dc.contributor.advisor Shragge, Jeffrey dc.contributor.author Oren, Can dc.date.accessioned 2022-10-06T17:28:15Z dc.date.available 2022-10-06T17:28:15Z dc.date.issued 2022 dc.identifier Oren_mines_0052E_12345.pdf dc.identifier T 9297 dc.identifier.uri https://hdl.handle.net/11124/15380 dc.description Includes bibliographical references. dc.description 2022 Spring. dc.description.abstract Wavefield migration and tomography are considered to be state-of-the-art methodologies used for subsurface geological characterization. Seismic tomography produces accurate velocity models that commonly serve as input into seismic migration algorithms that produce high-quality passive-source (e.g., microseismic) images or structural images of geological interfaces constructed using controlled-source energy (e.g., vibroseis truck or dynamite). Most existing wavefield migration and tomography techniques employed in the oil and gas industry are well-developed under the acoustic assumption. One of the main shortcomings of this assumption is that conventional acoustic imaging algorithms generally use single-component P-wave data and thus do not account for multicomponent elastic (P- and S-mode) data that can provide additional subsurface information such as fracture distributions and elastic properties. To account for more accurate wave physics in passive and active seismic scenarios, I propose a suite of novel full-wavefield methods for imaging and multiparameter (i.e., P- and S-wave) model estimation in elastic media. Passive-style image-domain elastic tomography operates with multicomponent P- and S-wave first-arrival waveforms of a microseismic event and optimizes the background velocity model by improving the quality of source images constructed by a procedure called time-reverse imaging (TRI). To formulate a robust image-domain inversion framework, I develop a 3D extended imaging condition for surface-recorded microseismic data based on the correlation of individual P- and S-wavefield energy as well as the energy norm. The proposed PS energy imaging condition not only effectively locates microseismic events for complex isotropic/anisotropic models but also provides useful information about P- and S-wave velocity model as well as anisotropy parameter $[\epsilon,\delta,\gamma]$ accuracy. Based on the kinetic energy term of the PS energy imaging condition, I propose an image-domain elastic wavefield tomography framework to build plausible P- and S-wave velocity models that improve the quality of microseismic event images. I present synthetic numerical experiments to demonstrate that the estimated model parameters result in enhanced source images, which greatly reduce event mispositioning errors. Finally, I apply the developed image-domain elastic inversion method on an active-source distributed acoustic sensing 3D vertical seismic profiling data set acquired in the North Slope of Alaska to investigate potential methane gas hydrate reservoirs. I exploit source-receiver reciprocity to create an acquisition configuration that resembles passive-seismic surface monitoring scenarios. I first validate the accuracy of the inverted elastic velocity models using a TRI-based source location analysis. Next, I construct numerous 3D structural images of the area of interest through elastic reverse time migration (RTM). The elastic RTM results exhibit coherent reflectivity associated with a complex near-surface ice-bearing permafrost zone, as well as two gas hydrate reservoirs that satisfactorily match the existing log data in well-ties due to the improved velocity model estimates. dc.format.medium born digital dc.format.medium doctoral dissertations dc.language English dc.language.iso eng dc.publisher Colorado School of Mines. Arthur Lakes Library dc.relation.ispartof 2022 - Mines Theses & Dissertations dc.rights Copyright of the original work is retained by the author. dc.subject computational seismology dc.subject distributed acoustic sensing dc.subject elastic wave propagation dc.subject microseismic dc.subject seismic imaging dc.subject seismic tomography dc.title Elastic time-reverse imaging and transmission tomography for microseismic and DAS VSP data dc.type Text dc.date.updated 2022-10-01T01:09:26Z dc.contributor.committeemember Sava, Paul C. dc.contributor.committeemember Bozdag, Ebru dc.contributor.committeemember Ganesh, Mahadevan dc.contributor.committeemember Walton, Gabriel thesis.degree.name Doctor of Philosophy (Ph.D.) thesis.degree.level Doctoral thesis.degree.discipline Geophysics thesis.degree.grantor Colorado School of Mines
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