الفهرس 
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Abstract
The present work deals with the subsurface formation evaluation ofNukhul and
Nubia formations encountered in eleven wells (Hil-Al , Hil-A2A, Hil-A3B, Hil-A4,
Hil-AS, Hil-A6A, Hil-A8, Hil-A9A, Hil-AIDA, Hil-AlIand Hil-A12A) scattered in
the study area, southern Gulf of Suez.
The area under studt is located in the south Ghara concession, southern Gulf of
Suez with latitudes 27° 48 and 27° 51’ N and longitudes 33° 42’ and 33° 44’ E.
The sedimentary sequence ranges in age from Pre-Camberian to Recent. The
investigated section includes Nukhul and Nubia formations of Miocene and
Paleozoic ages; respectively.
The Nukhul Formation consists mainly of sandstone and shale with variable
amount of anhydrite and limestone. The depositional environment of Nukhul
sandstone includes shallow marine and probably supratidal for the dolomitic
sandstone unit. It is considered as one of the main hydrocarbon bearing rock units in
the southern Gulf of Suez.
The Nubia Formation has a considerable thickness and composed mainly of
kaolinitic sandstone intercalated with shales. The depositional environment of Nubia
sandstone is shallow marine. It is considered as the main reservoir in the study area
and an important rock unit for petroleum prospectors, because of its high content of
hydrocarbons.
The available data used in the subsurface formation evaluation of the two
studied formations are in the form of resistivity log (deep induction log), porosity
tools (sonic, density and neutron logs), gamma log and conventional (routine) as well
as special core analysis. The most important conclusions revealed from” this study can
be summarized as follows:
Structural Configuration: The structural features of the study area have been
clarified from previous work of seismic data. It has been found that the main
structure of the field is a southwesterly dipping Pre-Miocene faulted block. These
faults are step-like horst and graben and some of which dissect the top of Nukhul and
Nubia formations. The Miocene evaporites provide ultimate seal for the structure.
The field is delineated by faults to the north, south and east, while the oil water
contact (o.w.c) controls the western field limit.
Graphical Well Logging Analysis: Such analysis is diversified into Porosity-
Resistivity (Pickett plots), Dia- and Tri-porosity cross plots. Porosity-resistivity cross
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plots are applied to determine the formation water resistivity (Rw), the water
tsoattaulraptoioronsit(ySw(0}t,). the hydrocarbon saturation (S,,), the formation factor (F) and the
The Dia-porosity cross plots (using the porosity tools pb, t.t and ON) are
applied to determ ine the volume aI’shale (Vsh), the effective pores ity an d the type 0 f
shale distributed in the rocks (laminar, structural and dispersed). Also, frequency
cross plots are Constructed between M values against log readings of dcnsity, sonic,
neutron and resistivity to determine the shale parameters (psh, Atsh, ONsh and Rtsh)
and to show the distribution of the plotted points among the pure minerals.
Moreover, such plots are used with the matrix parameters (pma)a and (Atmaj»
versus Vsh to determine the environment of deposition.
The Tri-porosity cross plots, on the other hand, are used to identify the
lithologic constituents of the studied rock units.
Anal tical Well La com nterized : The computcr program
(PETCOM) was applied for fonnation evaluation. The procedure followed in this
work includcs the determination of the formation water resistivity (Rw) at formatiol1
temperature. The total and the effective porosities (Ot, Oe) are calculated using
sonic, density and neutron logs. The gamma ray, resistivity and neutron logs were
used to estimate the shale volume (Vsh). The different values ofVsh are Corrected
and calibrated to give the optimum values required for further interpretation. The
determination and discrimination of the fluid saturations (Sw and S,,) are carried OUI
for both clean and shaly zones. Also, the percentages of the different constituents of
the rocks are calculated to achieve the lithologic identification.
graphTichaelly prroepccrsesseendtedweblly: logging results for the various investigated wells were
I) Lpiatrhaomloegtyer-ss.aturation cross plots to show the vertical variations of the calculated
2) Iso-parameter maps to show the lateral variations of the same parameters.
Subsurface Evaluation: includes a general study of the subsurface geology of the
Gulf of Suez in which the geological and stratigraphical informations were gathercd
from the studied wells and interpreted with respect to the prevailing geologic
conditions during depOsition. This study resulted in some modifications in the
subsurface maps (structure and isopach maps).
Such studies resulted in thickness variations maps and Lithofacies analysis
considering the two studied formations, as well as, frequency cross plots for
depositional environment determination. The study of isopach maps for the two
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evaluated formations reflects a marked increase in thickness towards the west and the
northwest directions. The lithofacies analysis of Nukhul Formation indicates that it is
composed of shale with varying proportions of sandstone, anhydrite and limestone.
The shale content increases to the north and northeast directions, while sandstone
increases towards the west and northwest directions. The anhydrite content increases
to the northwest and southwest directions. Carbonate rocks, on the other hand, show
a general increase to the northwest direction.
The lithofacies analysis of the Nubia Formation shows a 11011hand northeast
decreasing of shale content. Sandstone content on the other hand, tends to decrease in
the northeast and southeast directions associated with a marked increase in kaol initc
content from east to west and from south to north.
Moreover, the Frequency cross plots reveals a condition of sea level fluctuation
from an open sea (deep-marine) environment of deposition to shallow-marine and
epi-continental conditions at the latter depositional stages ofNukhul Formation. On
the other hand, a condition of shallow-marine environment of deposition is suggested
for minerals forming Nubia Formation.
Hydrocnrbon Potcntinlitics: the vertical and lateral distribution of the hydrocarbon
occurrence is represented in two ways: the first is the Litho-saturation cross plots or
the eleven evaluated wells and the second are a number of iso-pararneteric maps.
The Nukhul Formation consists mainly of shale associated with variable contents or
sandstone, anhydrite and limestone. A general decrease of carbonate matrices with
depth is observed. Nubia Formation is mainly composed of kaolinitic sandstone with
few contents of shale.
The effective porosity gradient ofNukhul Formation shows a general increase
from east to west and from south to northwest. On the other hand; with respect to
Nubia Formation, the effective porosity tends to increase from west to east and from
south to north.
The water saturation of Nukhul Formation is decreased from northeast to
southwest and from east to west and ranges from 15% to 100%. The water saturation
of the Nubia formation on the other hand, is decreased from southwest to the
northeast and ranged from }0% to }00%.
The hydrocarbon saturation ofNukhul Formation is increased from east to the west
and almost the same from southwest to the north and northwest and ranged from 70%
to 90%. Some gas content is only recorded in Nukhul Formation at the southwest.
The hydrocarbon saturation of Nubia Formation is decreased from the northeast to
the northwest and southwest and ranged from 50% to 1.00%.
The petroleum geology of the study area is also considered in terms of hydrocarbon
habitat (source, reservoir and cap rocks), hydrocarbon generation, migration and
accumulation and hydrocarbon entrapment (stratigraphic and structural traps).
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from the previous study, we recommended more study on the western side of Hilal
field area, which is Controlled with oil water Contact (o.w.c) and construct oil water
contact maps, then <lpplied such maps in future prospects.