Seismic Data Deghosting via Wavefield Separation
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Solution Overview
Problem
Seismic data acquired during subsurface explorations often contains ghost events due to the presence of a free surface near the source and receivers, leading to unwanted reflections that interfere with the seismic field of interest, reducing the usable bandwidth and complicating the identification of hydrocarbon reservoirs.
Innovation Solution
A method and system that utilize a seismic processor to determine a pressure derivative with respect to depth, apply a phase-shift filter, decompose the phase-shifted derivative into frequency and horizontal wavenumber components, and separate the wavefield into up-going and down-going waves using Hilbert Transform techniques to remove ghost events, thereby improving the quality of seismic data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If seismic surveys are conducted with sources and receivers near the free surface, then the seismic data can be acquired more easily and cost-effectively, but ghost reflections are generated that reduce the usable bandwidth and interfere with the seismic field of interest
Solution Approach 1:
The patent applies deghosting processing that converts the harmful ghost reflections into useful information by separating up-going and down-going waves in the frequency-wavenumber domain. The method uses the phase-shift filter and wavefield separation to transform the contaminated seismic data into clean images by removing the ghost interference while preserving the primary reflections
Solution Approach 2:
The patent changes the parameters of the seismic data by applying frequency-wavenumber domain filtering. The method transforms the seismic data into the frequency-wavenumber domain, applies phase-shift filters to separate up-going and down-going waves, and then transforms back to the time-space domain to produce deghosted seismic images with improved bandwidth and reduced interference
2Quantity of substance
If ghost events are present in the seismic data, then the recorded wavefield contains more reflections than the true reflectivity, but this population of ghost events causes notches in the spectrum and lowers the usable bandwidth
Solution Approach 1:
The patent extracts and removes the harmful ghost reflections from the recorded wavefield by separating up-going and down-going waves. The method uses wavefield separation techniques in the frequency-wavenumber domain to isolate and eliminate the down-going ghost waves while preserving the up-going primary reflections, thereby recovering the usable bandwidth
Solution Approach 2:
The patent changes the spectral parameters of the recorded wavefield by applying deghosting processing that removes the notches caused by ghost interference. The frequency-wavenumber domain filtering restores the spectral content by eliminating the periodic notches and recovering the full bandwidth of the seismic signal
3Loss of information
If deghosting processing is applied to remove ghost events, then the usable bandwidth is improved and ghost interference is reduced, but the processing complexity increases
Solution Approach 1:
The patent replaces complex time-domain deghosting methods with frequency-wavenumber domain filtering. By transforming the seismic data into the frequency-wavenumber domain and applying phase-shift filters, the method simplifies the deghosting process while achieving effective separation of up-going and down-going waves and recovery of the usable bandwidth
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
The method effectively deghosts seismic data, enhancing the accuracy and resolution of seismic images, which aids in the identification and characterization of hydrocarbon reservoirs, improving the efficiency of drilling operations by reducing noise and interference.
Implementation Method 1
determining a phase-shifted pressure derivative by applying a phase-shift filter to the pressure derivative
Implementation Method 2
separate the wavefield into up-going and down-going waves using Hilbert Transform techniques
Data Source
AI summary
Examples of methods and systems are disclosed. The methods include obtaining seismic data regarding a subsurface region of interest, wherein the seismic data comprises time-space pressure data. The methods also include determining, using a seismic processor, a pressure derivative with respect to depth. The methods further include determining, using the seismic processor, a phase-shifted pressure derivative. The methods still further include determining, using the seismic processor, a transformed phase-shifted pressure derivative. The methods also include determining, using the seismic processor, transformed phase-shifted pressure data based, at least in part, on the transformed phase-shifted pressure derivative. The methods further include determining, using the seismic processor, time-space filtered pressure data. The methods still further include determining, using the seismic processor, a first direction wavefield and a second direction wavefield. The methods also include generating, using the seismic processor, a seismic image based, at least in part, on the first direction wavefield.