Reservoir Characterization and Volumetric Analysis of Lona Field, Niger Delta, Using 3-D Seismic and Well Log Data

ABSTRACT 

An integrated 3-D seismic data, checkshot data and a suite of four well log located at the Lona field, Niger Delta were analysed with Petrel software for reservoir characterization and volumetric analysis of the field. The method adopted involves petrophysical analysis, structural analysis, volumetric analysis and reservoir classification. Detailed petrophysical analysis revealed three reservoirs.Average reservoir parameters such as porosity (0.25), gross thickness (27 m), hydrocarbon saturation (0.66)permeability (3734 md) and net-gross (0.54) were derived from the petrophysical analysis. Structural analysis of the data showed fault assisted anticlinal structures which serve as structural traps that prevent the leakage of hydrocarbon from the reservoirs. The analysis of the all the well sections revealed that each of the sand units extends through the field and varies in thickness with some unit occurring at greater depth than their adjacent unit that is possibly an evidence of faulting. The shale layers were observed to increase with depth along with a corresponding decrease in sand layers. From the analysis, particularly the resistivity log, all the three delineated reservoirs were identified as hydrocarbon bearing units across the four wells i.e Lona1, Lona2, Lona3 and Lona4.Volumetric study of the hydrocarbon in place shows that the reservoirs are of appreciable areas and thicknesses. The volume of hydrocarbon originally in place was estimated to be 550 thousand barrels of oil. The three reservoirs have been classified using average results of petrophysical parameters. And based on these, R1 is said to be the most prolific while R2 is the least prolific within Lona field.

TABLE OF CONTENT

TITLE PAGE i

CERTIFICATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

TABLE OF CONTENT v

LISTS OF FIGURES ix

LISTS OF TABLES xi

ABSTRACT xii

CHAPTER ONE: INTRODUCTION

1.1 Background 1

1.2 Purpose of study 2

1.3 Location ofthe study area 2

1.4 Geology of Niger Delta 4

1.4.1 Stratigraphy of the Niger Delta 4

1.4.2 Tectonics 7

1.4.3 Depobelts 8

1.4.4 Structural geology of Niger Delta 10

1.4.5 Hydrocarbon generation and its occurrence 14

1.4.6 Source rock 15

1.4.7 Reservoir rock 16

1.4.8 Traps and seals 17

1.4.9 Migration 19

1.5 Justification for the study 19

1.6 Expected contribution to knowledge 19

CHAPTER TWO:LITERATURE REVIEW

2.1 Review of previous geophysical surveysusing seismic and well log data in the Niger Delta 20

2.2 Review of previous geophysical survey using seismic and well log data in other parts of the world 23

CHAPTER THREE: THEORY, MATERIALS AND METHODS OF STUDY

3.1 Theory of seismic surveying 25

3.2 Seismic waves 25

3.2.1 Body waves 25

3.2.2 Surface waves 27

3.3 Elastic characteristics of solids 28

3.4 Velocity of seismic waves 31

3.4.1 Factors affecting seismic wave velocity 31

3.4.2 Propagation of seismic waves 33

3.4.3 Reflection and transmission coefficient 33

3.5 Seismic energy sources 35

3.6 Detection and recording of seismic waves 36

3.7 Seismic prospecting methods 37

3.7.1 Seismic reflection survey 38

3.7.2 Data acquisition 39

3.7.3 Seismic data processing 39

3.8 Log evaluation and Classification of geophysical well logs 40

3.8.1 Gamma ray logs 44

3.8.2 Sonic log 46

3.8.3 Density log 49

3.8.4 Resistivity logs 52

3.9 Data interpretation and procedure 55

3.9.1 Well data import 57

3.9.2 Delineation of lithologies 57

3.9.3 Identification of reservoirs Differentiation of hydrocarbon and non-hydrocarbonbearing zones 57

3.9.4 Well correlation 58

3.9.5 Determination of petrophysical parameters 58

3.10 Seismic data import 61

3.10.1 Picking of faults 61

3.10.2 Seismic to well tie 62

3.10.3 Mapping of horizons 62

3.10.4 Generation of time structure maps 62

3.10.5 Time to depth conversion 63

3.10.6 Generation of depth structure maps 63

3.11Reservoir area extent mapping 63

3.12 Volumetric Analysis 63

CHAPTER FOUR: RESULTS AND DISCUSSION

4.1 Qualitative interpretation 64

4.2 Quantitative interpretation 67

4.3 Reservoirs 67

4.3.1 Reservoir Classification 69

4.4 Structural analysis 71

4.4.1 Horizons and faults 71

4.4.2 Time structural map 71

4.4.3 Depth structural map 76

4.5 Volumetric analysis 80

CHAPTER FIVE: CONCLUSION AND RECOMMENDATION

5.1 Conclusion 81

5.2 Recommendation 82

REFERENCES 83