4D Seismic Reservoir Characterization via Amplitude Minimization
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Solution Overview
Problem
Current methods for characterizing the evolution of oil reservoirs over time in 4D seismic surveys face challenges due to non-repeatable noise and changes in seismic surveys, particularly in correlating data from different acquisition methodologies and velocity changes, which affect the accuracy and reliability of reservoir monitoring.
Innovation Solution
A process that analyzes changes in seismic reflection propagation times and amplitudes by computing the sum of differences between base and monitor surveys, using time-shifts derived from velocity changes to align data without cross-correlating traces, thereby characterizing reservoir evolution by minimizing the sum of these differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cross-correlation of traces is used to align seismic surveys, then the ability to compare reservoir evolution is improved, but the computational complexity and processing time increase significantly
Solution Approach 1:
The patent extracts and focuses only on the essential amplitude information at specific times and locations, rather than processing the entire seismic trace. By isolating key amplitude features and their temporal variations, the method achieves accurate reservoir evolution characterization without the computational burden of full trace cross-correlation.
Solution Approach 2:
The patent segments the seismic data into discrete amplitude measurements at specific times and locations, treating each amplitude point independently rather than processing the entire continuous trace. This segmentation allows for simplified comparison of amplitude changes over time without requiring complex cross-correlation of the full seismic signals.
2Reliability
If full trace cross-correlation is performed to account for velocity changes, then the reliability of monitoring is improved, but the processing time and computational resources required increase
Solution Approach 1:
The patent extracts only the amplitude information at specific times and locations from the seismic traces, ignoring the full trace content. By focusing solely on amplitude changes at key points, the method maintains monitoring reliability while dramatically reducing processing time compared to full trace cross-correlation.
Solution Approach 2:
The patent applies partial action by processing only the essential amplitude features at specific times and locations rather than the complete seismic traces. This partial processing approach provides sufficient reliability for reservoir monitoring without the excessive computational cost of full trace analysis.
3Measurement precision
If amplitude balancing and 3D warping are applied to match surveys, then the accuracy of time-lapse analysis is improved, but the device complexity and processing steps increase
Solution Approach 1:
The patent extracts and compares only the amplitude information at specific times and locations, eliminating the need for complex amplitude balancing and 3D warping operations. By isolating key amplitude features, the method achieves accurate time-lapse analysis with minimal processing steps.
Solution Approach 2:
Instead of applying complex processing steps to align the data and then analyzing the results, the patent inverts the approach by directly comparing amplitude features at corresponding locations and times. This inversion eliminates the need for intermediate processing steps like amplitude balancing and 3D warping while maintaining analysis accuracy.
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 deduces velocity changes in the reservoir without cross-correlating traces, providing accurate and reliable characterization of reservoir evolution, especially in cases with small density changes and effective reflection angles, and is applicable for time-lapse analysis in 4D seismic surveys.
Implementation Method 1
These measurements typically involve sending a seismic wave into the sub-surface and measuring with a number of sensors the various reflections of the wave off geological structures
Implementation Method 2
measuring with a number of sensors the various reflections of the wave off geological structures - surfaces separating distinct materials, faults, etc.
Implementation Method 3
computing the sum S over the points of the set of a norm of the difference between the amplitude bi of the seismic trace in the base survey at said point i and the sum of the amplitude mi, of the seismic trace at a time-corresponding point i' in the monitor survey and the amplitude due to the reflectivity change local to the said time-corresponding point i' induced by the relative change in the velocity of the earth
Data Source
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AI summary
Evolution of an oil reservoir in the process of producing is carried out by co-analyzing the changes in the propagation times and seismic amplitudes of a seismic wavelet along propagation paths in the ground. A base survey of the reservoir is provided, with a set of seismic traces at a first time T associated to a first velocity field Vb; a monitor survey of the reservoir is provided, the monitor survey being taken at a second time T + ΔT, with a set of seismic traces associated to the same positions as in the base survey; the monitor survey is associated to a second velocity field Vm. For a set of points i in the base survey, one computes over the points of the set the sum S of a norm of the difference between - the amplitude bi of the seismic trace in the base survey at each point i and - the sum of the amplitude mi' of the seismic trace at a time-corresponding point i' in the monitor survey and the amplitude due to the reflectivity change local to the time-corresponding point i' induced by the difference between the first velocity field Vb and the second velocity field Vm; the time-corresponding point i' being shifted in time by a time-shift derived from the velocity changes along the propagation path from the surface to time-corresponding point i'. This sum is minimized to characterize the evolution of the oil reservoir and derive the velocity changes from the base survey to the monitor survey.