Impact of Hydrate Dissociation on the Stiffness and Strength of Hydrate Bearing Sands

Ayebazibwe, Derrick

Impact of Hydrate Dissociation on the Stiffness and Strength of Hydrate Bearing Sands

dc.contributor.advisor	Priest, Jeffrey Alan
dc.contributor.advisor	Hayley, Jocelyn Louise
dc.contributor.author	Ayebazibwe, Derrick
dc.contributor.committeemember	Wong, Ron Chik-Kwong
dc.contributor.committeemember	Wan, Richard
dc.contributor.committeemember	Marriott, Robert
dc.contributor.committeemember	Singh, Devendra Narain
dc.date	2025-06
dc.date.accessioned	2024-12-04T22:13:11Z
dc.date.available	2024-12-04T22:13:11Z
dc.date.issued	2024-12-02
dc.description.abstract	The escalating global energy demand has propelled the exploration of unconventional energy resources, notably natural gas hydrates. These ice-like compounds, abundant in permafrost and marine sediments, harbor vast quantities of methane, a potent energy source. However, conventional methods for recovering methane gas from natural hydrate bearing sand (HBS) deposits requires dissociation of the hydrate, which has an impact on the mechanical stiffness and strength of the HBS. The safe and efficient production of methane from HBS reservoirs hinges on a comprehensive understanding of the intricate relationship between hydrate dissociation, hence reduction in hydrate saturation, and the mechanical behavior of the host sediments. This thesis investigates the impact of hydrate dissociation on the small-strain stiffness and shear strength of laboratory-synthesized methane hydrate-bearing sands. The excess gas method was employed to form methane hydrates within the sand specimens, simulating the conditions prevalent in many natural gas hydrate reservoirs. During hydrate formation and subsequent dissociation, resonant column tests were conducted to evaluate the changes in small strain stiffness and damping ratio that occurred. Triaxial shear compression tests were then conducted on each specimen, once a known volume of hydrate had been dissociated, to obtain their unique stress-strain response which was compared to the typical stress strain plot of intact hydrate bearing sand prepared exactly the same way and the stress strain plot of hydrate free host sands. The research findings reveal that hydrate formation significantly enhances the stiffness and strength of the sand, but dissociation, regardless of the method, leads to a substantial reduction in both properties. Notably, thermal stimulation causes a more rapid degradation of both mechanical properties compared to depressurization for the same degree of hydrate dissociation. The study also elucidates the distinct mechanisms governing the mechanical response of HBS during dissociation, highlighting the critical changes in hydrate morphology as thermal stimulation progresses that impact mechanical behaviour of HBS that undergoes thermal induced dissociation. The insights gained from this research contribute to a deeper understanding of the complex interplay between hydrate dissociation and the geomechanical behavior of HBS, providing a valuable foundation for the development of predictive models and the formulation of effective strategies for the safe and sustainable production of methane from hydrate reservoirs.
dc.identifier.citation	Ayebazibwe, D. (2024). Impact of hydrate sissociation on the stiffness and strength of hydrate bearing sands (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.
dc.identifier.uri	https://hdl.handle.net/1880/120155
dc.language.iso	en
dc.publisher.faculty	Schulich School of Engineering
dc.publisher.institution	University of Calgary
dc.rights	University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.
dc.subject	soil
dc.subject	stability-curve
dc.subject	testing
dc.subject	triaxial
dc.subject	resonant column
dc.subject	gas-hydrates
dc.subject	geotechnical
dc.subject.classification	Engineering--Civil
dc.subject.classification	Geotechnology
dc.subject.classification	Geochemistry
dc.subject.classification	Applied Sciences
dc.title	Impact of Hydrate Dissociation on the Stiffness and Strength of Hydrate Bearing Sands
dc.type	doctoral thesis
thesis.degree.discipline	Engineering – Civil
thesis.degree.grantor	University of Calgary
thesis.degree.name	Doctor of Philosophy (PhD)
ucalgary.thesis.accesssetbystudent	I do not require a thesis withhold – my thesis will have open access and can be viewed and downloaded publicly as soon as possible.