الفهرس 
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Abstract
The present work is dealing mainly with the interpretation of geophysical
data to evaluate the hydrocarbon potentials of South Siwa field, Egypt.
South Siwa field is located in the western side of Egypt between latitudes
28˚ 00` 00” N and 26˚ 30` 00” N and longitudes 26˚ 43` 00” E and 25˚ 00`
00” E.
Conoco (Continental Sahara Oil Company) explored the South Diyur and
adjacent South Siwa and Dakhla blocks in the 1970s. The exploration
program culminated in 1979 with the drilling of the Ammonite-1 and
Foram-1 exploration wells, both of which intersected Tertiary, Mesozoic
and Paleozoic strata and bottomed in commercial basement without
identifying oil or gas shows.
Seismic processing of 2D data set was built up to improve imaging of
seismic reflectivity in the area. The major problems affecting on the seismic
data imaging, were as follows,
1- Signal/Noise ratio was very poor.
2- Lateral resolution of the overall seismic section.
3- Velocity analysis and static correction.
We are selected one seismic line (UER-134) as a test line to evaluate,
discuss the main problems effect on seismic records.
There are four important steps in data enhancement:
1- Filtering and deconvolution: to improve the resolution and reduce
the noise components of individual trace.
2- Stacking: to improve the signal to noise ratio.
3- F-K and Dip filtering: to improve the lateral resolution of the overall
seismic section.
4- Velocity analysis and static correction.
The good 2-D data acquisition and processing with the optimum parameters
are necessary prerequisites for any seismic section.
The new 2-D processing sequence and parameters have improved the data
compared to the old processing sequence. This study shows that the user of
2-D optimal processing sequence and parameters, should enhanced
exploration and development efforts in the study area.
The seismic method is very important for petroleum exploration to detect
the locations of the exploratory wells, as well as for the development and
evaluation of the oil fields. The main target of the seismic data involves
determination of the geologic significances from the seismic data.
The picked time values and the locations of fault segments are posted on the
base map of the study area in order to construct four two-way time
reflection maps on the tops from the oldest to youngest: Cambrian -
Ordovician, Silurian, Upper Devonian, Lower Carboniferous, Jurassic and
Cenomanian Ages.
The faults in maps can be divided into two groups, according to the fault
trends E-W and NE-SW.
The study area was affected by four major geotectonic phase can be
recognized in the Phanerozoic in the Western Desert these are: Caledonian
(Cambrian- Devonian), Variscan-Hercynian (Late Paleozoic), Cimmerian /
Tethyian (Triassic Early Cretaceous), Sub-Hercynian- Early Syrian Arc
(Turonian- Santonian).
The Petrophysical analysis was performed for four wells penetrated in and
out the study area these are Foram-1, Ammonite-1, Kothyab-1and Bahrain-1
under investigation was aimed to evaluate the hydrocarbon potentialities in
the clastic zones that are encountered in Jurassic, Upper Devonian and
Lower Carboniferous Ages.
The output petrophysical results have been tabulated. Matrix
identification has been explained through lithological identification in
specific cross-plots. All resulted petrophysical parameters are represented
vertically in litho-saturation cross-plots and laterally in different types of
iso-parametric maps (iso-effective porosity, shale content, and thickness
variations).
Parameters of the Jurassic reservoirs:
The shale content show that the amount of clay volume decrease
gradually to the west trend and increase in the east part of the study area
shale content value ranging 1 to 10 %.
The effective porosity, shows an increase in the NE trend and decrease
in the SW trend of the study area effective porosity range from 18- 25%.
The isopach maps reveal that the reservoir thickness increases towards
the NE trend and decrease towards the SE trend range between 700-1080 ft.
The water saturation increases toward the North trend and decrease toward
SW range from 60-80%.
Parameters of the Lower Carboniferous reservoirs:
The shale content show that the amount of clay volume decrease
gradually to the W trend and increase in the SE part of the study area shale
content value range 2-16 %.
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The effective porosity, shows an increase in the SW trend and decrease
in the north trend of the study area effective porosity ranging from 18- to
26%.
The isopach maps reveal that the reservoir thickness increases towards
the SW trend and decrease towards the NW trend range between 700-1700
ft.
The water saturation increases toward the SW trend and decrease toward
NW range from 24-70%.
Parameters of the Upper Devonian reservoirs:
Thickness range from 100-1300 ft, water saturation range from 50-100%,
shale content range from 1-15% and effective porosity range from 14-20%
all results based on three well in this level.
from the subsurface and petrophysical information of this study we
can be in a clear vision on the petroleum potentialities in the area of study.
A detailed time and depth structure map of the study area at
Jurassic, Lower Carboniferous and Upper Devonian ages shows
multiple separate structural culminations during this study. The
maximum structural closure of the culminations is to the central part
of the study area at horst block and faults trend at E-W.
Three structural closures leads have been identified during
this study two of them are three way dip closure (B and C) and
another one (A) is four way dip closure additional to another
stratigraphic trap.
Detailed interpretation of seismic indicated the presence of block faulting
together with possible graben to pull-apart basins similar to those
described in the Kufra Basin (Craig, 2012). The Upper Proterozoic to
Lower Cambrian succession is expected to be present in the South Siwa
Block and the presence of an associated petroleum system is inferred.
This interpretation will need to be tested by stratigraphic-exploratory
drilling.
As a result of the present study, using the subsurface and petrophysical
evaluation, three locations is proposed to be a prospect area, that located on
such a three-way dip closure and four-way dip closure that is very suitable
place for hydrocarbon accumulation.
It is recommended to drill prospect wells in the central part of South
Siwa Concession, to drain the oil from the extended reservoirs
expected to be above OWC. Also recommended by 3D seismic
Acquisition to improve seismic data along with good covering for the
area.