Sea-Surface Reflector Imaging via Dual-Sensor Wavefield Decomposition
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Solution Overview
Problem
Current marine seismic data processing techniques face challenges in accurately imaging the sea-surface reflector due to the undetermined shape of the sea surface and the resulting spectral notches and phase shifts in recorded signals, which affect the quality of subsurface imaging and the identification of hydrocarbon deposits.
Innovation Solution
A method that decomposes pressure and normal velocity wavefields into up-going and down-going components on a flat observation level, iteratively extrapolates these components towards the sea surface, and determines the image point and reflection coefficient of the sea surface from the extrapolated wavefields, allowing for improved imaging of the sea-surface reflector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional marine seismic data processing techniques are used, then the processing can be performed with conventional methods, but the accuracy of sea-surface reflector imaging is degraded due to spectral notches and phase shifts
Solution Approach 1:
The patent uses the recorded ghost waves (which cause spectral notches and phase shifts) as useful signals to infer sea-surface topography and reflection coefficients. By treating the harmful interference as a carrier of useful information about the sea surface, the method converts the spectral notches from a problem into a source of data for improving imaging accuracy.
Solution Approach 2:
The patent introduces an intermediate processing step that decomposes the pressure wavefield into up-going and down-going components. This intermediary decomposition allows the separation and analysis of ghost wave components, enabling the extraction of sea-surface information while removing the harmful spectral notches and phase shifts from the final imaging process.
2Manufacturing precision
If the sea surface shape is not accurately known, then data acquisition can proceed without complex constraints, but the quality of subsurface imaging is degraded
Solution Approach 1:
The patent enables the seismic data processing system to automatically determine sea-surface topography and reflection coefficients from the recorded ghost wave information itself. The system uses the data already collected during normal seismic acquisition to self-calibrate and correct for sea-surface effects, eliminating the need for separate, complex sea-surface measurement systems.
3Reliability
If conventional single-sensor streamers are used, then the equipment complexity is lower, but the ability to separate up-going and down-going wavefields is insufficient
Solution Approach 1:
The patent segments the wavefield recording function by using separate pressure sensors and particle velocity sensors in a dual-sensor streamer configuration. This segmentation allows independent measurement of different wavefield components, enabling reliable decomposition into up-going and down-going waves that cannot be achieved with conventional single-sensor streamers.
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 enhances the accuracy of sea-surface topography and reflection coefficient determination, reducing spectral notches and improving the quality of seismic data processing, thereby aiding in the identification of hydrocarbon deposits with greater precision.
Implementation Method 1
a pressure sensor and a particle velocity sensor, each sensor having an associated depth and horizontal position... to decompose a pressure wavefield and a normal velocity wavefield measured on a smoothly shaped acquisition surface
Implementation Method 2
decompose the wavefield as recorded by receivers on an acquisition surface into its up-going and down-going components on a flat observation level
Implementation Method 3
extrapolate the up-going and down-going wavefields iteratively in steps from the observation level upwards toward the sea-surface
Implementation Method 4
the water surface is a good reflector and the reflection coefficient at the water surface is nearly unity in magnitude and is negative in sign for pressure waves
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A pressure wavefield and a normal velocity wavefield measured on a smoothly shaped acquisition surface by towed dual-sensor marine seismic streamers are decomposed into up-going and down-going pressure and particle velocity components on an observation level between the acquisition surface and a sea surface of undetermined shape. The up-going and down-going pressure and particle velocity components are extrapolated iteratively in steps from the observation level toward the sea surface. An image point and a reflection coefficient of the sea surface at the image point are determined from the iteratively extrapolated up-going and down-going pressure and particle velocity components.