Source Rock Depositional Processes in Different Marine Settings: Examples from

North African Basins

Von der Fakultät für Georessourcen und Materialtechnik

der Rheinisch-Westfälischen Technischen Hochschule Aachen

zur Erlangung des akademischen Grades eines

Doktors der Naturwissenschaften

genehmigte Dissertation

vorgelegt von M.Sc.

Bandar Ismail Hassan Ghassal

aus Makkah, Saudi Arabien

Berichter: Univ.-Prof.Dr.rer.nat. Ralf Littke

AOR Dr.rer.nat. Sven Sindern

Tag der mündlichen Prüfung: 20. Juli 2017

(Ausschließlich für elektronische Veröffentlichung bestimmt):

Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar

I

DECLARATION OF AUTHORSHIP

I certify that the thesis presented here is original and the result of my own investigations, except as acknowledged, and has not been submitted, either in part or whole, for a degree at this or any other University.

Aachen,

Bandar Ismail Ghassal

II

ACKNOWLEDGMENT

From the bottom of my heart, I would like to thank everyone who helped me to reach this

point of my education and career. Thank you very much, my mother, for being the

support and motivation who always drives me to succeed. Every success I reached or

will reach has your fingerprint on it. I would also like to sincerely express my gratitude

to my wife who sacrificed a lot for me to see me succeed and put my needs before hers.

Thank you for those beautiful paints that precedes Chapters 2-4. Thanks to my lovely kids

Jory and Rakan for being the hope especially in tough times. Your smiles and small

dreams made me work hard so you can be proud of your daddy! Big thank you to my

Sister Ghaddah and my brother Bassim who provided me with tremendous support

throughout my life. I hope your pieces of advice and help paid back. Thank you to the

great person who I wish he saw this day; My father who passed away when I was six years

old but left me with a golden reputation, tips and inspirations that paved the way for me

to be passionate to learn new things every day and to keep healthy relationships with

others.

Thank you very much for my employer Saudi Aramco for funding my Ph.D. program and

overcoming every obstacle that could have affected my studies. Special thanks to Mr.

Saleh Al Ammari, Dr. Sami Abdelbagi and Mrs. Aggie Copper from Saudi Aramco. Thank

you is a small expression that describes my appreciation. I would like to thank the person

whom I admire and who polished my academic and management skills, my advisor

Professor Ralf Littke for the fruitful Ph.D. program. It was an extraordinary experience

that went beyond only the thesis work but extended to teach in classes, advising Master

and Bachelor students, supervising the Rock-Eval laboratory and working on various

technical projects. Many thanks to Professor Sven Sindern who provided valuable

consultations in the XRF analyses and for being the second reviewer of this thesis. I am

very grateful to Dr. Bernard Krooß for his support and usual rich scientific discussions. I

learned a great deal from you. I would like to express my gratitude to Professor Jan

III

Schwarzbauer for his great help and valuable discussions in regards of the molecular

geochemistry field during my Ph.D. program. I sincerely appreciate all the support and

help given by my friend and one of my top coauthors Dr. Haytham El Atfy from the

Mansoura University, also for helping in the German abstract and providing the Nile Delta

and Western Desert wells. Many thanks to Dr. Victoria Sachse for the insightful

discussions and great support that helped me a lot during my program. It was a great

pleasure working with a very talented dedicated and professional technical group who I

enjoyed learning from. Thank you to Dipl.-Ing. Chemie Donka Macherey who helped in

preparing the microscopy samples. I extend my gratitude to Mrs. Kerstin Windeck for

making the carbon and sulfur measurements and Dipl.-Ing. Chemie Annette

Schneiderwind for helping in the molecular geochemical analysis. Special thanks to Mr.

Alexander Stock for helping in the sampling of the Tarfaya project core and to Miss Laura

Zeiger for helping in the German abstract. I would like to thank Ms. Diana Marcela Chaves

Saldaña and Mr. Jan Gronewald who assisted in the analysis of the same project. Many

thanks to Mr. Gregor Scholtysik for helping in the GPT-3 geochemical analysis. I thank the

micropaleontology group at the Kiel University very much for providing us with the core

samples from Tarfaya. Many thanks also to all coauthors and Editor in Chiefs who helped

in reviewing the three papers constituting major parts of my thesis.

Thank you God I did it!

IV

ABSTRACT

The current thesis assesses source rock characteristics in various shallow marine

settings using samples from the Nile Delta and Abu Gharadig basins in Egypt and the

Tarfaya Basin in Morocco. The methods include organic and inorganic geochemistry,

organic petrology, basin modeling, and palynology. The thesis comprises three main

studies. First, the Nile Delta Basin source rock potential is determined using organic

geochemistry and petrology as well as 1D basin modeling of two onshore wells. The Abu

Hammad-1 well located in the southeastern Nile Delta Basin hosts fair to good gas prone

source rocks within the Upper Jurassic and Lower Cretaceous section. The molecular

geochemical analyses indicate shallow marine depositional environment and mixed

marine and terrestrial organic matter. The burial and thermal numerical 1D model and

organic petrology results indicate thermally immature section. However, this Mesozoic

section is expected to have better potential and thermal maturity toward the northern

parts of the basin. The middle Miocene to Pleistocene section is examined in the

Matariya-1 well which is located in northeastern onshore Nile Delta Basin. It contains fair

gas prone source rocks in a middle Miocene lowstand wedge. This section has attained

onset oil generation stage. The great thickness of the section and proximity to the

reservoir facies upraise its source rock potential. The study recommends further

exploration in deep targets such as Mesozoic sections, especially in the offshore areas.

The second part of the thesis evaluates the source rock potential and paleoenvironment

of the Cenomanian to Santonian succession of the Bahariya and Abu Roash formations at

the GPT-3 well, Western Desert, Egypt. The study employed organic and inorganic

geochemical and palynological techniques. The results show that the succession

represents variable oxic shelf depositional environments with low organic matter

preservation excluding the Abu Roash “F” Member which shows two source rock facies.

The basal part of this member is rich in carbonate, TOC and marine organic matter. The

kerogen is relatively rich in organic sulfur (Sorg) due to the limited reactive Fe supply

upon deposition leading to excesses S incorporation into organic matter. The middle part

of the Abu Roash “F” Member is lean in organics and very rich in terrestrial elements (e.g.

V

Fe, Ti, Si) and associated with Botryococcus indicating sea regression. This facies overlain

by a suboxic marine oil prone source rock with lower Sorg contents. Both source rocks are

lower in Tmax as compared to the above and below sections implying thermal maturity

retardation possibly due to high liptinite contents, high pressures or lack of catalytic

elements. Moreover, two oil reservoirs were geochemically characterized. These findings

are vital for future hydrocarbon exploration and paleoenvironment reconstructions.

In the Tarfaya Basin, Cenomanian to Turonian source rocks are classified based on their

organic geochemical and petrological properties. The molecular geochemistry suggests

marine anoxic depositional environment with an extreme oxygen depletion attained at

the Cenomanian/Turonian boundary event (CTBE) associated with increased

cyanobacteria activities. The lower Cenomanian is characterized by higher silicate

contents compared to the rest of the section based on major elemental data. All samples

are dominated by submicroscopic organic matter. The lower Cenomanian is poor in

bituminite, whereas, the upper Cenomanian to Turonian samples show variable

bituminite contents. Furthermore, the samples show variable Sorg contents. The change

in organic matter type was controlled by early diagenetic kerogen sulfurization, which

depends on the interplay between S, Fe and organic matter, and upwelling processes. The

source rocks are classified into 1) low Sorg and moderately TOC-rich oil prone source

rocks (lower Cenomanian), 2) moderate Sorg and TOC-rich oil prone source rocks (upper

Cenomanian), 3) high Sorg and TOC-rich oil prone source rocks (Turonian) and 4) very

high Sorg and TOC-rich oil prone source rocks (CTBE). Types 2 to 4 will generate sulfur-

rich petroleum upon maturation or artificial oil shale retorting.

VI

ZUSAMMENFASSUNG

Diese Dissertation behandelt Edölmuttergesteine aus flach-marinen Sedimentfolgen des Nil-

Delta, des Abu-Gharadig Beckens in Ägypten und des Tarfaya Beckens in Marokko und ihre

charakteristischen Eigenschaften. Die Methoden umfassen organische und anorganische

Geochemie, organische Petrologie, Beckenmodellierung und Palynologie. Die Dissertation

umfasst drei Hauptkapitel. Zuerst wird das Muttergesteins-Potential von Proben aus dem

Nil-Delta mit Hilfe organischer Geochemie und Petrologie sowie der 1D-Beckenmodellierung

anhand zweier Onshore-Bohrungen bestimmt. Die Abu Hammad-1-Bohrung aus dem

südöstlichen Nil-Delta enthält mäßiggute bis gute Muttergesteine des Oberen Jura und der

Unterkreide. Die molekular-geochemischen Analysen zeigen ein flach-marines

Ablagerungsmilieu und den gemischten Eintrag von marinem und terrestrischem

organischen Material. Die thermische Reife ist gering. Allerdings wird erwartet, dass diese

Mesozoische Sektion in nördlichen Teilen des Beckens ein größeres Potential und eine

höhere thermische Reife aufweist. Der Abschnitt vom Mittleren Miozän bis zum Pleistozän

wurde anhand der Matariya-1-Bohrung untersucht, die aus dem nordöstlichen Onshore Nil-

Delta Becken stammt. Er enthält mäßiggute Muttergesteine im frühen Ölfenster. Die große

Mächtigkeit des Abschnitts und die Nähe zu geeigneten Reservoir-Gesteinen erhöhen jedoch

das Muttergesteins-Potenzial. Diese Studie empfiehlt eine weitere Exploration tieferer

Einheiten z.B. des Mesozoikums, vor allem in den Offshore-Gebieten.

Der zweite Teil der Dissertation beurteilt das Muttergestein-Potenzial und die

Paläoumweltbedingungen der Cenomanium-Santonium Schichtfolge der Bahariya- und Abu-

Roash Formationen aus der GPT-3-Bohrung aus der libyschen Wüste Ägyptens. Die

Ergebnisse zeigen, dass die Folge überwiegend, mit Ausnahme der Abu-Roash „F“

Subformation, das ein hohes Erdölbildungs-Potenzial besitzt, unter suboxischen bis oxischen

Bedingungenabgelagert wurde. Der Basalteil der Folge ist reich an Karbonat, TOC und

mariner organischer Substanz. Das Kerogen ist aufgrund der begrenzten Menge an reaktivem

Eisen während der Ablagerung relativ reich an organischem Schwefel (Sorg). Der mittlere Teil

des Abu-Roash „F“ Subformation ist arm an organischem Material und sehr reich an

terrestrischen Elementen (z.B. Fe, Ti, Si) und mit Botryococcus-Algen assoziiert, was eine

Regression des Meeres anzeigt. Diese Fazies wird von suboxisch abgelagerten, marinen

VII

Muttergesteinen mit niedrigeren Sorg-Anteilen überlagert. All diese Muttergesteine zeigen im

Vergleich zu den unter- und überlagernden Gesteinen niedrige thermische Reifen auf, was

eine thermische Reifungsverzögerung, möglicherweise aufgrund hoher Liptinitgehalte,

hoher Drücke oder wegen des Mangels an katalytischen Elementen, impliziert. Darüber

hinaus wurden aus dieser Bohrung zwei Öl-Reservoirs geochemisch charakterisiert. Diese

Erkenntnisse sind für zukünftige Kohlenwasserstoff-Explorationen und Paläoumwelt-

Rekonstruktionen von entscheidender Bedeutung.

Im Tarfaya Becken wurden Cenomanische bis Turonische Muttergesteine auf Grundlage

ihrer organischen geochemischen und petrologischen Eigenschaften klassifiziert. Die

Ergebnisse der molekularen Geochemie legen eine marin-anoxische Ablagerung nahe, die an

der Cenomanium/Turonium Grenze (CTBE) mit einer erhöhten Aktivität von

Cyanobakterien assoziiert war. Das Untere Cenomanium zeichnet sich durch höhere Silikat-

Gehalte im Vergleich zum Rest des Abschnitts aus. Alle Proben werden durch

submikroskopisch kleine organische Partikel dominiert. Das Untere Cenomanium ist arm an

Bituminit, während der Abschnitt vom Oberen Cenomanium bis zum Turonium variable

Bituminitgehalte zeigt. Darüber hinaus weisen die Proben variable Sorg-Gehalte auf. Die

Veränderung des Kerogentyps wurde durch eine frühzeitige diagenetische

Kerogenvulkanisation (Schwefel-Einbau) gesteuert, die von den Konzentrationen an S, Fe

und organischer Substanz in Zusammenhang mit Auftriebsprozessen abhängt. Die

Muttergesteine werden dementsprechend aufgrund ihres Kohlenwasserstoff-

Bildungspotenzials (HI-Werte), ihrer TOC-Gehalte und ihres Gehaltes an organischem

Schwefels in 4 Gruppen potentieller Erdölmuttergesteine unterteilt: 1) solche mit niedrigem

Sorg- und mittlerem TOC-Gehalt (Unteres Cenomanium), 2) solche mit moderatem Sorg- und

hohem TOC-Gehalt (Oberes Cenomanium), 3) solche mit gleichfalls hohem Sorg- und TOC-

Gehalt (Turonium) und jene mit sehr hohen Sorg- und hohen TOC-Gehalten (CTBE). Die

Gruppen 2 und 4 werden bei fortgeschrittener Reifung oder durch künstliche Ölextraktion

schwefelreiches Öl produzieren.

VIII

LIST OF ABBREVIATIONS

AOM Amorphous organic matter API American Petroleum Institute Corg Organic carbon CPI Carbon preference index CPPyGCMS Curie Point Pyrolysis Gas Chromatography Mass Spectrometry CTBE Cenomanian Turonian boundary event

GC-FID Gas Chromatography-Flame Ionization Detector GCMS Gas Chromatography-Mass Spectrometry HI Hydrogen Index OAE2 Oceanic anoxic event 2 OEP Odd over even predominance OI Oxygen Index Ph Phytane PI Production Index Pr Pristane S1 First flame ionization detector signal/peak of Rock-Eval 6 S2 Second flame ionization detector signal/peak of Rock-Eval 6 S3 The Infra-Red detector signal/peak of Rock-Eval 6

Sorg Organic sulfur TAR Terrestrial to aquatic ratio TIC Total inorganic carbon Tmax Rock-Eval temperature at maximum S2 yield TOC Total organic carbon TS Total sulfur UOM Unstructured organic matter from organic microscopy VRr Vitrinite reflectance at random orientations

IX

TABLE OF CONTENTS

DECLARATION OF AUTHORSHIP .......................................................................................................... I

ACKNOWLEDGMENT ..................................................................................................................................II

ABSTRACT ..................................................................................................................................................... IV

ZUSAMMENFASSUNG ............................................................................................................................... VI

LIST OF ABBREVIATIONS ................................................................................................................... VIII

TABLE OF CONTENTS .............................................................................................................................. IX

LIST OF TABLES ....................................................................................................................................... XIV

LIST OF FIGURES ....................................................................................................................................... XV

Chapter 1 | Introduction .......................................................................................................................... 1

1.1 Background ........................................................................................................................................ 1

1.2 General Remarks on Source Rock Depositional Settings ........................................... 2

1.3 Geological Setting of North Africa from Jurassic to Recent.................................... 4

1.3.1 Jurassic Period .......................................................................................................................... 5

1.3.2 Cretaceous Period ................................................................................................................... 6

1.3.3 Paleogene Period ..................................................................................................................... 7

1.3.4 Neogene Period ........................................................................................................................ 8

1.4 Source Rock Potential Overview of the Study Areas .................................................... 8

1.4.1 Source rock potential of Egypt .............................................................................................. 8

1.4.2 Source Rock Potential of Tarfaya Basin ............................................................................. 9

1.5 Research Objectives .................................................................................................................... 12

1.6 Thesis Outline ................................................................................................................................ 13

Chapter 2 | Source Rock Potential of the Middle Jurassic to Middle Pliocene, Onshore Nile Delta Basin, Egypt ....................................................................................................... 16

X

2.1 Abstract ............................................................................................................................................. 16

2.2 Introduction .................................................................................................................................... 17

2.3 Geological Setting ......................................................................................................................... 19

2.3.1 Tectonic setting ........................................................................................................................ 19

2.3.2 Stratigraphy ............................................................................................................................... 21

2.4 Samples and Methods .................................................................................................................... 23

2.4.1 Samples ........................................................................................................................................ 23

2.4.2 Elemental analysis .................................................................................................................. 24

2.4.3 Rock-Eval pyrolysis.................................................................................................................. 24

2.4.4 Organic petrography .............................................................................................................. 29

2.4.5 Source rock extraction and liquid chromatography .................................................. 29

2.4.6 GC-FID and GC-MS ................................................................................................................ 30

2.4.7 1D burial and thermal history modeling ........................................................................ 31

2.5 Results ................................................................................................................................................ 32

2.5.1 Elemental analysis .................................................................................................................. 32

2.5.2 Rock-Eval analysis .................................................................................................................. 32

2.5.3 Organic petrography .............................................................................................................. 35

2.5.4 Molecular geochemistry ....................................................................................................... 36

2.5.5 1D burial and thermal history modeling ........................................................................ 39

2.6. Discussion ....................................................................................................................................... 44

2.6.1 Depositional environments ................................................................................................. 44

2.6.2 1D burial and thermal history modeling ........................................................................ 49

2.6.3 Source rock potential ............................................................................................................. 49

2.7 The Mesozoic and Miocene Source Rocks In the Nile Delta-An Overview ..... 52

XI

2.8 Conclusions ..................................................................................................................................... 55

Chapter 3 | Depositional Environment and Source Rock Potential of the Upper Cretaceous Succession, Abu Gharadig Basin, Northern Western Desert, Egypt: An Integrated Geochemical and Palynological Study .................................................................. 58

3.1 Abstract ............................................................................................................................................. 58

3.2 Introduction .................................................................................................................................... 59

3.3 Geologic Setting ............................................................................................................................. 61

3.4 Material and Methods ........................................................................................................... 64

3.4.1 Samples ....................................................................................................................................... 64

3.4.2 Elemental analysis .................................................................................................................. 67

3.4.3 Rock-Eval pyrolysis ................................................................................................................ 68

3.4.4 Organic petrology .................................................................................................................... 68

3.4.5 Molecular organic geochemistry ....................................................................................... 69

3.4.6 Curie Point Pyrolysis-Gas Chromatography-Mass Spectrometry ........................ 69

3.4.7 Molecular geochemical parameters ................................................................................. 70

3.4.8 Palynology and palynofacies ............................................................................................... 71

3.5 Results ................................................................................................................................................ 71

3.5.1 Elemental analysis .................................................................................................................. 71

3.5.2 Rock-Eval pyrolysis ................................................................................................................ 76

3.5.3 Organic petrography .............................................................................................................. 79

3.5.4 Molecular organic geochemistry ....................................................................................... 81

3.5.5 CPPyGCMS .................................................................................................................................. 85

3.5.6 Palynology and palynofacies analysis ............................................................................. 87

3.6 Discussion ........................................................................................................................................ 91

3.6.1 Age assignment ........................................................................................................................ 91

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3.6.2 Depositional environments ................................................................................................. 92

3.6.3 Source rock potential ........................................................................................................... 101

3.6.4 Reservoir geochemistry ...................................................................................................... 102

3.7 Conclusions ................................................................................................................................... 103

Chapter 4 | Depositional Environment and Source Rock Potential of Cenomanian and Turonian Sedimentary Rocks of the Tarfaya Basin, Southwest Morocco ...... 107

4.1 Abstract ........................................................................................................................................... 107

4.2 Introduction .................................................................................................................................. 108

4.3 Geological Setting ....................................................................................................................... 112

4.4 Samples and Methods .............................................................................................................. 114

4.4.1 Samples ..................................................................................................................................... 114

4.4.2 Elemental analysis ................................................................................................................ 114

4.4.3 Rock-Eval Pyrolysis .............................................................................................................. 116

4.4.4 Organic petrology .................................................................................................................. 117

4.4.5 Source rock extraction ........................................................................................................ 117

4.4.6 Gas Chromatography and Gas Chromatography-Mass Spectrometry .............. 118

4.4.7 Curie-Point Pyrolysis Gas Chromatography-Mass Spectrometry ....................... 118

4.4.8 Molecular geochemical parameters ............................................................................... 119

4.5 Results .............................................................................................................................................. 119

4.5.1 Elemental Analysis ................................................................................................................ 119

4.5.2 Rock-Eval Pyrolysis .............................................................................................................. 136

4.5.3 Organic Petrology .................................................................................................................. 138

4.5.4 Molecular Geochemistry ..................................................................................................... 142

4.5.5 Curie-Point-Pyrolysis Gas Chromatography-Mass Spectrometry ...................... 144

4.6 Discussion ...................................................................................................................................... 145

XIII

4.6.1 Depositional environment ................................................................................................. 145

4.6.2 Source rock potential and organic matter type ......................................................... 152

4.6.3 Kerogen diagenesis and properties ................................................................................ 154

4.7 Conclusions ................................................................................................................................... 155

Chapter 5 | Thesis General Discussion ........................................................................................ 157

5.1 Introduction .................................................................................................................................. 157

5.2 Studied Parameters .................................................................................................................. 157

5.3.1 Sedimentation systems and organic matter productivities .................................. 159

5.3.3 Bottom water conditions .................................................................................................... 161

5.3.5 Tmax and source rock properties ...................................................................................... 164

5.4 New Geochemical Proxies ...................................................................................................... 165

Chapter 6 | Conclusions ....................................................................................................................... 167

References .................................................................................................................................................. 170

Curriculum Vitae .................................................................................................................................... 187

XIV

LIST OF TABLES

Table 2-1 Rock-Eval 6 and elemental data of the Abu Hammad-1 and Matariya-1 wells. Units: *(mgHC/gRock), ** (mgCO2/gRock), *** mgHC/gTOC, **** mgCO2/gTOC. ...................... 25

Table 2-2 Gas chromatography data of selected samples from the Abu Hammad-1 and Matariya-1 wells. .......................................................................................................................................... 38

Table 2-3 Biomarker data of selected samples from the Abu Hammad-1 and Matariya-1 wells. ................................................................................................................................................................. 40

Table 3-1 Carbon, sulfur and Rock-Eval data of the Bahariya and Abu Roash formations, GPT-3 well, north Western Desert, Egypt. * (mg HC/gRock), ** (mg CO2/gRock), ***

(mgHC/gTOC), **** (mgCO2/gTOC). .................................................................................................. 64

Table 3-2 Elemental data of selected samples using XRF analysis from the Abu Roash “F”, “E” and “G” members, GPT-3 well, north Western Desert, Egypt. ............................................ 74

Table 3-3 Biomarker data of selected samples from the Bahariya and Abu Roash formations, GPT-3 well, north Western Desert, Egypt. ................................................................ 83

Table 3-4 Curie Point Pyrolysis Gas chromatography mass spectrometry data of selected samples from The Abu Roash “F” Member, GPT-3 well, north Western Desert, Egypt. .. 86

Table 3-5 Palynofacies data of selected samples from the Bahariya and Abu Roash formations. AOM: amorphous organic matter. ................................................................................ 87

Table 4-1 Elemental and Rock-Eval 6 data. Units: *mgHC/Rock, **mgCO2/gRock, ***mgHC/gTOC, ****mgCO2/gTOC. T: Turonian, CT: CTBE, UC: Upper Cenomanian, LC: Lower Cenomanian A: Albian ............................................................................................................... 123

Table 4-2 XRF data of selected samples from each stratigraphic units. T: Turonian, CT: CTBE, UC: Upper Cenomanian, LC: Lower Cenomanian. ........................................................... 135

Table 4-3 Maceral compositional analysis data. *: Calculated, submicroscopic organic matter. T: Turonian, CT: CTBE, UC: Upper Cenomanian, LC: Lower Cenomanian. .......... 140

Table 4-4 Molecular geochemistry data of the aliphatic fractions. ....................................... 143

Table 4-5 Total thiophenes/total benzenes data from CPPyGCMS data used as a proxy of Sorg/Corg ......................................................................................................................................................... 144

XV

LIST OF FIGURES

Fig. 1-1 Schematic diagram of common source rock depositional settings. Pink polygons are anoxic/oxygen minimum zones. ...................................................................................................... 4

Fig. 1-2 Paleogeographic reconstructions modified after Blaeky 2012. The yellow dot is for Morocco and the magenta dot is for Egypt. “Global Paleogeographic Maps © 2012 Colorado Plateau Geosystems Inc., used with permission from Ron Blakey”. ....................... 6

Fig. 1-3 Source rock potential traffic light map of the Tarfaya basin based on published data by Sachse et al., (2011, 2012, 2014), Ghassal et al., (2015) and Wenke (2014)....... 11

Fig. 1-4 Geothermal gradient map of the Tarfaya basin modified after Zarhloule (2003) and Ghassal et al. (2015) .......................................................................................................................... 11

Fig. 2-1 Nile Delta Basin map showing important structures, wells, and gas fields (modified after Abdel Aal et al. 2001; Shaaban et al. 2006). The gray shaded area represents basalt. ........................................................................................................................................ 19

Fig. 2-2 Generalized stratigraphic column of the Nile Delta Basin (modified after El Nady 2007; Guiraud and Bosworth 1999) ........................................................................................................ 22

Fig. 2-3 Depth plotted versus TOC, CaCO3, TS, HI, and Pr/Ph of the Abu Hammad-1 and Matariya-1 wells .......................................................................................................................................... 33

Fig. 2-4 TOC plotted versus TS (a) and CaCO3 (b) of the Abu Hammad-1 and Matariya-1 wells ................................................................................................................................................................. 34

Fig. 2-5 TOC plotted versus S2 of the investigated samples. ...................................................... 35

Fig. 2-6 Gas chromatographs of the saturated hydrocarbon fractions of the a) Kafr El Sheikh Formation, b) Qawasim Formation, c) Upper Sidi Salem Formation, d) Lower Sidi Salem Formation, e) Kharita Formation, f) Upper Alam El Bueib Formation, g) Lower Alam El Bueib Formation, h) Masajid Formation, and i) Khatatba Formation. Note that n-C17 and n-C20 are marked. ..................................................................................................................... 37

Fig. 2-7 Burial/thermal history diagrams of the a) Abu Hammad-1 and b) the Matariya-1 wells in the next page. ............................................................................................................................... 41

Fig. 2-8 Pr/n-C17 versus Ph/n-C18 for selected samples from the Abu Hammad-1 and Matariya-1 wells, in comparison to other published data. ......................................................... 46

Fig. 2-9 a) Cross section demonstrates Oligocene and Miocene stratigraphy at the eastern Nile Delta Basin (modified after Shaaban et al. 2006). B) Cross section shows Nile Delta

XVI

stratigraphy from the onshore to the offshore areas (modified after Abdel Aal et al. 2001). ............................................................................................................................................................................ 50

Fig. 2-10 HI versus OI of the samples from the Abu Hammad-1 and Matariya-1 wells. PFM-1 well data are published in Khaled et al. (2014). .......................................................................... 51

Fig. 2-11 TOC and HI map of the Matariya-1 well and published data of the Sidi Salem Formation source rock. Published data sources: Abu Madi-1, Abu Madi-3, Abadiya-1, Kafer El Shiekh-1, Abu Madi-1, and Abu Madi-3 (El Nady 2007); Sidi Salem-1 (El Nady and Harb 2010); AbuMadi-9 well (Keshta et al. 2012); and S.W. Bilqas-1, Port said-1, Qantara-1, and Port Fouad-1 (Shaaban et al. 2006). ..................................................................... 54

Fig. 3-1 a) A location map of the studied GPT-3 well and the main sedimentary basins in the north Western Desert, Egypt. B) Paleogeographic map at ~94 Ma of North Egypt and the surrounding areas (modified after Phillip, 2003)................................................................... 60

Fig. 3-2 Lithostratigraphic column of the GPT-3 well, north Western Desert, Egypt (after GPC, 1984). The associated biozones are after El Beialy et al. (2010). .................................. 63

Fig. 3-3 Total organic carbon (TOC), CaCO3, Total sulfur (TS) and Rock-Eval data versus depth, Bahariya and Abu Roash formations, GPT-3 well, north Western Desert, Egypt. The Abu Roash “F” source rocks are classified as Transgression phases I and II. * CaCO3 is calculated from total inorganic carbon. ............................................................................................. 72

Fig. 3-4 XRF elemental data of the Abu Roash “F” Member, GPT-3 well, north Western Desert, Egypt. ................................................................................................................................................ 73

Fig. 3-5 K/Al ratio versus (a) Si/Al ratio and (b) CaCO3 of selected samples from the Abu Roash “E”, “F” and “G” members, GPT-3 well, north Western Desert, Egypt showing possible depositional environment, climate and clay mineral composition. ...................... 75

Fig. 3-6 SiO2-5*Al2O3-2*Ca ternary diagram demonstrating lithological differences among the Abu Roash “E”, “F” and “G” samples, GPT-3 well, north Western Desert, Egypt. ........ 75

Fig. 3-7 Total organic carbon-iron-total sulfur ternary diagram of selected samples from Abu Roash “G”, “F” and “E” members, GPT-3 well, north Western Desert, Egypt. ............. 76

Fig. 3-8 CaCO3 versus total organic carbon (TOC), GPT-3 well, showing two distinctive trends. The samples of Abu Roash “F” have a positive trend, whereas samples from other rock units denote a weak negative relation. ..................................................................................... 77

Fig. 3-9 Total sulfur (TS) versus total organic carbon (TOC) showing the difference between the Abu Roash “F” Member and other studied rock units. The samples are classified into three groups which are 1) Abu Roash “F” Member Transgression-1:, 2) Abu Roash “F” Member Transgression-2: and 3) oxic/suboxic shelf: the samples from the rest of the geological units. Value%: CaCO3 calculated from total inorganic carbon. ............... 77

XVII

Fig. 3-10 Pseudo van Krevelen diagram of the studied rock units, GPT-3 well, north Western Desert, Egypt. Note that the high HI readings from the Abu Roash “D” samples are from a reservoir section. .................................................................................................................. 78

Fig. 3-11 Rock-Eval pyrograms and gas chromatograms of the Abu Roash “C” and “D” reservoirs as well as Abu Roash “F” source rock sections, GPT-3 well, north Western Desert, Egypt. ................................................................................................................................................ 79

Fig. 3-12 Organic petrography of the Abu Rash “F” samples under fluorescent light, GPT-3 well, north Western Desert, Egypt.................................................................................................... 80

Fig. 3-13 a) Total organic carbon (TOC) versus terrestrial to aquatic ratio (TAR). b) Pristane/phytane ratio versus steranes/hopanes ratio (str/hop), GPT-3 well, north Western Desert, Egypt. ............................................................................................................................. 82

Fig. 3-14 C27, C28 and C29 steranes ternary diagram of selected samples from the Bahariya and Abu Roash formations, GPT-3 well, north Western Desert, Egypt. ................................. 84

Fig. 3-15 C29 ββ/(αα+ββ) steranes versus C29 ααα20S/(20S+20R) steranes indicating maturity in the studied rock units, GPT-3 well, north Western Desert, Egypt. Please refer to Table 4 for sample assignment. ........................................................................................................ 84

Fig. 3-16 Curie-Point-Pyrolysis Gas Chromatography-Mass Spectrometry Chromatograms of representative samples from the Abu Roash “F” Member indicating a high organic sulfur contents in transgression phase-I, Abu Rash “F” Member, GPT-3 well, north Western Desert, Egypt. ................................................................................................................. 85

Fig. 3-17 Ali-Be-T ternary diagram (alaphitic- hydrocarbonsn-C6 to n-C14-Benzenes-Thiophenes) based on Curie-Point-Pyrolysis-Gas-chromatography-mass-spectrometer data of selected samples from the Abu Roash “F” source rocks, GPT-3 well, north Western Desert, Egypt. ................................................................................................................................................ 86

Fig. 3-18 APP ternary plot (Tyson, 1993) of selected samples from the Bahariya and Abu Roash formations, GPT-3 well, north Western Desert, Egypt. ................................................... 88

Fig. 3-19 Pristane (Pr)/n-C17 versus phytane (Ph)/n-C18 illustrating the organic matter type of selected samples from the studied rock units, GPT-3 well, north Western Desert, Egypt. ............................................................................................................................................................... 93

Fig. 3-20 Generalized depositional model of the Abu Roash “F” Member based on the current geochemical and palynological interpretation. ............................................................... 99

Fig. 4-1 Overview map of the Tarfaya Basin showing the location of the studied well (S-4) and some of the previously studied wells (modified after Michard et al., 2008). ...... 109

XVIII

Fig. 4-2 Cross section showing the extent of the onshore/offshore stratigraphy of the Tarfaya Basin (modified after Wenke, 2014), including Cap Juby well. Surface geology in the small map modified after Saadi et al. (1985). CJ: Cap Juby well. ..................................... 111

Fig. 4-3 Stratigraphic column representing the common lithologies in the Tarfaya Basin from coastal to deep marine areas (modified after Davison, 2005; Sehrt, 2014). ........... 115

Fig. 4-4 Depth plots TS, TOC, CaCO3 and TS/TOC ratio of all stratigraphic units. ........... 121

Fig. 4-5 Cross plots between CaCO3 versus TOC and TS. The correlation of CaCO3 and TOC relationship changes significantly from positive in the Lower Cenomanian to negative in the Turonian. The CaCO3 and TS correlations are always negative with variable regression coefficients. ........................................................................................................................... 133

Fig. 4-6 Elemental data versus depth shows increase in silicate and rutile forming elements with depth. It also shows a strong increase in P2O5 before the CTBE. .............. 134

Fig. 4-7 CaCO3 versus Fe2O3 and TiO2 Cross plots show inverse relationship in all studied intervals. ....................................................................................................................................................... 135

Fig. 4-8 Pseudo van Krevelen diagram of bulk Rock- Eval-6 samples of the various stratigraphic intervals. ............................................................................................................................ 137

Fig. 4-9 Rock-Eval HI, OI and Tmax versus depth plot. It shows the apparent difference between the Cenomanian to Turonian source rocks. On the basis of microscopic observations the Tmax shift is interpreted to be caused by a change in the organic facies rather than thermal maturity. .............................................................................................................. 138

Fig. 4-10 Micrograph of representative samples of each organofacies type and stratigraphic interva ................................................................................................................................ 139

Fig. 4-11 Organic matter volume vs. TOC weight percent. The samples that show very low visible organic matter were assigned as 0.2% for the sake of simplicity. .......................... 141

Fig. 4-12 Pr/C17 vs. Ph/C18 diagram suggests marine and thermally immature organic matter for all sample. The classification method is from Shanmungam (1985). ............. 142

Fig. 4-13 C27-C29 steranes ternary diagram indicates shallow open marine depositional environment. ............................................................................................................................................... 143

Fig. 4-14 TS versus TOC cross-plot shows that the majority of the Cenomanian to Turonian samples are plotted below the normal marine line of Berner (1984) unlike the majority of the Lower Cenomanian samples which plot above the line .............................. 150

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Fig. 4-15 TS versus Fe shows that the majority of the samples from Cenomanian to Turonian are plotted above the Pyrite line indicating that the sulfur in theses samples is present in other forma than pyrite. ................................................................................................... 151

Fig. 4-16 OM-CaCO3-Silicates trinary diagram (modified after Littke, 1993) showing that the best organic preservation is achieved at CaCO3 concentration between 45 to 80%. .......................................................................................................................................................................... 153

Fig. 5-1List of the investigated terrigenous, biogenic and early diagenesis geochemical parameters. ................................................................................................................................................. 158

Fig. 5-2 Al2O3 versus K2O, TiO2, MnO and Fe2O3 cross-plots. Note the positive correlations indicating similar terrigenous origin. ............................................................................................... 158

Fig. 5-3 Geochemical conceptual model summarizing the differences between the three main depositional environments investigated in the current thesis. ................................... 160

Fig. 5-4 Carbonate-original organic matter-silicate diagram of selected samples from the Nile Delta (matariya-1 and Abu hammad-1 wells), The Abu Gharadig Basin (GPT-3 well) and the Tarfaya Basin (SON-4). ........................................................................................................... 161

Fig. 5-5 MnO versus a) oxygen index and b) Pr/Ph plots showing positive correlations of selected samples from the Tarfaya Basin (SON-4) and the Abu Gharadig Basin (GPT-3). .......................................................................................................................................................................... 162

Fig. 5-6 Oxygen Index versus thiophenes/benzenes ratio of selected samples from the Tarfaya Basin (SON-4) and the Abu Gharadig Basin (GPT-3). ................................................. 163

Fig. 5-7 Mn/S ratio versus hydrogen Index relationships illustrating positive correlation for the Abu Gharadig basin samples (GPT-3 well). ...................................................................... 163

Fig. 5-8 TiO2 versus S/Fe ratio relationship used as an example of the inverse relationship between terrigenous elements and S/Fe ratio. ................................................... 164

Fig. 5-9 Tmax versus Thiophenes/Benzenes ratio of selected samples from the Tarfaya (SON-4) and Abu Gharadig basins (GPT-3) showing tow clusters. ....................................... 165

Fig. 5-10 S/Fe versus Al2O3 ratios of selected samples from the Tarfaya and Abu Gharadig basins. ............................................................................................................................................................ 166

1

Chapter 1 | Introduction

1.1 Background

Source rock studies witnessed noteworthy developments after the shale gas/oil booms

in the United States, Europe, and China over the second decade of this Century. The

increased interest in the unconventional resources related to source rocks motivated

academia and industry to refine their assessment methods toward detailed

characterizations that surpass bulk evaluations. Thus, the integration of the variable

geological and petroleum engineering data and methodologies became leading research

trends influencing conventional and unconventional exploration strategies. First, they

enhance the understanding of source rock formation processes at different geological

settings which helps in predicting source rock facies in a regional context and therefore,

identifying and prioritizing new prospects. Moreover, they assist in distinguishing

productive zones and their hydrocarbon generative capabilities in vertical and spatial

distribution. These studies also have a significant influence on regional petroleum

exploration and paleoenvironmental reconstruction studies. The current work integrates

various organic and inorganic geochemical techniques with petrological, palynological

and basin modeling methods.

Many factors play roles in petroleum source rock deposition in marine and lacustrine

environments such as and the sea level changes or tectonic activities. The quality and

composition of the organic matter also depend on the proximity to the shoreline, the

bottom water oxygen contents, the origin and productivity of organic matter and the

interplay between the dissolved elements in the water and the organic matter. In this

chapter, the main marine source rock depositional settings, as well as the major climatic

and tectonic events that occurred in North Africa since the Mesozoic are discussed. This

is followed by a general overview of the common source rocks in Egypt and the Tarfaya

Basin located in Morocco. The chapter ends with the aims and the outline of the thesis.

2

1.2 General Remarks on Source Rock Depositional Settings

Source rocks are fine-grained carbonate or siliciclastics organic-rich sedimentary rocks

that are expected to generate fluid hydrocarbons when attaining elevated thermal

maturity levels (Littke et al., 1997; Tissot and Welte, 1984). The richness and quality of

source rocks are controlled by organic matter productivity, preservation, and

depositional conditions. The organic matter can be transported (allochthonous) or in situ

(autochthonous). The former is usually from a terrestrial origin whereas the latter is

from marine and terrestrial source (e.g. Bustin, 1988; Katz, 2012; Littke et al., 1997).

Extensive studies were carried out to understand the organic matter production,

preservation, and kerogen formation pathways in several depositional environments.

Deltas as terrestrial to marine transitional environments are characterized by mostly

high proportions of higher plant tissue (allochthonous) and smaller proportions of

aquatic algae (autochthonous) (Bustin, 1988; Littke et al., 1997; Tissot and Welte, 1984).

The deltaic environments include three main types which are river-dominated, wave-

dominated, and tide-dominated (Galloway 1975). They differ in their sediment supply

and types which significantly influence the depositional conditions. The typical examples

of prolific petroleum deltaic petroleum systems are 1) the Mississippi, 2) the Niger and

3) Mahakam deltas which represent the river-dominated type (e.g. Peters et al., 2000;

Michele et al., 1999). The Nile Delta, on the other hand, is classified as wave-dominated

type (Coe et al., 2003). The river-dominated system type is well understood compared to

the other types of deltas regarding petroleum potential.

The organic matters in river-dominated delta environments are subjected to many

factors that control their composition and quality. These factors may partially apply on

other types of deltas. Rivers transport terrigenous input that would constitute vitrinite,

inertinite, coal particles and fresh/brackish water algae. Rapid water circulation

increases the oxygen contents of the bottom water and organic matter oxidation. Due to

its low density, the liptinite macerals are attributed to selective transportation (Bustin,

1988). These processes indeed, will modify the Rock-Eval HI and OI values. These

3

characteristics differ outward from the delta front to more marine dominating organic

matter. Moreover, the interplay between fluvial and marine systems due to relative sea

level changes considerably alter the bottom water conditions and consequently the

organic matter types and qualities. Therefore, the Delta petroleum system is considered

one of the challenging systems to investigate. The current work selected the Nile Delta

Basin to address the organic matter richness and quality in wave-dominated delta

environments. Note that this kind of delta does not, commonly, favor source rock

deposition (Allen and Allen 2005). Thus, this thesis aims to explain the high hydrocarbon

potential found in the Nile delta basin in Chapter 2.

Marine source rocks are developed in three main settings which are oxygen minimum

zones along continental shelves, upwelling zones and silled/barred basins (Fig.1-1) (e.g.

Katz, 2012; Littke et al., 1993; Selley, 1998). Oxygen minimum zones are caused due to

oxygen consumption by decay of biomass and lack of circulation and photosynthesis in

deeper, dark water that omits oxygen resupply (Selley, 1998). The position of this zone

is highly dependent on the temperature and salinity of the marine water (Katz, 2012).

Source rock developments within upwelling zones account for almost half of the world

organic rich source rocks (Parrish, 1987). This is basically due to the remarkably high

biological productivity that outpaces the productivity of normal shelves by ~3 times

(Ryther, 1969; Koblentz-Mishke et al., 1970; Katz 2012). When global greenhouse

warming climate prevails, the alongshore winds move the marine coastal warm waters

allowing upwelling nutrient-rich water to replace it (Bakun, 1990) (Fig.1-1).

Consequently, the bioproductivity increases which leads later to high rate of deposition

of organic matter (Bakun, 1990; Parrish, 1987). The high productivity causes the bottom

water oxygen to decrease which creates favorable condition for organic matter

preservation (Parrish, 1987; Katz 2012). Note that the intensity of the upwelling process

lowers during cold climate (Bakun, 1990; Parrish, 1987). Due to wind direction variation

and the Coriolis Effect resulting from Earth rotation, upwelling zones are pronounced

along the western continental margins (e.g. Katz 2012).

4

The source rock development in barred basins occur principally due to density

stratifications where less saline, less dense water overlies the saline, denser water. This

process develops bottom water anoxia. The second mechanism is attributed to thermal

stratification where warm waters rests on cooler waters. The barred basins usually occur

in tropical regions where the wind stress and the change in seasonal temperature are

minimal (Gluyas and Swarbrick, 2013; Katz 2012).

Fig. 1-1 Schematic diagram of common source rock depositional settings. Pink polygons are anoxic/oxygen minimum zones.

1.3 Geological Setting of North Africa from Jurassic to Recent

North Africa acted as part of Gondwana supercontinent and the southern passive margin

of the Neotethys after the break-up of Pangea during the late Triassic Period (Berra and

Angiolini, 2014; Bosworth 1994; Golonka, 2007; Guiraud and Bosworth 1997; Guiraud et

al., 2005; Stampfli and Borel 2002). The northwestern African corner, however, was part

of the south North Atlantic region (e.g. Tarfaya basin). Since the early Jurassic, many

factors controlled the deposition of the Mesozoic to Cenozoic sedimentary sequence in

North Africa. These include global warming/cooling climates, oceanic anoxic events,

pronounced sea level changes, and major tectonic events such as Gondwana break-up,

the opening of the Atlantic Ocean, Jurassic rifting, and the opening of the Red Sea, the

5

Syrian arc event and Messinian Salinity Crisis. Fig.1-2 illustrates the tectonic evolution

from Jurassic to Neogene demonstrating the paleographic reconstruction of three time-

slices. A literature review is provided herein to address the major tectonic and climatic

factors that controlled basin formations. Then in the next chapters, a geological overview

of each basin is provided.

1.3.1 Jurassic Period

Major tectonic events played an important role in the development of North African

basins. Variable settings characterized the Liassic times. In the Eastern Mediterranean

region, active faulting took place in marine/marginal settings coeval with carbonates and

shallow marine sediment deposition. In the Tunisian/Algerian Sahara, marginal marine

settings prevailed and resulted in evaporite deposition. Moreover, active rifting occurred

in the Atlas basins, where some areas remained subaerial (Guiraud et al., 2005). The

extensional regime in North Africa is mainly related to the opening of the Central Atlantic

from the west and the drift of the Turkish-Apulian terrain in the North (Guiraud et al.,

1987). A period of sea transgression and E-W half graben development characterizes the

Middle Jurassic in Egypt. On the other hand, thermal subsidence occurred in the Central

Atlantic margin related to the opening of the Atlantic Ocean (Guiraud et al., 2005).

Moreover, the spreading of the Atlantic Ocean completely detached Africa from North

America (Berra and Angiolini, 2014). Many North African basins witnessed prolific

petroleum source rock deposition during the Middle Jurassic (e.g. Masajid Formation,

Egypt). Higher sea level prevailed during the Late Jurassic and rifting started in some

Western Desert basins such as the Abu Gharadig Basin. However, some of the Jurassic

deposits were eroded later during Upper Cretaceous and Cenozoic inversions (Guiraud

and Bosworth, 1999). Along the southwestern Moroccan Atlantic margin, regression

took place shifting the depositional environment to shallow marine facies (Hafid et al.,

2008). At the Jurassic- Cretaceous boundary major deformation occurred in the North

6

African basins related to the Cimmerian/Berriasian orogenic affecting also southeastern

Europe (Guiraud et al., 2005: Stampfli et al., 2001).

Fig. 1-2 Paleogeographic reconstructions modified after Blaeky 2012. The yellow dot is for Morocco and the magenta dot is for Egypt. “Global Paleogeographic Maps © 2012 Colorado Plateau Geosystems Inc., used with permission from Ron Blakey”.

1.3.2 Cretaceous Period

Active E-W/NW-SE rifting characterizes the Lower Cretaceous in North Africa

contemporaneously with the Arabian-Nubian Block separation from the South American

7

plate (Guiraud et al., 2005). During Aptain, the connection between the NeoTethys Ocean

and Central Atlantic was complete, and the sea level rose (Berra and Angiolini, 2014). The

rifting persisted in most North African basins till Santonian. Warm climate cycles

coexisted with highest recorded Phanerozoic sea transgressions which invaded

northwestern and central African basins during the Middle to Late Cretaceous and which

led to oceanic anoxic events (e.g. OAE2 and OAE3), (Fig.1-2) (Guiraud et al., 2005: Haq et

al, 1987). These periods witnessed intense organic carbon deposition and increased

bottom water anoxia (Jenkyns, 2010). Furthermore, widespread warm bottom waters

characterized the North Atlantic as well as the tropical oceans leading to positive δ13C

isotope excursions (Friedrich et al., 2012). Moreover, northern Egypt and southwestern

Morocco acted as carbonate platforms (Phillip et al., 2013). During Santonian, major

tectonic events took place including the ophiolite obduction in Oman, the change in poles

of rotation of the Atlantic Ocean and the Laramide phase of the Alpine orogeny. The later

were responsible for propagating major fold belts such as the Atlas chain and the Syrian

Arc in the Levant and Northern Egyptian basins (Guiraud and Bosworth 1997: Guiraud

et al., 1987; Tawadros, 2011). These movements caused regional unconformities

throughout the North African basins as will be discussed in the case of Northern Egypt in

the flowing chapters. Rejuvenation and acceleration of rifts spanned the Campanian to

Maastrichtian ages in North Africa with infrequent occurrences of magmatic activities

such as in offshore Libya (Guiraud and Bosworth, 1997, 1999).

1.3.3 Paleogene Period

A new E-W compressional tectonic phase occurred at the Maastrichtian-Paleocene

boundary that was responsible for accentuating the Santonian fold belts in northeastern

Africa (Guiraud and Bosworth, 1997). However, this shortening phase started earlier in

northwestern Africa such as in Algeria (Aris et al, 1998). Consequently, a significant

hiatus unconformity in the Tarfaya Basin occurred from Santonian to Pliocene (Davidson,

2005). A pronounced sea transgression occupied major parts of North Africa during the

Paleocene to Eocene times and deposited shallow marine sediments (Guiraud et al.,

2005). In the Eocene to Oligocene times, a compressional event evolved in North Africa

8

especially in the Maghrebian Atlas in northwestern Africa and the Syrian Arc in the

Eastern Mediterranean region (Guiraud and Bosworth, 1999; Guiraud et al., 2005). The

event was coeval with the opening of the Atlantic and Indian oceans and the movement

of Africa toward southern Eurasia and the gradual closure of NeoTethys (Berra and

Angiolini, 2014). Through the Early Oligocene, North Egypt witnessed high sea level

before maximum tectonic shortening of Syrian Arc that ceased the basin subsidence in

the Western Desert. On the other hand, the Tarfaya Basin area was uplifted due to the

orogeny affecting northwest Africa (see above) and created an erosional surface till the

Miocene (Ruiz et al., 2010; Wenke, 2014).

1.3.4 Neogene Period

The Miocene Epoch witnessed significant extensional and compressional tectonic events

that considerably affected Northeast Africa. These include the initiating of the Red Sea

rifting, the opening of the Gulf of Aqaba, and development of the River Nile (e.g. Bosworth

et al., 2005). Also, it witnessed variable sea level changes with a global sea level

regression leading to thick evaporites in the Messinian (Messinian Crises). The

Quaternary is characterized by widespread fluvial deposits (Guiraud et al., 2005).

1.4 Source Rock Potential Overview of the Study Areas

1.4.1 Source rock potential of Egypt

In Africa, Egypt is the largest non-OPEC oil producer and the second natural gas producer

(US Energy Administration Information, 2015). It comprises three main petroleum

provinces which are the Western Desert, Nile Delta and Gulf of Suze areas. It is worth

noting that the Red Sea and southern Egypt can also have petroleum potential but has

not been fully explored.

The Paleozoic source rocks, in general, are poorly understood, and about 40 wells in the

Western Desert penetrated the Precambrian or Paleozoic (Doloson et al., 2000). The

Silurian and Devonian successions host highly prolific petroleum systems in Libya and

Saudi Arabia (e.g. Macgregor, 1996; Mahmoud et al., 1992). This indicates that Egypt

could have equivalent prolific source rocks or migrated hydrocarbons from Libyan

9

basins. One of the Western Desert wells tested gas condensates in a Carboniferous

section, but no geochemical data was released for this gas (Doloson et al., 2000).

The Jurassic source rocks are better studied in the Western Desert than in the Nile Delta

and Gulf of Suez basins. The Jurassic source rocks in the Western Desert include the

Khatatba, Shaltut, Kharita and Masajid formations (e.g El Nady et al., 2015; Maky and

Saad, 2009; Shalaby et al., 2012). The Cretaceous source rocks in the Western Desert are

found in Alam El Bueib Formation, the “G”, “F” and “E” members of the Abu Roash

Formation as well as occasionally the Bahariya and Khoman formations (e.g. El Nady,

2016; Zobaa et al., 2011). In the Western Desert, the Miocene source rocks are less

common, but they can be found in Dabba and Moghra formations (Maky and Saad, 2009).

In the Nile Delta Basin, limited information is available on the Jurassic and Cretaceous

source rocks (Shaaban et al., 2006). The current work (chapter 2) shed lights on the

Jurassic and Lower Cretaceous potential source rocks. The Middle Miocene Sidi Salem

Formation contains one of the major source rocks of the basin (e.g. El Nady, 2007).

The Gulf of Suez hosts prolific source rocks within the Cretaceous Brown Limestone in

middle and northern areas (e.g. Robison, 1995) and excellent Miocene source rocks

within Rudeis and Kareem formations (e.g. El Atfy et al, 2014,). Along the Red Sea

coastline, organic-rich beds of the upper Cretaceous Dakhla and Duwi formations show

excellent source rock potential (e.g. El Kammar et al., 1990). Good Miocene source rock

qualities are expected along the Red Sea basins such as the source rocks found in Saudi

and Sudanese coastlines (e.g. Cole et al., 1995)

1.4.2 Source Rock Potential of Tarfaya Basin

The Tarfaya basin is considered one of the most important petroleum basins among

Moroccan petroleum provinces. (Dyni, 2006). In the following, the potential source rocks

of the Tarfaya basin are summarized (Fig, 1-3).

Outcrop samples within the Ordovician, Devonian, Carboniferous and Lower Cretaceous

except for the Albian have poor source rock potential. All of the samples are thermally

immature based on microscopic and pyrolysis results (Sachse et al., 2011). The samples

10

from the Ordovician, Devonian, Carboniferous and Lower Cretaceous have TOC values of

less than 0.50%. Geochemical evaluations of three onshore wells and outcrop samples

prove good to excellent petroleum source rock potential within the late Albian, Upper

Cretaceous and Eocene successions (Sachse et al., 2011, 2014). On the other hand, the

Albian source rocks show high quality in the coastal areas, and this diminishes toward

the eastern part of the basin. The difference is explained by changes in the depositional

environment from marine to non-marine to the eastern hinterland.

Cenomanian outcrop samples show variable petroleum source rock potential. Along the

present day coastline, the Cenomanian is rich in marine organic matter with TOC

contents averaging 4 and excellent kerogen quality attested by average HI values of 600

mgHC/g TOC (Sachse et al., 2011). Furthermore, the samples are lean in vitrinite and rich

in liptinite which suggests excellent oil prone source rocks. The overlying Upper

Cenomanian and the lower Turonian witnessed one of the most significant Oceanic

Anoxic Events in the Earth history (OAE 2) (Kolonic et al., 2002). The inland outcrop

samples from the Cenomanian/Turonian boundary are of a terrestrial or lagoonal

environment, whereas the well samples close to the coast represent fully marine

conditions (Sachse et al., 2011). The Coniacian and Santonian intervals partly represent

OAE 3 and are also rich in TOC having high HI values (Sachse et al., 2014). Several outcrop

samples from the Eocene show variable source rock qualities. The TOC ranges from 0.05

to 7.20 %, and HI varies from 89 to 694 mgHC/gTOC (Sachse et al., 2011).

Kinetic experiments on some of the Cretaceous samples indicate a temperature of an

onset of petroleum generation between 101-115 °C (Sachse et al., 2011). Therefore, these

samples if buried at an approximate depth of 4000 m will start to generate oil assuming

a geothermal gradient of 25 to 30 °C/km (Fig.1-4). Therefore, a great oil source potential

for the late Albian to the Eocene especially in the coastal and offshore areas is suggested.

In the coastal regions, maturity is not sufficient for petroleum generation, but the thick

sediments might act as oil shales for retorting. In some offshore areas, sufficient

temperature and maturity might be reached for petroleum generations. Figure. 1-3

summarizes the probability of source rock potential based on research work by Ghassal

11

et al. (2015). Further details on the petroleum systems of the Tarfaya Basin is given in

Chapter 4.

Fig. 1-3 Source rock potential traffic light map of the Tarfaya basin based on published data by Sachse et al., (2011, 2012, 2014), Ghassal et al., (2015) and Wenke (2014).

Fig. 1-4 Geothermal gradient map of the Tarfaya basin modified after Zarhloule (2003) and Ghassal et al. (2015)

12

1.5 Research Objectives

Hydrocarbon exploration strategic planning depends on many factors. From a geological

point of view, understanding the basin formation is essential to predict the source rock

reservoir and seal distributions. In the unconventional shale resources, detailed

characterization of organic matter richness, type and thermal maturity, as well as

porosity and permeability, is the key to determine their prospectivity. Organic

geochemistry is an essential subject that helps in reducing exploration risk from the

industrial perspective and a tool that assists in paleoenvironmental reconstruction

studies on the academic side. The thesis combines both perspectives and focuses on the

source rock characterization using conventional and new methods.

The general aim of the thesis is to provide common source rock characteristics of deltaic

and shallow marine environments and their expected hydrocarbon types using data from

three different basins which are the Nile Delta and Abu Gharadig basins in Egypt and the

Tarfaya Basin in southwestern Morocco. Under this topic, the research work investigates

the consequences of the interactions between organic matters and various elements in

the sea bottom using three different integrated approaches. The studied source rocks

cover a wide time span and variable source rock types. The study of each area was

designed specifically to suit their research goals but with emphasizing the general thesis

theme.

In the last few years, the Nile Delta Basin became a very appealing exploration target for

natural gas, yet it lacks a well-established organic geochemical inventory especially for

the Jurassic and Lower Cretaceous successions. Moreover, distribution of the source

rocks is not well documented. The present study aims to 1) characterize the source rock

potential and depositional environment using organic geochemical methods and 2)

model the burial and thermal history using organic petrography and 1D conceptual

modeling. At the end, a summary of the Nile Delta basin source rock potential will be

provided. This study attempts to highlight the source rock characteristics of a poorly

understood wave-dominated delta type.

13

The source rock characteristics in the Abu Gharadig Basin are also poorly understood.

Here, integrated organic and inorganic geochemical and palynofacies data were used to

determine source rock depositional environment and petroleum potential. The study

will examine the effects of the bottom water chemical composition and the interplay

between some elements and organic matter on the source rock quality. The last goal is to

pinpoint the depositional environment changes within Cenomanian to Santonian times

in the Abu Gharadig Basin.

The Tarfaya Cenomanian to Turonian source rocks in Morocco are famous oil shale

deposits. However, they lack detailed organic petrological and organic sulfur richness

information. The study aims to characterize the potential source rocks, then classify

them based on their microscopic features and organic sulfur contents.

Finally, the data of the three studies that represent different shallow marine

environments will be integrated. This will enable us to draw a broad picture of the

changes of source rock facies versus deposition proximity to shorelines. The data will be

retrieved from three different independent basins which should highlight the general

changes that can be applied to any basin avoiding local effects. The overview of the

variations in the source rock richness and quality from deltaic to outer shelf depositional

environments will help in studying frontier or poorly understood basins and executing

lower risk strategic exploration planning beyond the studied areas.

1.6 Thesis Outline

The current thesis comprises three different integrated studies followed by general

discussion and conclusions. The first study (Chapter 2) assesses the Jurassic, Lower

Cretaceous, and Miocene source rocks in the Nile Delta Basin using state of the art organic

geochemical and petrological methods integrated with 1D basin modeling. The study

provides new information about southern and northeastern Nile Delta Basin thermal and

burial histories as well as regional source rock characteristics. It was published in the

Arabian Journal of Geoscience in 2016.

14

The Second study (Chapter 3) uses an integrated geochemical and palynological

approach to investigate the paleoenvironment and source rock potential in the

Cenomanian to Santonian succession in the Abu Gharadig Basin in Egypt. It elucidates the

source rock properties of the Cenomanian-Turonian boundary section (Abu Rash “F”

Member) and highlights remarkable changes in lithologies and kerogen types within this

short geological period. The study area represents shallow marine/terrigenous shelf. It

was submitted to the International Journal of Coal Geology in 2017.

The last study (Chapter 4) aims to comprehensively characterize Cenomanian to

Turonian organic-rich oil shale deposits in the Tarfaya basin in southwest Morocco and

classifies it based on organic sulfur richness. This result is significant for scientific and

industrial communities as the organic sulfur-rich oil shale requires special treatment

upon retorting. This paper was published in a special issue entitled "Selected

contributions from the XIV ALAGO Congress" in Geologica Acta Journal in 2016.

Chapter 5 integrates data from these studies with other published data to highlight

possibly new parameters/proxies for assessing source rock quality at different

depositional settings. Finally, a general synopsis is provided at the end of the thesis in

Chapter 6.

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An oil paint of an allochthonous coal particle in a Middle Jurassic Khatatba source rock sample. Artist: Esrraa Abunar

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Chapter 2 | Source Rock Potential of the Middle Jurassic to Middle Pliocene, Onshore Nile Delta Basin, Egypt1

2.1 Abstract

Organic geochemical characterization of cutting samples from the Abu Hammad-

1 and Matariya-1 wells elucidates the depositional environment and source rock

potential of the Jurassic and Lower Cretaceous successions and the Middle

Miocene to Pleistocene section in the southern and eastern Nile Delta Basin. The

burial and thermal histories of the Mesozoic and Miocene sections were modeled

using 1D basin modeling based on input data from the two wells. This study

reveals fair to good gas-prone source rocks within the Upper Jurassic and Lower

Cretaceous sections with total organic carbon (TOC) averaging 2.7% and

hydrogen index (HI) up to 130 mg HC/g TOC. The pristane/n-C17 versus

phytane/n-C18 correlation suggests mixed marine and terrestrial organic matter

with predominant marine input. Burial and thermal history modeling reveals low

thermal maturity due to low heat flow and thin overburden. These source rocks

can generate gas in the western and northern parts of the basin where they are

situated at deeper settings. In contrast, the thick Middle Miocene shows fair source

rock quality (TOC averaging at 1.4%; HI maximizing at 183 mg HC/g TOC). The

quality decreases towards the younger section where terrestrial organic matter is

abundant. This section is similar to previously studied intervals in the eastern Nile

Delta Basin but differs from equivalents in the central parts where the quality is

1 Ghassal, B. I., El Atfy, H., Sachse, V., & Littke, R. (2016). Source rock potential of the Middle Jurassic to Middle Pliocene, onshore Nile Delta Basin, Egypt. Arabian Journal of Geosciences, 9 (20), 744.

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better. Based on 1D modeling, the thick Middle Miocene source rocks just reached

the oil generation stage, but microbial gas, however, is possible.

2.2 Introduction

The Nile Delta Basin is considered as one of the most productive petroleum basins

in Egypt and the eastern Mediterranean region especially for gas resources and

constitutes approximately 60,000 km2 equally onshore and offshore (Fig. 2-1;

Barakat 2010). It is triangular in shape and is bounded by the Western Desert with

several subbasins such as Natrun and Abu Gharadig to the west and southwest,

Sinai to the east, and the deep Mediterranean to the north (Fig. 2-1). Petroleum

exploration activities started in the 1940s, which led to several gas and

condensate discoveries (Abdel Halim 1999; Shaaban et al. 2006). The basin even

gained greater interest after the recent super giant gas field discovery, Zohr field,

in offshore Nile Delta Basin in 2015 (Esestime et al. 2016). The majority of the

discovered gas and oil fields are located in the northern onshore and the offshore

areas, whereas in the central and southern onshore areas, there are no commercial

accumulations except for some small oil discoveries in 2006 in Messinian

reservoirs located in the vicinity of Mansoura City, e.g., El Tamad Field (Abdel Aal

et al. 2001; El Nady 2007; Leila M., personal communication). Generally, at least

three petroleum plays were identified, i.e., (i) oils sourced from the Late

Cretaceous/Paleogene found in Miocene/Oligocene reservoirs, (ii) thermogenic

gas in the Miocene sections, and (iii) biogenic gas in the Pliocene intervals (Abdel

Halim 1999; Abdel Aal et al. 2001; El Nady 2007; Khaled et al. 2014). Within the

basin, petroleum systems are not yet fully understood; for example, the Jurassic

and Cretaceous sections encompass key source rocks in the region such as in the

north Western Desert and Gulf of Suez basins, but very limited information is

available for equivalent units in the Nile Delta Basin due to limited penetration of

these sections (Shaaban et al. 2006). The southern areas were geochemically

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poorly investigated so far compared to the northern areas, and most of the work

was on Miocene sections (Abdel Halim 1999).

The current study aims to investigate source rock potential of the Middle Jurassic

to Upper Cretaceous as well as the Middle Miocene to Middle Pliocene in the

southeastern and eastern Nile Delta Basin using samples from the Abu Hammad-

1 and Matariya-1 wells, respectively (Fig. 2-1). In addition, the organic

geochemical data will be used to investigate the depositional environment of these

intervals. Moreover, 1D basin models were constructed to quantify burial and

temperature history as well as maturation and petroleum generation and to

evaluate thermogenic gas potential of the assessed source rocks. Deltas are one of

the sedimentary settings that favor source rock deposition and classified into

three types: (1) fluvial dominated, (2) tide dominated, and (3) wave dominated

(Galloway 1975). The first two types are characterized by low energy and favor

source rock deposition more than the high-energy wave-dominated type (e.g., Nile

Delta) that lacks optimum source rock deposition and preservation conditions

(Allen and Allen 2005). Nevertheless, numerous gas fields have been discovered

regardless of the many unexplored sections (Fig. 2-1). Therefore, such integrated

study that combines organic geochemistry and burial and thermal history

modeling should provide a means for a better understanding of source rock

distribution and quality as well as maturity, which might help in future

exploration.

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Fig. 2-1 Nile Delta Basin map showing important structures, wells, and gas fields (modified after Abdel Aal et al. 2001; Shaaban et al. 2006). The gray shaded area represents basalt.

2.3 Geological Setting

2.3.1 Tectonic setting

Northern Egypt is a part of the North African platform which extends from Morocco in

the west to Egypt in the East and was covered by the Neotethys since the Jurassic

(Kerdany and Cherif 1990). The Nile Delta Basin is one of the most important basins in

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northern Egypt and situated between three major tectonic elements: the Red Sea Rift, the

African-Anatolian plate boundary, and the Syrian Arc. Moreover, the basin history was

altered by several tectonic events since the beginning of the Mesozoic, which influenced

the sediment distribution and facies and controlled the formation of structural elements

such as petroleum traps (Kerdany and Cherif 1990; Said 1990; Meshref 1990; Zaghloul

et al. 1999a). The Nile Delta Basin is subdivided into a southern block located on the

unstable shelf (where the study area is located) and a northern block situated on the

steeply faulted continental shelf (Fig. 2-1; Zaghloul et al. 1999b; Kerdany and Cherif

1990; Meshref 1990).

The opening of the Atlantic in the Early Jurassic resulted in two major sets of tectonic

elements in northern Egypt, which are north-northwest-trending folds with thrust faults

and left lateral east-northeast-trending strike-slip faults (Meshref 1990; Dolson et al.

2000; Abedl Aal et al. 2001). Later, sedimentation was affected by Upper

Cretaceous/Lower Eocene compression (Syrian Arc event: ENE-trending structures)

simultaneously with the closure of the Tethys (Kerdany and Cherif 1990; Zaghloul et al.

1999a) that was responsible for regional erosion. Several tectonic events during the

Tertiary including the Red Sea rifting, the opening of Gulf of Aqaba, the Baltim rift, and

the offshore Mediterranean Rosetta and Temsah faults rejuvenated the older structures

(Abedl Aal et al. 2001; Khaled et al. 2014). Rosetta and Temsah faults were activated

during Upper Cretaceous and Neogene times and resulted in the formation of anticlines

that followed those trends and trapped gas especially in the offshore area (Abedl Aal et

al. 2001; Khaled et al. 2014; Fig. 2-1). A period of NESW faulting occurred after the

Messianian event in the offshore, especially in the eastern area, and intersected the

anticlines (Dolson et al. 2000; Abedl Aal et al. 2001; Khaled et al. 2014). On the other

hand, fault movements were mostly pre-Messinian in the western part of the offshore

area (Abdel Aal et al. 2001). In general, the offshore area appears to be more complex in

terms of structures compared to the onshore area, especially towards the north.

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2.3.2 Stratigraphy