CSS and SAGD recovery processes in Canadian bitumen resources. In this contribution, we report on experimental investigation of solvent addition to Vertical well Steam Drive (VSD). The investigation focused on understanding of the key physics accompanying diluent (multicomponent solvent) addition to a steam drive and its impact on recovery mechanism, ultimate recovery and oil steam ratio improvement. The process was studied using an in-house core flooding experimental set-up with a CT scanner used to monitor the fluid saturation distribution over time. The experimental program consisted of 6 experiments, each specifically designed to explore different regions of the displacement process. The emphasis was put on effects associated with timing and duration of the solvent injection. Solvent addition to steam (CWE) was 15 volume % of the total injection rate. The experimental results were history matched using Shell’s in-house numerical reservoir simulator MoReS. A 2D numerical model was used to arrive at a history match. The model consisted of a calibrated compositional PVT model (9 pseudo components), universal set of Corey parameters for oil-water and gas-oil relative permeabilities. Special emphasis was put on history matching of inherent heat losses. The simulations show that the dominant recovery mechanism is facilitated through the formation of a solvent bank with miscible displacement. Solvent addition is accompanied by a distinct gravity override, improved steam conformance and chromatographic separation of the diluent throughout the reservoir. Fine gridding is required to correctly capture bitumen uplift and formation of the solvent bank. The grid resolution was chosen such that the numerical longitudinal dispersion of 1 mm grid cells compares to mechanical dispersion in the used core with the grain size of ~300 microns. The bitumen recovery improvement observed during the experiments ranges between 3 to 8.3% of STOIIP depending on the injection scheme. The history match provided valuable insights into solvent trapping mechanism/solvent loss. The enhanced understanding of the recovery mechanism and ability to model the processes enables optimal design and interpretation of the ongoing steam-solvent field pilot on Shell’s Peace River lease using pipeline diluent as an additive.