الفهرس 
GEOLOGICAL SETTINGSOnly 14 pages are availabe for public view
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Abstract
The Bahariya Oasis is a topographic depression located in the Western Desert, 370 km southwest of Cairo. It is set in a depression covering over 2000 Km2 representing the lowest point in Egypt. It is located in the center of the Western Desert of Egypt between latitudes 27° 48` and 28° 30` North and longitudes 28° 32` and 29° 10` East. The Bahariya Formation type locality is the Bahariya Oasis which is consisting of sandstones with several intercalations of ferruginous layers, and termed the lowermost sandstone beds as the ‘Dinosaur bed’ at Gabal El Dist.
This study was carried out on two ways, surface and subsurface studies. The surface study was carried on 37 hand spacemen from Gabal El-Dist which investigated by radiometric measurements, while the subsurface study was carried on five representative wells (KH-14, KH-17, KH-19, KH-21 and KH-24) in Khalda oil field obtained from Khalda Petroleum Company for purpose of evaluation of hydrocarbon potentially.
The objectives of the surface study were to illustrate the measurements of natural radiation in rocks. This radiation comes essentially from only 3 elemental sources, the radioactive elements of Thorium series, Uranium-Radon series and radioactive isotope of Potassium K40.
Gamma ray spectrometry is an analytical method that allows the identification and quantification of gamma emitting isotopes in a variety of matrices.
There are two ways of radiometrical measurement, one of them is measured in the field by RS230 for each one meter from the bottom to the top of Gabal El-Dist and the other type was a chivied by measuring the
collecting samples in geochemical exploration lab by sodium iodide (NaI) Gamma ray spectrometer in Nuclear Material Authority (NMA).
The gamma ray spectrometry and well log analysis as GR log, density log, neutron log and resistivity log and others were used in this research for identification the reservoir rocks.
The thorium – potassium crossplots method, gives accurate information about the clay minerals in the rocks using the diagram of Schlumberger (1995), and this method was carried on all the studied wells which have a spectral gamma data to study the clay minerals in Bahariya Formations.
Thorium normalization is a new exploration method has been developed by Saunders et al. (1993) using surface and aerial gamma-ray spectral measurements in prospecting for petroleum in stratigraphic and structural traps.
Well log analysis objectives for subsurface study are to shows the analysis for logs of Bahariya Formations in Khalda oil field wells include:
1. Editing and correcting the log data.
2. Normalizing the log data.
3. Determination the volume of shale and the lithology of formation.
4. Determining the values of porosity and permeability.
5. Determining the fluid types within the reservoir and calculates the reserves.
There different logging tools and methods were used through this study as Nuclear, Electric, Sonic and Caliper Logs.
The well log analysis procedures applied on the studied logs of the study area were performed in five phases, Digitizing well logs, Data gathering, Data base editing, Multi-well normalization and Formation evaluation tasks.
1. Results of Radiometry
Surface results
There are relationship between sodium iodide lab measurements and the measurements of field taken by device RS230. The relationship illustrates that the field data mean is 3.75 ppm for eU, while the average of eTh is 3 ppm and the mean of K% is 1%. The total count ranging from 10 to 113 Api. The laboratory measurements illustrate that eU mean is 3.5 ppm; while the eTh mean is 7 ppm and the K average is 1%. The total count ranging from 18 to 113 Api.
Subsurface results
The mean value of K % concentration in this formation is 1.11 %. The eU concentration mean is about 2.30 ppm, while the mean value of the eTh concentration in this well is about 5.37 ppm.
2. Results of the thorium – potassium crossplots
The main clay minerals which present in Bahariya Formation in all the studied wells are Montmorillonite, Chlorite, mixed layer, Illite clay and some traces of Mica and Glauconite clay minerals. The thorium – potassium crossplot clear that the lithology of Bahariya Formation in the study wells is composed mainly of sandstone zone and this Formation considers a good oil reservoir.
3. Results of XRD
The result shows that the types of clay mineral in the random samples which taken form study area are Montmorillonite and Kaolinite.
4. Results of thorium normalization
By applying the thorium normalization technique on the Bahariya Formation in the study area that can determine the oil bearing zones, and it surging by the analysis of conventional ell logs data. The results illustrate that there a high amount of hydrocarbon were detected in five Khalda oil Wells. That was confirmed by positive DRAD values which indicate directly to the oil bearing zone.
5. Results of radiogenic heat production
There are two methods were used for RHP calculations, the method of Bucker & Rybach (ABR) and method of Rybach only (AR). The results illustrate that GR logs values (ABR) which vary between 0.41 to 1.43, 0.31 to 1.47, 0.16 to 1.25, 0.38 to 1.54 and 0.3 to 1.4 μW/m3 for Wells 14, 17, 19, 21 and 24 respectively that compared with SGR and bulk density logs values (AR) ranging between 0.25 to 2.07, 0.15 to 1.49, 0.12 to 1.02, 0.46 to 1.83 and 0.34 to 1.63 μW/m3 for Wells 14, 17, 19, 21 and 24 respectively.
6. Results of well log analysis
The results of well log analysis for all wells illustrate that, the lithology of Bahariya Formation composed mainly of clay sand, they have a percent of shale volume about 37 % in average, although the total porosity records 35% in average, and the effective porosity ranging is 10 to 55 %. The percent of water saturation in all wells record less than 50 % in average and the hydrocarbon saturation ranging from 10 to 75%. These results can be concluded that the Bahariya Formation is a very good reservoir rock.
It can conclude that these all results were agreement with the results of well log analysis with percent 79.44% for the same zones in the same wells.