Reverse Time Migration False Image Removal via Wavefield Segmentation
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Solution Overview
Problem
Reverse time migration (RTM) techniques in seismic data processing suffer from imaging noise due to unwanted cross-correlation of source and receiver wavefields at nonreflecting points, leading to false images in earth subsurface layer imaging, which hinders high-resolution depth imaging essential for reservoir exploration.
Innovation Solution
The method involves dividing wavefields into overlapping windows and calculating down-going and up-going components using Fourier transformations and Hilbert transformations, allowing for the elimination of false image components by summing these components with tapering in overlapping areas, thereby enhancing the accuracy of seismic depth imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wave equation based seismic depth migration techniques (RTM) are used for high resolution depth imaging, then imaging resolution is improved, but imaging noise and false images are generated due to unwanted cross-correlation of source and receiver wavefields
Solution Approach 1:
The patent divides the wavefield into multiple windows in the spatial domain, applying different processing to different segments. By segmenting the wavefield and applying directional filtering to each segment, the method separates true reflectors from false images while maintaining high resolution imaging capability.
Solution Approach 2:
The patent applies different quality characteristics to different parts of the wavefield by using directional filtering (down-going vs. up-going components) in different spatial regions. This allows true reflectors to be enhanced while false images are suppressed, resolving the contradiction between resolution and noise.
2Area of stationary object
If conventional RTM imaging condition is applied to source and receiver wavefields, then imaging coverage is improved, but false images are generated from erroneous propagation direction combinations
Solution Approach 1:
The patent segments the wavefield components by propagation direction (down-going and up-going) and applies appropriate imaging conditions to each segment. This segmentation allows true reflectors to be imaged with correct propagation directions while false images from erroneous combinations are eliminated.
Solution Approach 2:
The patent changes the parameter of propagation direction by decomposing the wavefield into down-going and up-going components. This parameter change enables selective application of imaging conditions based on correct propagation directions, improving imaging accuracy while maintaining coverage.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively removes false images and noise from RTM results, improving the resolution and accuracy of earth subsurface layer imaging, enabling better estimation of properties for oil and gas exploration.
Implementation Method 1
Hilbert transformation of the positive component of the Fourier transformation of the source wavefield
Implementation Method 2
positive component of Fourier transformation of the source wavefield
Data Source
AI summary
The present disclosure describes methods and systems, including computer-implemented methods, computer program products, and computer systems, for removing false image in reverse time migration (RTM). One computer-implemented method includes dividing volume of a source wavefield and a receiver wavefield into a plurality of windows, calculating a down-going component of the source wavefield and an up-going component of the receiver wavefield for each window in the plurality of windows and at a particular value of time, calculating a down-going component of the source wavefield at the particular value of time by summing the down-going component of the source wavefield in each window of the plurality of windows, and calculating an up-going component of the receiver wavefield at the particular value of time by summing the up-going component of the receiver wavefield in each window of the plurality of windows.