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Radioactivity and Reservoir Characteristics
of Lower Miocene Rocks in Belayim Marine
Oil Field, Gulf of Suez, Egypt
By
Ibrahim Mohammad Moustafa Al-Alfy (M.Sc in Geophysics)
A thesis for the
Philosophy Doctor Degree of Science In Geophysics
Under supervision of
Prof. Dr. El-Sayed Mahmoud El-Kattan Dr. Mohammad Maher GadAllah
Professor of Applied Geophysics, Associate Professor of Geophysics,
Ex-Chairman of Geology Dept., Damanhour Faculty of
Egyptian Nuclear Materials Authority. Science, Alexandria University.
Dr. Reefat Ahmed El-Terb Associate Professor of Geophysics,
Exploration Division, Nuclear Materials Authority.
Geology Department
Faculty of Science
Zagazig University
2008
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ACKNOWLEDGEMENT
Firstly, I would like to thanks “Allah” who supplied me with strength and
patience to complete this work “Thanks God”.
I wish to express my sincere thanks and express my great appreciation to
Prof. Dr. El-Sayed Mahmoud I. El-Kattan Prof. of Applied Geophysics,
Nuclear Materials Authority, for his support, encouragement, constructive
advice through out his supervision.
I’m deeply indebted and special thanks to Dr. Mohamed Maher A. Gad
Allah Associate. Prof. of Geophysics, Geology Department, Damanhour
Faculty of Science, Alexandria University, for his support, helpful discussions
and being a great teacher, but no words of thanks and feelings are sufficient.
I would like to thank Dr. Reefat Ahmad El-Terb Associate. Prof. of
Applied Geophysics, Well Logging Department, Exploration Division, Nuclear
Materials Authority for his guidance and support during my research. Many
thanks to Prof. Dr. Said Rabie the head of Exploration division, Nuclear
Materials Authority
Further, I would like to express my gratitude to Prof. Dr. Fekry Abu-El
Ainain the head of Geology Department, Faculty of Science, Zagazig
University, many thanks to Prof. Dr. Ezat Abd-El Shafy and all the staff
members of the department and all staff members in NMA.
I wish to thank Petrobel for providing the data needed for this research.
Last but not least, this thesis is dedicated to Allah and I hope to accept it
from me. And then to My Parents, to My Wife and finally to My children's
Moaaz and Alaa.
Ibrahim Mohammad M. El-Alfy
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ABSTRACT
This thesis aimed to studying the radioactive characteristics and
evaluates the reservoir properties of the Lower Miocene rocks in Belayim
marine oil field, Gulf of Suez, Egypt. The available data include gamma
ray spectrometric data of the Lower Miocene rocks in seven wells, well
logging data of nine wells and core data of three wells of the study area.
The gamma ray spectrometric data were used to determine the oil
bearing zones, to define the clay type minerals and also to differentiate
between the radioactive elements in the shale content which effected
directly in the porosity values and oil accumulation. The radiometric
studies of the Lower Miocene rocks in the area under study show that,
there is no any high concentration of radioactive minerals.
Petrophysical studies on the reservoir rocks play an important role
in the discovery, evaluation and distribution of the productive zones. The
petrophysical properties of rock depend mainly on depositional
environment, mineralogy, geology and pore space framework.
Digitizing, gathering well log data and applying environmental
corrections are important to good log analysis. Multiwell normalization is
necessary to ensure that the results are accurate, consistent and
comparative from well to well, by using histograms. Interpretations of
well logs for estimating the clay volume, porosity, net pay thickness,
water saturation, hydrocarbon saturation and oil in place.
Plotting the reservoir characteristics in the form of 3D gives a clear
picture about the reservoir in the study area hence it is able to
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understanding and imaging the distribution of reservoir parameters in all
parts in the Rudeis Formation in the study area.
From the statistical analysis of the porosity and permeability in the
core samples, it is concluded that the lower Miocene Formations are a
good reservoirs. Studying the capillary pressure method play an important
role in determination the irreducible water saturation in the rock samples
and determined many other parameters for the reservoir rocks.
Integrating the available gamma ray spectrometric data and other
conventional well logs data in addition the core analysis data are used to
ensuring the thorium normalization method and studying the effect of the
clay mineral type to the pore geometry and the porosity permeability
relationship.
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v
CONTENTS
Page
Acknowledgement………………………………………………………….... i
Abstract……………………………………………………………………... ii
List of figures……………………………………………………………….... vi
List of tables………………………………………………………………..... xii
Chapter 1: INTRODUCTION 1
Chapter 2: GENERAL GEOLOGY 6
I) Stratigraphy………………………….……………………………….... 6
1.1) Kareem Formation…………………………………………….... 8
1.2) Rudeis Formation……………………………………………….. 11
II) Structure Geology…………………………………………..………..... 13
Chapter 3: RADIOACTIVITY 16
1) General……………..….……………………………………………… 16
1.1) Uses……………………………………………………………. 17 1.2) Spectral gamma ray tool……………………………………….... 17 2) Spectral gamma analysis……………….……………………………..... 18 2.1) Statistical analysis……….……………………………………..... 18 2.1.1) Kareem Formation……….……………………………….. 18 2.1.2) Rudeis Formation……….……………………………….... 22 2.2) Histogram………………………….…………………………..... 26 3) Clay minerals identification.……………….........……………………... 29 3.1) Thorium – Potassium crossplots...……….…………………….... 31 3.2) Scanning Electron Microscope Photographs………….………..... 38 4) Thorium Normalization……..………………………………………..... 38 4.1) General………….…………………………………………….... 38
4.2) Results and interpretations………….………………………….... 44
Chapter 4: CORE ANALYSIS TREATMENTS 52
4.1) Conventional core analysis…………………...…………………….... 53
4.1.1) Porosity……………………………………………………….. 53
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4.1.1.1) Statistical analysis of porosity data………………............ 57
4.1.2) Permeability………………………………………………….. 61
4.2.3) Porosity – Permeability relationship…………………………... 69
4.2.4) Permeability – Permeability relationship.………..……………. 72
4.2) Special core analysis……………………………………………….. 73
Formation resistivity factor…………………………………………... 74
Formation resistivity index………………………………………….... 75
4.3) Capillary pressure…………………………………………………… 77
4.4) Capillary pressure measurements..........................………………....... 79
4.5) Pore size distribution .................................................……………...... 91
Chapter 5: WELL LOG ANALYSIS 95
5.1) Data set available for well logging analysis……………………......... 96
5.2) Well log analysis……………………………………………………. 99
5.2.1) Digitizing well logs…………………………………………..... 101
5.2.2) Data gathering………………………………………………… 101
5.2.3) Data base editing tasks………………………………………. 101
5.2.4) Multi-well normalization tasks……………………………….... 104
5.2.5) Formation evaluation tasks…………………………………..... 112
5.2.5.1) Clay volume determination…………………………….... 112
5.2.5.2) Porosity models……………………………………….... 114
5.3) Input data and Interpreted results………...............………………….. 117
5.4) Tying between results of thorium normalization technique and thewell logs analysis results..................................................................... 132
5.5) Reservoir mapping………………………………………………….. 140 5.5.1) Iso-parameter maps…………………………………………... 140 5.5.2) Decision map………………………………………………….. 145 5.6) Reservoir 3-D slicing and cut off…………………………………...... 145
Chapter 6: SUMMARY AND CONCLUSIONS 165
REFERENCES 169
ARABIC SUMMARY 178
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LIST OF TABLES Table
No.
Page
(3-1)
Statistical analysis of spectral gamma of Kareem Formation in wells
BM 30, BM 35, BM 37, BMNW – 2, 113 M 27, 113 M 34 and total
Kareem Formation in Belayim marine oil field, Gulf of Suez, Egypt... 19
(3-2)
Statistical analysis of spectral gamma of Rudeis Formation in wells
BM 30, BM 35, BM 37, BM 57, BMNW – 2, 113 M 27, 113 M 34
and total Rudeis Formation in Belayim marine oil field, Gulf of Suez,
Egypt.................................................................................................... 23
(4-1)
Descriptive statistical analysis for the porosity of wells, 113-M-11
and 113-M-13, Kareem Formation, Belayim Marine oil field, Gulf of
Suez, Egypt........................................................................................... 57
(4-2)
Descriptive statistical analysis for the porosity of wells, 113-M-11
and 113-M-81, Rudeis Formation, Belayim Marine oil field, Gulf of
Suez, Egypt........................................................................................... 59
(4-3)
Descriptive statistical analysis for the horizontal permeability of
wells, 113-M-11 and 113-M-13, Kareem Formation, Belayim Marine
oil field, Gulf of Suez, Egypt................................................................. 64
(4-4)
Descriptive statistical analysis for the vertical permeability of well
113-M-13, Kareem Formation, Belayim Marine oil field, Gulf of
Suez, Egypt.......................................................................................... 66
(4-5)
Descriptive statistical analysis for the permeability of wells, 113-M-
11 and 113-M-81, Rudeis Formation, Belayim Marine oil field, Gulf
of Suez, Egypt........................................................................................ 67
(4-6)
Results derived from capillary pressure data of Kareem Formation in
well 113-M-11. Belayim marine oil field, Gulf of Suez, Egypt............ 81
(4-7)
Results derived from capillary pressure data of Rudeis Formation in
well 113-M-11. Belayim marine oil field, Gulf of Suez, Egypt............ 82
(5-1) Direct and indirect measurements of well log tools...................... 100
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(5-2) Available logging tools in every well.................................................... 100
(5-3) Shifts required for data normalization of Belayim marine wells........... 112
(5-4) Formation evaluation tasks.................................................................... 113
(5-5)
Tying percentage between thorium normalization results and well log
analysis results....................................................................................... 132
(5-6) Results of well log analysis of Rudeis Formation 140
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LIST OF FIGURES Figure
No. Page
(1-1)
Location map of the study area (Belayim marine oil field, Gulf of
Suez, Egypt)…………………………………………………………. 2
(2-1)
Stratigraphic column of Belayim oil fields, Gulf of Suez, Egypt.
(After Belayim Petroleum Co. 2005)……………………………….... 9
(3-1)
Histogram and cumulative frequency of K%, eU ppm and eTh ppm
radioactive elements of Kareem Formation in Belayim marine oil
field, Gulf of Suez, Egypt…………………………………………….. 28
(3-2)
Histogram and cumulative frequency of K%, eU ppm and eTh ppm
radioactive elements of Rudeis Formation in Belayim marine oil
field, Gulf of Suez, Egypt…………………………………………….. 30
(3-3)
Type of clay minerals identification by Thorium-Potassium crossplot
of Kareem Formation in Wells BM – 30 and BM – 35 in Belayim
marine oil field, Gulf of Suez, Egypt………………………………..... 32
(3-4)
Type of clay minerals identification by Thorium-Potassium crossplot
of Kareem Formation in Wells M - 37 and BMNW -2 in Belayim
marine oil field, Gulf of Suez, Egypt……………….………………… 33
(3-5)
Type of clay minerals identification by Thorium-Potassium crossplot
of Kareem Formation in Wells 113 - M - 27, 113 - M - 34 and total
Kareem Formation in Belayim marine oil field, Gulf of Suez,
Egypt………………………………………………………………… 35
(3-6)
Type of clay minerals identification by Thorium-Potassium crossplot
of Rudeis Formation in Wells BM – 30 and BM - 35 in Belayim
marine oil field, Gulf of Suez, Egypt…………………......................... 36
(3-7)
Type of clay minerals identification by Thorium-Potassium crossplot
of Rudeis Formation in Wells BM - 37 and BM - 57 in Belayim
marine oil field, Gulf of Suez, Egypt……………........................……. 37
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x
(3-8)
Type of clay minerals identification by Thorium-Potassium crossplot
of Rudeis Formation in Wells 113 - M – 27 and 113 - M - 34 in
Belayim marine oil field, Gulf of Suez, Egypt...................................... 39
(3-9)
Type of clay minerals identification by Thorium-Potassium crossplot
of Rudeis Formation in Wells BMNW - 2 and total Rudeis Formation
in Belayim marine oil field, Gulf of Suez, Egypt…………………...... 40
(3-10)
Scanning Electron Photographs illustrate the clay minerals of Rudeis
Formation, in Belayim marine oil field, Gulf of Suez, Egypt………... 41
(3-11)
Processed KD%, eUD% and DRAD data of wells BM - 30, BM - 35
and BM - 37 in Belayim marine oil field, Gulf of Suez, Egypt………. 45
(3-12)
Processed KD%, eUD% and DRAD data of wells BM - 57 and
BMNW - 2 in Belayim marine oil field, Gulf of Suez, Egypt………... 47
(3-13)
Processed KD%, eUD% and DRAD data of wells 113 - M - 27
and 113 - M - 34 in Belayim marine oil field, Gulf of Suez, Egypt….. 49
(4-1)
Histogram and cumulative frequency of total porosity of Kareem
Formation in well 113-M-11, Belayim Marine oil field, Gulf of Suez,
Egypt…………………………………………………………………. 58
(4-2)
Histogram and cumulative frequency of total porosity of Kareem
Formation in well 113-M-13, Belayim Marine oil field, Gulf of Suez,
Egypt………………………………………………………………….. 58
(4-3)
Histogram and cumulative frequency of total porosity of Rudeis
Formation in well 113-M-11, Belayim Marine oil field, Gulf of Suez,
Egypt………………………………………………………………… 60
(4-4)
Histogram and cumulative frequency of total porosity of Rudeis
Formation in well 113-M-81, Belayim Marine oil field, Gulf of Suez,
Egypt…………………………………………………………………. 61
(4-5)
Histogram and cumulative frequency of horizontal permeability of
Kareem Formation in well 113-M-11, Belayim Marine oil field, Gulf
of Suez, Egypt………………………………………………………... 65
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x
(4-6)
Histogram and cumulative frequency of horizontal permeability of
Kareem Formation in well 113-M-13, Belayim Marine oil field, Gulf
of Suez, Egypt………………………………………………………… 65
(4-7)
Histogram and cumulative frequency of vertical permeability of
Kareem Formation in well 113-M-13, Belayim Marine oil field, Gulf
of Suez, Egypt………………………………………………………… 67
(4-8)
Histogram and cumulative frequency of permeability of Rudeis
Formation in well 113-M-11, Belayim Marine oil field, Gulf of Suez,
Egypt…………………………………………………………………. 69
(4-9)
Histogram and cumulative frequency of permeability of Rudeis
Formation in well 113-M-81, Belayim Marine oil field, Gulf of Suez,
Egypt………………………………………………………………….. 69
(4-10)
Porosity-permeability relationship of Kareem Formation in well 113-
M-11, Belayim Marine oil field, Gulf of Suez, Egypt………………... 70
(4-11)
Porosity- horizontal permeability relationship of Kareem Formation
in well 113-M-13, Belayim Marine oil field, Gulf of Suez, Egypt…... 71
(4-12)
Porosity- vertical permeability relationship of Kareem Formation in
well 113-M-13, Belayim Marine oil field, Gulf of Suez, Egypt…… 71
(4-13)
Porosity-permeability relationship of Rudeis Formation in well 113-
M-11, Belayim Marine oil field, Gulf of Suez, Egypt………………... 72
(4-14)
Permeability- permeability relationship of Kareem Formation in well
113-M-13, Belayim Marine oil field, Gulf of Suez, Egypt…………... 72
(4-15)
Relationship between porosity and formation resistivity factor for
Rudeis formation, in well 113-M-81, Belayim marine oil field, Gulf
of Suez, Egypt………………………………………………………… 75
(4-16)
Relationship between resistivity index and water saturation for
Rudeis Formation, in well 113-M-81, Belayim marine oil field, Gulf
of Suez, Egypt………………………………………………………… 77
(4-17)
Relationships between the porosity and pressure for Rudeis
Formation samples in well 113-M-81 of Belayim marine oil
field, Gulf of Suez, Egypt...................................................................... 78
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(4-18)
Relationship between pressure and porosity for Rudeis Formation in
113-M-81 well, Belayim marine oil field, Gulf of Suez, Egypt............ 79
(4-19)
Capillary pressure and brine water saturation relationship of Kareem
Formation, Belayim marine oil field, Gulf of Suez, Egypt…………... 82
(4-20)
Capillary pressure and brine water saturation relationship of Rudeis
Formation, Belayim marine oil field, Gulf of Suez, Egypt….......…… 83
(4-21)
Relationship between irreducible water saturation and different
capillary pressure parameters of Kareem Formation, Belayim marine
oil field, Gulf of Suez, Egypt................................................................. 84
(4-22)
Relationship between effective porosity and different capillary
pressure parameters of Kareem Formation, Belayim marine oil field,
Gulf of Suez, Egypt............................................................................... 85
(4-23)
Relationship between different capillary pressure parameters of
Kareem Formation, Belayim marine oil field, Gulf of Suez, Egypt...... 86
(4-24)
Relationship between irreducible water saturation and different
capillary pressure parameters of Rudeis Formation, Belayim
marine oil field, Gulf of Suez, Egypt.............................................. 88 (4-25)
Relationship between effective porosity and different capillary
pressure parameters of Rudeis Formation, Belayim marine oil
field, Gulf of Suez, Egypt.................................................................. 89
(4-26) Relationship between different capillary pressure parameters of
Rudeis Formation, Belayim marine oil field, Gulf of Suez, Egypt....... 90
(4-27)
Relationship between pore throat radius and pore size distribution for
some samples of Rudeis Formation, Belayim marine oil field, Gulf of
Suez, Egypt........................................................................................... 93
(4-28)
Relationship between pore throat radius and pore size distribution for
some samples of Rudeis Formation, Belayim marine oil field, Gulf of
Suez, Egypt........................................................................................... 94
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i
(4-29)
Relationship between pore throat radius and pore size distribution for
all Rudeis Formation, Belayim marine oil field, Gulf of Suez,
Egypt................................................................................................... 94
(5-1)
Normalization histogram of gamma ray log in well BMNW-2,
Belayim marine oil field, Gulf of Suez, Egypt...................................... 107
(5-2)
Normalization histogram of density log in well BMNW-2, Belayim
marine oil field, Gulf of Suez, Egypt..................................................... 108
(5-3)
Normalization histogram of neutron log in well BMNW-2,
Belayim marine oil field, Gulf of Suez, Egypt.............................. 110
(5-4) Normalization histogram of Sonic log in well BMNW-2, Belayim
marine oil field, Gulf of Suez, Egypt. 111
(5-5)
Input data and interpreted analysis of well (BM 30), Kareem and
Rudeis Formations, Belayim marine oil field, Gulf of Suez, Egypt...... 119
(5-6)
Input data and interpreted analysis of well (BM 35), Kareem and
Rudeis Formations, Belayim marine oil field, Gulf of Suez, Egypt...... 120
(5-7)
Input data and interpreted analysis of well (BM 37), Kareem and
Rudeis Formations, Belayim marine oil field, Gulf of Suez, Egypt...... 122
(5-8)
Input data and interpreted analysis of well (BM 57), Kareem and
Rudeis Formations, Belayim marine oil field, Gulf of Suez, Egypt...... 123
(5-9)
Input data and interpreted analysis of well (BMNW-2), Kareem and
Rudeis Formations, Belayim marine oil field, Gulf of Suez,
Egypt.................................................................................................... 125
(5-10)
Input data and interpreted analysis of well (BMNW-3), Kareem and
Rudeis Formations, Belayim marine oil field, Gulf of Suez,
Egypt.................................................................................................... 126
(5-11)
Input data and interpreted analysis of well (113-M-27), Kareem and
Rudeis Formations, Belayim marine oil field, Gulf of Suez,
Egypt.................................................................................................... 128
(5-12)
Input data and interpreted analysis of well (113-M-34), Kareem and
Rudeis Formations, Belayim marine oil field, Gulf of Suez,
Egypt................................................................................................... 129
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(5-13)
Input data and interpreted analysis of well (113-M-81), Kareem and
Rudeis Formations, Belayim marine oil field, Gulf of Suez,
Egypt................................................................................................... 131
(5-14)
Relationship between thorium normalization results and well log
analysis results of BM-30 well for Rudeis Formation in Belayim
marine oil Field, Gulf of Suez, Egypt.................................................. 133
(5-15)
Relationship between thorium normalization results and well log
analysis results of BM-35 well for Rudeis Formation in Belayim
marine oil Field, Gulf of Suez, Egypt.................................................. 134
(5-16)
Relationship between thorium normalization results and well log
analysis results of BM-37 well for Rudeis Formation in Belayim
marine oil Field, Gulf of Suez, Egypt.................................................. 135
(5-17)
Relationship between thorium normalization results and well log
analysis results of BM-57 well for Rudeis Formation in Belayim
marine oil Field, Gulf of Suez, Egypt.................................................. 136
(5-18)
Relationship between thorium normalization results and well log
analysis results of BMNW-2 well for Rudeis Formation in Belayim
marine oil Field, Gulf of Suez, Egypt.................................................. 137
(5-19)
Relationship between thorium normalization results and well log
analysis results of 113-M-27 well for Rudeis Formation in Belayim
marine oil Field, Gulf of Suez, Egypt.................................................. 138
(5-20)
Relationship between thorium normalization results and well log
analysis results of 113-M-34 well for Rudeis Formation in Belayim
marine oil Field, Gulf of Suez, Egypt.................................................. 139
(5-21)
Formation evaluation parameters of Rudeis Formation, Belayim
marine oil field, Gulf of Suez, Egypt..................................................... 142
(5-22)
Formation evaluation parameters of Rudeis Formation, Belayim
marine oil field, Gulf of Suez, Egypt................................................... 144
(5-23)
Decision map to development the Rudeis Formation wells in Belayim
marine oil field, Gulf of Suez, Egypt..................................................... 145
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(5-24)
Reservoir 3D Slicing and Cut Off of Shale Volume of Rudeis
Reservoir in Belayim Marine Oil Field, Gulf of Suez, Egypt............... 149
(5-25)
Reservoir 3D Slicing and Cut Off of Total porosity of Rudeis
Reservoir in Belayim Marine Oil Field, Gulf of Suez, Egypt............... 152
(5-26)
Reservoir 3D Slicing and Cut Off of Effective porosity of Rudeis
Reservoir in Belayim Marine Oil Field, Gulf of Suez, Egypt............. 154
(5-27)
Reservoir 3D Slicing and Cut Off of Water Saturation of Rudeis
Reservoir in Belayim Marine Oil Field, Gulf of Suez, Egypt............... 156
(5-28)
Reservoir 3D Slicing and Cut Off of Hydrocarbon Saturation of
Rudeis Reservoir in Belayim Marine Oil Field, Gulf of Suez, Egypt... 158
(5-29)
Reservoir 3D Slicing and Cut Off of Bulk Pore Volume of Rudeis
Reservoir in Belayim Marine Oil Field, Gulf of Suez, Egypt............... 161
(5-30)
Reservoir 3D Slicing and Cut Off of Oil in Place of Rudeis Reservoir
in Belayim Marine Oil Field, Gulf of Suez, Egypt................................ 163
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Chapter -1 Introduction
1
CHAPTER - ONE INTRODUCTION
Belayim marine oil field was discovered in 1961. Since 1961 till
now, more than 150 wells were drilled for development of this field. This
extensive development phase in such field is based mainly on the
evaluation of reservoir characteristics. Accordingly, the main goal for the
present study is to contribute through the petrophysical laboratory
measurements and well logging analysis to discover the reservoir
characterization of the Kareem and Rudeis Formations in this area for
more development and exploration activities.
Belayim marine oil field is located between Latitude 28○ 34` 45`` -
28○ 38` 32`` N and Longitude 33○ 05` 17`` - 33○ 10` 38`` E in the eastern
side of the Gulf of Suez, 165 Kms southeast of the Suez City. The field
covers an area of about 9 Km2 when it discovered in 1961, but with more
exploration the Field covers now an area more than 25 Km2 at the west of
Sinai shoreline (Fig. 1-1) and generally in deep marine water (30-40 m.).
Belayim marine oil field produces oil from the Miocene and Pre-Miocene
reservoirs. The Miocene reservoirs include the Kareem and Rudeis
Formations. The Kareem and Rudeis Formations are of prime interest in
this work, where rocks of high hydrocarbon potential in terms of source,
reservoir and seal are encountered in these units.
Well logging and core analysis data were obtained from the
Egyptian General Petroleum Corporation (EGPC) and the Belayim
Petroleum Company (Petrobel). Nine well logs which represent the
Lower Miocene rocks and subsurface core analysis reports for 3 wells
were available for this research.
There are 7 wells having the gamma ray spectrometric logs
involving the total gamma ray log, equivalent Uranium log, equivalent
thorium log and Potassium percent log were used to studying the
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Chapter -1 Introduction
2
Fig. (1-1): Location m
ap of the study area of Belayim
marine oil field, G
ulf of Suez, Egypt
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Chapter -1 Introduction
3
radioactive properties of the Lower Miocene rocks in Belayim marine oil
field.
Spectrometric data play a very important role in reservoir
evaluation because it gives a good idea about the rock radiation and rocks
lithology. The clay mineral identification from the spectrometric logs
guide to know what the effect of the porosity upon permeability, where
the effect different according to the clay mineral type. We also can
determined the oil bearing zones in the reservoir by the thorium
normalization technique which applied first time using the well logging
data in this research.
Core analysis is very important part of an overall reservoir
evaluation. Conventional and special core analysis provide direct
evaluation of reservoir properties and also furnish a basis for calibrating
other evaluation tools such as logs. Conventional core analysis data in
this research include porosity, permeability and density, while special
core analysis data includes the electrical properties of the rocks such as
water saturation, resistivity index and capillary pressure. From the
capillary pressure we determined the irreducible water saturation for the
different core sampler at different pressures. The studied core analysis
have been investigated using available data in three wells, they are 113-
M-11, 113-M-13 and 113-M-81.
Formation evaluation involves the use of core analysis, logging
after drilling (LAD) to estimate certain formation characteristics such as
shale volume, porosity, water saturation, net pay thickness and oil in
place. Electric logs are used to determine fluid type and amount,
calculation of reserves, determination of productivity and determination
of lithology. The studied oil field has been investigated using available
data in nine representive wells, for the purpose of evaluation of
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Chapter -1 Introduction
4
hydrocarbon potentiality. They are: BM-30, BM-35, BM-37, BM-57,
BMNW-2, BMNW-3, 113-M-27, 113-M-34 and 113-M-81.
Plotting the reservoir characteristics in the form of 3D gives a clear
picture about the reservoir in the study area and helps to understanding
and imaging the distribution of reservoir parameters in all parts in the
Rudeis Formation in the study area. To fulfill the objectives of this thesis, the following plan of study was suggested:
Aims of study:
1- Studying the radioactive characteristics of the Lower Miocene
rocks.
2- Evaluate the reservoir parameters of the Lower Miocene rocks.
3- Plotting the lower Miocene reservoir in the form of 3 Dimension
using the available well logging data.
Office work:
1- Determined the radioactive zones in the study rocks.
2- Making statistical analysis for the gamma ray spectrometric data
and defined the clay type minerals.
3- Digitizing the well log data, data base editing, Multiwell
normalization.
4- Evaluate the reservoir parameters and determining the volume of
shale, water saturation, hydrocarbon saturation, total porosity,
effective porosity and oil in place.
5- Output the well log analysis in form of 3 dimension
6- Using the core sample analysis to evaluate the reservoir
parameters.
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Chapter -1 Introduction
5
To perform these aims, all the available analog data are digitized
using median scanner and grapher program (2.04). The SPSS software
program is used to making interpolation for the data and some statistical
process. Editing and arranging of well logging data in the data base are
performed to be ready for applying environmental corrections. The
spectrometric gamma ray log data are used to evaluate the significant
radioactive zones in the Lower Miocene reservoir. The environmental
corrections include mud weight, borehole and salinity and then
calculation petrophysical parameters by using log wizard software.
Plotting the reservoir parameters in the 3 dimension form by using the
Tec-plot 10 software.
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Chapter -2 General Geology
6
CHAPTER - TWO GENERAL GEOLOGY
I- STRATIGRAPHY: According to Brooks and Hagras (1971) the Miocene sea laid
down sediments upon widely different surfaces (pre-Cambrian Basement,
Cretaceous, Eocene and Oligocene). The Miocene sediments are
deposited on a surface of marked relief. This has a strong bearing on the
understanding of the rapid lateral facies changes.
The Gulf represented, moreover, a subsiding graben in which fault
activity accentuated these considerable differences in facies and
thickness. Two clearly distinct phases can be recognized in the Miocene.
The first phase was the clastic phase with filling-up of the Gulf and a
consequent smoothing affect of the strong pre-Miocene relief (Rudeis and
Kareem sediments). This is succeeded by an evaporitic phase, with the
Formation of typical evaporate deposits (Belayim, South Gharib and Zeit
Formations). Rapid lateral facies changes are a striking feature of the
Miocene evaporates. From paleontological evidence in some areas, the
anhydrites of the lower evaporate group (gypsum I & II) grade into shales
and marls.
In some areas (Morgan, F-2, Belayim marine, Hurghada, etc..), the
Markha member is absent. This suggests that these areas were all
structurally high during lower Kareem time, probably immediately after
the deposition of the Markha which must have been locally removed.
Movement is thought to have been taken place from time to time
along the faults (or fault zones) bounding the basins with consequent
intermittent replenishment of source materials. The interbedded sands and
shales of Belayim and Morgan fields might seem to suggest a large
number of minor uplifts in the source areas. Wherever, it seems more
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Chapter -2 General Geology
7
reasonable to assume that both fields lay in areas near the limit of sand
transportation, and that sand percentage would increase toward the source
area (Brooks and Hagras, 1971).
The stratigraphic succession penetrated in the study area, Fig. (2-1),
ranges between Paleozoic to Recent. The data obtained from the wells
indicated the presence of an important unconformity between the
Miocene and Pre-Miocene (Barakat, 1982).
The Miocene rocks in the study area can be divided into two main
groups; Lower Miocene (Gharandal) and Middle Upper Miocene (Ras
Maalab) from the bottom to the top. The Gharandal group includes the
Nukhul, Rudeis and Kareem Formations, while the Ras Maalab group
comprises Belayim, South Gharib and Zeit Formations. The Nukhul
Formation is the term used for the oldest Miocene which was deposited in
the Gulf. This unit is defined by age rather than rock type as it consist of
shale, marl, sand, sandstone, limestone and conglomerate.
The Belayim Formation is formally subdivided into four members.
The upper one is composed mainly of shale with sand and sandstone
streaks, this member is usually referred to as the Belayim clastics which
stand for the formal name (Hammam Faraun member). The lower three
members are from top to bottom ; Feiran, Sidri and Baba, which are
collectively referred to as Belayim evaporates.
South Gharib Formation is divided into two subunits; An upper one
consisting of several anhydrite and salt beds with subordinate shale and
sand streaks. A lower one which is composed of two massive salt bodies
separated by much thinner anhydrite and shale beds, these salts are
locally Known as salt 6 and 6-A
Zeit Formation is usually composed of thin shale, anhydrite
intercalations, sand and sandstone, the thickness of Zeit Formation is
generally increases in the Southwest direction.
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Chapter -2 General Geology
8
The Lower Miocene (Kareem and Rudeis Formations) are of prime
interest in the study area, as them composed of rocks with hydrocarbon
potentials in terms of source, seal and excellent reservoir. (Nasser M.
Hassan et al., 1995).
I.1- Kareem Formation: In Belayim marine oil field as in the others (Morgan, Amal,
Hurghada, Matarma and Sukheir), the contact between Kareem and
Rudeis is problematic due to the absence of the Markha member. (Brooks
and Hagras, 1971). In Belayim marine field, the Kareem Formation lies
conformably between Rudeis and Belayim Formations, the Rudeis-
Kareem contact is taken according to the predominance of the shale in the
section and on electric log correlations. Lithological composition and
thickness vary to a considerable extent.
Although the sandy materials increase from northwest to southeast,
generally the Kareem section is mainly composed of calcareous shale
(more than 80%). North of the Belayim marine field, the Kareem
Formation is composed of shale only as in (K-1 and Rahmi wells). The
sands of Kareem are oil-bearing. The sandstone reservoirs show porosity
ranging from 12% to 22% and oil productive in Kareem. (Brown, 1978)
and (El Kawa et al., 1990). The Kareem Formation is dominated by
sandstone where productive, but one-third of Belayim reserves are in
carbonates. (Salah and Alsharhan, 1997) reported that Kareem net-pay
thickness to 195 meters, porosity from 9-33%, and permeability from 20-
730 millidarcies.
The Kareem Formation conformably overlies the Rudeis Formation
and consists mainly of interbedded sandstone, shale and carbonates with
thin streaks of anhydrite in the lower part of the section. Generally, the
sand percentage increases toward the marginal boundaries, (Tawfik et
al., 1993). The thickness of the Kareem Formation in the southern Gulf of
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Chapter -2 General Geology
9
Fig. (2-1): Stratigraphic column of
Belayim oil fields, Gulf of Suez,
Egypt. (After Belayim Petroleum
Co. 2005)
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Chapter -2 General Geology
10
Suez varies from 15 to 539 m. The depositional setting of the Kareem
Formation was shallow, partly open marine, with localized lagoonal
conditions.
Hassan N. M. et al. 1995 Reported that, the Kareem Formation
deposition is in the form of a fan system. A large fan trending NE-SW
observed across El Morgan field. Another fan is located in the western
side. The possible sand source for such fans may be from the Sinai
mountains in the eastern side of the Gulf of Suez.
The Kareem Formation is 1400 ft thick and is the youngest
Formation in the Gharandal Group. It is composed of grey, highly
calcareous shales, grading to marl, with occasional grey argillaceous
limestone intercalations in the upper part, and white to light grey massive
anhydrite interbeds in the lower part. The Kareem Formation is
subdivided into two members, a lower Markha and an upper Shagar
(Said, 1990).
Faunally, the Kareem Formation is separated from the Rudeis by
the first occurrence of Orbulina suturalis at its base, and it encompasses
the entire N9-11 planktonic foraminiferal as well as the NN5
Sphenolithus heteromorphus nannoplankton zones. (El-Heiny and
Martini, 1981; Arafa, 1982; Evans, 1988). The Kareem Formation
straddles the Langhian/Serravalian boundary (Evans, 1988) or is of
Langhian age (Said, 1990) within the Middle Miocene. This contradicts
the Early Miocene age reported by the Stratigraphic Subcommittee of
the National Committee of Geological Sciences (1974).
Deposition of the Kareem Formation is inferred to have occurred
under outer shelf to upper bathyal environments, based on benthonic
foraminiferal biofacies and decreasing planktonic to benthonic ratios
(Evans, 1988). This was also confirmed by the findings of (Ahmed and
Pocknall, 1994), who recorded a higher percentage of marine
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Chapter -2 General Geology
11
palynomorphs in a number of onshore and offshore wells drilled in the
Gulf of Suez. The Kareem Formation is considered by some authors to be
the main oil source rocks in the Gulf area (Schlumberger, 1984). It
carries the Pay Zones IV-A and V of the Belayim land oil field (Said,
1990). The interpreted sands in the Kareem Formation provide excellent
reservoirs with porosities ranging from 11–24% (Schlumberger, 1984).
Dinoflagellate cyst assemblages indicate deposition of the Kareem
Formation under marine conditions in its lower and middle parts. The
upper part of the Formation was deposited under continental (deltaic)
conditions. El Beialy and Ali, (2002).
Aly et al; 1995 Reported that, in Belayim marine oil field,
according to the laboratory measurements, the Kareem Formation is
composed of calcareous shaly sandstone, while in well logging analysis it
is formed of arenaceous shaly limestone. This is due to that the selected
core samples were cut from the sandstone bodies encountered within the
Kareem Formation and accordingly, the sandstone content is higher than
the limestone content. the Kareem Formation is considered as good
reservoir rocks due to their high values of effective porosity and
permeability. The determined hydrocarbon saturation (Sh) in both
analyses indicates that the Kareem Formation is considered of high
potentiality for producing large quantities of oil in this study area.
I.2- Rudeis Formation: According to (Takasu, et al. 1982), the Rudeis Formation lies
conformably between Nukhul and Kareem Formations. The thickness of
the Rudeis Formation varies between 320 m to 884 m in west Bakr oil
field. The Rudeis Formation is mainly represented by sandstone and
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Chapter -2 General Geology
12
shales. The thickness of Rudeis Formation decreased generally toward the
west, northwest and southwest directions.
The Rudeis Formation varies greatly in lithology and thickness in
response to the irregular paleorelief over which sedimentation took place.
It consists mainly of shale and limestone interbedded with sandstone. The
unit varies in thickness from about 11 to 1304 m. The depositional setting
of the Rudeis Formation is considered shallow to deep marine,
(Alsharhan and Salah 1994).
The Net Pays of Rudeis are present over most of the Gulf of Suez.
The Rudeis sandstone has produced oil from four fields in the region. It
has an average porosity of 22% and a net pay thickness ranging from
about 6 to 36 m. Three major alluvial fans of sand are recorded in the
southern Gulf of Suez: 1. a northern fan, with a 14% average porosity,
whose source is Gebel Zeit; 2. an eastern fan with a 25% average
porosity, whose source is Sinai Massif; and 3. a southern fan with a 20%
average porosity, whose source is the Esh El Mellaha Range, (Alsharhan
and Salah 1994).
The Rudeis Formation was deposited in a relatively deep water
environment, based on the abundance fluctuations in miospores and
dinoflagellates. However, the miospores recovered from the Rudeis
Formation give an equivocal signal with respect to depositional
environment. Such observed incursions of terrestrial elements in the
Rudeis Formation could indicate that they might have been carried about
within the basin of deposition by the waters of the Mediterranean Sea, or
that they were displaced into a deep water setting. (El Beialy and Ali
2002).
The basal part of the Rudeis Formation contains occasional thin
yellowish grey massive sandy limestones. The Formation contains high
ratios of planktonic and benthonic species (Evans, 1988) and belongs to
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Chapter -2 General Geology
13
the Globigerinoides trilobus and Globigerinoides sicanus/Praeorbulina
glomerosa foraminiferal zones (El-Heiny and Martini, 1981; Said,
1990). The Rudeis Formation also contains nannoplankton of Martini’s
(1971) zones NN3-NN4. Its age is assigned to the Early Miocene (Early–
Middle Burdigalian) according to these authors (Balduzzi et al., 1978;
Evans, 1988; Youssef et al., 1988; Said, 1990). Other workers consider
the basal Rudeis of N5 age (Scott and Govean, 1985). However (Evans,
1988) and (El-Heiny and Martini, 1981) interpret the basal Rudeis as no
older than NN3, or 19 Ma. Deposition of the Rudeis Formation is thought
to have taken place under open marine (EGPC, 1964) or upper bathyal to
upper middle bathyal conditions (Evans, 1988), based on the occurrence
of deep water phenotypes of Uvigerina, Bulimina, Cassidulina and
Dentalina. The sandstones present in the Rudeis Formation are attributed
to submarine fan deposition, derived from the cliffs of basement
bordering of the Gulf rift valley (Balduzzi et al., 1978).
The Lower Rudeis Formation was deposited during the rift-climax
stage at which time many of the intra-block faults became inactive and
fault activity was progressively localized onto the master after the start of
rifting (Patton et al., 1994; Sharp et al., 2000b; Gawthorpe et al.,
2003; Jackson et al., 2006).
II- STRUCTURE GEOLOGY The present-day Gulf of Suez rift, together with the Red Sea
oceanic basin and the Aqaba–Dead Sea transform systems, comprise the
Sinai triple junction, which initiated during the northeasterly movement
of Arabia away from Africa. The age of such movements is mainly
Neogene (Fichera et al., 1992). The rifting commenced in the pre-
Miocene, with the maximum tectonic subsidence, accompanied by
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Chapter -2 General Geology
14
magmatic events, occurring in the late Oligocene–early Miocene
(Gandino et al., 1990).
Interpretation of geological and geophysical data indicates that the
Gulf of Suez consists of elongated troughs containing several submarine
ridges (elongated structural highs). Both troughs and highs have the same
trend as the Gulf of Suez (northwest-southeast). These highs are dissected
by some high-angle discordant elements that trend northeast-southwest
and east-northeast– west-southwest. These later elements are viewed as
cross faults that segment the highs. The distinctive structural and
stratigraphic features within the subbasins of the rift vary in both the
northern and central provinces of the Gulf, and even within the same
province. The stratigraphic succession and depth to basement also varies
from one structural high to another and also within the same high
(Rashed, 1990; Saoudy, 1990). The temperature gradient is in agreement
with the proposed dog-leg model for the Suez rift. This may be explained
by the axis of the rift being associated with thin crust and upwelling of
hot mantle by convection (Meshref, 1990).
The Suez Rift forms the NW–SE-trending arm of the Cenozoic
Red Sea rift system that formed in response to Late Oligocene–Early
Miocene rifting of the African and Arabian plates (Garfunkel and
Bartov, 1977; Colletta et al., 1988; Lyberis, 1988; and Patton et al.,
1994). The rift is 300 km long and up to 80 km wide and is delineated on
both margins by large-scale NW–SE-striking normal fault zones that
define half-grabens.
The general structures of the area shows that the area was subjected
to two types of faults, the major type trends to the northeast and
southwest direction parallel to the gulf trends of the northwest and
southeast direction parallel to the Aqaba trend producing three structural
element, approximately parallel to each other, almost running NW – SE
-
Chapter -2 General Geology
15
along the Gharib basin, that incorporates about 18 traps with qualified
reservoirs in the Miocene overlap and in the pre-Miocene pre-existing
fault blocks. The nature of the fault systems that exist in such basin
accounted for a general NE tilt for the majority of the fault blocks
(Takasu, et al, 1982).
It can be concluded that, the surface of Kareem Formation was
affected by two major right lateral strike-slip faults trending in ENE
direction are extended from the eastern side of the Sinai plate to the
central part of the Gulf. They restricted between them several
mesostructures from faults and folds which demonstrate the excepted
interaction between the different tectonic trends prevalent in the area. The
faults are oriented in the NW- and NNW directions while the folds are
trending in N-S direction, (Mounir, A.I., 1995).
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Chapter – 3 Radioactivity
16
CHAPTER – THREE
RADIOACTIVITY 1 – GENERAL:
Natural radiation in rocks comes essentially from only three elemental
sources: the radioactive elements of the thorium family, of the uranium –
radon family and of the radioactive isotope of potassium K40 (Adams and
Weaver, 1958). Quantitatively, potassium is by far the most abundant of the
three elements but its contribution to the overall radioactivity in relation to
its weight is small. In reality, the contribution to the overall radioactivity of
the three elements is of the same order of magnitude, the abundance seeming
to be the inverse of the contribution in energy: a small quantity of uranium
has a large effect on the radioactivity; a large quantity of potassium has
small effect.
The gamma ray log is a record of a formations radioactivity. The
radiation emanates from naturally occurring uranium, thorium and
potassium. The simple gamma ray log gives the radioactivity of the three
elements combined, while the spectral gamma ray log shows the amount of
each individual element contributing to this radioactivity. The geological
significance of radioactivity lies in the distribution of these three elements.
Most rocks are radioactive to some degree, igneous and metamorphic rocks
more so than sediments. However, amongst the sediments, shales have by
far the strongest radiation. It is for this reason that the simple gamma ray log
has been called the "shale log", although modern thinking shows that it is
quite insufficient to equate gamma ray emission with shale occurrence. Not
all shales are radioactive, and all that is radioactive is not necessarily shale.
(Rider, 1996)
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Chapter – 3 Radioactivity
17
1.1 – USES:
The gamma ray log is still principally used quantitatively to derive
shale volume. Qualitatively, in its simple form, it can be used to correlate, to
suggest facies and sequences and, of course, to identify lithology
(shalyness). The spectral gamma ray can be used additionally to derive a
quantitative radioactive mineral volume and a more accurate shale volume.
Qualitatively it can indicate dominant clay mineral types to give indications
of depositional environment and indicate fractures and help to localize
source rocks.
1.2 – Spectral gamma ray tool:
The spectral gamma ray tool consists of a scintillation counter and
photo multiplier, the sodium iodide crystal has a much great volume,
typically 5 cm in diameter and 20 cm long and so gives the tool of much
better counting sensitivity. When a gamma ray passes through a scintillation
crystal, it not only causes a flash, but the intensity of that flash depends on
the energy of the incident gamma ray. This characteristic is used by the
spectral gamma ray tool, with its large scintillator crystal, to identify the
gamma radiations in several, pre-defined energy bins or windows. These
windows are designed to separate the distinctive energy peaks of the
individual radioactive elements namely bracketing the energies of 2.62 MeV
for thorium, 1.76 MeV for uranium and 1.46 MeV for potassium.
In the present study the spectral gamma ray log is recorded in seven
wells, the data of these wells were digitized by using simple scanner and
Grapher 2.03 software, the digitized data for all wells at different depth
intervals can be converted to a one meter regular interval by using SPSS
software (ver. 10). After data gathering and editing it in data base tasks, the
data were analyzed and using to determination the clay type minerals and the
oil bearing zones in the rocks.
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Chapter – 3 Radioactivity
18
2 – Spectral gamma analysis:
The digitized spectrometric gamma ray data were analyzed to known
the distribution of each radioactive element in the formation rocks. The
spectral gamma data were analyzed by two methods, the statistical analysis
and histogram.
2.1 – Statistical analysis:
The statistical analysis of the spectral gamma ray data of the study
rocks (Kareem and Rudeis formations) in the seven wells, BM 30, BM 35,
BM 37, BM 57, BMNW 2, 113 M 27 and 113 M 34 are computed.
2.1.1 – Kareem Formation:
The spectral gamma ray data for Kareem formation in the study area
are available only in six wells; the statistical analysis of the three radioactive
elements will be mentioned in all wells.
2.1.1.1 – Well BM 30:
The summary of descriptive statistical analysis of the spectral gamma
in this well is represented in table (3-1a). From this table, it can be observed
that, the potassium percent (K%) values in this well are ranges from 0.63 %
to 1.35 % and the mean value is 0.93 % while the stander deviation is about
0.16 % for 36 readings. The mean equivalent uranium concentration (eU
ppm) in this well is about 3.01 ppm and the concentration of it ranging from
1.46 ppm to 4.21 ppm, while the stander deviation is 0.64 ppm. For 36
equivalent thorium concentration readings (eTh ppm) the mean value of
them is 6.26 ppm and the concentration of eTh ranges from the minimum
value 3.44 ppm to the maximum value 8.7 ppm, the value of 1.27 ppm is the
stander deviation of the eTh readings in this well.
2.1.1.2 – Well BM 35:
The potassium values in this well as in table (3-1b) ranging between
0.41 % and 1.14 % and its mean is about 0.81 %, while the stander deviation
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Chapter – 3 Radioactivity
19
Table (3-1): Statistical analysis of spectral gamma of Kareem Formation in the
studied wells of Kareem Formation in Belayim marine oil field, Gulf
of Suez, Egypt.
K % eU ppm eTh ppm Mean 0.81 2.21 5.69 St. Dev. 0.19 0.77 1.37 Min. 0.41 1.38 2.83 Max. 1.14 4.06 7.33 Sum 48.89 132.58 341.32 Count 60.00 60.00 60.00
(A) BM - 30 Well (B) BM-35 well
K % eU ppm eTh ppm Mean 0.98 1.53 5.95 St. Dev. 0.20 0.83 1.29 Min. 0.32 0.19 2.20 Max. 1.43 4.27 8.80 Sum 304.55 475.16 1850.75 Count 311.00 311.00 311.00
(C) BM-37 well (D) BMNW-2 well
K % eU ppm eTh ppm Mean 0.73 1.34 2.15 St. Dev. 0.20 0.53 1.03 Min. 0.35 0.50 0.36 Max. 1.43 3.09 6.11 Sum 129.45 239.38 382.42 Count 178.00 178.00 178.00
(E) 113 - M - 27 Well (F) 113 - M - 34 Well
K % eU ppm eTh ppm Mean 0.87 1.89 4.56 St. Dev. 0.23 1.04 2.05 Min. 0.21 0.19 0.36 Max. 1.52 5.51 8.80 Sum 708.44 1534.15 3695.63 Count 811.00 811.00 811.00
(G) Kareem Formation in all the studied wells
K% eU ppm eTh ppm Mean 0.93 3.01 6.26 St. Dev. 0.16 0.64 1.27 Min. 0.63 1.46 3.44 Max. 1.35 4.21 8.70 Sum 33.62 108.29 225.42 Count 36.00 36.00 36.00
K % eU ppm eTh ppm Mean 0.81 2.12 4.67 St. Dev. 0.19 0.43 1.12 Min. 0.35 1.20 2.04 Max. 1.07 3.11 6.35 Sum 39.45 103.96 229.02 Count 49.00 49.00 49.00
K % eU ppm eTh ppm Mean 0.86 2.68 3.77 St. Dev. 0.27 1.30 1.75 Min. 0.21 0.46 0.88 Max. 1.52 5.51 8.27 Sum 152.48 474.78 666.70 Count 177.00 177.00 177.00
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Chapter – 3 Radioactivity
20
value is 0.19 5 for 60 readings. The minimum value for equivalent uranium
(eU ppm) is 1.38 ppm and the maximum value is 4.06 ppm, while the mean
of these readings is 2.21 ppm and the stander deviation is about 0.77 ppm.
The table clarify that, the equivalent thorium concentration in this well is
ranging from 2.83 ppm to 7.33 ppm and it has mean value about 5.69 ppm,
while its stander deviation value is about 1.37 ppm. 2.1.1.3 – Well BM 37:
Table (3-1c) show that, the mean value of K % is about 0.81 % and
the values ranging between the minimum value 0.35 % to the maximum
value 1.07 %, the stander deviation of these reading is 0.19 %. The mean
value of about 49 readings for the equivalent uranium in this well is about
2.12 ppm for data ranging from 1.2 ppm to 3.11 ppm and the stander
deviation for these data is 0.43 ppm. The minimum value for equivalent
thorium is 2.04 ppm while the maximum value for the same readings is 6.35
ppm and the mean is 4.67 ppm while these data have a 1.12 ppm for the
stander deviation value.
2.1.1.4 – Well BMNW 2:
The values of potassium concentration in this well have the minimum
value about 0.35 % and the maximum value is 1.43 and mean of these values
is 0.98 %, and the stander deviation value is about 0.2 % for 311 readings as
it shown in table (3-1d). The equivalent uranium concentration values
ranging from 0.19 ppm to 4.27 ppm value and the mean of them is about
1.53 ppm, while the stander deviation value for the same readings is 0.83
ppm. The mean value of the equivalent thorium concentration in this well is
about 5.95 ppm where these readings are ranging between the minimum
reading 2.2 ppm and maximum reading 8.8 ppm, while the stander deviation
is about 1.29 ppm.
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Chapter – 3 Radioactivity
21
2.1.1.5 – Well 113 M 27:
Table (3-1e) shows that, the mean of potassium concentration in this
well is about 0.86 % and the minimum value is 0.21 % while the maximum
is 1.52 % and the stander deviation value for these readings is 0.27 %. The
equivalent uranium readings in this well are ranging from 0.46 ppm to 5.51
ppm and the mean value is 2.68 ppm, while the stander deviation is about
1.3 ppm for 177 readings. On the other hand the equivalent thorium readings
have 3.77 ppm mean value and the smallest value of eTh is 0.88 ppm while
the largest value is 8.27 ppm and the stander deviation is about 1.75 ppm.
2.1.1.6 – Well 113 M 34:
As it shown in table (3-1f), the mean value of potassium percent
concentration in this well is about 0.73% and the reading is ranging from
minimum value 0.35 % to maximum value 1.42 % and the stander deviation
of theses readings which are 178 reading is 0.2 %. The values of equivalent
uranium in this well have the minimum value 0.5 ppm and maximum value
3.09 ppm. On the other hand the mean is 1.34 ppm, where the stander
deviation value is about 0.53 ppm. The mean of equivalent thorium reading
is 2.15 ppm and the values ranging from 0.36 ppm to 6.11 ppm, while the
stander deviation is about 1.03 ppm
2.1.1.7 – Total Kareem Formation:
The values of potassium concentration in this formation have the
minimum value about 0.21 %, the maximum value is 1.52, the mean of these
values is 0.87 %, and the stander deviation value is about 0.23 % for 811
readings as it shown in table (3-1g). The equivalent uranium concentration
values are ranging from 0.19 ppm to 5.51 ppm value, the mean of them is
about 1.89 ppm, while the stander deviation value for the same readings is
1.04 ppm. The mean value of the equivalent thorium concentration in this
well is about 4.65 ppm where these readings are ranging between the
-
Chapter – 3 Radioactivity
22
minimum reading 0.36 ppm and maximum reading 8.8 ppm, while the
stander deviation is about 2.05 ppm.
From the statistical analysis of the radioactive elements in the
Kareem Formation, it is clear that, the equivalent thorium eTh is the main
radioactive element in this formation and the values of eTh is higher than the
values of potassium and equivalent uranium and this is indicate that, the
lithology of Kareem Formation is mainly shale because the thorium is shale
indicator.
2.1.2 – Rudeis Formation:
The spectral gamma ray data for Rudeis formation in the study area,
are available in all seven wells, the statistical analysis of the three
radioactive elements will be mentioned in all wells.
2.1.2.1 – Well BM 30:
The summary of descriptive statistical analysis of the spectral gamma
in this well is represented in table (3-2a). From this table, it can be observed
that, the potassium percent (K%) values in this well are ranging from 0.11 %
to 1.38 % and the mean value is 0.61 %, while the stander deviation is about
0.38 % for 135 readings. The mean equivalent uranium concentration (eU
ppm) in this well is about 2.68 ppm and the concentration of it ranging from
1.21 ppm to 4.17 ppm, while the stander deviation is 0.68 ppm. For 135
equivalent thorium concentration readings (eTh ppm) the mean value of
them is 3.94 ppm and the concentration of eTh ranges from the minimum
value 0.38 ppm to the maximum value 7.43 ppm. The value of 1.88 ppm
represents the stander deviation of the eTh readings in this well.
2.1.2.2 – Well BM 35:
The potassium values in this well as in table (3-2b) are ranging
between 0.07 % and 2.74 % and its mean is about 0.73 %, while the stander
deviation value is 0.31 5 for 617 readings. The minimum value for
equivalent uranium
-
Chapter – 3 Radioactivity
23
Table (3-2): Statistical analysis of spectral gamma of Rudeis Formation in the studied
wells of Rudeis Formation in Belayim marine oil field, Gulf of Suez,
Egypt.
K % eU ppm eTh ppm Mean 0.73 2.52 4.01 St. Dev. 0.31 0.99 1.89 Min. 0.07 0.85 0.49 Max. 2.47 8.61 9.06 Sum 449.79 1555.18 2476.57 Count 617.00 617.00 617.00
(A) BM - 30 Well (B) BM-35 well
K % eU ppm eTh ppm Mean 0.88 4.17 5.34 St. Dev. 0.31 2.39 2.00 Min. 0.18 1.09 1.07 Max. 1.71 15.01 13.75 Sum 149.34 708.07 908.12 Count 170.00 170.00 170.00
(C) BM-37 well (D) BM-57 well
K % eU ppm eTh ppm Mean 0.86 2.26 4.44 St. Dev. 0.37 1.18 1.92 Min. 0.21 0.30 0.10 Max. 2.48 5.05 9.47 Sum 220.27 577.55 1137.43 Count 256.00 256.00 256.00
(E) 113 M – 27 Well (F) 113 M - 34 Well
K % eU ppm eTh ppm Mean 0.77 2.57 4.33 St. Dev. 0.33 1.32 1.91 Min. 0.07 0.30 0.10 Max. 2.48 15.01 13.75 Sum 1509.47 5020.16 8456.92 Count 1955.00 1955.00 1955.00
(G) BMNW-2 well (H) Rudeis Formation in all studied wells
K % eU ppm eTh ppm Mean 0.61 2.68 3.94 St. Dev. 0.38 0.68 1.88 Min. 0.11 1.21 0.38 Max. 1.38 4.17 7.43 Sum 82.54 362.43 531.94 Count 135.00 135.00 135.00
K % eU ppm eTh ppm Mean 0.72 2.39 5.03 St. Dev. 0.25 0.66 1.29 Min. 0.09 0.96 1.67 Max. 1.16 4.85 7.54 Sum 194.70 643.38 1352.53 Count 269.00 269.00 269.00
K % eU ppm eTh ppm Mean 0.76 2.53 3.78 St. Dev. 0.36 1.30 2.08 Min. 0.15 0.39 0.74 Max. 1.81 5.56 9.78 Sum 304.67 1017.53 1517.66 Count 402.00 402.00 402.00
K % eU ppm eTh ppm Mean 1.02 1.47 5.03 St. Dev. 0.23 0.66 1.04 Min. 0.51 0.33 1.87 Max. 1.53 4.04 7.35 Sum 108.16 156.02 532.67 Count 106.00 106.00 106.00
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Chapter – 3 Radioactivity
24
(eU ppm) is 0.85 ppm and the maximum value is 8.61 ppm, while the mean
of these readings is 2.52 ppm and the stander deviation is about 0.99 ppm.
The table clarify that, the equivalent thorium concentration in this well is
ranging from 0.49 ppm to 9.06 ppm and it have mean value about 4.1 ppm,
while its stander deviation value is about 1.89 ppm.
2.1.1.3 – Well BM 37:
Table (3-2c) show that, the mean value of K % is about 0.72 % and
the values are ranging between the minimum value 0.09 % to the maximum
value 1.16 %, the stander deviation of these reading is 0.25 %. The mean
value of about 269 readings for the equivalent uranium in this well is about
2.39 ppm. For the same data it ranges from 0.96 ppm to 4.85 ppm and the
stander deviation for these data is 0.66 ppm. The minimum value for
equivalent thorium is 1.67 ppm. The maximum value for the same readings
is 7.54 ppm and the mean is 5.03 ppm while these data have a 1.29 ppm for
the stander deviation value.
2.1.2.4 – Well BM 57:
The values of potassium concentration in this well have the minimum
value about 0.18 %, the maximum value is 1.71, mean of these values is 0.88
%, and the stander deviation value is about 0.31 % for 170 readings as it
shown in table (3-2d). The equivalent uranium concentration values are
ranging from 1.09 ppm to 15.01 ppm value and the mean of them is about
4.17 ppm, while the stander deviation value for the same readings is 2.39
ppm. The mean value of the equivalent thorium concentration in this well is
about 5.34 ppm where these readings are ranging between the minimum
reading 1.07 ppm and maximum reading 13.75 ppm, while the stander
deviation is about 2 ppm.
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Chapter – 3 Radioactivity
25
2.1.2.5 – Well 113 M 27:
Table (3-2e) shows that, the mean of potassium concentration in this
well is about 0.76 % and the minimum value is 0.15 % while the maximum
is 1.81 % and the stander deviation value for these readings is 0.36 %. The
equivalent uranium readings in this well are ranging from 0.39 ppm to 5.56
ppm and the mean value is 2.53 ppm, while the stander deviation is about
1.3 ppm for 402 readings. On the other hand the equivalent thorium readings
have a 3.78 ppm mean value, the smallest value of eTh is 0.74 ppm while
the largest value is 9.78 ppm and the stander deviation is about 2.08 ppm.
2.1.2.6 – Well 113 M 34:
As it shown in table (3-2f), the mean value of potassium percent
concentration in this well is about 0.86 % and the reading is ranging from
minimum value 0.21 % to maximum value 2.48 % and the stander deviation
of this readings which are 265 reading is 0.37 %. The values of equivalent
uranium in this well have the minimum value 0.3 ppm and maximum value
5.05 ppm and the mean is 2.26 ppm, where the stander deviation value is
about 1.18 ppm. The mean of equivalent thorium reading is 4.44 ppm and
the values are ranging from 0.1 ppm to 9.47 ppm, while the stander
deviation is about 1.92 ppm.
2.1.2.7 – Well BMNW 2:
The values of potassium concentration in this well have the minimum
value about 0.51 % and the maximum value is 1.53 and mean of these values
is 1.02 %, and the stander deviation value is about 0.23 % for 106 readings
as it shown in table (3-2g). The equivalent uranium concentration values are
ranging from 0.33 ppm to 4.04 ppm value and the mean of them is about
1.47 ppm, while the stander deviation value for the same readings is 0.66
ppm. The mean value of the equivalent thorium concentration in this well is
about 5.03 ppm where these readings are ranging between the minimum
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Chapter – 3 Radioactivity
26
reading 1.87 ppm and maximum reading 7.35 ppm, while the stander
deviation is about 1.04 ppm.
2.1.2.8 – Total Rudeis Formation:
The values of potassium concentration in this formation have the
minimum value about 0.07 % and the maximum value is 2.48 and mean of
these values is 0.77 %, and the stander deviation value is about 0.33 % for
1955 readings as it shown in table (3-2h). The equivalent uranium
concentration values ranging from 0.3 ppm to 15.05 ppm value and the mean
of them is about 2.57 ppm, while the stander deviation value for the same
readings is 1.32 ppm. The mean value of the equivalent thorium
concentration in this well is about 4.33 ppm where these readings are
ranging between the minimum reading 0.1 ppm and maximum reading 13.75
ppm, while the stander deviation is about 1.91 ppm.
From the statistical analysis of the radioactive elements in the Rudeis
Formation, it is clear that, the main radioactivity in this Formation is due to
the present of uranium family and the concentration of equivalent uranium in
this Formation is more than it in Kareem Formation. Also this formation
contain a moderate amount of equivalent thorium concentrations, thus the
Rudeis Formation according to the radioactivity consists mainly of
sandstone have rare radioactive uranium elements and also consists of
mainly shale in some zones because as previous the thorium is shale
indicator and the uranium is good radioactive element indicator.
2.2 – Histogram:
The spectral gamma ray data of the study rocks (Kareem and Rudeis
formations) are analyzed by histogram method as it mentioned below.
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Chapter – 3 Radioactivity
27
2.2.1 – Kareem Formation:
As shown in Figure (3-1a) the potassium mineral concentration in this
Formation is ranging from 0.7 % to about 1.6 %, if potassium percent cut off
of 0.4 % is applied, only 2.59 % of the potassium has this value, but about
35.14 % of potassium readings have values are ranging from 0.4 % to 0.8 %,
while about 55.24 % of potassium readings have a concentration values
between 0.8 % and 1.2 % in Kareem Formation in all studied wells. The
potassium concentration readings which have values more than 1.2 % in this
Formation are about 7.03 % from all readings .
The concentration of equivalent uranium (eU ppm) in the Kareem
Formation is ranging between values from 1 ppm to 6 ppm, only 0.86 %
from all readings have values higher than 5 ppm, while if the equivalent
uranium concentration cut off of 2 ppm about 20.22 % readings have this
value. On the other hand about 75.34 % from the equivalent readings have
values are ranging from 2 ppm to 4 ppm as it revealed from Figure (3-1b).
The thorium equivalent minerals (eTh ppm) consider the main
radioactive minerals in Kareem Formation in all the studied wells, where it
have concentration values ranging from 1 ppm to 9 ppm. As in Figure (3-1c)
only 1.97 of all eTh readings have concentration values more than 8 ppm,
also there are about 2.47 % from the total eTh readings if it cut off at 1 ppm.
On the other hand, about 95.56 % from the eTh readings have values ranging
from 2 ppm to 8 ppm, but the most readings have concentration values of
6ppm and 7 ppm.
2.2.2 Rudeis Formation
The distribution of the radioactive elements (K %, eU ppm and eTh
ppm) in Rudeis Formation are illustrated by Histogram as it will mention:
Figure (3-2a) reveals that, the value of 0.9 % is the main
concentration value of potassium in all the studied wells, where there are
about 33.09 % of all readings have this value.
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Chapter – 3 Radioactivity
28
Bin Freq. Cumu.
% 0 0 0.00%
0.2 0 0.00% 0.4 21 2.59% 0.6 90 13.69% 0.8 195 37.73% 1 261 69.91%
1.2 187 92.97% 1.4 50 99.14% 1.6 7 100.00%
More 0 100.00%
Bin Freq. Cumu.
% 0 0 0.00% 1 164 20.22% 2 347 63.01% 3 166 83.48% 4 98 95.56% 5 29 99.14% 6 7 100.00%
More 0 100.00%
Bin Freq. Cumu.
% 0 0 0.00% 1 20 2.47% 2 109 15.91% 3 97 27.87% 4 100 40.20% 5 95 51.91% 6 150 70.41% 7 151 89.03% 8 73 98.03% 9 16 100.00%
More 0 100.00%
Fig. (3-1): Histogram and cumulative frequency of K%, eU ppm and eTh ppm
radioactive elements of Kareem Formation in Belayim marine oil field, Gulf
of Suez, Egypt.
0
60
120
180
240
300
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 MoreK %
Freq
uenc
y0%
20%
40%
60%
80%
100%
0
100
200
300
400
0 1 2 3 4 5 6 More
eU ppm
Freq
uenc
y
0%
25%
50%
75%
100%
0
40
80
120
160
0 1 2 3 4 5 6 7 8 9 Mo reeTh ppm
Freq
uenc
y
0%
25%
50%
75%
100%
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Chapter – 3 Radioactivity
29
If the potassium concentration readings cut off of 0.6 % it will be noticed
that, 32.43 % of the potassium readings have a values less than the
potassium cut off. Also the readings which have values more than 1.5 %
consider only 1.59 % from the total readings. The readings which have
potassium values are ranging from 0.9 % to 1.5 % consider the main values
in this formation where them about 65 % from all readings.
The readings of equivalent uranium concentration in Rudeis
Formation are ranging from 1 ppm to 16 ppm, but if the eU concentration
cut off of 8 ppm we will noticed that, only 0.46 % of the total readings have
eU concentration more than the cut off. The 4 ppm equivalent uranium
concentration value considers the main value in this Formation where about
52.43 % from all readings have this value as it shown in Figure (3-2b).
Figure (3-2c) reveals that, the equivalent thorium concentration readings
in Rudeis Formation are ranging from 2 ppm to 14 ppm. If the eTh readings cut
off of 10 ppm is applied, it will be noticed that, only about 0.1 % from the total
readings have a values higher than the eTh cut off, while the concentrations from
4 ppm to 8 ppm consider the main concentration values in this Formation where
them consist about 85.17 % from the total readings.
The histogram analysis of the equivalent thorium in Kareem and Rudeis
Formations revealed that, the concentration values of eTh present in wide range
and have near percent distribution in the rock, this means that, the equivalent
thorium minerals are stable and fixed in the rock and not mobiles from or to the
Formations rock.
3 – Clay minerals identification Spectral gamma ray method plays an important role in determination the
type of clay minerals in the studied rocks. Identification the clay type minerals in
reservoir rocks is very important because the clay type mineral affected directly
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Chapter – 3 Radioactivity
30
Bin Freq. Cumu.% 0 0 0.00%
0.3 164 8.39% 0.6 470 32.43% 0.9 647 65.52% 1.2 483 90.23% 1.5 160 98.41% 1.8 21 99.49% 2.1 7 99.85% 2.4 0 99.85% 2.7 3 100.00%
More 0 100.00%
Bin Freq. Cumu.
% 0 0 0.00% 2 706 36.11% 4 1025 88.54% 6 199 98.72% 8 16 99.54%
10 2 99.64% 12 5 99.90% 14 0 99.90% 16 2 100.00%
More 0 100.00%
Bin Freq. Cumu.
% 0 0 0.00% 2 288 14.73% 4 557 43.22% 6 719 80.00% 8 354 98.11%
10 35 99.90% 12 1 99.95% 14 1 100.00%
More 0 100.00%
Fig. (3-2): Histogram and cumulative frequency of K%, eU ppm and eTh ppm
radioactive elements of Rudeis Formation in Belayim marine oil field,
Gulf of Suez, Egypt.
0
200
400
600
800
0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 More
K%Fr
eque
ncy
0%
25%
50%
75%
100%
0
300
600
900
1200
0 2 4 6 8 10 12 14 16 More
eU ppm
Freq
uenc
y
0%
25%
50%
75%
100%
0
200
400
600
800
0 2 4 6 8 10 12 14 More
eTh ppm
Freq
uenc
y
0%
25%
50%
75%
100%
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Chapter – 3 Radioactivity
31
on the porosity and permeability of the rocks, as the effect of kaolinite mineral
on porosity and permeability is very low while the montmorillonite clay mineral
has a very high effect on them where it can be increased his volume by eight
times when it saturated by water.
The clay type minerals in Lower Miocene sediments (Kareem and Rudeis
Formations) determined by two methods, thorium – potassium crossplots and
Scanning Electron Microscope (SEM) photographs. The (SEM) method is very
expensive because it carried out on the core samples, but it's very accurate. On
the other hand the thorium potassium method is very sheep.
3. 1 – Thorium – Potassium crossplot
The Th / K ratio gives accurate information about the clay minerals in the
rocks using the diagram of Schlumberger (1995), and this method was carried
on all the studied wells which have a spectral gamma data to study the clay
minerals in both Kareem and Rudeis Formations as it mentioned.
3.1.1 – Kareem Formation
The thorium – potassium crossplots carried out on Kareem Formation of
the studied wells. The main clay minerals in BM-30 well are montmorillonite and
chlorite, and some plotted points are located in the field of mixed layer clay as it
shown in Figure (3-3a).
In BM-35 well the thorium – potassium crossplot reveals that, the main
clay minerals are Montmorillonite, chlorite and mixed layer clay as it shown in
Figure (3-3b). Also these minerals of clay are founded in the BM-37 well as
shown in Figure (3-4a).
Figure (3-4b) reveals that, the clay type minerals in ell BMNW-2 well are
mainly composed of mixed layer clay, montmorillonite, chlorite and some plotted
points are located in the field of kaolinite mineral.
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Chapter – 3 Radioactivity
32
Well BM-30
Well BM-35
Fig. (3-3): Type of clay minerals identifications by thorium potassium crossplots
of Kareem Formation in wells BM-30 and BM-35 in Belayim marine
oil field, Gulf of Suez, Egypt.
A
B
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Chapter – 3 Radioactivity
33
Well BM-37
Well BMNW-2
Fig. (3-4): Type of clay minerals identifications by thorium potassium crossplots
of Kareem Formation in wells BM-37 and BMNW-2 in Belayim
marine oil field, Gulf of Suez, Egypt.
A
B
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Chapter – 3 Radioactivity
34
The main clay minerals in 113-M-27 well as it shown in Figure (3-5a) are
montmorillonite, chlorite, mixed layer clay and some plotted point in the field of
illite. Same clay minerals are found in 113-M-34- well but the glauconite mineral
is present in this well as it reveals from Figure (3-5b).
Figure (3-5c) reveals that the main clay minerals which present in Kareem
Formation in all the studied wells by using the thorium – potassium crossplot are
Montmorillonite, chlorite, mixed layer clay and some traces of kaolinite, illite
and