Reflection FWI Velocity Modeling to Prevent Seismic Cycle Skipping
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Solution Overview
Problem
Conventional full waveform inversion (FWI) methods suffer from cycle skipping, leading to inadequate seismic velocity models, which hinder the accurate transformation of seismic data from the time domain to the depth domain for locating hydrocarbon reservoirs.
Innovation Solution
The method involves decomposing the seismic velocity model into low-wavenumber and high-wavenumber components, using dynamic image warping to correct traveltime shifts, and applying local similarity based on shaping regularization to condition traveltime shift data, iteratively refining the seismic velocity model to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional full waveform inversion (FWI) methods are used to determine the seismic velocity model, then the seismic velocity model can be obtained, but cycle skipping occurs resulting in inadequate model accuracy
Solution Approach 1:
The patent segments the seismic velocity model into two distinct components: a low-wavenumber component (first seismic velocity model) and a high-wavenumber component (second seismic velocity model). This segmentation allows each component to be determined through separate inversion processes, preventing cycle skipping by ensuring the low-wavenumber component provides a reliable background velocity structure that avoids local minima in the inversion algorithm.
Solution Approach 2:
The patent applies different inversion strategies to different components of the velocity model. The low-wavenumber component is determined using a regularization approach that emphasizes smoothness and global structure, while the high-wavenumber component captures local velocity variations. This local quality differentiation ensures that each component is optimized for its specific role, improving overall model accuracy while preventing cycle skipping.
2Measurement precision
If the seismic velocity model is used to transform seismic data from time domain to depth domain, then the transformation can be performed, but inadequate velocity models result in inaccurate hydrocarbon reservoir location
Solution Approach 1:
By segmenting the velocity model into low-wavenumber and high-wavenumber components, the patent ensures that both broad-scale and fine-scale velocity variations are accurately captured. This segmentation prevents information loss during the time-to-depth transformation, as each component contributes specific necessary information for accurate imaging and hydrocarbon reservoir location.
Solution Approach 2:
The patent creates a composite velocity model by combining the low-wavenumber component (providing smooth background velocity) and the high-wavenumber component (providing detailed local velocity variations). This composite approach ensures that the final velocity model contains all necessary information for accurate seismic data transformation, preventing loss of information and improving hydrocarbon reservoir location accuracy.
Data Source
AI summary
Systems and methods are disclosed. The method may include receiving observed seismic data, and a first and a second seismic velocity model, each pertaining to a subterranean region of interest and, iteratively, determining synthetic reflection data based on the first and second seismic velocity model, determining traveltime shift data between the synthetic observed seismic data, and determining warped observed seismic data by applying the traveltime shift data to the observed seismic data. The method further includes determining conditioned traveltime shift data using local similarity based on shaping regularization from the synthetic reflection data, the warped observed seismic data, and the traveltime shift data, and determining a seismic velocity model based on the first seismic velocity model and the conditioned traveltime shift data. The method also includes determining a seismic image from observed seismic data and the seismic velocity model, and a location of a hydrocarbon reservoir using the seismic image.