Seismic Sensor Depth Determination via Wave Equation Autocorrelation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current seismic surveying techniques face limitations in bandwidth due to ghost reflections from the water surface, which interfere with primary reflections and reduce the usability of seismic data, necessitating improved methods for determining accurate sensor depths for effective deghosting.
Innovation Solution
The method employs wave equation autocorrelation and redatuming operators to determine and quality control sensor depths, allowing for accurate deghosting without relying on vertical ray approximations, and uses a range of depth increments to align the up-going wavefield with the ghost component, enabling precise removal of ghost reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ghost reflections are present in seismic data, then the data can be recorded with simple sensor deployment, but the bandwidth and quality of seismic data are reduced due to interference with primary reflections
Solution Approach 1:
The patent converts the harmful ghost reflections into a useful signal by applying wave equation autocorrelation. The ghost reflections, which were previously causing interference and reducing bandwidth, are now used as the input signal to determine sensor depth. The autocorrelation process transforms the ghost-containing seismic data into a depth spectrum where the sensor depth can be accurately identified, thus converting the harmful interference into a beneficial depth-determination mechanism.
2Device complexity
If vertical ray approximations are used to determine sensor depths, then the processing is simpler, but the accuracy of sensor depth determination is reduced
Solution Approach 1:
The patent replaces the mechanical/geometric vertical ray approximation method with a wave equation-based autocorrelation approach. Instead of using simple geometric relationships that assume vertical ray propagation, the invention uses the full wave equation to autocorrelate the seismic data, which accounts for the actual wave propagation physics. This substitution of the mathematical model from simple geometry to wave physics enables accurate sensor depth determination without relying on vertical ray approximations.
3Reliability
If deghosting is applied to remove ghost reflections, then the bandwidth of seismic data is improved, but accurate sensor depth determination is required which increases processing complexity
Solution Approach 1:
The patent performs sensor depth determination as a preliminary step before applying deghosting. By using wave equation autocorrelation to accurately determine sensor depth first, the invention prepares the necessary parameter information needed for effective deghosting. This preliminary determination of sensor depth allows the subsequent deghosting process to be applied with accurate knowledge of the sensor position, thereby improving bandwidth while managing processing complexity through staged processing.
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 ghost reflections, enhancing the bandwidth and quality of seismic data by accurately determining sensor depths, thereby improving the resolution and interpretation of subsurface geophysical characteristics.
Implementation Method 1
a wave equation based autocorrelation is performed on the measured seismic data to determine sensor depths
Implementation Method 2
depth extrapolation of the measured seismic data to a range of depth lags is performed
Implementation Method 3
a range of redatuming operators are applied to the measured seismic data
Implementation Method 4
The seismic source when actuated generates an acoustic signal that propagates through the water column
Implementation Method 5
The acoustic signal is refracted and reflected by acoustic impedance boundaries, e.g., at boundaries between the various formation layers
Implementation Method 6
Acoustic signals travelling upwardly in the water layer will be reflected with opposite polarity from the air/water interface. Such reflected signals are termed 'ghost' reflections
Data Source
AI summary
A method for determining seismic sensor depths in a body of water includes accepting as input to a computer measurements of seismic signals made by a plurality of seismic sensors disposed in a body of water. A depth increment and a range of sensor depths for correlation of signals from each of the plurality of seismic sensors is defined. In the computer, the input seismic measurements are extrapolated to each depth increment in the range. A depth of each seismic sensor is determined by correlating the seismic signal measurements with depth-extrapolated measurements of the seismic signal measurements.