Post-CHOPS EOR using Gas Solvents and Air

  • Author / Creator
    Soh, Ye-Ji
  • As a follow-up method after CHOPS (Cold Heavy Oil Production with Sands), CSI (Cyclic Solvent Injection) was widely accepted in the oil industry. After injected gas solvents with high pressure are dissolved in a heavy-oil reservoir, produced oil shows dispersed gas-phase in the oil, which is known as “foamy oil”. This thesis reports an experimental study of foamy oil created by various gas solvents, such as CH4, CO2, mixture-form of CH4 and C3H8, or a combination of gas solvents with air. The particular focus was on air used as an EOR (enhanced oil recovery) agent due to its low cost. Experimental data shows that methane live oil -primary- production by depletion gave about 14% oil recovery. But, with additional CO2 huff ‘n’ puff, recovery increased by around 15%, totaling 29% recovery. Methane-propane mixture only recovered about 5% due to decreased foamy effect by good mixing property of propane. Next, different pressure depletion rates, namely -0.23, -0.51, and -1.53 psi/minute, were applied and more oil was produced with increasing depletion rates. Two schemes using air (alternate injection and co-injection) were carried out with CH4 and CO2 and three huff-n-puff cycles were tested. As a result, air huff-n-puff (HnP) followed by 2-cycles of CH4 HnP showed 36.21% recovery, while air HnP followed by 2-cycles of CO2 HnP yielded 30.36% oil recovery. When gas solvents and air were injected together, air 50%-CO2 50% and air 50%-CH4 50% recovered 29.85% and 23.74% of total oil-in-place, respectively. A numerical study was also conducted in core-to-field-scale, predominantly on methane foamy oil production in various scenarios; e.g. by assigning different well patterns and injection/soaking periods. The solution GOR (gas oil ratio) versus saturation pressure data from methane depletion experiments was matched using the Peng-Robinson equation of state method and the K-values were generated by the Crookston equation. The K-values, which model equilibrium condition of the fluid, were used with reaction coefficients, which helped in representing non-equilibrium status of foamy oil. Core-scale simulation showed mostly less than 5% error, which can be accepted as a valid match. These matched data were used in a field-scale model to analyze the performance of cyclic methane injection. In field scale modeling, 15-well data from a CHOPS field in Alberta, Canada were history matched and 6-cycle CSI performances were followed as post-CHOPS with different well patterns (central, peripheral, all-wells). In field scale modeling, all-well huff ‘n’ puff-type pattern brought about slightly higher oil recovery than central and peripheral well patterns. Sensitivity analyses were carried out with a variety of scenarios by changing injection/soaking period and pressure decline rates. The ratio of injection to soaking period was observed to be more important than the injection period itself in terms of production efficiency.

  • Subjects / Keywords
  • Graduation date
  • 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.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
    • Department of Civil and Environmental Engineering
  • Specialization
    • Petroleum Engineering
  • Supervisor / co-supervisor and their department(s)
    • Tayfun Babadagli (Department of Civil and Environmental Engineering)
  • Examining committee members and their departments
    • Ergun Kuru (Department of Civil and Environmental Engineering)
    • Huazhou Li (Department of Civil and Environmental Engineering)