Both gravity-based and cyclic processes for heavy oil/bitumen recovery may involve the use of hydrocarbon (nalkane) solvent at relatively high solvent/oil ratios. Previouswork at ARC has shown that at high solvent loadings, the oil/solvent mixture partitions into a solvent-rich oil phase and a heavy-ends-rich (mostly asphaltene) oil phase. The liquid phases have significantly different densities and viscosities. The partitioning phenomenon could have a significant impact on the performance of gravity based processes such as Vapex involving solvents where the low-viscosity liquid phase carries the bulk of the oil production, and the heavier liquid phase consisting of mostly asphaltene is essentially immobile. The solvent-rich phase will consist of the upgraded (de-asphalted) oil. Production of upgraded oil thus would not only enhance the production rate, but also have both economic and pipelining dvantages. Data on the physical properties (viscosity and density) and the composition of both the partitioned phases are needed to design and optimize solvent-based processes in reservoir engineering calculations.
Phase partitioning experiments conducted at the Alberta Research Council Laboratories along with the experimental data are presented in this paper.
Both gravity-based and cyclic processes for heavy oil recovery may involve the use of solvent which dissolves in heavy oil or bitumen at relatively high solvent/oil ratios. Earlier works at ARC, and recent work in the Thermal Gravity trategic area, have shown that at high loadings the oil/solvent mixture partitions into a solvent-rich oil phase and a heavyends- rich oil phase. The two liquid oleic phases have significantly different densities and viscosities. The phase partitioning may have significant impact on the performance of a solvent-based heavy oil recovery process. In particular, VAPEX and other gravity based processes involving solvents may have their performance enhanced if the low-viscosity phase carries the bulk of the oil production, and the heavy-ends-rich phase contains most of the asphaltene and is essentially immobile.
Data on the physical properties (viscosity and density) and the composition of both liquid phases are needed to design and optimize solvent-based heavy oil recovery processes. Laboratory experiments were designed and performed on selected oil/solvent combinations used in other ARC experiments on both cyclic and gravity-based processes to extract data on multiple liquid phase formation. Numerical simulation of solvent based processes enhanced by liquid-liquid phase partitioning will require also measurements of the viscosity of both liquid phases, as well as data required to develop an asphaltene separation model pertinent to the systems under study.
Paraffinic solvents have been used for many years to deasphalt heavy hydrocarbons1. Some of the early works in the area of solvent use for bitumen recovery have been in the area of supercritical extraction using light hydrocarbons2. Funk3 experimentally studied the dissolution of bitumen using excess amount of low-molecular-weight paraffinic solvent at ambient temperatures. The paraffinic solvents separate the bitumen into de-asphalted oil and an asphaltene fraction. Zhao4 conducted an experimental study of the solubility of propane (at 2.2 MPa and 40 °-180 °C) in the heavy oil from Burnt Lake, Alberta.
