Near surface investigation with DAS for CO2 sequestration and monitoring

Qu, Luping

Near surface investigation with DAS for CO2 sequestration and monitoring

dc.contributor.advisor	Innanen, Kris
dc.contributor.author	Qu, Luping
dc.contributor.committeemember	Dettmer, Jan
dc.contributor.committeemember	Martin, Eileen
dc.contributor.committeemember	Liao, Wenyuan
dc.contributor.committeemember	Trad, Daniel
dc.date	2024-02
dc.date.accessioned	2024-01-17T19:14:19Z
dc.date.available	2024-01-17T19:14:19Z
dc.date.issued	2024-01-11
dc.description.abstract	In this thesis, I investigate near-surface seismic properties and several geophysical methods mainly including surface wave dispersion inversion (SWDI) and full waveform inversion (FWI) for CO2 monitoring, focusing on the capabilities of Distributed Acoustic Sensing (DAS) technology. The study is underpinned by data collected from Newell County Facility, Alberta, Canada, employing seismic data acquired from both surface-deployed and vertical seismic profi le (VSP) DAS fiber. DAS data, characterized by broadband and dense spatial sampling, facilitate the extraction of high-resolution near-surface velocity pro les due to their enhanced signal-to-noise ratio and resolution in low-frequency components and multimode dispersion curves. The first segment of the study introduced several types of dispersion curves, explores trans-dimensional (TD) inversion, employing multimode dispersion curves and reversible-jump Markov Chain Monte Carlo (MCMC) sampling to generate probabilistic posterior density (PPD) estimates of model parameters. This approach yields inversion results that align well with known lithological data. This research showcases the potential of horizontal DAS data in high-resolution, near-surface investigations. Additionally, I developed a multi-step multiscale surface wave FWI. Utilizing DAS recorded surface waves, high-resolution S-wave velocity (Vs) and attenuation (quality factor Qs) models of the near-surface are obtained through FWI, offering improved lateral resolution and depth penetration compared to conventional surface-wave analysis. The inclusion of low-frequency components in DAS data effectively mitigates the cycle skipping challenge commonly associated with FWI, leading to high-resolution VS models that capture lateral variations effectively. I also addressed the challenge of noise in seismic data, particularly its impact on acoustic and elastic FWI models. By incorporating the data covariance matrix into the mis t function, this approach mitigates the effects of noise, improving the accuracy of the FWI models. Building on these methods, I applied anisotropic FWI with variable density to DAS recorded walk-away VSP data for characterizing subsurface velocity, anisotropy, and density structures. This technique, essential for time-lapse studies of CO2 injection and storage, proved effective in providing more accurate P-wave velocity, density models, and anisotropy parameters compared to isotropic FWI. In conclusion, this thesis demonstrates the potential of using DAS technology and advanced geophysical methods for near-surface investigation and CO2 monitoring. The integration of DAS data with trans-dimensional and varied FWI approaches, alongside noise mitigation strategies, offers a signi cant step forward in accurate and e cient subsurface characterization, crucial for environmental monitoring and carbon capture and storage initiatives.
dc.identifier.citation	Qu, L. (2024). Near surface investigation with DAS for CO2 sequestration and monitoring (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.
dc.identifier.uri	https://hdl.handle.net/1880/117944
dc.identifier.uri	https://doi.org/10.11575/PRISM/42788
dc.language.iso	en
dc.publisher.faculty	Graduate Studies
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	Near Surface
dc.subject	DAS
dc.subject	FWI
dc.subject.classification	Geophysics
dc.title	Near surface investigation with DAS for CO2 sequestration and monitoring
dc.type	doctoral thesis
thesis.degree.discipline	Geoscience
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.