In situ recovery of heavy oil and bitumin using vaporized hydrocarbon solvents

Abstract

The aim of this research was to develop an efficient technique for recovering the huge natural resources present in the form of heavy oil and bitumen. In the proposed process called "Vapex" - Vapour extraction, vaporized hydrocarbon solvents (propane or butane) are used to extract heavy oil and bitumen using the concept of gravity drainage. The study was focused to understand the mechanism of the process and assess its performance under various conditions. The results of experiments carried out in Hele-Shaw cells show that with deasphalting the extraction rates are higher than those without deasphalting. This indicates that asphaltene deposition may not be a constraint for the process. This was confirmed later in experiments carried out in packed models. It was observed that deasphalting occurs when the solvent is near its saturation pressure. A hypothetical "Vapex Parameter" was defined to scale or compare the results of these experiments. It was possible to calculate the diffusivity of the solvent-bitumen system from these parameters. The mechanism of the process in porous media was studied in experiments carried out in a scaled packed model using butane as a solvent. Production rates in porous media were observed to be proportional to the square root of permeabilities. The flow rates achieved in packed cells were higher than those obtained by scaling up the results of Hele-Shaw cell experiments using identical conditions of temperature and pressure. Higher interfacial area of contact in the porous media, capillary imbibition, surface renewal and transient mass transfer are considered to be the reasons behind this enhancement. Extraction rates are higher in upward leaching when there is a countercurrent extraction process. Experimental results show that extraction at higher pressure in the presence of a non-condensible gas performs equally well. In field operations mixtures of hydrocarbon solvent and natural gas may be used to give operating pressures close to the original reservoir pressures. Flow rates predicted from these results indicate that the process has a potential for field applications.