الفهرس 
LOCATION OF THE STUDIED AREA
AIMS AND OBJECTIVESOnly 14 pages are availabe for public view
 |  | from | 148 |  |  |
| | | from | 148 | | |
Abstract
The area under study lies in the southern part of the Gulf of Suez, Egypt. Integrated
geophysical study has been carried out in the study area for estimating and recognizing
the geological features, especially Salt Dome Structures and fault element trends, then
focusing our study on Hilal Oil Field which lies between latitudes 27 º 46’ N and 27 º
51’ N and longitudes 33 º 42 ’ E and 33 º 47 ’ E.
The regional structural features in this province is bounded from the north by the
Morgan hinge zone passing from the northern end of Esh El Mellaha to Ras Shukheir
to the north of well LL 87-1, then the offshore north of Gebel Araba on the eastern
bank. It is characterized by the occurrence of surface outcrops of Miocene, Pre-Miocene
sediments and basement rocks in Gebel El Zeit and Esh El Mellaha ranges. The regional
dip of strata is towards southwest as the Northern Province and the main Clysmic and
cross faults throw towards northeast and southeast, respectively. Galala and Morgan
hinge zones are shifted southwards on the eastern bank of the Gulf of Suez some 45 km
at Zeneima and 30 km at Gebel Nakus, respectively.
The complexity of the pre-salt reflectors is due to the presence of the massive salt
and anhydrite overburden. The main problem with the massive salt and anhydrite is the
difficulty of imaging the pre-salt reflectors due to the significant lateral velocity
variations, distortion of raypaths and time pull-up created by salt. The geological nature
of the Gulf of Suez contains the Zeit Formation with low velocity shale beds and
anhydrite beds with high velocity. This geologic sequence formed by shale and
anhydrite cause a lot, and different orders of multiples. In addition to other reasons due
to the complex geology of Gulf of Suez, arising from the broken blocks with different
types of faults caused a big lateral change of velocity.
The main objectives of this study are the delineation of the subsurface geological
conditions and structural framework favoring the accumulation and entrapment of
hydrocarbons in the study area. In order to achieve these targets, the available
geological and geophysical data are analyzed to give integrated and reliable picture for
the study area.Chapter one discusses the location of the study area, aims and objectives of the
study, the available data, methodology and techniques used, and the exploration history
and activities done in the study area.
Chapter two deals with the geologic setting, which includes four main items.
Firstly, discus the subsurface stratigraphy of the Gulf of Suez, with special
reference to the area under investigation.
Secondly, the structure pattern result of the tectonic effect on the study area.
Thirdly, the tectonic effect on the study area.
Finally, the arrangement of various stratigraphic, structural and tectonic framework
in a compiled form to reflect the geologic history of the study area.
Chapter three discusses gravity data interpretation of the available gravity
anomaly map in the southern part of the Gulf of Suez to detect the regional structural
trends and fault elements.
It is recommended that we use a detailed gravity map scaled 1:10000 but it was not
available in the southern part of the Gulf of Suez, so we used 1:100000 Bouguer gravity
map.
Chapter four discusses a suite of well logs analysis including the gamma ray,
spontaneous potential, resistivity logs, and density logs in the study area were evaluated
to obtain the various petrophysical parameters.
Petrophysical reservoir characteristics were been evaluated for Nubia reservoir
encountered in four wells in the study area and its vicinity by applying Techlog software.
Starting with the determination of shale content (Vsh) through the mono-tools as the
gamma ray, self-potential, the resistivity and neutron were comprised the neutrondensity, sonic-density, and neutron-sonic, later this information had been used to
calculate the lithology content. Then, it was possible to determine the fluid contents as
water and hydrocarbon saturation for shale zones.
Hydrocarbon potential in the study area was been assessed through vertical
distribution. The vertical distribution of the hydrocarbon events was displayed through
the Litho-saturation cross plots. The plots demonstrate the primary lithology of the
Nubia Formation. It is made essentially of sandstone .This analysis recorded good thickness for the studied section in HIL-A16, HIL-A4,
HIL-A9A wells for Nubia Formation with good reservoir properties. The major
prospect is toward Hilal A16, which produced oil from Nubia formation.
It is recommended that re-logging most of the wells in Hilal oil field must be run
again because of missing of some logs.
Chapter five explains the conventional seismic data interpretation that was very
difficult for estimation of the subsurface geological features due to the complex geology
of the Gulf of Suez. This complexity is arising from the broken tilted fault blocks with
different types of faults and the presence of high-velocity layers like Miocene salts and
anhydrites within the sedimentary sequence enhances the reflection coefficient along
their shallower interfaces with consequently apparent resolution of these horizons on
seismic sections and absence of any beneficial seismic event below this evaporate
section.
We recommend of using seismic attributes because of the geology complexity.
That is why seismic attributes in chapter six, has been used for solving this complexity
and it was very useful approach with the help of well-to-seismic tie for identifying and
picking reflection horizons on the tops of the interested geological formations. Then,
depth structure maps have been constructed.
Chapter six dealing with the different types of seismic attributes such as Dip of
Maximum Similarity, Smoothed Dip of Maximum Similarity, Trace Envelope,
Similarity, Similarity Variance, Dip Variance, Instantaneous Lateral Continuity, Event
Continuity etc., which have helped us to detect the reflection horizons and the normal
fault elements accompanying the salt border. Several seismic attributes have been
extracted for the detection of the subsalt layers. We found that Event Continuity
attribute and Instantaneous Phase are the best ones to show the subsalt horizons in the
study area.
The challenge in this work is to improve the focus on the seismic data underneath
the salt dome, in order to reduce drilling risk.
The plan was to combine the gravity and seismic results, leading to the production
of a final salt model with optimal gravity and seismic response.Unfortunately, there was no available gravity data for the model, so we tried several
types of attribute to improve the seismic data underneath the salt dome and we found
that Event Continuity attribute and Instantaneous Phase are the best ones to show the
subsalt horizons (Basement, Nubia, and Kareem Formations).
It concluded that Hilal Oil Field characterized by structural highs suitable for
hydrocarbon accumulations representing good structural traps of tilted fault blocks.
All the previous studies, gravity interpretation, well-logging analysis, seismic
structural interpretation and seismic attributes were tied together to get a complete
understanding of the hydrocarbon potentiality in the area of study.