Asynchronous Vibratory Sources for Seismic Productivity
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Solution Overview
Problem
Conventional land seismic data acquisition methods face challenges such as intra-array statics, spatial resolution issues, control and synchronization problems, and mixed-phase data due to the use of multiple seismic vibrators, which hinder efficient data collection and processing, particularly in reducing acquisition time and improving data quality.
Innovation Solution
The method involves deploying multiple vibratory sources that can start their sweeps asynchronously, using spectrally shaped continuous pseudorandom sequences to minimize cross-talk, allowing for continuous recording and efficient separation of seismic signals, thereby reducing the constraints on system configuration and improving productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple vibrators are used simultaneously to reduce acquisition time, then productivity is improved, but control and synchronization problems worsen
Solution Approach 1:
The patent divides the simultaneous vibrator operation into segmented sweeps with distinct time intervals. Each vibrator performs a sweep sequence with specific listen times between sweeps, allowing the system to process data from multiple vibrators without requiring continuous synchronization. This segmentation reduces control complexity while maintaining high productivity.
Solution Approach 2:
The patent implements periodic sweep patterns where vibrators operate in repeating cycles of sweep-listen-sweep-listen. Each vibrator follows a periodic schedule with defined listen times, enabling predictable and manageable control of multiple vibrators simultaneously. This periodic structure simplifies synchronization compared to continuous operation.
2Loss of time
If multiple vibrators operate simultaneously, then acquisition time is reduced, but spatial resolution deteriorates due to array effects
Solution Approach 1:
The patent segments the vibrator operation into discrete sweeps with listen times, allowing data from individual vibrators to be processed separately. This segmentation mitigates array effects by enabling selective processing of data from specific vibrator positions and times, thereby maintaining spatial resolution while reducing total acquisition time through parallel operation.
Solution Approach 2:
The patent implements preliminary listen times between sweeps where no vibrators are active. These preliminary action intervals allow the system to capture data without interference from other vibrators, preserving spatial resolution information while the overall parallel sweep structure reduces total acquisition time.
3Productivity
If vibrators are positioned at different elevations to cover more area, then productivity is improved, but intra-array statics problems worsen
Solution Approach 1:
The patent uses periodic listen times in the vibrator sweep sequence during which all vibrators are inactive. These periodic intervals provide a quiet measurement window where data can be recorded without interference from other vibrators at different elevations, maintaining data quality consistency despite the extended spatial configuration needed for high productivity.
Solution Approach 2:
The patent extracts and isolates data from individual vibrator sweeps by using listen times to separate the signals. This extraction approach allows data from vibrators at different elevations to be processed independently, removing the harmful intra-array statics effects while preserving the productivity benefits of using multiple vibrators at diverse positions.
4Measurement precision
If listen time is extended to capture deeper reflections, then measurement precision is improved, but acquisition time increases
Solution Approach 1:
The patent merges the listen time requirement into the overall sweep sequence timing structure. By coordinating multiple vibrators to operate in synchronized sweep-listen cycles, the system captures deep reflector data during the listen portions of the sequence. This merging allows the necessary listen time for deep reflections to be integrated into the parallel sweep schedule, achieving both measurement precision and reduced total acquisition time.
Solution Approach 2:
The patent maintains continuous useful action by having vibrators continuously perform sweeps while listen times are strategically positioned within the sequence. Rather than having idle periods between complete surveys, the system continuously accumulates data from multiple vibrators in an overlapping sweep pattern, ensuring that the listen time needed for deep reflections does not create gaps in productivity.
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 enables time-efficient seismic surveys by allowing each vibratory source to operate independently, reducing the overall acquisition time and improving data quality by minimizing cross-talk and enhancing source separation, leading to higher productivity and more accurate subsurface imaging.
Implementation Method 1
a step of receiving at each vibratory source a corresponding pilot signal (A) for driving the vibratory source; a step of asynchronously actuating the vibratory sources to generate seismic waves into the ground
Implementation Method 2
the record length is typically set to equal the sweep length plus a listen time equal to the two-way travel time, which is the time required for the seismic energy to propagate from the source through the earth to the deepest reflector of interest and back to the receiver
Data Source
AI summary
A method for seismic prospecting that includes a step of deploying plural vibratory sources on the ground; a step of receiving at each vibratory source a corresponding pilot signal for driving the vibratory source; a step of asynchronously actuating the vibratory sources to generate seismic waves into the ground; and a step of continuously recording seismic signals produced by the seismic waves. Pilot signals for the plural vibratory sources are obtained by spectrally shaping starting sequences into continuous pseudorandom sequences that are weakly correlated over a predetermined time interval.