radioactivity and reservoir characteristics of lower miocene rocks in belayim marine oil...

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

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

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

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.

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

v

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

i

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

i

(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

i

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)


of Kareem Formation in Wells M - 37 and BMNW -2 in Belayim

marine oil field, Gulf of Suez, Egypt……………….………………… 33

(3-5)


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)


of Rudeis Formation in Wells BM – 30 and BM - 35 in Belayim

marine oil field, Gulf of Suez, Egypt…………………......................... 36

(3-7)


of Rudeis Formation in Wells BM - 37 and BM - 57 in Belayim

marine oil field, Gulf of Suez, Egypt……………........................……. 37

x

(3-8)


of Rudeis Formation in Wells 113 - M – 27 and 113 - M - 34 in

Belayim marine oil field, Gulf of Suez, Egypt...................................... 39

(3-9)


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


Egypt………………………………………………………………….. 58

(4-3)

Histogram and cumulative frequency of total porosity of Rudeis


Egypt………………………………………………………………… 60

(4-4)

Histogram and cumulative frequency of total porosity of Rudeis


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

x

(4-6)

Histogram and cumulative frequency of horizontal permeability of


of Suez, Egypt………………………………………………………… 65

(4-7)

Histogram and cumulative frequency of vertical permeability of


of Suez, Egypt………………………………………………………… 67

(4-8)

Histogram and cumulative frequency of permeability of Rudeis


Egypt…………………………………………………………………. 69

(4-9)

Histogram and cumulative frequency of permeability of Rudeis


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

i

(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)


some samples of Rudeis Formation, Belayim marine oil field, Gulf of

Suez, Egypt........................................................................................... 94

i

(4-29)


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)



(5-7)



(5-8)



(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


Egypt.................................................................................................... 126

(5-11)

Input data and interpreted analysis of well (113-M-27), Kareem and


Egypt.................................................................................................... 128

(5-12)



Egypt................................................................................................... 129

i

(5-13)



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)




(5-16)




(5-17)




(5-18)


analysis results of BMNW-2 well for Rudeis Formation in Belayim


(5-19)


analysis results of 113-M-27 well for Rudeis Formation in Belayim


(5-20)


analysis results of 113-M-34 well for Rudeis Formation in Belayim


(5-21)

Formation evaluation parameters of Rudeis Formation, Belayim


(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


v

(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


(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


(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


(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

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


2

Fig. (1-1): Location m

ap of the study area of Belayim

marine oil field, G

ulf of Suez, Egypt


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


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.


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.

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


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.


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


9

Fig. (2-1): Stratigraphic column of

Belayim oil fields, Gulf of Suez,

Egypt. (After Belayim Petroleum

Co. 2005)


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


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


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


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


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


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).

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)


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.


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


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


(C) BM-37 well (D) BMNW-2 well


(E) 113 - M - 27 Well (F) 113 - M - 34 Well


(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




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.


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


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


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.


(A) BM - 30 Well (B) BM-35 well


(C) BM-37 well (D) BM-57 well


(E) 113 M – 27 Well (F) 113 M - 34 Well


(G) BMNW-2 well (H) Rudeis Formation in all studied wells






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:


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





reading 1.07 ppm and maximum reading 13.75 ppm, while the stander

deviation is about 2 ppm.


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:


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






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.


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.


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%


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


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%


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.


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


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


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

radioactivity and reservoir characteristics of lower miocene rocks in belayim marine oil...

Documents