In this project, mixed CO2 flooding is selected for its volumetric sweep efficiency and minimum mixing pressure (MMP). The main problem in this project is that the initial reservoir pressure for the Malaysian oil field is too low to achieve mixed displacement and therefore the application of mixed CO2 flooding is not recommended. Therefore, this project will focus on the study of possible methods to reduce the minimum mixing pressure to ensure that the mixed displacement can be achieved in the Malaysian oil field.
In this study, the effects of the injected gas composition on the Dulang crude oil are investigated through 1D Slim Tube simulation by the ECLIPSE 300 reservoir simulator. And not forgetting my friends, especially those who have worked with me as a team with their help and support throughout this project.
INTRODUCTION
- BACKGROUND OF STUDY
- PROBLEM STATEMENT
- Significant of Project
- OBJECTIVES AND SCOPE OF STUDY
- The Scope Of Study
- RELEVANCY OF PROJECT
- FEASIBILITY OF THE PROJECT WITHIN THE SCOPE AND TIME
Therefore, methods are needed to reduce the MMP of crude oil to achieve miscibility in Malaysian oil fields. Several injection gas composition scenarios were investigated to lower the MMP of the crude oil to achieve miscible displacement. Therefore, the evaluation of the effect of injected gas compositions on the reduction of MMP of crude oil is necessary when reviewing oil field mixed flooding projects in Malaysia.
The study on the minimum mixing pressure (MMP) of the crude oil will be simulated to determine the reduction of the MMP by changing the gas composition. To determine the MMP of Malaysian crude oil samples at different attainable temperature and pressure.
LITERATURE REVIEW
OVERVIEW OF GAS FLOODING
CARBON DIOXIDE FLOODING
MISCIBLE AND IMMISCIBLE DISPLACEMENT
- First Contact Miscible Process (FCM)
- Multiple Contacts Miscible Process (MCM)
In response to the problems faced by immiscible displacement, recent activity in mixed flooding has focused on the mixed CO2 process. On the other hand, mixed process is more favorable than non-mixed displacement due to high oil recovery, high displacement efficiency as well as higher blow factor in mixed process (Yongmao & Italic, 2004). The first contact mixing process is the most direct and simplest method of achieving mixture displacement by injecting a solvent that mixes directly with the oil in all proportions.
The miscible multi-contact process is a function of both temperature and pressure; but in an isothermal reservoir pressure is the only concern. Vaporizing Gas Drive is a multi-contact mixing mechanism; it depends on the vaporization of medium molecular weight hydrocarbon from the reservoir oil.
MINIMUM MISCIBILITY PRESSURE (MMP) DETERMINATION
- EXPERIMENTAL APPROACHES
- CORRELATION TECHNIQUES
- ANALYTICAL MODELS
Oil recovery increases with flood pressure and the recovery range will narrow as pressure increases at the MMP or higher. The rising bubble device was designed in the early 1980s, with features such as a flat glass tube mounted vertically so that the evolution of the shape of bubbles rising up through the oil column can be clearly observed, and a hollow needle placed at the bottom used to inject a liquid. gas bubble, where the driving force of the gas will lift the gas bubble through the column and mix with oil. Using visual observation over a pressure range in Figure 7 and Figure 6, the MMP is determined at a constant temperature.
During the experiment, a hanging drop of oil is created at the tip of the syringe needle. A precise interfacial profile of the pendant droplet is obtained through computer digital image analysis and processing techniques. Furthermore, they assumed that if the oil bubble pressure in the reservoir is greater than the CO2 MMP, the bubble point is the MMP.
2009) discussed that empirical correlations generally overpredict MMP for light oils and underestimate MMP for heavy oils. Johns and Wang developed a generalized n-component phase equilibrium approach to estimate the MMP for a two-phase system (Johns et al. 1996, Wang et al. 1998). EOS is used to calculate the distribution of components between the phases present.
The MMP is determined at the lowest pressure where the length of one of the key bond lines becomes zero. The MMP is determined from an arbitrary bend in the recovery versus pressure curves (Jarrell 2002). They developed a new mixture method to determine the MMP for systems with any number of components.
FACTORS AFFECTING MISCIBILITY PRESSURE
- Carbon Dioxide Purity
- Oil Composition
- Reservoir Temperature
A decrease in API oil density resulted in an increase in MMP, reflecting the reduced extractable hydrocarbon content. This is because a high molecular weight will reduce the solubility of the hydrocarbon in CO2. For heavy crude containing few C5 to C20 intermediates, extraction was inefficient under all conditions (Alston 1985).
This was supported by Silva and Orr Jr. 1987), in which they reported that molecular weight distribution in the oil is the main factor influencing MMP. National Petroleum Council (1976) has proven that a higher reservoir temperature results in a higher minimum mixing pressure, all other things being equal. In addition, Holm (1986) has pointed out that a minimum CO2 density is required to extract C5-C30 from the crude oil and that the reservoir temperature is only a variable to determine the pressure required to achieve the required CO2 density. reaches.
This is because when the temperature drops; the amount of injected CO2 is reduced, which increases the density of CO2. Since the density of CO2 is proportional to the amount of hydrocarbon extracted, this will reduce the MMP.
KNOWN METHODS TO REDUCE MMP
METHODOLOGY
- RESEARCH METHODOLOGY
- Data Gathering
- Simulation Modelling
- PROJECT WORKFLOW
- Simulation Workflow
- Studied Cases
- KEY MILESTONES
- GANTT CHART
- TOOLS REQUIRED
In this project, the simulation investigation began by collecting parameters and input data for reservoir and fluid properties. Parameters for such as injection pressure and injected gas composition will be varied at constant reservoir temperature to investigate their effect on MMP and oil recovery factor. Characterization of the reservoir fluid sample is performed using a compositional simulator known as Pressure-Volume-Temperature (PVTi) analysis software.
In this project, the Peng-Robinson equation of state (EOS) was used to characterize the reservoir fluid composition using the PVTi module of the ECLIPSE simulation software. Critical reservoir fluid properties are obtained and exported to ECLIPSE 300 for fluid behavior simulation. A basic example used pure carbon dioxide as the injection gas to determine the minimum miscible pressure (MMP) of Dulang crude oil.
In the second scenario, the synthetic manufactured gases were made by alternating the gas compositions. This study was conducted to simulate a possible gas flow that could lower the MMP below Dulang's initial reservoir pressure. MMP of each case is determined and analyzed Simulation on Synthetic Gas Composition Simulation on different injected gas composition.
ECLIPSE reservoir simulation software provides a complete and robust set of numerical solutions for fast and accurate prediction of dynamic behavior – for all types of reservoirs and degrees of complexity, including structure, geology, fluids and development schemes. ECLIPSE 300 is used to solve the reservoir flow equations for composition of hydrocarbon description and thermal simulation. ECLIPSE PVTi is a compositional PVT equation-of-state-based program used to characterize a set of fluid samples for use in the ECLIPSE simulator.
RESULT AND DISCUSSION
RESERVOIR FLUID CHARACTERIZATION
EFFECTS OF GAS COMPOSITION ON MINIMUM MISCIBILITY
- Pure CO2
- Hydrogen Sulphide (H 2 S)
- Ethane (C 2 )
- Propane (C 3 )
- Butane (C 4 )
- Pentane (C5)
The same procedure was repeated to determine the effects of adding 10 mol%, 20 mol% and 30 mol% H2S to the CO2 gas stream. From Figure 20 we can observe that the MMP decreased as the mole percentage of H2S in CO2 increased. Finally, with 30 mol % H2S in gas stream; the MMP significantly reduced to 2499psia, which is 1029 psia compared to pure CO2 gas stream.
The MMP is decreased as a result of methane addition as shown in Figure 21. By adding 30 mol % of C4 to the CO2 gas stream, it managed to decrease the MMP from 2646 psia to 1617 psia which is lower than the initial reservoir pressure. However, the MMP managed to reach 1470 psia after 30 mol% of C5 was added to the CO2 gas stream.
In an assessment of the results of the above simulation studies, 16 gas samples demonstrated the effects of increasing or decreasing the MMP. In addition, the MMP rose to 3822 psia in Gas 3 and Gas 4 with the higher N2 contamination in gas streams. This indicates that the presence of N2 in the gas stream has increased the MMP of crude oil.
On the other hand, the presence of H2S, C3 and C4 in CO2 gas streams can lower the MMP of crude oil. However, a small decrease in MMP was observed when C4 and CO2 were added to C5; just lowered the MMP by 1470 psia from 3528 psia. Increasing C4 to 25 mol% further lowered the MMP to 1617 psia, where it is below the initial reservoir pressure.
DISCUSSION
The price has increased from ethane to butane, so an economic analysis must be done to avoid excessive cost investment in the CO2 miscible flooding. WAG (Water Alternate Gas) scheme is implemented to prevent gas breakthrough and helps to maintain a stable front for the CO2 flux.
CONCLUSION AND RECOMMENDATIONS
CONCLUSION
RECOMMENDATIONS FOR FUTURE WORK
Enhanced Oil Recovery - An Analysis of the Potential for Enhanced Oil Recovery from Known Fields in the United States - 1976 to 2000, Washington, DC, December. A study of minimum miscibility pressure for CO2-rich injection gases with pentanes plus fraction. More Recovery in Frac Spreads Help Gas processors, Positive Short-term Catalyst, http://marketrealist.com/2013/07/more-recovery-in-frac-spreads-helps-gas-processors/ (accessed July 30, 2013) .
Effects of impurities on minimum miscibility pressures and minimum enrichment levels for CO2 and rig-gas displacement (in English). Minimum Miscibility Pressure Studies for a Gas Injection EOR Project in the Al Shaheen Field, Offshore Qatar. Compositional Pathways in Four-Component Systems: Effect of Dissolved Methane on 1D CO2 Flooding Performance (in English).
Effect of oil composition on minimum miscibility pressure-Part 1: Solubility of hydrocarbons in dense CO2 (in English). Evaluation of CO2 Gas Injection for Major Oil Production Fields in Malaysia - Experimental Approach Case Study: Dulang Field. Paper SPE 72106 presented at the SPE Asia Pacific Improved Oil Recovery Conference, Kuala Lumpur, Malaysia.
