Stability and Mobility of Foam Generated by Gas-Solvent/Surfactant and Gas-Solvent/Nanoparticles under Reservoir Conditions

  • Author / Creator
    Wang, Chao
  • Foam can be a feasible means to remedy the low sweep efficiency of solvent flooding (e.g., CO2 and/or C3H8) resulting from viscous fingering and gravity segregation. It works as a good mobility control agent that decreases the mobility difference between the displaced oil and the displacing agent. Solvent-alternating-surfactant is a feasible way to create foam under reservoir conditions. However, most of the surfactant-stabilized foams are normally unstable and thermally degradable, especially with the presence of salt and oil at high temperatures. To recover more oil from a depleted reservoir, the foam needs to maintain a long-term stability in the reservoir. With the continuing innovation of nanoparticle technologies, the challenges encountered by surfactant-stabilized foam can be remedied by using nanoparticles instead of surfactant as foaming agents. Solid particles need high energy to be adsorbed to, and desorbed from the fluid interfaces; therefore, the nanoparticle-stabilized foam can be highly stable even under harsh conditions (e.g., elevated temperature and the presence of oil). In this study, firstly, the static foam stability and dynamic mobility of solvent/surfactant/pseudo-heavy-oil system under reservoir conditions have been examined experimentally by using a pressure/volume/temperature (PVT) system and a glass beadpack, respectively. The following factors are considered in the static foam stability experiments: surfactant concentration, salinity, temperature, and the presence of pure n-C16H34 as pseudo-heavy oil. It is found that increasing surfactant (Triton X-100) concentration contributes to an increase in C3H8 foam stability; C3H8 foam stability is insensitive to surfactant concentration when the surfactant concentration is above the threshold CMC. The stability of C3H8 foam is negatively affected by an increasing salinity, temperature, and the presence of oil. The C3H8 foam is much more stable than CO2 foam at any conditions. In addition, it is found that alternating injection of C3H8 and Triton solution (SAG) results in a larger pressure difference, hence leading to a higher mobility reduction effect than alternating C3H8 and water (WAG) through the porous media. Secondly, the static foam stability of nanoparticle-stabilized C3H8 foam is examined under different reservoir conditions. Nanocrystalline cellulose (CNC), which is naturally hydrophilic and cannot act as foam stabilizer alone, has been chosen as the nanoparticle for foam stabilization purpose. Cationic CTAB is used to modify the surface of bare anionic CNC in situ from being hydrophilic to relatively hydrophobic and surface active. We examine the effects of particle coating, surfactant concentration, salinity, temperature, and the presence of oil on C3H8/CNC/CTAB foam stability. It is found that the stability of CTAB-coated CNC stabilized foam increases with an increase in CTAB concentration, salinity and temperature. It is less sensitive to the presence of oil. Other foams formed by recipes of C3H8/CNC/Tween 20, C3H8/CNC/Tween 80, and C3H8/CNC/Triton X-100 are also tested to explore the synergistic effect on foam stability due to the use of CNC and non-ionic surfactants. It is found that, if a non-ionic surfactant is a foaming agent, the synergistic effect of CNC nanoparticle and non-ionic surfactant enhances the foam stability. In other words, a stable foam can be formed by introducing both foam forming agent (surfactant) and foaming booster (nanoparticle). By comparing the stability of foam formed by CTAB-coated CNC and CNC/non-ionic surfactant mixtures, foam stability of CTAB-coated CNC stabilized foam is stronger than that of CNC/non-ionic surfactant mixtures. This is probably because the electrostatic interaction of CTAB with CNC is stronger than the synergistic effect due to the use of non-ionic surfactant and CNC, leading to a more stable foam thereof. Finally, the dynamic mobility of foam flow through porous media is examined by alternatively injecting C3H8 and CTAB-coated CNC or CNC/non-ionic surfactant mixtures (SAG). The experimental results indicate that if a non-ionic surfactant is used as a foaming agent, the synergistic effect of CNC and non-ionic surfactant enhances the reduction in foam mobility. In addition, foam formed by alternatively injecting CTAB-coated CNC and C3H8 shows a higher mobility reduction effect than that formed by alternatively injecting CNC/non-ionic surfactant and C3H8, which is consistent with the results of the static stability tests. In the SAG tests (either CTAB/CNC or Triton X-100/CNC stabilized C3H8 foam) conducted with an oil-saturated beadpack, the presence of CNC nanoparticles is able to enhance the oil recovery due to a mobility control mechanism.

  • Subjects / Keywords
  • Graduation date
    Fall 2016
  • 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.