Life Cycle Assessment (LCA) of Oil Sands-Derived Transportation Fuels Produced from the Vapor Solvent-Based Extraction Process

  • Author / Creator
    Soiket, Mohammad Ikthair Hossain
  • Oil sand is a mixture of sand, clay, water, bitumen and other minerals. Production of transportation fuels like gasoline, diesel, jet fuel, etc. from the oil sands reserved in deep underground reservoirs require external stimulant to lower the viscosity of bitumen. The established thermal extraction techniques like steam assisted gravity drainage (SAGD), cyclic steam stimulation (CSS) are energy- and greenhouse gas (GHG) intensive. Among several new technologies to reduce the GHG of transportation fuels produced from oil sands, the solvent extraction process (SEP) is a promising energy-saving technology that uses superheated solvent for bitumen extraction. However, with limited understanding of this technology, more detailed investigation is required to understand its impact on energy consumption and GHG emissions throughout the life cycle of bitumen produced from oil sands. To estimate life cycle (LC) energy consumption and GHG emissions from oil sands-derived transportation fuels, several life cycle assessments (LCAs) have been conducted by different researchers. Most of these studies use deterministic point estimates with insufficient uncertainty analysis. Because of lack of transparency and differences in emissions results reported by previous oil sands projects, it has become important to accurately quantify and provide realistic ranges of project-specific life cycle energy consumption and GHG emissions. In this study we developed a bottom-up data-intensive model to evaluate the WTW energy consumption and GHG emissions of the oil sands obtained from the SEP. The model was designed based on a production capacity of 25,000 barrels per day (bpd). Three pathways were developed to examine all the operations required to produce transportation fuels from bitumen (extraction and surface processing, upgrading, transportation, refining, and transmission and distribution) along with identifying the key energy and emissions sensitive parameters. In pathway I bitumen is upgraded through delayed coker upgrading before refining, in pathway II bitumen is directly refined without upgrading, and in pathway III bitumen is upgraded through hydroconversion process and then refined. The upgrading and refining processes were simulated. A comprehensive LCA for transportation fuels (gasoline, diesel, and jet fuel) was conducted in which the developed pathways for solvent extracted bitumen were explored. Refinery sub-process level (mass-basis) allocation was used to allocate GHG emissions among the products. Further, conservative statistical distributions for the sensitive inputs were developed from the literature and simulated through Monte Carlo simulations. GHG emissions from vapor solvent extraction and recovery range from 24.8-29.1 kg CO2 eq./bbl of bitumen, which represents a wide range of variability in input parameters. The SEP is an electricity-sensitive extraction process (it consumes 48.7% of the total energy required), unlike steam assisted gravity drainage (SAGD), and the solvent-to-oil ratio (SORsolvent) is the key parameter affecting GHG emissions. Hydroconversion upgrading is more energy- and GHG-intensive than delayed coker upgrading but yields more synthetic crude oil (SCO). The SCO produced from the upgraders has fewer heavy fractions and a major fraction of the SCO (42-51%) distillates as fuel gas in deep conversion refineries. Since the produced bitumen has inherently low asphaltene and a high API (American Petroleum Institute) gravity, bitumen can be refined without upgrading, the credit of which is attributed to the extraction process. LC GHG emissions range from 92.4-120.0 g-CO2 eq./MJ of gasoline and 103.6-248.9 g-CO2 eq./MJ of diesel, respectively, depending on the pathway and uncertainty in well-to-refinery (WTR) GHG emissions (excluding transportation emissions) range from 101.3-143.3, 132.2-169.9, and 82.7-109.3 kg CO2 eq./bbl of bitumen in pathways I, II and III, respectively. The results from this study will assist government and industry in strategic decision making on environmental comparisons with traditional bitumen extracting processes and on potential implementation in the oil sands energy industry.

  • Subjects / Keywords
  • Graduation date
    Fall 2017
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.