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
Acknowledgments iv
Table of Content vi-viii
List of Figures ix-x
CHAPTER ONE BACKGROUND TO STUDY
- Introduction 1
- Aims and Objectives 3
- Introduction 4
- Regional geology of the area 7
- Stratigraphy of the Niger delta basin 7
- Tectonic setting of the Niger delta 14
- Regional geology of the area 7
BASIC PRINCIPLES OF SEISMOLOGY
- Seismic survey 15
- Materials and methodology
| 3.3.1 Spontaneous potential log | 22 | |
| 3.3.2 Gamma ray log | 22 | |
| 3.3.3 Resistivity log | 22 | |
| 3.3.4 Formation density log | 20 | |
| 3.3.5 Neutron log | 23 | |
| 3.4 | Presentation and analysis of seismic data | 24 |
| 3.5 | Interpretation Procedure | 25 |
| 3.5.1 Well correlation | 25 | |
| 3.5.2 Seismic to well tie | 25 | |
| 3.5.3 Mapping of fault | 26 | |
| 3.5.4 Mapping of reflection horizons | 26 | |
| 3.5.5 Loop tying of horizons | 26 | |
| 3.5.6 Time depth conversion curve | 27 | |
| 3.5.7 Contouring | 27 | |
| 3.5.8 Generation of structural maps | 28 |
CHAPTER FOUR RESULTS
| IntroductionSeismic interpretation | 29 |
| 4.2.1 The base map | 29 |
| 4.3 Well correlation panel of hydrocarbon reservoirs | 32 |
| 4.3.1 Identified reservoirs | 34 |
| 4.4 Computed thickness of the reservoir | 38 |
| 4.5 Seismic interpretation | 40 |
| 4.5.1 Structural interpretation on seismic section | 36 |
| 4.6 Time structural maps | 44 |
- 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 Basins | 9 | |
| 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 procedures | 20 | |
| 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 wells | 36 | |
| 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) time | slice. | 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
