Optimal Application Conditions for Variable Temperature Solvent Injection into Sands and Carbonates for Heavy-Oil and Bitumen Recovery

• Author / Creator

  Leyva Gomez, Hector

• Steam injection is the most common technique in heavy-oil/bitumen recovery. However, the emission of greenhouse gases into the atmosphere, its water requirements, and excessive operational cost associated entail finding alternative solutions. One approach is combining steam and solvent injection by taking advantage of steam injection, preheating the reservoir for a more effective solvent recovery application. In this case, the performance of subsequent solvent injection strictly depends on the temperature and pressure in the reservoir. Recent experimental studies on superheated solvent injection showed that solvent in the gas formed near the saturation line yields an optimal recovery, minimizing the asphaltene precipitation and maximizing the recovery. This research investigates this process through a numerical modeling exercise and experiments under solvent injection to formulate the optimal pressure and temperature conditions for different reservoir conditions and hydrocarbon solvents. We first report the results of numerical simulation of previous laboratory experiments performed elsewhere, in which heavy-oil was exposed to solvent vapours at high temperatures. The injection of propane into sand packs or consolidated sandstones at elevated temperatures was simulated and a sensitivity analysis was carried out to identify the key parameters in the processes. Our results and observations showed that exist a critical temperature that yields a maximum recovery and its value depends on the solvent considered and the pressure and temperature of the experiment. Next, a hypothetical field scale numerical model was constructed and the key parameters identified during the aforementioned sensitivity analysis were incorporated. Then, injection process was simulated for a two-horizontal injection/production pattern. An optimization study was performed to identify the relative contributions of the effective parameters (pressure, temperature, and injection rate) and to propose an optimal application scheme using genetic algorithm. The critical pressure and temperature yielding maximum production and highest profit considering solvent retrieval were defined for different injection rates and application scenarios. Finally, we conducted a series of dynamic experiments in which liquid solvent (propane, heptane, and distillated oil) was injected into heavy oil saturated artificially fractured Berea sandstone, Indiana limestone, and naturally fracture vuggy carbonate samples with and without pre-thermal injection. To account for the effect of wettability on the process, experiments with Berea sandstone were repeated on the samples exposed to wettability alteration (more oil-wet) process. During the experiments, hot solvent was injected continuously through artificially fractured cores followed by hot water (or steam injection) phase. The optimal temperatures for heavy oil recovery and solvent retrieval, in the subsequent hot water injection, for each kind of rock sample and type of solvent were determined. Our results showed that heavy oil recovery increase was due not only to temperature but also to the solvent carbon number. When the temperature is higher than the saturation curve, the recovery decreases and the lightest component of the heavy oil are dragged out the core by the gas stream. Additionally, it was observed that for a successful solvent retrieval by hot water injection, temperature of water should be equal to or higher than the saturation temperature of liquid solvent, retained in the rock matrix.

• Subjects / Keywords

  • Solvent injection
  • Fractured carbonates
  • Heavy oil
  • Numerical simulation

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3WP9TF6W

• 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.