Experimental Analysis of Optimal Thermodynamic Conditions for Heavy-Oil/Bitumen Recovery Considering Effective Solvent Retrieval

Abstract

Summary Light-hydrocarbon solvent injection is an effective process to improve heavy-oil/bitumen recovery from oil sands. In this process, oil production is achieved by gravity drive, which is enhanced through the dilution of oil by injected solvent. However, solvent retrieval is one of the major economic concerns in defining the viability of this technique. In this research, a sandpack experimental study was conducted, and the solvent retrieval was determined on the basis of thermodynamic conditions and fluid characterization. Two heavy-oil samples (8.6°API and 10.28°API) from different fields in Alberta, Canada, and four light-hydrocarbon solvents (propane, n-hexane, n-decane, and distillate hydrocarbon) were used in this experimental scheme. Results showed that solvent retrieval increases when light-hydrocarbon solvents (propane and distillate hydrocarbon) are used compared with solvent with high molecular weight (n-hexane and n-decane). Temperature and pressure highly influenced the solvent retrieval. The percentage of solvent retrieval increased when the hydrocarbon solvent was closer to the vapor phase (dewpoint). However, oil recovery showed significant reduction when propane and n-hexane were injected because of high asphaltene deposition on the sandpack. The maximum solvent retrieval was calculated to be nearly 98% at 120°C and 698.47 kPa when propane-and-distillate hydrocarbon was used as solvent. Formation damage, on the other hand, may increase when propane is used as solvent because of the high asphaltene deposition.