Physical and numerical modeling of permeability and drainage height effects in VAPEX

This research was focused on developing a deeper understanding of the "VAPEX" - Vapour Extraction - process as a non-thermal recovery technique for the heavy oil and bitumen resources. In this technique, vaporized hydrocarbon solvents are used to extract heavy oil and bitumen using the concept of gravity drainage. Both experimental and numerical simulation studies were undertaken to better understand the mechanisms involved in the process. The main focus was on the scale up issues related to the translation of the experimental results to the real field conditions.; VAPEX is the solvent analogue of the SAGD process and uses essentially the same well configuration. A solvent vapour is injected instead of steam and the viscosity reduction occurs due to the dissolution of the solvent in the oil. The economic viability of VAPEX remains uncertain due to much lower oil production rates predicted by scale-up of observed laboratory model results using the transmissibility based scaling criteria.; The results of a series of semi-scaled sand-packed VAPEX experiments conducted in differently sized physical models in this study, indicate that the currently used scaling methods under-predict the increase in oil production rate with increasing drainage height. A larger height dependency of the oil rates than the currently used square root functionality was observed experimentally. It was confirmed that the production rate in this process is proportional to the square root of permeability.; Another experimental setup was designed to produce reliable and adequate PVT data for the oil-solvent system used in the VAPEX experiments. These PVT data were vital information required for the simulation work.; Numerical simulation of the laboratory experiments was carried out using a commercial compositional simulator (GEM) to history match the experimental results and investigate the role of molecular diffusion and mechanical dispersion in VAPEX experiments. Some of the important and helpful issues regarding the VAPEX simulation were addressed and are discussed. The simulation results show that in addition to molecular diffusion, convective dispersion is involved in the process. It was found that the dispersivity values required to numerically model the process is a height dependent value. However, these values are grid-sensitive and should be treated carefully in VAPEX simulation. It was also found that numerical dispersion is a major factor affecting the simulation results. A very fine griding system is required to reduce the magnitude of numerical dispersion and capture the physics involved in the thin diluted bitumen layer.