ExxonMobil and its Canadian affiliate Imperial Oil Resources are pursuing an integrated research program targeted at developing the next generation of heavy oil recovery processes which utilize hydrocarbon solvents as a mobilizing agent.The key benefits of solvent-based processes are improved environmental performance, improved economics and recovery of resource that is impractical with thermal processes.The integrated research program encompasses fundamental laboratory work, analytical modeling, advanced numerical modeling, scaled physical modeling in the laboratory, a solvent-only pilot which is in the design phase, an operating solventassisted SAGD pilot and a first commercial scale application of a solvent-assisted cyclic steam stimulation (CSS) process known as Liquid Addition for Steam Enhanced Recovery (LASER). This paper provides a systematic review of the scope, technical challenges, benefits and successes of research efforts in each of the areas cited above. In general, the results of laboratory modeling and simulation studies are strongly supportive of the potential success of solvent-assisted and solventbased recovery processes. Reliably demonstrating solvent recovery processes at the field scale remains a key challenge that can only be addressed through well designed field pilot programs and enhanced reservoir surveillance programs for commercial scale applications. These challenges are highlighted in the paper utilizing specific examples from the integrated research program.In conclusion, there are some very significant technical challenges that need to be addressed before solvent-assisted and solvent-based heavy oil recovery processes will be broadly commercialized. Nonetheless, consideration of the results across the full breadth of ExxonMobil's integrated technology program provides strong support that a new generation of solvent recovery processes will emerge as an economically competitive option for heavy oil recovery with significant environmental benefits relative to today's thermal recovery processes .
ExxonMobil and its affiliate Imperial Oil Resources are currently operating a Solvent-Assisted Steam-Assisted Gravity Drainage (SA-SAGD) experimental pilot plant at Cold Lake, Canada. During pilot operation, up to 20 percent by volume of a light hydrocarbon solvent will be injected with dry steam in a dual horizontal well SAGD configuration. The pilot scope consists of two horizontal well pairs (four wells total), six observation wells, associated steam and solvent injection facilities, artificial lift, and dedicated production measurement and testing facilities. Previous experimental and computer modeling work completed by the Alberta Research Council (ARC) (Nasr, 2003), Imperial Oil Resources, and ExxonMobil indicates that the addition of solvent to the dry steam increases bitumen production rates and decreases the steam oil ratio (SOR) relative to conventional SAGD processes. A key objective of this pilot is to safely collect high-quality field data to support these findings and quantify process improvement. This paper will focus on the pilot design approach taken to ensure that the multi-year pilot is successful as well as highlight early pilot performance and operation. Specific design aspects which will be discussed include the choice for the pilot location, the use of detailed geologic models to design and place the horizontal wells, and solvent measurements. Early field results are consistent with expectations. However, longer term operation is required to make a more quantitative assessment. In addition, the pilot operation has demonstrated excellent control of injection pressure, which is critical to the application of this technology in settings with bottom water or top gas.
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