Sedimentary
and petrophysical characteristics of Paleozoic rocks of north Gabal Qabaliat, south west
Sinai, Egypti
M. A. Ragab, I. M. Hassanien1 and
M.A.E. Kassab
National Research Center, Earth Sciences Dept., Cairo, 1Egyptian
Petr.
Research Inst., Exploration Dept., Cairo, Egypt., |
Paleozoic rocks exposed at N Gebal Qabaliat,
South West Sinai can be distinguished into:
- Araba Fm (Early Cambrian) shallow marine and tidal zone arenitic and ferruginous
sandstone, claystone and sandy claystone;
- Naqus Fm (Cambrian) aeolian arenitic and ferruginous sandstone, and
- Abu Durba Fm (Carboniferous) fluviomarine clayey sandstone and dolostone.
Their effective porosity may be of secondary origin due to diagenesis that affected these
rocks (compaction, cementation, precipitation of gypsum and halite, and decomposition of
feldspars). The electrical resistivity measurements of dolostone are high due to their
lower effective porosity and higher density and cement material, whereas the electrical
resistivity of the sandy claystone is the lowest due to their higher clay content and
mounce potential, and lower tortuosity. The differences in electrical resistivity values
in horizontal and vertical directions show that the samples have anisotropic fabric. The
ultrasonic velocity of the dry samples increases by decreasing effective porosity and
clastic materials, whereas that of the saturated samples by brine solution of high
concentration depends mainly upon the clay content. The sandstone rocks of the Naqus Fm
therefore are considered good reservoir rocks, due to their high reservoir properties
(effective porosity and permeability).
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