A New Fluidics Method to Determine Minimum Miscibility Pressure

Abstract

Summary The miscible gas injection has been broadly used in many oil fields as an enhanced oil recovery (EOR) method. Minimum Miscibility Pressure (MMP) is a critical parameter both for modeling and field operations. The slim-tube method is recognized as the most reliable for MMP measurement. However, conducting the experiment takes a long time (4–6 weeks), and the sample volume requirement is substantial. Therefore, the slim-tube experiment is very costly and sometimes is not possible due to a lack of sample volume. Many other methods have been proposed, like rising bubbles and vanishing interfacial tension in various versions. Due to the limitations of these methods, there is still no experimental method that can replace the traditional slim-tube for MMP measurements. Micro and nano-fluidics devices have attracted increasing attention in the oil industry. Reduced cost and sample volume requirements, fast turnover, and visualization are clear advantages for lean operation. In this study, we designed a new slim-tube method to determine MMP on a micro-scale fluidics chip. The design is significantly different from previous efforts on fluidics chips with an open flowing tube. In the new design, we introduced porous media fillings similar as in the slim-tube method. The objective is to produce a true multi-contact process in the gas displacement. We tested the new fluidics device using three reservoir fluids, and both hydrocarbon gases and CO2 as injection gases. For pressure lower than MMP, we observed noticeable reservoir oil remained after injection gas passed. For pressure higher than MMP, the miscible displacement front was developed. Behind the miscible displacement front, the oil saturation came down to neglectable. We used a visual sensor to detect the oil saturation after gas flooding for each pressure. MMP was detected at the intersection of miscible pressures and immiscible pressures in a similar way as in the slim-tube test after multiple measurements. All three microchip MMP tests have almost identical results as the slim-tube tests. The new fluidics method is a miniaturization of the slim-tube method on the microchip. The study shows excellent results for the three selected reservoir oils combined with hydrocarbon gas and CO2 as injection gases. The new method has imminent business potential due to its reliability, visualization, low cost, low sample requirement, and fast turnaround. The MMP test threshold will be much lower than before, which will significantly benefit many gas-based EOR projects.