Abstract
Fifteen surface sandstone samples of Late Cretaceous age were compiled from Wadi Kareem area in Eastern Desert, Egypt. Samples were subjected to permeability and porosity measurements to show their distributions and possibility of separating them into different hydraulic flow units. It is known that hydraulic flow unit is a volume of rock within a reservoir that has petrophysical and lithological attributes that affect flow properties and differ from those of surrounding units. It was found out that the normal application of Amaefuleʼs hydraulic flow unit approach using the relation of normalized porosity index (ϕZ) versus reservoir quality index (RQI) and FZI values at (ϕZ) = 1 leads to deviation of predicted permeability from the measured one in case of scattered data of (ϕZ-RQI) relation having a unit slope trend line. In the present study, the additional new processing leads to close matching between the measured and predicted permeability, hence reservoir description improvement. This is simply done through differentiation of all samples that lie on the unit slope trend line and those lie scattered on both sides of it, into three sub-flow units regardless their slopes and the use of (FZI) arithmetic average for each sub-unit instead of that at (ϕZ) = 1. Permeability prediction has been improved after applying the new additional processing. Capillary pressure-derived parameters for some selected samples as micropores, mesopores, and macropores, used to support the new concept .
Highlights
The Nubian Sandstone is applied to depict the terrigenous clastic sandstone sequence that overlies on the Precambrian rocks and underlies the Quseir variegated marine shale Formation of the Late Cretaceous age
The present study aims to improve the permeability prediction in uncored wells, using hydraulic flow unit approach but with new additional processing for the measured data
It was necessary to classify the samples into zones to reduce the data scattering and improve the permeability prediction, and this was done through plotting φZ versus reservoir quality index (RQI) (Fig. 4), according to the approach of Amaefule et al (1993), and we have three hydraulic flow units through three parallel unit slope trend lines, but the problem is deviation of predicted permeability using Eq (4) than the measured one as seen in Table 2, and this is due to the data scattering around the trend lines for some flow units, especially units (1) and (3)
Summary
The Nubian Sandstone is applied to depict the terrigenous clastic sandstone sequence that overlies on the Precambrian rocks and underlies the Quseir variegated marine shale Formation of the Late Cretaceous age. In case of ideal (φZ-RQI) relation for a given hydraulic flow unit, all samples would be lie on or very close from the unit slope trend line, and no scattering could be seen and FZI value that results from the intercept of the trend line at (φZ) = 1, equals or nearly equals FZI arithmetic average of these samples (Eq 3), and predicted permeability equals or is very close to measured one (actual), and the difference between them is the lowest.
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