9 research outputs found
Surveillance 4D avec inversion de forme d'onde complète
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Surveillance 4D avec inversion de forme d'onde complète
No full textL'auteur n'a pas donné de résuméL'auteur n'a pas donné de résum
Surveillance 4D avec inversion de forme d'onde complète
No full textL'auteur n'a pas donné de résuméL'auteur n'a pas donné de résum
Surveillance 4D avec inversion de forme d'onde complète
No full textL'auteur n'a pas donné de résuméL'auteur n'a pas donné de résum
Surveillance 4D avec inversion de forme d'onde complète
No full textL'auteur n'a pas donné de résuméL'auteur n'a pas donné de résum
4D FWI with Short Offset Data: a Reflection Oriented Approach
No full textInternational audienceMain objectives To present an integrated 4D FWI workflow based on the combination of reflection based "joint full waveform inversion" and simultaneous time lapse strategy for short offset data. New aspects covered The integrated workflow incorporates a hierarchical approach utilizing both reflection based "joint full waveform inversion" and simultaneous time-lapse strategy. Here, the hierarchical approach consists of 4D macromodel estimation based on combination of JFWI and simultaneous time lapse strategy, and followed by high resolution 4D model estimation based on simultaneous time lapse inversion
4D FWI with Reflection Oriented Workflow: Application to CO2 Monitoring at Sleipner Field
No full textInternational audienceThe Sleipner CCS facility has been the first offshore storage operation at industrial scale and the longest operated in the world since 1994. For many years, Sleipner CO2 injection site has been monitored by three dimensional seismic surveys. Several studies utilize full waveform inversion to estimate the CO2 properties in this area directly from seismic data. The common challenge on these FWI studies is the offset limitation in the available streamer data. Therefore, FWI is very challenging in this scenario. Additionally, muti-parameter reconstruction of CO2 plume properties is not yet discussed. In our case study, we apply a reflection oriented workflow, which utilizes both diving and reflected waves through Joint Full Waveform Inversion (JFWI). It helps up to compensate the offset limitation of the data by utilizing the transmitted energy between the reflectors and the receivers to constrain the low wavenumber component of the velocity along the reflection wavepath. This naturally brings us to consider the monitoring problem in a multi-parameter sense as JFWI, in the acoustic approximation, works with a parameterization separating the P-impedance and the P-wave velocity. We thus obtain both structural and quantitative properties based on impedance and velocity models in a single workflow
CO2 monitoring at Sleipner field using reflection oriented full waveform inversion: part 2 - 4D investigation
No full textInternational audienceIn this work, we apply a dedicated 4-D full waveform inversion workflow to short offset streamer data from the Sleipner CO storage field in the North Sea. We consider a baseline data set acquired in 1994 and a monitor data set acquired in 2008. Accessing to only short offset data raises significant difficulties for full waveform inversion. In this case the penetration of diving waves, which controls the depth where quantitative updates of the velocity can be expected, do not reach the zone of interest where the CO is injected. For this reason, we propose to combine an efficient time-lapse full waveform inversion strategy, which we call simultaneous, with a reflection oriented full waveform inversion workflow. The latter has been introduced in the literature as a way to circumvent short-offset limitation and increase the ability of full waveform inversion to update the macro-velocity model at depth by exploiting the reflection paths, using a prior step of impedance reconstruction. We first illustrate the interest of this combined strategy on a 2-D synthetic model inspired from the Sleipner area. Then we apply it to the Sleipner field data, using as baseline model the one we present in a companion paper, where our reflection oriented workflow is presented. Our combined approach yields reliable estimates of the changes due to the CO injection, characterized by velocity reductions of up to 400 m s and strong impedance contrasts at depths of 800–1000 m, which consistent with previous full waveform inversion studies. Furthermore, the spatial distribution of CO changes aligns with conventional seismic time-migration results from earlier studies, following a north–south migration trend
CO2 monitoring at Sleipner field using reflection oriented full waveform inversion: Part 1 - baseline reconstruction
No full textInternational audienceIn this study, we illustrate the application of a 3D reflection oriented workflow for full waveform inversion (FWI) to the offset data from the Sleipner field. The data set is having maximum offset of less than 2000 m, and has been pre-processed with a low-cut filter below 6 Hz, imposing strong challenges for the FWI application. To tackle these challenges, a reflection oriented full waveform inversion is applied to the data set, which utilize joint full waveform inversion (JFWI) to constrain the low wavenumber updates at the deepest part of the reconstructed model. It consists of two steps, an impedance model building serving as a prior reflector information followed by a velocity model building. In this case, JFWI workflow is taking advantage of the pseudo-time formulation to honor the zero offset travel time, fast and robust asymptotic preconditioner for impedance model building, and graph space optimal transport misfit function to mitigate cycle skipping. To show the effects of limited offset, conventional FWI is performed. In this case, it is clear that the meaningful updates coming from the diving waves are restricted to the shallow part no deeper than 500 m of depth, while no meaningful perturbation are observed beyond the diving waves penetration. Taking advantage of the meaningful shallow updates, diving wave only inversion is performed prior to the impedance model building, and then followed by the JFWI workflow. The results of the field data application show that JFWI is able to produces meaningful velocity updates both in shallow part and the deeper part. The result is supported by satisfactory fit of the calculated data based on the JFWI model compared to the observed data. In addition, the velocity model fits the low wavenumber trend of the well log data. A subsequent run of conventional FWI is performed starting from JFWI model, in order to improve the resolution of the velocity model. The results is able to introduce higher wavenumber content to the velocity model, producing satisfactory fit with the observed data, and matching the well log data
