الفهرس 
GEOLOOY AND STRATIGRAPHY OF THE STL1HED AREA
General tectonic considerationsOnly 14 pages are availabe for public view
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Abstract
SUMMARY AND CONCLL’SIONS
The present work deals with the application of
computer techniques for the quantitative estimation of
lithologies in subsurface sedimentary sequences on the
bas is of well-log data. The obtained results are used
for stratigraphical and sedimentological interpretations.
The method elaborated in this work is applied to six
wells drilled in the July Oilfield, Gulf of Suez area,
Egypt.
The thesis includes several aspects in order to
clarify the used procedure and its relation to the interpretation
of sedimentary sequences.
( 1) The first aspect of the thesis deals with the
geology, stratigraphy and general structural setting
of the Gulf of Suez and the Red Sea regions
in general and of the July Oilfield in particular.
The discussions are, here, illustrated by a geological
map of the Red Sea and Gulf of Suez regions,
maps showing the main faults in the July
Oilfield at different horizons and a correlation
chart for the six wells studied in the present
work. This last mentioned correlation chart is
drawn by the author on the basis of data given
in composite logs ( as provided by the 6eologists
of GL’PCO). The sediments drilled in the
July Oilfield range in age from Holocene to Late
Paleozoic.
(2 The Second aspect deals with the synthesis of the
information available in the literature on well
logging techniques and on the methods of interpretation
used for the processing of well-logging
data for the quantitative estimation of lithologies.
This aspect of the thesis is covered by
briefly describing the devices used in welllogging
and by discussing the nature of the various
and most probable lithology combinations
that are likely to be encountered during drilling.
The latter discussion deals also with the tectonic
movements of the Earth’s crust inducing the
development of various types of sedimentary associations.
This aspect of the thesis aims at
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clarifying certain concepts related to the relationship
between tectonism and sedimentation.
These concepts help in the prope+ interpretation
of well logs.
(3) The third aspect of the thesis deals with a description
and discussion of the procedure followed
in the quantitative estimation of lithologies.
This includes a discussion of the method followed
to prepare the well-log data in a form that can
be fed to the computer, together with a thorough
presentation of computer programmesprepared to
undertake the calculations involved in the procedure.
( 4) The fourth aspect of the thesis deals with the
use of the results of the processing of the welllog
data for stratigraphical and sedimentological
interpretation of the logged sequences in the
six wells considered in the present work. The
formations involved in this study are : the South
Gharib, Balayim, Kareem, Rudeis and Nukhul Formations
(of Miocene age) and the Nubia Sandstone
(of Early Cretaceous and Late Paleozoic
age:’. The discussions involved in this part of
the ·•·ork are illc.strated by a quantitative lithologic
log for each well. These logs present
graphically the results of the quantitative estirnation
of lithologies in the studied intervals.
They present also the stratigraphic subdivisions
proposed in the present work together with the
stratigraphical subdivisions ;;iven by the geologists
of GCPCO, on their composite logs, for
the considered intervals. The data of these six
logs are. fc.rthermore, summarized in a correlation
chart for the logged intervals in the six
wells involved in the present study.
The stratigraphic and sedimentological results or
the above mentioned inn:stigations may be summarized
as follows :
(1) A comparison of the lithologic logs obtained by
the procedure followed in the present work and
those given by the geologists of GUPCO, based on
the qualitative interpretation of electric logs
and the examinationof cuttings, shows that both
results match fairly well. Furthermore, it can
be noticed that the quantitative method used in
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this work provideBmore information on the detailed
lithologic constitutions of the studied stratigraphic
intervals and on the vertical changes in
lithology encountered in the logged sequences.
(2) It was possible to determine some important lithological
and sedimentological characteristics of
the logged rock units by using the results of the
programmes prepared during the present work. These
characteristics may be summarized as follows, for
each rock unit, arranged from top to base :
The South Gharib Formation consists of alternations
of anhydritic salt, clayey, dolomitic anhydrite
and sandy, clayey limestone. This formation
shows a lithology typical for the ”evaporite
association” deposited under fluctuating
extremely arid to subarid climates in a restricted
intracratonic basin.
The Balayim Formation is represented by its four
members (Hammam Faraun, Sidri, Feiran and Baba).
These members are alternations of shallow marine
(Hamman Faraun and S idri) and eva pori tic (Fe iran
and Baba) sequences. This formation seems
to have been deposited under similar climatic
conditions as those that prevailed during the
sedimentation of the South Gharib Formation in
a generally restricted intracratonic bas in with
intermittent periods of humid climates and or
free communication with the open sea (probably
from the north! .
The Kareem Formation is only logged in one of
the SIX studied wells. from the descriptions of
this formation provided by the composite logs of
the studied wells, it may be assumed that it
generally represents open marine sedimentation.
Only the lower part of the clayey Shagar ~!ember
and the evaporitic >larkha ~!ember of this formation
are quantitatively studied in the present
work. The lithology of this Markha Member (anhydritic
salt) suggests sedimentation in a restricted
intracratonic basin under extremely
arid climates. Thus, the Markha Member may be
considered to mark an episode of restricted (evaporitic)
development before the main phase of
open marine sedimentation which prevailed over
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the Gulf of Suez during the time of deposition of
the upper member of the Kareem Formation.
Tile Rudeis Formation was subdivided for the first
time-rnto four members by using the output of programmes’
LITHOL<X1Y’ and ’LDIKAGE’. These members
are Mreir, Asl, Hawara Sand and a sequence of
alternating clayey, calcareous sands and calcareous
shales, which may represent in i”L~ totalit·.·
or in part, the Mheiherrat ~!ember. Thec ::ower
boundary of the Rudeis Formation coulc not be
traced wit.~-] accuracy, as it was very dl:ficult
to differentiate the Mheiherrat }!ember ::>i the
Rudeis Formation from the ~ukhul Formatio~ by
purely petrographic methods (based on lithologlc
determinations from well logs).
Tile ~!reir >!ember of the Rudeis FormatioD consists
of shales. This is probably a sequence that was
laid down in a sedimentary basin under humid c: limates.
lt is interesting to note that this episode
of pellitic sedimentation precede in the
Gulf of Suez another phase of sedimentation characterized
by the deposition of evaporite ! ~larkha
~!ember of Kareem Format ion) . These two t~:pes of
deposits have been probably laid down in the same
closed basin but under different climatic conditions.
I’l-.e Asl \:ember of the Rudeis Formation co:J.sists
of ope,-, :narine marls, sometimes dolomi t i·: . The
Ha·”·ara Sand :,;ember. on the other hand. is composed
of coarse clastics, denoting that lt has
~)~·en d£>posited i~ a more dynamic enYironment.
However, the appreciable amounts of clavs !ound
ir. these sands suggest that the sea was still
deep enough to prevent effective winno”’·ing of
”’’e sediments. Tr.e influ..x of sand in :he Gulf
of Suez sedimentary basin may be either d:oe to a
period of ’tectonic activity or to a highly humid
c 1 ima tic phase, with in tense drainage of the
surrot:nding lands, or to both factors.
The seqt:ence of clayey, calcareous sands and calcareo:
os shales underlying the Hawara Sand in the
studied wells is probably marine and c’quivalent
to the· :\!beiherrat ~lember of the Rudeis Formation.
It may also, however. ;>clang partly to the upper
part of the ~ukhul Formation.
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The ::l:ukhul Formation in the drilled wells consists
of calcareous or dolomitic shales and dolomitic
marls or limestones. Referring this sequence, of
probably marine beds, to the Nukhul Formation remains,
however, questionable as long as no more
evidence of the detailed lateral variations is
available.
In the drilled wells there is no Oligocene sediments.
The marine Eocene, Paleocene and cpper
Cretaceous rocks are not properly logged, as they
were not suspected to contain hydrocarbons. The
Nubia Sandstone, however, was carefully logged,
because this formation constitutes the reservoir
for hydrocarbons in the well J 25. This formation
is subdivisible into three informal rock
units or ”series” (the ”A”, ”B” and ”C” series of
petroleum geologists). According -r:o these geologists,
the upper unit is probably ~!esozoic (corresponding
to the facies of the Nubia Sandstone
exposed over wide areas in Egypt). The ”B” and
”C ·• series, on the other band, are probably Paleozoic.
The ’\uO:Jia Sa:1dstone consists of clayey s:<:ods,
calcareous clayey sandstones, calcareotc!’o s:cales
and rare dolonitic clayey l::.:nestones. ::: :s
probably a paralic and or deltaic i::t ori;::·.
(3. :::~e pre,·iousl:; discussed s-r:ratigraphical a:1d
sedine::ttological results of the in-r:erpre:ation
o: :::e quantitati·;·~ lithological daw. oiJtalned
bY pro2essinh well-log data ~re o:1J..:,· pro’:isional
as lon~ as they ar2 ~ot supported ~~d cu~ple~ed
b·; ~,:ieq·~a:e micropaleontolo,:ical ar:d pe:ro:.:,-aphic
irn·es tiga tions on samples.
It can be concluded that -r:h•? metl:.od el:::.’ora-r:ed
in t!1e presen-r: study prm·ides a rapid meaCJs 10:!:” obtainin;;
a huge amount of detailed quantitative ll::l:ologic
data from well log information. The accuracy o! the
method can be better evaluated by comparing -r:he a:J.ta
provided from the analysis of cores with the resc:lts
based on •rell logging for the same cored inte-rvals.
The method can be systematically applied to the
in-r:ervals for which sufficient well log data are available
in order to revise with greater precision the
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stratigraphy of the different subsurface sedimentary
basins in Egypt. These studies must be accompanied by
parallel investigations on samples from the studied
intervals. In this ·way it is possible to consider that
subsurface geologists are pro\”ided with an optimum
me”t;,odology for subsurface stratigraphic work and syn”
t:C.es is.