Characterization of magnetic nanoparticles as contrast agents and their application for quantitative magnetic susceptibility monitoring of the waterflooding of heavy oil in real time

• Author / Creator

  Petrov, Petar A

• Waterflooding is one enhanced oil recovery process used in heavy oil reservoirs such as at Cold Lake in North-Eastern Alberta. However, little has been published in terms of imaging heavy oil waterfloods, mainly due to the similar densities of water and heavy oil, which makes it difficult to track the process by methods such as computer tomography (CT) scanning. This thesis will first present the results of physical and magnetic characterization of four magnetic nanoparticle compositions for potential use as magnetic contrast agent tracers for tracking the waterflooding of a heavy oil saturated sandpack. The magnetic properties of the nanoparticles were examined at both room temperature and typical reservoir temperatures. The most favourable candidate nanoparticle composition subsequently underwent stability experiments in order to produce long term stable dispersed nanoparticle suspensions. The magnetic nano-fluid was then used in experiments to track the waterflooding of a heavy oil saturated sandpack in real time using magnetic susceptibility scanning. Attempts to track the process were also undertaken with CT scanning for comparison. The successful waterflood 2 experiment revealed the formation, growth and movement of a significant positive magnetic susceptibility peak. This peak formed at the injection end of the flow cell and migrated towards the production end as the waterflooding progressed. The peak was likely due to the higher concentration of nanoparticles collecting at the main water-heavy oil interface(s). This result was significant as it provided a means to quantitatively track the progression of the waterflood in real time. The increased accumulation of nanoparticles at the water-heavy oil interface(s) was further supported by the material collected in the production jars. While the CT attenuation profiles showed some correspondence with the magnetic results, they were not able to track the progression of the waterflood, most likely due to the low CT contrast between the nano-fluid and the heavy oil. Once the main water-heavy oil interface(s) had passed through the sandpack the magnetic profiles had a constant shape similar to the porosity profile (as determined by the CT derived porosity variation). The results suggested that the magnetic technique has potential for monitoring larger scale commercial waterflooding operations. The potential retention of magnetic nanoparticles after water-flushing was also examined. These results were then compared to a case study where naturally occurring hematite nanoparticles in a tight gas reservoir were shown to have a detrimental effect on the reservoir quality by reducing the permeability. The comparison showed that the concentrations of retained nanoparticles in a series of laboratory water flushing experiments were significantly less than the concentrations causing the detrimental effects in the tight gas reservoir case study. A further study was conducted on the magnetic properties of hematite nanoparticles. Although hematite nanoparticles were initially considered as possible magnetic contrast agent tracers for reservoir characterization, one sample exhibited an unexpected diamagnetic magnetic susceptibility signal during initial room temperature measurements. A search of the literature also revealed another apparent “diamagnetic” result in another sample of hematite nanoparticles. These results were unusual as hematite is expected to have canted antiferromagnetic behaviour at room temperature. This led to an investigation of whether the hematite nanoparticles were behaving diamagnetically themselves or if the observed magnetic signal was due to the diamagnetic matrix overwhelming a weak canted antiferromagnetic signal from the hematite nanoparticles. After comprehensively investigating three different sizes of hematite nanoparticles it was concluded that the nanoparticles were not diamagnetic but that the “diamagnetic” magnetic susceptibility signal resulted from the diamagnetic matrix (in which the nanoparticles were dilutely dispersed) overwhelming the weak hematite signal.

• Subjects / Keywords

  • Contrast
  • Quantitative
  • Application
  • Waterflooding
  • Oil
  • Nanoparticles
  • Characterisation
  • Waterflood
  • Magnetic
  • Susceptibility
  • Retention
  • Stability
  • Monitoring
  • Agents
  • Flow
  • Reservior

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R34M91R8V

• 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.