With dwindling worldwide petroleum supplies, there is an ever increasing pressure on the oil industry to develop new reservoir recovery mechanisms or maximise the effectiveness of those currently utilised. Fluctuations of reservoir recovery as a result of nearby seismic activity has been observed, initiating a range of studies into what is causing this effect. The generation of ultrasonic wave fields due to the dispersion of seismic wave fields as they travel through saturated porous rock has been shown, both analytically and experimentally. The feasibility of these generated ultrasonic waves being capable of this observed modification to reservoir is investigated. For the initial stage of this research, the feasibility of changing the behaviour of fluid in rock using an ultrasonic field is considered. Research into the interaction between acoustic waves, the porous rock and the pore fluid indicates two key areas of permeability enhancement - increasing rock permeability and modifying the fluid behaviour within the pores. By increasing the permeability of the rock, previously unobtainable sources may be recovered and less energy would be necessary to obtain these reserves. Cavitation erosion or localised rock weakening due regions of high stress resulting from complex internal wave interactions are the two mechanisms proposed to increase permeability. Modification of the relative fluid behaviours within the rock as a result of mechanical agitation of the fluid from peristaltic transport and cavitation bubbles generated due to the acoustic field was explored. Sandstone cores saturated partially with tap water were placed in a degassed fluid and a low or high acoustic field applied. Tensile strength measurements are taken following exposure to the acoustic field and measurements compared to control samples. Samples were weighed prior to and following testing to determine fluid and gas motion between the surrounding fluid and pore volume. Samples exposed to the low amplitude acoustic pressure field showed no change in tensile strength when compared to control samples. The high pressure acoustic field caused samples to have an increase of strength when compared to the control batch of samples. The partial saturation of the samples exposed to the acoustic pressure field showed an increased in mass following exposure. An exchange of gas bubbles trapped within the pores and fluid with the surrounding degassed water explains this mass increase during testing.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:739241 |
| Date | January 2018 |
| Creators | Campbell, Eimear |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/8782/ |
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