Seismic Imaging Repeatability via Signal-to-Distortion Ratio
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Solution Overview
Problem
Seismic imaging for monitoring geological regions over time faces challenges in repeatability due to positioning errors during redeployment of sources and receivers, leading to high levels of 4D noise, which complicates the characterization of changes in geological regions.
Innovation Solution
The introduction of the Signal-to-Distortion Ratio (SDR) attribute as a measure of time-lapse repeatability, combined with the estimation of coherency length (Lcoh), allows for the prediction of 4D noise levels by quantifying the energy of time-lapse differences and identifying maximum geometry errors, enabling improved seismic imaging methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If seismic imaging is repeated over time to monitor geological regions, then data collection capability is improved, but positioning errors during redeployment cause high 4D noise that reduces measurement precision
Solution Approach 1:
The patent applies preliminary action by estimating the coherency length from the base dataset before conducting the time-lapse acquisition. This pre-characterization of the geological region's coherency properties allows for optimized acquisition parameter selection that anticipates and compensates for potential positioning errors, thereby maintaining measurement precision while enabling repeated data collection
Solution Approach 2:
The patent employs parameter changes by using the estimated coherency length to dynamically adjust acquisition parameters such as sensor layout spacing and acquisition frequency. This adaptive parameter selection optimizes the balance between data collection density and noise reduction, allowing repeated monitoring while maintaining measurement precision through coherency-based optimization
2Measurement precision
If more data is collected in areas requiring monitoring, then characterization accuracy is improved, but the complexity of determining whether changes are due to the monitored region or imaging conditions increases
Solution Approach 1:
The patent introduces the coherency length as an intermediary parameter that mediates between the raw seismic data and the interpretation of geological changes. This intermediary characteristic, estimated from the base dataset, serves as a reference that simplifies the analysis by providing a baseline for comparing time-lapse data, thereby reducing the complexity of determining whether changes originate from the monitored region or imaging conditions
3Reliability
If positioning errors are reduced through careful redeployment, then repeatability is improved, but the time and cost of acquisition increases
Solution Approach 1:
The patent applies parameter changes by using the estimated coherency length to determine optimal sensor spacing and acquisition frequency. This allows for relaxed positioning tolerances while maintaining repeatability, as the acquisition parameters are specifically tuned to the coherency characteristics of the geological region, reducing the time and cost associated with highly precise redeployment
Data Source
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AI summary
A data set comprises data obtained by seismic imaging of a region of interest during an observation period (T). An intrinsic geological variability of a region (i,,j) is determined from the comparison of reception signals (G0,..., G6) for neighbour bins as a function of a difference in signal geometry for the neighbour bins.