{"title":"Low-frequency Model Update Using Adjustive FWI at Clair Ridge","authors":"A. Bullock, S. Roy","doi":"10.3997/2214-4609.201900054","DOIUrl":"https://doi.org/10.3997/2214-4609.201900054","url":null,"abstract":"Summary Clair Ridge, located West of Shetland, is the new development phase for the Clair field in an area with near-surface velocity variability that causes challenges for traditional full-waveform inversion (FWI). A hard seabed with fast velocities and an inversion below, as well as shallow channelling, pock marks, and gas within the overburden, result in image distortion and severe multiple challenges. To prepare for the new ultra-dense ocean-bottom node (OBN) data set, a pre-acquisition model building strategy made use of legacy data sets to simplify the initial model and conclude the first successful FWI in this area. Adjustive FWI enabled this solution at Clair field by mitigating the requirements for standard least-squares methods that are difficult to meet in this area. Imaging with a simplified initial model and adjustive FWI delivers structural simplicity, enhanced amplitudes, and continuity, giving significant improvements from the overburden to the reservoir level. Reflection based FWI was tested and added details outside the coverage of diving-wave penetration and improved structural imaging around the reservoir. The addition of reflections also allows the velocity update to be extended deeper.","PeriodicalId":350524,"journal":{"name":"Second EAGE/PESGB Workshop on Velocities","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130068710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Sample Size Automation in a Pseudo-random Model Uncertainty Workflow","authors":"T. Martin","doi":"10.3997/2214-4609.201900037","DOIUrl":"https://doi.org/10.3997/2214-4609.201900037","url":null,"abstract":"Summary Velocity model building (VMB) using tomography produces one credible realization of an earth model, which, in turn, generates one conceivable subsurface image. The inversion, by its nature, is highly non-linear, and can lead to uncertainty with a single model and image approach. Uncertainty can be quantified by using a model population, rather than a single realization. In this scenario, all models must equally explain the data by producing flat gathers from the inversion. Defining what is an appropriate sample size for a nonlinear system using a pseudo-random approach to model uncertainty is critical for cost and turnaround. We automate a real-time constraint on the expanding model population using statistical relevance to the attributes produced through the uncertainty process. Analysis using cumulative distribution functions (CDFs) of the deviation in the model population define an automated threshold. The sample size threshold is met when there is no additional statistical relevance for the output attributes; the process stops and the model uncertainty metrics defining spatial reliability of the data are output. We demonstrate this method on data from the North Sea.","PeriodicalId":350524,"journal":{"name":"Second EAGE/PESGB Workshop on Velocities","volume":"436 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133353643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Integrating FWI Models and Broadband Data for Elastic Property Generation, What is Appropriate?","authors":"T. Martin, C. Reiser","doi":"10.3997/2214-4609.201900043","DOIUrl":"https://doi.org/10.3997/2214-4609.201900043","url":null,"abstract":"Summary Full waveform inversion (FWI) produces high-resolution earth models, the use of which can improve seismic imaging. FWI can also help create absolute inversion products, by filling the low frequency spectral gap in the integration with amplitude seismic data. However, what frequency should be used for FWI to cost-effectively estimate absolute elastic properties remains an open question. We present analysis from a case study in the Norwegian Sea. Initially we demonstrate how imaging challenges have been overcome by the use of FWI and high-end imaging. Following this, we reveal there is a cost-benefit sweet-spot for the low frequency models from FWI and broadband seismic amplitude data in the generation of absolute seismic inversion products.","PeriodicalId":350524,"journal":{"name":"Second EAGE/PESGB Workshop on Velocities","volume":"124 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133401742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. Korkidi, R. Litvak, C. Ayache, R. Levy, Z. Koren
{"title":"Azimuthally Anisotropic Effective Parameters from Full-azimuth Reflection Angle Gathers","authors":"L. Korkidi, R. Litvak, C. Ayache, R. Levy, Z. Koren","doi":"10.1190/SEGAM2018-2995956.1","DOIUrl":"https://doi.org/10.1190/SEGAM2018-2995956.1","url":null,"abstract":"Summary We present an efficient and stable procedure for estimating second- and fourth-order azimuthally-dependent effective parameters from full-azimuth residual moveouts. The residual moveouts are automatically picked at depth image points along full-azimuth angle domain reflection angle gathers. It is assumed that the azimuthally varying residual moveouts are due to fracture systems within compacted sand/shale sediment layers which were not accounted for in the seismic migration. The extracted (up to eight) effective parameters can then be used to obtain local (layer) effective parameters, characterizing the intensity and orientation of the fracture systems at each layer. Finally, the local effective parameters can be inverted to obtain interval anisotropic (e.g., orthorhombic) model parameters to be used in orthorhombic seismic migration.","PeriodicalId":350524,"journal":{"name":"Second EAGE/PESGB Workshop on Velocities","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124554268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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