for the Jurassic marine sediments in Gebel El Maghara massif whereas the impacts of the diagenetic effects have been identified from a detailed microfacies analysis. The Jurassic marine sediments in Gebel El Maghara are represented by the Rajabiah Formation (292 m) is composed mainly of ferruginous calcareous quartz arenite (clastic microfacies) at its lower parts and mudstone microfacies (SMF 23) at the other parts, Bir El Maghara Formation (442 m) is composed of mudstone microfacies (SMF 23), whereas the Masajid Formation (575 m) is composed of foraminiferal and molluscan mudstone microfacies (SMF 19), oolitic grainstone microfacies (SMF 16) and foraminiferal and algal sparitic mudstone microfacies (SMF 19 & 21). These microfacies were deposited in restricted platform conditions (Fz. 8) with some oscillation into shelf lagoon conditions (Fz. 7) in the middle parts of the Masajid Formation. The petrographical description of the pore spaces indicates that most of the studied pore spaces are matrix porosity with few channels and vug porosity filled later by microsparite and silica cement. Primary intergranular porosity was restricted to the lower parts of the Rajabiah Formation. Cementation by microsparite and later by silica is the main porosity dishancing factor through the whole parts of the studied samples, whereas dissolution and leaching out is the sole porosity enhancing factor at the lower parts of the section. Grain compaction and fracturing are restricted to the clastic ferruginous calcareous quartz arenite microfacies in the lower parts of the Rajabiah Formation. From the petrophysical point of view, the bulk density is dependent mainly porosity, whereas permeability on the channel diameter, porosity and the irreducible water saturation. The formation resistivity factors were measured at 10 and 50 kppm, both are affected mainly by the effective porosity and electric tortuosity. A lime-mud effect could be recorded for some Masajid samples, with no effect for the other samples. The Jurassic marine sediments in Gebel El Maghara complex have poor storage capacity properties except for the lower parts of the Rajabiah Formation, so it is recommended to deal with the present rocks as a source of building and ornamentation stones. | ||
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