Time-Variant Deghosting Filter for Marine Seismic Data
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Solution Overview
Problem
Conventional methods for de-ghosting marine seismic data often require special acquisition geometries or hardware, and existing computer-based de-ghosting processes either amplify noise or are not backward compatible with existing data, limiting their effectiveness in preserving primary wave data.
Innovation Solution
A method and system that use a time-variant deghosting filter, optimized by a cost function with constraints to preserve primary wave data, applied to seismic trace data to attenuate ghost reflections without amplifying noise, utilizing a processor and memory to generate and apply this filter based on seismic source and receiver depths and sea-surface reflection coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional de-ghosting processes are applied to remove ghost reflections, then ghost reflections are attenuated, but primary wave data is amplified or distorted
Solution Approach 1:
The patent applies a time-variant deghosting filter whose characteristics change over time to adapt to varying seismic data conditions. This dynamic approach allows the filter to effectively remove ghost reflections at different time intervals while preserving primary wave data, resolving the contradiction between ghost attenuation and primary data preservation
Solution Approach 2:
The patent modifies filter parameters dynamically based on the seismic data being processed. By changing filter characteristics (such as cutoff frequencies and attenuation levels) as processing progresses through different time intervals, the system can selectively remove ghost reflections while maintaining integrity of primary wave data
2Object-affected harmful factors
If special acquisition geometries or hardware are used to de-ghost seismic data, then ghost reflections are reduced, but device complexity and acquisition difficulty increase
Solution Approach 1:
The patent replaces complex mechanical/acquisition-based de-ghosting methods (such as slanted streamers, over-under configurations, or dual sensors) with a computational approach using time-variant filtering. This substitution maintains effectiveness in removing ghost reflections while eliminating the need for specialized acquisition hardware or geometries
Solution Approach 2:
The patent creates a computational model of the ghost reflection process and uses this model to generate filter characteristics that mirror the ghost behavior. By copying and reversing the ghost effect through the time-variant filter, the system removes ghosts without requiring special acquisition configurations
3Measurement precision
If shallow source and receiver arrays are used to counter notch effects, then high frequency coverage is improved, but low frequency information is damaged
Solution Approach 1:
The time-variant filter dynamically adjusts its frequency response characteristics during processing. At different time intervals, the filter can emphasize different frequency ranges, allowing it to preserve low frequency information early in the trace while maintaining high frequency coverage later, thus resolving the frequency trade-off
Solution Approach 2:
The patent applies filtering in periodic time intervals rather than as a single static operation. This periodic application allows the filter to address different frequency components at different stages of the seismic trace processing, preserving both low and high frequency information that would otherwise be lost
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
Effectively removes ghost reflections from seismic data while preserving primary wave data, avoiding the need for special acquisition geometries or hardware, and is compatible with previously acquired data, thereby improving the accuracy and clarity of subsurface imaging.
Implementation Method 1
Ghost reflections are caused by the sea-surface operating as a mirror and reflecting up-going pressure-waves
Implementation Method 2
the mirror effect which produces the ghost reflections changes the phase of the reflection by 180 degrees such that, in some circumstances, the energy constructively interferes with the desired signal to magnify it and, in other circumstances, destructively interferes with and destroys the desired signal
Data Source
AI summary
Presented are methods and systems for deghosting seismic trace data. A cost function and one or more applicable constraints are selected and used to generate a time-variant deghosting filter. The time-variant deghosting filter can be recalculated for predetermined time intervals over the span of the associated seismic data. The time-variant deghosting filter is then applied to the seismic trace data to attenuate ghosts within the predetermined time interval. A plurality of seismic trace data can be stacked before generating and applying the time-variant deghosting filter.