الفهرس 
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Abstract
The present study deals with the Cenomanian Bahariya Formation in the Western Desert, characterizing Upper Member of Bahariya Formation as it is one of the most important reservoirs in Egypt. The study area located at the north Western Desert, East Abu Gharadig basin, between Latitude 29⁰ 35ʼ 2.4ʼʼ N and 29⁰ 33ʼ 36ʼʼ N and between Longitude 29⁰ 48ʼ 28.8ʼʼ E and 29⁰ 50ʼ 52.8ʼʼ E. The main objective of this study is to investigate subsurface and reservoir characteristics to evaluate hydrocarbon potentialities of Upper Member of Bahariya Formation.
Subsurface stratigraphic column of Heba-100 oilfield ranges in age from Upper Creataceous Bahariya Formation to Eocene Apollonia Formation. The study area shows a NE trend asymmetrical fold dissected by NE normal fault and structural highs and lows anomalies, separated by fault polygons.
In the present study, a correlation is constructed between the studied four wells of Heba-100 oilfield to represent the lateral facies change and thickness variation. The Upper Member of Bahariya Formation is classified into seven zones named from top to bottom: (UB 1, UB 2, UB 3, UB 4, UB 5, UB 6 and UB 7). from the constructed correlation chart and isopach maps of Upper part of Bahariya Formation, there is no big difference in thickness between wells which indicate that Upper Member of Bahariya Formation has been deposited at stable tectonic environment so, the sedimentation is approximately equal along the wells, based on stratigraphic interpretation.
According to ditch cutting lithology description, it is concluded that the depositional environment of the study area is shallow marine environment, where the percentage of sandstone ranges from 44.80 % to 55.37%, Siltstone ranges from 23.14% to 41.10%, Shale ranges from 5.85% to 19.92%, and Limestone ranges from 1.98% to 8.18%.
The petrophysical analysis of Upper Member of Bahariya Formation includes grain density, porosity and permeability measurements. There are several methods by which the grain density of rocks can be determined such as saturation method, where the grain density of the Upper Bahariya samples varies between 2.61 gm/cc and 3.05 gm/cc. The distributions of grain values of Upper Member of Bahariya Formation show that the grain density data shows bi-modal (M1 = 2.66 gm/cm3, M2 = 2.98 gm/cm3). The study of the relationship between the helium porosity with fluid porosity of the rock and its grain density, shows two reservoir groups (G1 and G2) which indicates that we have at least two rock population in the Upper Member of Bahariya Formation. The number of samples in G2 is very limited (only four). It can be noticed that there is a general tendency for the increase of the permeability of the rock sample with the decrease in its grain density. The two rock populations groups (G1 and G2) were confirmed and obtained again by Grain density – permeability relationships. Most of the studied samples are falling in G1 as obtained with samples of porosity plots.
There are several methods by which the porosity of rocks can be determined (such as saturation method and helium Porosimeter). Porosity has been determined for all samples where Helium porosity samples ranged from 3.53 up to 24.76 and fluid porosity samples ranged from 1.872 to 33.06, the other hand the frequency distribution curve of Helium porosity data is unimodal where the crest at 30 %, also frequency distribution data of fluid porosity data or saturation porosity data is unimodal where the crest equal 18 %. Cross-plots are constructed between Helium porosity and Horizontal permeability and Helium porosity and vertical permeability characterized by a correlation coefficient (r=0.6277) and (r=0.6961) respectively. Also cross-plots are constructed between fluid porosity and horizontal permeability, fluid porosity and vertical permeability and fluid porosity and Helium porosity respectively. The data points of these figures represent a poor correlation coefficient where (r=0.21133930, r=0.34454 and r= 0.4451707) respectively which means that the porosity are not the main contributor for the rock permeability values.
Permeability determination with the gas used as well as the mean pressure existing in the core at the time of measurement. The study of the permeability histogram and cumulative frequency curve for the Upper Bahariya Formation samples shows that the permeability data don’t have a normal distribution as the histogram is asymmetrical. Statistically this type of data is said to have a skewed distribution. The vertical permeability histogram, indicates that the minimum value is 0.002, the maximum value is 43.031 and the mean is 1.13 mD, while the examination of the horizontal permeability distribution, the minimum value is 0.001, the maximum value is 96.006 and the mean is 2.522 mD.
The average value of reservoir quality index is 0.043467, the average porosity value is 15.81 and the permeability average value is 1.13 mD, indicates that Upper Member of Bahariya Formation is characterized by a good reservoir quality.
Porosity and permeability measurements of the Upper Bahariya core samples, could be used to estimate various reservoir parameters derived from water injection, such as displacement pressure, irreducible water saturation and recovery efficiency. Relationship between the water recovery efficiency and displacement pressure of Upper Bahariya Formation samples, shows that this relationship is characterized by correlation coefficient (r=0.96) which is considered to be excellent. The relationship between the water recovery efficiency and laboratory permeability of Upper Bahariya formation samples, shows that this relationship is characterized by correlation coefficient (r=0.68) so, the relation is seems to be good so, it appears that recovery efficiency is affected by displacement pressure and permeability.
Reservoir analysis includes data editing and zonation to detect the zone of interest by identifying the response of the wireline logs, shale volume calculation, effective porosity calculation, water saturation calculation, hydrocarbon saturation calculation and stock tank oil initially in place calculation so the results in the studied four wells are: the volume of shale ranges from (9% to 11%), average effective porosity ranges from (16 to 17%), average water saturation ranges from (51% to 99%), the average hydrocarbon saturation ranges from (1% to 42%) and calculation of STOIIP which is done for the reservoir of the study area equals 40641044 bbls.