| The vapour extraction (VAPEX) process is a promising enhanced heavy oil recovery technology. Its major oil recovery mechanism is significant heavy oil viscosity reduction through sufficient solvent dissolution and possible asphaltene precipitation. Although the VAPEX process has been extensively studied in the past two decades, physical modeling is still required in order to effectively exploit tremendous heavy oil resources by applying the solvent-based oil recovery technology. This experimental work studies the heavy oil recovery and analyzes the solvent chamber evolution in the VAPEX process. More specifically, eleven VAPEX tests are conducted by using a rectangular visual sand-packed high-pressure physical model to examine the detailed effects of the permeability, operating pressure, accumulative produced solvent-oil ratio, solvent type, and asphaltene precipitation on the heavy oil and solvent production rates and on the solvent chamber evolution as well. In the experiment, a butane mixture and a pure propane are chosen as two respective solvents to extract heavy oil from two different sand-packs at a constant temperature and different pressures. Two important physical phenomena are observed during the VAPEX heavy oil recovery process: the solvent chamber development and asphaltene deposition. It is found that the operating pressure of the VAPEX test and the phase state of the extracting solvent are dominant factors in determining the heavy oil and solvent production rates and in-situ upgrading the produced heavy oil. Based on the experimental data obtained in this study, a field prediction of the VAPEX process is made. |
