Regional Stratigraphic and Structural Framework of Parts of the Eastern Coastal Swamp Depo-Belt of the Niger Delta.

ABSTRACT 

Facies geometry, stratigraphic configuration, structural style, hydrocarbon type and distribution within the paralic Agbada Formation of Middle to Late Miocene age across several fields in the Eastern part of the Coastal Swamp depo-belt were studied using regional 3D seismic, wire-line well logs and biostratigraphic data. The study involved analyses of sequence stratigraphic framework across nine fields using information obtained from twenty- four wells. Ten major stratigraphic bounding surfaces (five each of sequence boundaries (SB) with ages ranging from 13.1 Ma through 8.5 Ma. and maximum flooding surfaces (MFS) with ages between 12.8 Ma. and 7.4 Ma respectively) were identified, correlated and mapped across several wells and seismic sections. Four depositional sequences were delineated and stratigraphic flattening at various MFS(s) indicates that there is a shift of the depositional center from north to south. Three major stacking patterns (progradational, retrogradational and aggreadational) were delineated and interpreted as Lowstand Systems Tract (LST), Highstand Systems Tract (HST) and Trangressive Systems Tract (TST) using their bounding surfaces. The alternation of the reservoir sands of the LST and HST and the shale units of the TST offers good stratigraphic traps for hydrocarbon. The Gross Depositional Environment spans through incised Canyons, Channels, Inner Mid Shelf, Shelf Margin and Slope Margin. Paleobathymetric maps show generally, that sediments were deposited within Neritic through Bathyal environments at different times, aligning with the progradational pattern of deposition of the Niger Delta. Structural analyses reveal the occurrence of Back to Back Horst Block (Trapezoid Zone), Collapse Crest Structures, Simple/Faulted Rollovers, Regional Foot Walls/Hanging Walls and Sub-detachment structures dominating within the mainly extensional zone and these constitute the major hydrocarbon traps in the area. Revalidated and newly identified leads at intermediate and deeper horizons indicate that detailed mapping of stratigraphy and structures are critical in hydrocarbon evaluation of deeper prospects in the Niger Delta.

TABLE OF CONTENTS

TITLE i

CERTIFICATION ii

DEDICATION iii

ACKNOWLEDGMENTS iv

ABSTRACT v

TABLE OF CONTENTS vi

LIST OF FIGURES x

LIST OF TABLES xv

CHAPTER ONE 1

1.0 GENERAL INTRODUCTION 1

1.1 Introduction 1

1.2 Location of the basin and the study area 2

1.3 Literature Review 5

1.4 Aims/scope of study 9

CHAPTER TWO 10

2.0 GEOLOGIC FRAMEWORK 10

2.1 Regional Tectonic Setting 10

2.2 Regional Stratigraphic Setting 14

2.2.1 Akata Formation 11

2.2.2 Agbada Formation 15

2.2.3 Benin Formation 19

2.3 Depobelts 19

CHAPTER THREE 22

3.0 METHODOLOGY 22

3.1 Data Set 22

3.1.1 Data quality and software resources 24

3.2 Delineation of Lithofacies and Depositional Environments 29

3.3 Stacking Patterns and Parasequences 29

3.4 Key Stratigraphic Surfaces, Systems Tracts and Depositional Sequences 34

3.5 Well Correlation 35

CHAPTER FOUR 40

4.0 DATA ANALYSIS AND INTERPRETATIONS 40

4.1 Lithofacies and Depositional Environments 40

4.1.1 Coarse Grained Basal Sandstone Facies 40

4.1.2 Shaly-Sandstone Facies 40

4.1.3 Mudrock Facies 41

4.1.4 Heterolithic Facies 41

4. 2 Sequence Stratigraphic Analysis 45

4.2.1 Maximum Flooding Surface (MFS) 45

4.2.2 Sequence Boundary (SB) and Transgressive Surface of Erosion (TSE) 45

4.2.3 Depositional Sequences and Systems Tracts 58

4.2.4 Well Correlation 61

4.3 Seismic 72

4.3.1 Semblance cube / time slice generation 72

4.3.2 Seismic Stratigraphic / Facies Interpretation 72

4.4 Well to Seismic Tie / Integration 74

4.4.1 Fault Mapping/Interpretation 79

4.4.2 Horizon Mapping/Interpretation 79

4.5 Field trapping structure identification 83

4.6 Lead identification / revalidation 83

4.7 Gross Depositional Environment and Paleobathymetry 83

4.8 Hydrocarbon data integration 84

CHAPTER FIVE 91

5.0 RESULTS AND DISCUSSION 92

5.1 Sequence stratigraphic framework 92

5.1.1 Depositional Sequence Architecture 93

5.2 Structural Framework 94

5.3 Hydrocarbon occurrence and distribution / trend 95

5.4 Hydrocarbon leads and potentials 96

SUMMARY AND CONCLUSION 99

RECOMMENDATION 102

REFERENCES 103

APPENDICES 113