Testing the Feasibility of Using PERM to Apply Scattering-Angle Filtering in the Image-Domain for FWI Applications

Handle URI:
http://hdl.handle.net/10754/333066
Title:
Testing the Feasibility of Using PERM to Apply Scattering-Angle Filtering in the Image-Domain for FWI Applications
Authors:
Alzahrani, Hani Ataiq ( 0000-0002-7572-4172 )
Abstract:
ABSTRACT Testing the Feasibility of Using PERM to Apply Scattering-Angle Filtering in the Image-Domain for FWI Applications Hani Ataiq Alzahrani Full Waveform Inversion (FWI) is a non-linear optimization problem aimed to estimating subsurface parameters by minimizing the mis t between modeled and recorded seismic data using gradient descent methods, which are the only practical choice because of the size of the problem. Due to the high non-linearity of the problem, gradient methods will converge to a local minimum if the starting model is not close to the true one. The accuracy of the long-wavelength components of the initial model controls the level of non-linearity of the inversion. In order for FWI to converge to the global minimum, we have to obtain the long wavelength components of the model before inverting for the short wavelengths. Ultra-low temporal frequencies are sensitive to the smooth (long wavelength) part of the model, and can be utilized by waveform inversion to resolve that part. Un- fortunately, frequencies in this range are normally missing in eld data due to data- acquisition limitations. The lack of low frequencies can be compensated for by uti- lizing wide-aperture data, as they include arrivals that are especially sensitive to the long wavelength components of the model. The higher the scattering angle of a 5 recorded event, the higher the model wavelength it can resolve. Based on this prop- erty, a scattering-angle ltering algorithm is proposed to start the inversion process with events corresponding to the highest scattering angle available in the data, and then include lower scattering angles progressively. The large scattering angles will resolve the smooth part of the model and reduce the non-linearity of the problem, then the lower ones will enhance the resolution of the model. Recorded data is rst migrated using Pre-stack Exploding Re ector Migration (PERM), then the resulting pre-stack image is transformed into angle gathers to which an angle ltering process is applied to remove events below a certain cut-o angle. The ltered pre-stack image cube is then demigrated (forward modeled) to produce ltered surface data that can be used in waveform inversion. Numerical tests con rm the feasibility of the proposed ltering algorithm. However, the accuracy of the ltered section is limited by PERM's singularity for horizontally-traveling waves, which in turn is dependent on the velocity model used for migration and demigration
Advisors:
Alkhalifah, Tariq
Committee Member:
Laleg-Kirati, Taous-Meriem ( 0000-0001-5944-0121 ) ; Mahmoud, Sherif
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Program:
Earth Sciences and Engineering
Issue Date:
Sep-2014
Type:
Thesis
Appears in Collections:
Theses; Physical Sciences and Engineering (PSE) Division; Earth Science and Engineering Program

Full metadata record

DC FieldValue Language
dc.contributor.advisorAlkhalifah, Tariqen
dc.contributor.authorAlzahrani, Hani Ataiqen
dc.date.accessioned2014-10-22T13:11:49Z-
dc.date.available2014-10-22T13:11:49Z-
dc.date.issued2014-09en
dc.identifier.urihttp://hdl.handle.net/10754/333066en
dc.description.abstractABSTRACT Testing the Feasibility of Using PERM to Apply Scattering-Angle Filtering in the Image-Domain for FWI Applications Hani Ataiq Alzahrani Full Waveform Inversion (FWI) is a non-linear optimization problem aimed to estimating subsurface parameters by minimizing the mis t between modeled and recorded seismic data using gradient descent methods, which are the only practical choice because of the size of the problem. Due to the high non-linearity of the problem, gradient methods will converge to a local minimum if the starting model is not close to the true one. The accuracy of the long-wavelength components of the initial model controls the level of non-linearity of the inversion. In order for FWI to converge to the global minimum, we have to obtain the long wavelength components of the model before inverting for the short wavelengths. Ultra-low temporal frequencies are sensitive to the smooth (long wavelength) part of the model, and can be utilized by waveform inversion to resolve that part. Un- fortunately, frequencies in this range are normally missing in eld data due to data- acquisition limitations. The lack of low frequencies can be compensated for by uti- lizing wide-aperture data, as they include arrivals that are especially sensitive to the long wavelength components of the model. The higher the scattering angle of a 5 recorded event, the higher the model wavelength it can resolve. Based on this prop- erty, a scattering-angle ltering algorithm is proposed to start the inversion process with events corresponding to the highest scattering angle available in the data, and then include lower scattering angles progressively. The large scattering angles will resolve the smooth part of the model and reduce the non-linearity of the problem, then the lower ones will enhance the resolution of the model. Recorded data is rst migrated using Pre-stack Exploding Re ector Migration (PERM), then the resulting pre-stack image is transformed into angle gathers to which an angle ltering process is applied to remove events below a certain cut-o angle. The ltered pre-stack image cube is then demigrated (forward modeled) to produce ltered surface data that can be used in waveform inversion. Numerical tests con rm the feasibility of the proposed ltering algorithm. However, the accuracy of the ltered section is limited by PERM's singularity for horizontally-traveling waves, which in turn is dependent on the velocity model used for migration and demigrationen
dc.language.isoenen
dc.subjectPERMen
dc.subjectExploring Reflectoren
dc.subjectAngel Filteringen
dc.subjectFWIen
dc.subjectSeismic Inversionen
dc.titleTesting the Feasibility of Using PERM to Apply Scattering-Angle Filtering in the Image-Domain for FWI Applicationsen
dc.typeThesisen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberLaleg-Kirati, Taous-Meriemen
dc.contributor.committeememberMahmoud, Sherifen
thesis.degree.disciplineEarth Sciences and Engineeringen
thesis.degree.nameMaster of Scienceen
dc.person.id124223en
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