Thermo-Kinetic Modeling of Asphaltene Flocculation during Gas Miscible Injection Flow in Shale Oil

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In recent years, the development of unconventional oil reservoirs has played a critical role in the rapid increase of oil production in the United States, thereby decreasing the dependence on foreign oil. Although unconventional oil reservoirs can be tapped using hydraulic fracturing in horizontal wells, production with this technology typically recovers only 4 to 6% of the available oil. Gas injection technologies currently used to unlock the remaining oil are limited by changes that occur in the oil properties when the gas is injected. This leads to deposition of heavy organic solids known as asphaltenes that are suspended in the oil. Deposition of asphaltenes ultimately requires more wells to be drilled, as it reduces rock permeability, damages the formation, and plugs the formation pores and well tubing. This project is expected to develop and experimentally validate a model capable of predicting the thermodynamics and kinetics of asphaltene flocculation under injection of miscible gas mixtures, extending past studies based on continuous gas injection to the promising new mode of cyclic injection. This modeling work is expected to aid in the development of new gas injection processes that will improve U.S. shale oil recovery rates, decrease the energy needed for oil extraction, and reduce the need for drilling new wells. Educational activities involving high-school students and teachers will enhance understanding of oil production technologies.Current models do not fully describe how shale oil composition, gas composition and pressure, and injection timing affect asphaltene flocculation, one of the critical components impacting oil production and recovery efficiency. In this research program, two sets of experimental studies will explore asphaltene flocculation in shale oil. First, batch studies will be used to determine the minimum miscibility gas pressure (MMP) for gas mixtures of carbon dioxide and nitrogen at temperatures and pressures that extend beyond prior studies. The analysis of the flocculation kinetics of asphaltene colloidal particles will be carried out using confocal microscopy imaging techniques and the size distribution of flocculated asphaltene as function of time will be used to validate a newly developed kinetic model. Parametric analysis of the MMP and colloidal particles will allow quantification of flocculation kinetics. Second, a flow-through filtration apparatus will be used to quantify asphaltene thermodynamic and kinetic flocculation properties during cyclic and continuous gas injection under miscible injection conditions, extending and validating models developed during the batch studies. The newly developed thermo-kinetic model will be the first model of its kind that combines thermodynamic and kinetic descriptions of asphaltene aggregation in one model. These research efforts will lead to a new, simple, accurate, and universal mathematical model that can be used to minimize asphaltene deposition upon miscible gas-injection in the field, compensating for variations in oil composition, pressure, temperature, time, and gas injection composition.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.