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Minimum Miscibility Pressure
Transcript of Minimum Miscibility Pressure
The minimum pressure at which a crude oil will be miscible with carbon dioxide at reservoir temperature.
Miscible displacement processes in the oil reservoirs are usually divided into two classes:
The development of dynamic miscibility at pressures above MMP may occur via two idealized mechanisms:
An injected gas becomes miscible with oil when enough light hydrocarbons concentrate in the gas for the gas and liquid to become mutually soluble.
Experimental Techniques for Gas-Oil Miscibility
Widely known experimental methods to evaluate gas-oil miscibility conditions under reservoir conditions are:
Considering the fact that the success rate of CO2 EOR is highly dependent to the MMP requirement, the study of MMP and other factors related to it is evidently essential.
First Contact Miscible Processes (FCMP)
Multi-Contact Miscible Processes (MCMP)
Displacements in which the injection fluid and the in-situ reservoir fluid form a single phase mixture for all mixing proportions.
Processes in which the injected fluid and the reservoir oil are not miscible in the first contact but miscibility could develop after multiple contacts (dynamic miscibility).
Vaporizing Gas Drive Mechanism (VGDM)
In this case, intermediate hydrocarbon species evaporate from the oil to the sweeping lean injection, such that the composition of the gas approaches that of the reservoir oil.
Condensing Gas Drive Mechanism (CGDM)
In CGDM mechanism, the intermediate hydrocarbons condense from the rich injection gas into the oil, shifting the oil composition towards that of the injection gas.
“Miscible displacement is achieved at the flooding pressure or minimum miscibility pressure (MMP) where about 95% of the oil in the tube is recovered after about 1.3 pore volumes of fluid have been injected.” (Holm L.W., 1986)
Gases become miscible only when their density is high, generally greater than 0.5 g/cc.
Vanishing Interfacial Tension (VIT)
Slim-tube test is the most common and has been commonly accepted as the “petroleum industry standard” to determine gas-oil miscibility.
Injection gas is introduced at one end of a long, small diameter coiled tube at a certain pressure and temperature while the displaced oil is collected at the other end of the tube.
Ability to include the interaction of flow with phase behavior
The miscibility determined might not represent the thermodynamic miscibility
Imposibility to simulate several important factors such as viscous fingering, gravity over ride, dispersion and reservoir heterogenity.
Rising bubble is a technique which is commonly used for quick and reasonable estimates of gas-oil miscibility.
Miscibility is determined based on visual observation of changes in shape and appearance of bubbles of injected gas as they rise through a visual high-pressure cell filled with reservoir crude oil.
Suffers from subjectivity in interpreting the bubble geometry.
Short run time.
The gas-oil miscibility conditions are then determined by extrapolating the plot of inter-facial tension against pressure or enrichment to zero interfacial tension.
In this method, the gas-oil inter-facial tension is determined by measuring the capillary rise in a high-pressure optical cell heated at the reservoir temperature and varying pressure or enrichment levels.
Provide quantitative result
Rapid and cost effective
Unable to fully represent the interaction between flow and phase equilibrium behavior.