Processing Unconventional Oil: Partial Upgrading of Oilsands Bitumen

Unconventional oil, irrespective of whether it is a bio-oil, coal oil, petroleum oil, or waste oil, is an oil that is too viscous to effectively transport in its native state. Processing of unconventional oil to enable transport is imperative to get the oil to its primary market, namely, petroleum refineries. 'What is the most profitable amount of processing to meet the technical requirements for transport and marketability of the oil product? The impact of oil composition on petroleum refining is discussed in terms of refinery constraints and petroleum economics. The constraints explored are distillation, sulfur treatment capacity, hydrogen availability, and crack spread. Using oilsand-derived bitumen as a case study, three different approaches to deliver unconventional oil to the market are presented: dilution without any upgrading, full upgrading by the combination of cracking and hydroprocessing, and partial upgrading without the use of hydrogen. The concept of partial upgrading assumes that there is an economical optimum amount of processing between the two extremes of dilution and full upgrading. Potential partial upgrading processes that are reviewed are limited to the categories of visbreaking, coking, solvent deasphalting, and olefin treating without hydrogen. Comparative material balances, oil properties, capital costs, and utility requirements are presented and discussed in the context of partial upgrading. The study concludes that there is a limited prospect for single-step partial upgrading processes to produce an oil with sufficiently reduced viscosity, density, and olefin content to meet pipeline specifications without a substantial yield loss. Cracking necessitates olefin treatment, and process options for olefin treatment without hydrogen are less well developed than olefin treatment with hydrogen. While not concluding that multistep processes cannot meet the dual objectives of increasing profitability and transport requirements, it is pointed out that increasing complexity erodes the economic incentive by which partial upgrading is justified.