An integration work flow between detailed log data analysis, characterization methodology, and core data { petrophysical, XRD, thin sections, petrological and sedimentological description } is very important to detect the diagenetic constraints for reservoir quality in shaly-sand reservoirs in order to build a more robust petrophysical model. The work flow enables the identification of the types of clay minerals which detected during this study that affect porosity/permeability relationship. The dispersed distribution of clay minerals complicate the petrophysical analysis when using conventional tools to identify the different reservoirs zones, hence we resorted to another Petrophysical approach in reservoir characterization such as probabilistic petrophysical approach corrected to core data and thin sections analysis which have a significant clarification of the clay minerals that help in porosity preservation. This study will allow the understanding of the factors which have a direct effect on the petophysical parameters and properties (porosity, permeability, fluid identification and characterization, fluid saturations) as well as tracking the influence of clay minerals typing (Chlorite, Kaolinite, Illite) that will lead to better detection of reservoir characterization to improve enhanced oil recovery (EOR). However, the dissolution of initial carbonate cement and the unstable feldspar grains may be the most diagenetic factor that enhanced the Bahariya reservoir quality. The proposal of this workflow is to build a petrophysical model of this field and can provide with better porosity and fluid saturation, hence these parameters will affecting the calculations of net pay in the reservoirs.

Some reservoirs exhibit low electrical resistance and high estimated water saturation, despite it can produce hydrocarbon, associated with low water cut. These types of reservoirs are considered as unconventional reservoirs and well known as low resistivity pays (LRP). The identification and evaluation of such kind of unconventional reservoirs are very challenging and important for some oil and gas reservoirs. Low resistivity contrast between the low resistivity hydrocarbon -bearing zones, adjacent to the water zones and shaly zones could mislead the hydrocarbon evaluation and leads to bypassing of a considerable volume of resources. Evaluation of the laminated sand-shale sequence is controlled by some factors, such as; the lithology, mineral composition, compaction, thickness and resistivity. The thin beds may have a low resistivity value due to the effect of presence within a conductive thick shale bodies. The present study imposes an advanced interpretation technique for more accurate identification of the thin beds intervals, which are usually bypassed in case of using the conventional log tools. For better evaluation of the thinly bedded laminated sections and in order to maximize the hydrocarbon potentiality. By application of both the traditional log tools and resistivity images logs as well as Thomas -Stieber Method on Bahariya Formation in Yomna Field; it was found that the porosity, hydrocarbon saturation and net pay thickness for all the Bahariya reservoirs were enhanced with a different percent, based on the laminated and thin beds interval for each well. It is highly recommended to adjust the current study in next the wells with nuclear spectroscopy and NMR logs for calibration of clay volume, porosity and estimation of volumes of conductive Intervals.