Downward Continuation for Asymmetric Borehole Seismic Data
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Solution Overview
Problem
Conventional surface seismic velocity analysis methods are inadequate for processing borehole seismic data due to the asymmetry introduced by placing receivers in boreholes, which prevents effective analysis of seismic profiles.
Innovation Solution
The use of downward continuation to simulate the seismic source at the depth of borehole receivers, allowing for the application of conventional surface seismic velocity analysis methods by mathematically shifting the seismic data, and employing techniques like finite difference modeling, Berryhill-style wave equation extrapolation, or Huygen's-style Kirchhoff-like extrapolation to achieve symmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If receivers are placed in boreholes to increase seismic frequency content and detail, then measurement precision is improved, but the asymmetry introduced by borehole placement makes conventional surface seismic velocity analysis methods inadequate
Solution Approach 1:
The patent creates a synthetic seismic profile by copying and shifting the actual seismic profile down to the borehole receiver depth. This synthetic profile mimics what the seismic data would look like if the source were at the same depth as the receiver, thereby copying the asymmetric borehole geometry into a symmetric virtual model that can be processed with conventional methods.
Solution Approach 2:
The patent explicitly addresses the asymmetry introduced by borehole placement by using downward continuation to create a symmetric virtual seismic profile. The method transforms the asymmetric borehole geometry into a symmetric virtual source-receiver configuration, allowing conventional symmetric velocity analysis methods to be applied effectively.
2Adaptability or versatility
If downward continuation is applied to simulate seismic source at borehole receiver depth, then compatibility with conventional velocity analysis methods is improved, but processing complexity increases
Solution Approach 1:
The patent applies downward continuation as a preliminary processing step before velocity analysis. By pre-computing the synthetic seismic profile at the borehole receiver depth, the method prepares the data in advance for subsequent conventional velocity analysis, separating the complex transformation from the standard analysis workflow.
Solution Approach 2:
The synthetic seismic profile acts as an intermediary between the actual asymmetric borehole data and the conventional symmetric velocity analysis methods. This intermediate virtual profile bridges the gap between the two incompatible frameworks, allowing conventional methods to process borehole data without fundamental modifications.
Data Source
AI summary
Geophysical prospecting may be achieved using borehole seismic data and processing velocity seismic profiles using downward continuation to simulate the seismic source being at the depth of the borehole receivers. Such methods may involve collecting seismic data for a subterranean formation with at least one borehole receiver; grouping the seismic data into a one common receiver gather corresponding to each borehole receiver; performing a downward continuation on at least one of the common receiver gathers to produce corresponding downward continued common receiver gathers; performing a normal moveout analysis on at least one of the downward continued common receiver gathers to produce corresponding semblance velocity spectra; and analyzing at least one of the semblance velocity spectra for a zone of interest in the subterranean formation.