ABSTRACT
Waterflooding is the most secondary oil recovery method and its is mainly due to the general availability of , the relative ease of injecting water, the ability of water to spread easily through an oil-bearing formation and the efficiency of water in displacing oil.
However, waterflooding is not without its . Factors such as reservoir heterogeneity, lateral and vertical variations in permeability and presence of discontinuities greatly affect this process.
This study is aimed at optimizing waterflooding in a case study using geostatistical reservoir characterization and simulation techniques.
The impact of in kV/kH ratios across the reservoir on the performance of waterflooding is analyzed. The analysis of the effects of zones of production and injection as well as the waterflood pattern selected on cumulative recovery from a waterflooded reservoir was carried out.
The waterflood patterns considered were the regular five-spot, the direct line drive and the staggered line drive patterns.
The results were analyzed by evaluating trends of average reservoir pressure, oil producing rate, cumulative oil production and field water-cut over time for several scenarios of the waterflood.
These trends were also compared to a base case; a case of reservoir depletion without waterflooding. The results showed that variations in kV/kH ratio play a significant role in the performance of waterflooding.
Finally, the optimal waterflood pattern of all the patterns studied was the direct-line waterflood pattern which gave the highest oil recovery.
This study has demonstrated that geostatistical reservoir characterization and simulation techniques are good tools for reservoir management.
It has also shown that variation in kV/kH ratios, zones of injection and production and the waterflood pattern used to produce the oil affect the performance of a waterflooding process greatly.
TABLE OF CONTENTS
ABSTRACT…….iii
ACKNOWLEDGEMENTS…….iv
DEDICATION…..v
TABLE OF CONTENTS….vi
LIST OF FIGURES..viii
LIST OF TABLES….xiv
CHAPTER 1 INTRODUCTION
1.1 Study Background……..1
1.2 Statement of Problem……2
1.3 Objectives of this Study…….3
1.4 Scope of this Work….3
1.5 Structure of the Report…..4
CHAPTER 2 LITERATURE REVIEW
2.1 Overview of Oil and Gas Recovery……..5
Figure 2.1: A typical underground oil reservoir, Asadollahi, 2012…….5
2.2 Waterflooding…….6
2.3 Reservoir Characterization and Simulation……….9
2.3.1 Overview of Reservoir Characterization…..9
2.3.2 Overview of Reservoir Simulation..9
2.4 Optimization of Oil and Gas Production……..10
2.4.1 Overview of some methodologies for waterflood optimization..10
2.4.2 This Study Approach…………13
CHAPTER 3 STUDY METHODOLOGY
3.1 Introduction…………15
3.2 Case Study: The T-1 Reservoir…15
3.3 Map Digitization………17
3.4 Estimation of Petrophysical Parameters of Interest…17
3.4.1 Net Pay Thickness (Net/Gross)…….17
3.4.2 Shale Volume (Vsh)..18
3.5 Reservoir Characterization and Modelling…..18
3.5.1 Data Analysis….18
Total Porosity……22
Permeability………24
Net-To-Gross…..26
3.5.2 Building of Reservoir Realizations…..28
3.5.3 Static Modeling……..31
3.6 Estimation of Original Oil in Place (OOIP)….36
3.6.1 Ranking of Static Reservoir Models Built…….36
3.7 Estimation of Horizontal and Vertical permeabilities….38
3.8 Reservoir Simulation and Waterflood Performance Analysis……..38
3.8.1 Reservoir Simulation Model Initialization…38
3.8.2 Waterflooding of the T-1 Reservoir…….39
CHAPTER 4 RESULTS AND DISCUSSION
4.1 Introduction……44
4.2 Analysis of Waterflood Performance……44
4.2.1 Effects of kV/kH Ratios on Waterflood Performance……..44
4.3 Waterflood Optimization………53
4.3.1 Effects of Zones of Production and Injection on Waterflood Performance……53
4.3.2 Effects of Waterflood Patterns on the Performance of the Waterflood…..61
CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS
5.1 Introduction….66
5.2 Conclusions……66
5.3 Recommendations.. ……..67
NOMENCLATURE 68
REFERENCES…69
APPENDIX……..74
INTRODUCTION
1.1 Study Background
To meet the ever-increasing demand for petroleum worldwide, it has become increasingly necessary to produce oil and gas fields more economically and efficiently.
Since a significant number of prominent oil fields are mature fields and the number of new discoveries per year is decreasing, it has become more imperative to use secondary oil recovery processes (Nwaozo, 2006).
Waterflooding is one of the most widely used secondary oil recovery means after the exhaustion of the primary depletion energy of a reservoir and it is said to be responsible for high oil production rates in mature oil fields in the U.S and Canada (Craig, 1971).
It basically involves pumping water through an injection well into the reservoir. The water then forces itself through the pore spaces and sweeps the oil towards another set of wells known as producers. As a result, there is an increment in the total oil production from the reservoir.
However, the percentage of water in the produced fluids steadily increases. On average, this process can lead to the recovery of about one-third of the original oil in place (OOIP), leaving behind about two-thirds (Meshioye et al., 2010).
Other secondary recovery methods include CO2 flooding and hydrocarbon gas injection. These other processes require a nearby source of the inexpensive gas in sufficient volume.
It is commonly said that the high level of production rate and reserves around the world today is as a result of the popularity of water injection (Asadollahi, 2012).
REFERENCES
Abbaszadeh M., Ohno K., Okano H. and Morale
s J., Reservoir Characterization and CO2-EOR Injection Studies in Chicontepec Turbidite Reservoirs, Mexico. Paper IPTC 12637 presented at the International Petroleum Technology Conference held in Kuala Lumpur, Malaysia, 3–5 December 2008.Ahmed T., Reservoir Engineering Handbook, Third Edition, Gulf Professional Publishing, 2006, pp 909 – 916, 927 – 931.
Arenas, A. and Dolle N., Smart Waterflooding Tight Fractured Reservoirs Using Inflow Control Valves, paper SPE 84193 presented at the SPE Annual Technical Conference and Exhibition held in Denver, Colorado, 5 – 8 October, 2003.
Asadollahi M., 2012. Waterflooding Optimization for Improved Reservoir Management, Ph.D dissertation, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
Asheim H. 1988. Maximization of Water Sweep Efficiency by Controlling Production and Injection Rates. Paper SPE 18365 presented at the SPE European Petroleum Conference, London, UK, October 16-19, 1988.
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