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sep:research:theses:sep153 [2014/07/17 07:06]
adam
sep:research:theses:sep153 [2015/05/27 02:06] (current)
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//by [[http://sepwww.stanford.edu/sep/adam|Adam Halpert]]// //by [[http://sepwww.stanford.edu/sep/adam|Adam Halpert]]//
-Full thesis (link/sep153/sep153.pdf|PDF)+Full thesis [[http://sepwww.stanford.edu/data/media/public/docs/sep153/sep153.pdf|PDF]]
**Table of contents** **Table of contents**
-  * Chapter 1: link/sep153/chap1.pdf|Introduction +  * Chapter 1: [[http://sepwww.stanford.edu/data/media/public/docs/sep153/chap1.pdf|Introduction]] 
-  * Chapter 2: link/sep153/chap2.pdf|Interpreter-guided seismic image segmentation +  * Chapter 2: [[http://sepwww.stanford.edu/data/media/public/docs/sep153/chap2.pdf|Interpreter-guided seismic image segmentation]] 
-  * Chapter 3: link/sep153/chap3.pdf|Efficient velocity model evaluation]] +  * Chapter 3: [[http://sepwww.stanford.edu/data/media/public/docs/sep153/chap3.pdf|Efficient velocity model evaluation]] 
-  * Chapter 4: link/sep153/chap4.pdf|Integrated model building workflow: field data example+  * Chapter 4: [[http://sepwww.stanford.edu/data/media/public/docs/sep153/chap4.pdf|Integrated model building workflow: field data example]]
     
**Abstract** **Abstract**
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If multiple salt scenarios lead to several possible velocity models being created, these models can be quickly tested by synthesizing new source and receiver wavefields from an initial image. Both wavefields are generated using prestack velocity information from the initial image, via a generalized form of Born modeling. This allows the velocity inaccuracies present in the initial model to be identified and, ideally, corrected in future model iterations. Because the synthesized receiver wavefield is imaged with an areal source function (both obtained with the initial velocity model), a single shot can be migrated using any other velocity model to provide an image of targeted locations within the model. Crosstalk issues arising from interfering events in the subsurface offset domain can be mitigated by imaging only sparsely-spaced model locations; alternatively, several separate experiments can be performed at different model locations, and the resulting images summed to provide a more detailed final image. If qualitative inspection is insufficient to determine the most accurate model among those being tested, a measure of image focusing can provide a quantitative comparison based on the proportion of an image's energy focused at or near zero-subsurface offset. This strategy is shown to be effected for synthetic and field datasets, in 2D and 3D. If multiple salt scenarios lead to several possible velocity models being created, these models can be quickly tested by synthesizing new source and receiver wavefields from an initial image. Both wavefields are generated using prestack velocity information from the initial image, via a generalized form of Born modeling. This allows the velocity inaccuracies present in the initial model to be identified and, ideally, corrected in future model iterations. Because the synthesized receiver wavefield is imaged with an areal source function (both obtained with the initial velocity model), a single shot can be migrated using any other velocity model to provide an image of targeted locations within the model. Crosstalk issues arising from interfering events in the subsurface offset domain can be mitigated by imaging only sparsely-spaced model locations; alternatively, several separate experiments can be performed at different model locations, and the resulting images summed to provide a more detailed final image. If qualitative inspection is insufficient to determine the most accurate model among those being tested, a measure of image focusing can provide a quantitative comparison based on the proportion of an image's energy focused at or near zero-subsurface offset. This strategy is shown to be effected for synthetic and field datasets, in 2D and 3D.
-The image segmentation and model evaluation tools are designed to work together to alleviate the salt interpretation bottleneck in model building. Using a wide-azimuth survey from the Gulf of Mexico, image segmentation is used to isolate a sedimentary inclusion within a salt body, and to define two alternate interpretations of the base of salt. The efficient model evaluation scheme is then used to test these two models, along with one provided with the dataset, in a fraction of the time required for full migrations. Qualitative and quantitative analysis of the results indiates that one of the alternate models is most desirable, and a subsequent remigration of the full dataset with this model provides an image with improved clarity and continuity of subsalt reflectors.+The image segmentation and model evaluation tools are designed to work together to alleviate the salt interpretation bottleneck in model building. Using a wide-azimuth survey from the Gulf of Mexico, image segmentation is used to isolate a sedimentary inclusion within a salt body, and to define two alternate interpretations of the base of salt. The efficient model evaluation scheme is then used to test these two models, along with one provided with the dataset, in a fraction of the time required for full migrations. Qualitative and quantitative analysis of the results indicates that one of the alternate models is most desirable, and a subsequent remigration of the full dataset with this model provides an image with improved clarity and continuity of subsalt reflectors.
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