A Core Scale Investigation of Asphaltene Precipitation during Simultaneous Injection of Oil and CO_2: An Experimental and Simulation Study

摘要

Although CO_2 injection significantly increases the amount of oil recovered, it can cause asphaltene deposition in oil reservoirs. Asphaltene deposition leads to formation damage, in which treatment is a costly and problematic operation. In this work, impact of asphaltene precipitation and deposition during CO_2 injection are investigated for recombined oil both in sandstone and carbonate core samples through dynamic flow experiments. Injection of oil and CO_2 was performed simultaneously. Then, pressure drops along the core were recorded continuously to estimate permeability reductions during the experiments. Online viscosity of injected fluid was measured by a designed capillary viscometer. Damaged permeabilities were calculated using Darcy equation from the pressure drops and measured viscosity data. The results show that permeability reduction behavior is completely different in sandstone and carbonate core samples. A core scale simulation study with tuned equation of state parameters was carried out to evaluate the experimental results. Then, sensitivity analysis is performed on injection rate and matching parameters, such as adsorption coefficient, plugging coefficient, and critical velocity. Simulation results only match experimental data at final injected pore volumes. The results of this work can be helpful for CO_2 injection applications and simulation of asphaltene deposition in oil reservoirs.