الفهرس 
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Abstract
The area under consideration covers about 26600 km2 in the
central Sinai between latitudes 29030’ - 310 13’ N and longitudes 330
-
340 30’ E.
Geomorphologically, the study area can be subdivided into three
geomorphic units; 1- The first unit, named Egma- Tih unit, occupying the
southern part of the prospected area, and is of high topography (upto
1620 m). 2- The second geomorphic unit lies to the North of the Egma-
Tih unit, and is represented by hilly land of the compressional folds of
the Syrian arc. 3- The third geomorphic unit is the Mediterranean coastal
zone extending in an E-W direction and attaining an average width of 20
km.
The main target of the present work is mainly devoted to study and
interpretation of the gravity and magnetic data as well as to clarify the
causes of the dry wells in the study area and vizualize its hydrocarbon
possibilities. This is accomplished through; (1) delineating the
subsurface geological conditions, (2) defining the structural framework,
thickness variations and different facies change, as well as throwing
some light on the geologic history, and (3) Evaluating the Lower
Cretaceous and Cenomanian units, which has some oil potentialities in
(Misri, Raad, Ja 90/2, and JB 91/3 wells).
The statisyical study of the potential gravity and magnetic
anomalies shows that the area is mainly affected by five tectonic trends.
They are N 45° - 65°E (Syrian arc trend), N4S0W (Suez trend), E-W (Mediterranian trend), N65°W (WNW trend) and NI5°E (Aqaba trend).
These tectonic trends seems to be rejuvenated during several oroginies
through out geologic history of the area.
Isolation of residual and regional gravity and magentic anomalies
are carried out using griding and 2-D linear wave length techniques.
Such isolation is rather arbitrary and subjective. Regional anomalies
extand over large areas, having high amplitudes and are associated with
the larger and deeper features within the basement and its surface. On the
other hand, the weaker and more localized anomalies, i.e. residual, are
superimposed upon the regional pattern and are characterized by higher
frequency. These are expressed as small closures or noses with
accompaning flattening and steeping of the contour lines.
The comparative studies and critical analysis of the regional and
residual potential maps, deduced from the griding and recent filtering
methods indicate that; (1) The 2-D filtering technique is less successful
in isolation of potential fields than griding method, while the residual
maps prepared by filtering method gave anomalies of more generalized
nature that may reflect the deeper structures in the Basement complex.
(2) The tectonic trends E-W, NW-SE, andNNW-SSE are more frequent
in the shallow levels and (3) The tectonic trends Nl SOE(Aqaba), E-W
(Medeterranian) and N45°W (Suez) are the most frequent in the deep
seated structures.
Analysis of the filtering maps shows that (i) Gravity and magnetic
maps with 21.3 units regional filter is the best for defining the larger elements of deep depths (ii) Maps with 8 unit residual filter seems better
in delineating the smaller elements of shallow depths.
Filon and Fourier transform spectral, Bott & Smith and Peter’s
techniues were applied through fourty eight gravity and magnetic
profiles to detail specifically the depths of the causative subsurface
features.
To confirm the tectonic framework in the study area, especially the
depth to basement surface, eight gravity profiles across the area are
modelled using 2-D density modelling algorithm. The study clarified that
; i) 2-D gravity modelling seems to be avery powerful tool in defining
basement parameters e.g, composition as reflected by density values,
depth, attitude, size of the different blocks and their fabric. ii) The
basement rocks in the study area vary greatly in their composition as
reflected by the wide range of density contrast (2.65 - 2.71 gm/cm’) of
different blocks. This is most probably due to the vertical uplifted of the
Earth’s crust. iii) The depth to basement reached the maximum values of
5 km in the eastern part of the study area; while the minimum value 2.2
km recorded in the western part.
A basement relief map and its 3-D representation is constructed
using the surface and subsurface geologic data, residual and regional
gravity maps, results of gravity and magnetic trends and depth
detremination techniques as well as the result of 2-D density modelling.
This map gives a quantitative picture about the thickness of the
sedimentary section and the available sedimentray basins. Further more, the tectonic map of the study area is constructed
using the different interpretation techniques applied to magnetic and
gravity data as well as drill hole information. Both basement relief and
tectonic maps indicated that; (1) The regional structural framework is
characterized by a number of swells and troughs, along which the largest
structural gradients is flooring the basement surface. They are disected
by a number of major normal faults having NE-SW, NW-SE, E-W and
NNE directions. (2) The basement depth ranges from about 5.2 km in the
south eastern part to about 2.2 km at central part. It seems to be
shallower in the southern part than the northern one.
Besides, different techniques of qualitative and quantitative
interpretation have been applied to the different types of well log data
dervied from boreholes Misri, Raad, Ja 90/2 and Jb 91/3 wells drilled in
the study area.
The aim of such work is to study the subsurface and formation
evaluation of Lower Cretaceous and Cenomanian rock units in the
Northeastern part of the Sinai Peninsula.
A comprehensive quantitative formation evaluation has been
carried to determine shale content, matrix types and fractions, porosity
and fluid saturations.
Shale parameters (Rsh, Atsh, psh, cPNsh and Grsh) have been
estimated using different crossplots relating (M) values against log
reading of resistivity, sonic, density, neutron and gamma ray. On the
other hand, shale content has been evaluated using a single and two curve shale indicators. The first include gamma ray, (SP) and (Rt), while
the latter comprises Density-Sonic combination (dia-porosity crossplots).
With respect to rock discrimination, the three porosity logs of
density, neutron and sonic were utilized in the form of two crossplots.
The M-N, K-A and Mid tri-porosity crossplots for Misri, Raad, Ja 90/2
and Jb 91/3 wells.
Porosity and fluid saturation have been estimated using graphical
and computational approaches. The first includes the construction of
crossplots between resistivity logs (deep and shallow) and porosity tools,
this is known as the Mono-porosity crossplot, from which the values of
matrix transit time (Atma); matrix density (pma) and neutron matrix
($Nma) have been evaluated. The latter comprises a series of equations
that solve porosity and saturation determination.
Graphical and computational approaches Yield an estimation of
corrected porosity, formation water resistivity, saturation of invaded and
uninvaded zones, besides movable and residual oil saturations.
The obtained results of formation evaluation were represented by
schematic correlation charts and iso -parametric maps in both vertical
and horizonal directions respectively. Also the average effective
porosity, average, water and hydrocarbon saturations and average value
of shale content, were calculated and represented for both Lower
Cretacesus and Cenomanian units in each well. In addition, some elastic constants as Bulk and Shear modulie,
poisson’s ratio, Elastic deformation coefficient and seirmic impedance
were calculated. The average values of these parameters were illustrated
as schematic correlation charts. These charts indicated that all parameters
are largely affected by the lithological charateristics, particulary the
presence of shaliness.
Generally the elastic constant give an idea about the mechanical
proparties (strength, fracturing, and hardness) of the studied sections.
These constants, when compared with rock strength limits, would prove
that the studied Lower Cretaceous and Cenomanian units are high
strength.
Finally, it can be stated that the present study has clarified the
subsurface geological and structural conditions, as well as the different
characteristics of Lower Cretaceous and Cenomanian ages in North Sinai
area in a clear manner.