Convergence of a full waveform inversion scheme based on PSPI migration and forward modeling-free approximation: procedure and validation
| atmire.migration.oldid | 5900 | |
| dc.contributor.advisor | Lines, Laurence | |
| dc.contributor.advisor | Ferguson, Robert | |
| dc.contributor.author | Guarido de Andrade, Marcelo | |
| dc.contributor.committeemember | Innanen, Kristopher | |
| dc.contributor.committeemember | Lawton, Donald | |
| dc.contributor.committeemember | Cary, Peter | |
| dc.contributor.committeemember | Maini, Brij | |
| dc.date.accessioned | 2017-08-29T18:30:01Z | |
| dc.date.available | 2017-08-29T18:30:01Z | |
| dc.date.issued | 2017 | |
| dc.date.submitted | 2017 | en |
| dc.description.abstract | Full waveform inversion is a least squares technique that estimates rocks parameters by finding the model that reduces the difference between synthetic and acquired seismic data. This project is focused on acoustic inversion. The main goal is to understand and develop an FWI algorithm that is cheap and provides a higher quality inversion. The steepest-descent method is shown to be robust with some level of guarantee to converge, when the geology is simple, and when the starting model is close to the global minimum. Understanding that the gradient can be estimated by any pre-stack depth migration of the residuals, the RTM (reverse-time migration) is replaced by a PSPI (phase shift plus interpolation) migration, to reduce cost. Even though the method was shown to be expensive, mostly by the number of synthetic shots required and the pre-stack migration. By using a monochromatic averaged gradient combined with a conjugate gradient algorithm, inversion is possible for more complex geology, like a simulation on a 2D acoustic Marmousi model. However, the cost to run the process increased significantly, as each frequency on a selected band is migrated separately to form a pseudo-gradient, and are weighted averaged for the update. Inversion is simplified by applying an impedance inversion on the reflection coefficients based gradient using a band-limited impedance inversion (BLIMP) algorithm. Cost is reduced, being comparable to the standard steepest-descent, and the inverted model resolution is kept similar to the one using the monochromatic averaged gradient. Later, we came with a new interpretation of the gradient, understood to be the difference between current model and the impedance inversion of the migrated acquired data. No forward modeling or source estimation are required to compute the gradient. The cost per iteration is the same of the PSPI migration. A post-stack method is shown to be even cheaper and promising. Using a well sonic log to calibrate the gradient reduces method cost and improves its resolution, and is our most impressive solution. | en_US |
| dc.identifier.citation | Guarido de Andrade, M. (2017). Convergence of a full waveform inversion scheme based on PSPI migration and forward modeling-free approximation: procedure and validation (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/25459 | en_US |
| dc.identifier.doi | http://dx.doi.org/10.11575/PRISM/25459 | |
| dc.identifier.uri | http://hdl.handle.net/11023/4048 | |
| dc.language.iso | eng | |
| dc.publisher.faculty | Graduate Studies | |
| dc.publisher.institution | University of Calgary | en |
| dc.publisher.place | Calgary | en |
| 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 | Geophysics | |
| dc.subject.other | Full waveform inversion | |
| dc.subject.other | FWI | |
| dc.subject.other | impedance inversion | |
| dc.subject.other | forward modeling | |
| dc.subject.other | forward modeling-free gradient | |
| dc.subject.other | fast fwi | |
| dc.subject.other | fast full waveform inversion | |
| dc.title | Convergence of a full waveform inversion scheme based on PSPI migration and forward modeling-free approximation: procedure and validation | |
| dc.type | doctoral thesis | |
| thesis.degree.discipline | Geology and Geophysics | |
| thesis.degree.grantor | University of Calgary | |
| thesis.degree.name | Doctor of Philosophy (PhD) | |
| ucalgary.item.requestcopy | true |