SEISMIC INTERPRETATION OF “XY” FIELD IN THE SOUTH-EASTERN NIGER DELTA

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ABSTRACT

Prospective evaluation of “XY” field in southwestern offshore Niger Delta was carried out with a view to delineate the structural and stratigraphic traps present in the study area.

The research methodology involved horizon and fault mapping to produce subsurface structural maps. Attributes used to analyze the field under study includes: Variance time slice which was used to illuminates the main fault structure on the field and aid as guide to proper mapping. Similarly, this was used to delineate the orientation of the fault across the field while Wireline log signatures were employed to identify hydrocarbon bearing sands. The data set used consists of Petrel simulation software 2013, general well data, well heads, well logs, well tops, checkshot, 3-D Siesmic in SEGY format.

Three (3) hydrocarbon bearing reservoirs were identified and they fall within the Agbada Formation (Reservoir 1, 2, and 3), with gross thickness ranging from 50ft to 123ft. Besides, due to the fact that the sands aren‟t entirely clean the three reservoirs have a net thickness ranging from 40ft to 100ft. Three (3) major faults were mapped on the seismic inlines, two were major faults while the last one was a minor fault. After mapping the faults, horizons were picked along the seismic inlines and xlines and a two way time graph was plotted to generate a linear function.

The amplitude attribute overlay time slice generated conform to structure which indicate accumulation of hydrocarbon. The high amplitude zone also doubled as the boundary of the hydrocarbon reservoirs (fluid contact) as they also conform to structure. The prospect can be chosen from any portion of the high amplitude zone recognized in the study.

TABLE OF CONTENTS

Page

Title page                                                                                                                                i

Certification                                                                                                                            ii

Dedication                                                                                                                               iii

Acknowledgments                                                                                                                  iv

Abstract                                                                                                                                   v

Table of Content                                                                                                                     vi-viii

List of Figures                                                                                                                         ix-x

List of Tables                                                                                                                          xi

CHAPTER ONE BACKGROUND TO STUDY

  1. Introduction                                                                                                                1
    1. Justification                                                                                                                 3
    1. Aims and Objectives                                                                                                   3
    1. Location and Geomorphology of the study area                                                        3

CHAPTER TWO LITERATURE REVIEW

CHAPTER THREE

BASIC PRINCIPLES OF SEISMOLOGY

 3.3.1    Spontaneous potential log22
3.3.2    Gamma ray log22
3.3.3    Resistivity log22
3.3.4    Formation density log20
3.3.5    Neutron log23
3.4Presentation and analysis of seismic data24
3.5Interpretation Procedure25
 3.5.1    Well correlation25
 3.5.2    Seismic to well tie25
 3.5.3    Mapping of fault26
 3.5.4    Mapping of reflection horizons26
 3.5.5    Loop tying of horizons26
 3.5.6    Time depth conversion curve27
 3.5.7    Contouring27
 3.5.8    Generation of structural maps28

CHAPTER FOUR RESULTS

IntroductionSeismic interpretation29
4.2.1    The base map29
4.3       Well correlation panel of hydrocarbon reservoirs32
4.3.1    Identified reservoirs34
4.4       Computed thickness of the reservoir38
4.5       Seismic interpretation40
4.5.1    Structural interpretation on seismic section36
4.6       Time structural maps44
  • Depth structural maps                                                                                                 47
    • Attribute extraction with depth overlay                                                                      50

CHAPTER FIVE

CONCLUSION AND RECOMMENDATION

  • Conclusion                                                                                                                  52
    • Recommendation                                                                                                        52

REFERENCES

LIST OF FIGURES

Figures 
1.1 Map of Niger delta 2
2.1 Map of Nigeria showing the Sedimentary Basins9 
2.2 Niger delta petroleum system 11
2.3 Diagram showing a Growth fault 13
3.1 Diagram showing the direction of propagation of seismic waves 17
3.2a Diagram showing Seismic Acquisition on land 19
3.2b Diagram showing Seismic Acquisition on water 19
3.3 Seismic interpretation procedures20 
4.0The Base map of the study area showing inlines and crosslines and the location of the two
wells 31
4.1 Well correlation panel showing the two wells and the reservoirs. 33
4.2a Well correlation panel showing the first reservoir across the two wells36 
4.2b Well correlation panel showing the second reservoir across the two wells 36
4.2c Well correlation panel showing the third reservoir across the two wells 37
4.3a 3-D view of the variance time slice showing the three faults in the area 41
4.3b Xline panel showing the three fault planes in the area 41
4.3c 3-D view of inline and crossline on seismic structural smooth (realized) timeslice.42
4.3d Inline panel of the seismic showing the interested horizons. 42
4.3e 3-D view of the interpreted horizon 43
4.4a Time structural map of Reservoir 1 45
4.4b Time structural map of Reservoir 2 45
4.4c Time structural map of Reservoir 3 46
4.5a Depth structural map of reservoir 1 48
4.5b Depth structural map of reservoir 2 48
  • c Depth structural map of reservoir 3                                                                                49
    • Amplitude attribute overlay on map                                                                                 51

LIST OF TABLES

Tables

  • Inline and Cross line numbers with their corresponding coordinate                                30
    • Showing the gross thickness, net thickness and net/gross of Reservoir 1                       39
    • Showing the gross thickness, net thickness and net/gross of Reservoir 2                       39
    • Showing the gross thickness, net thickness and net/gross of Reservoir 3                       39

CHAPTER ONE BACKGROUND TO STUDY

1.1               INTRODUCTION

The Niger Delta is one of the World‟s largest Tertiary delta systems and an extremely prolific hydrocarbon province (Doust, 1990). For any successful hydrocarbon exploration, there must be a detailed economic evaluation and production planning of optimum recovery method for the new accumulation or reservoir.

Reservoir dimension is a very important factor that affects the quantity of hydrocarbon that can be produced from the reservoir, Schlumberger (1989).

A full assessment of hydrocarbon potential involves evaluation of the field and ranking of all identified prospects. Hydrocarbons are found in geologic traps, that is, any combination of rock structure that will keep oil and gas from escaping either vertically or laterally. These traps can either be structural, stratigraphic or a combination of both (Doust and Omatsola, 1979). Decision-making by oil managers could then be based on the results of the estimates.

Petrophysical analysis involves identification and qualification of hydrocarbon reservoirs in the subsurface and evaluation of its fluid properties. A major application of petrophysics is in studying reservoirs for the hydrocarbon industry.

SEISMIC INTERPRETATION OF “XY” FIELD IN THE SOUTH-EASTERN NIGER DELTA