In this work, a workflow of the semi-compositional approach with oil characterization and reasonable validation has been proposed. Solid-liquid K-values have been extended to a wide range with limited experimental data to predict the asphaltene precipitating behavior. A novel numerical model by cooperating with the calculated solid-liquid K-values has been built for investigating detailed mechanisms in DME-VAPEX. In a DME-based vapor extraction process, the API of the Athabasca bitumen can be in-situ upgraded from less than 8 to 13–18 degrees at different operating conditions. A heat addition can alleviate reservoir damage around a wellbore.