Fluid distributions during light hydrocarbon charges into oil reservoirs using multicomponent Maxwell-Stefan diffusivity in gravitational field

•A reservoir fluid geodynamics model was developed to model asphaltene gradients in oil columns during gas charges.•Asphaltene instability was also analyzed by the thermodynamic model with the same parameters in the RGF model.•Asphaltene is unstable at the base of the oil column due to a late gas charge in Well 2.•A tar mat was formed when asphaltene flocculation occurs at the base of the oil column over geological time.