Ocean Bottom Seismometer Positioning via Linearized Inversion
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Solution Overview
Problem
Determining the accurate position and timing of ocean bottom seismic (OBS) units is challenging due to internal clock drift and limited communication during deployment, leading to potential inaccuracies in seismic data processing.
Innovation Solution
A system and method using a conventionally accurate clock and a linearized inversion scheme to determine OBS positions and timing with high accuracy, accounting for clock drift and estimating the accuracy of position and timing determinations through direct arrivals and triangulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventionally accurate clock is used in OBS units, then device complexity and cost are reduced, but timing accuracy deteriorates due to clock drift during deployment
Solution Approach 1:
The system uses acoustic signals transmitted between the OBS unit and the surface vessel to provide feedback on timing accuracy. The OBS unit receives timing information from the vessel and adjusts its internal clock accordingly, creating a feedback loop that compensates for clock drift without requiring a highly accurate clock to begin with.
Solution Approach 2:
The acoustic communication system acts as an intermediary between the OBS unit's internal clock and the actual timing reference. Instead of relying solely on the OBS unit's internal clock accuracy, the system uses acoustic signals as a mediator to transfer timing information from the vessel to the OBS unit, enabling timing correction without requiring expensive high-accuracy clocks.
2Measurement precision
If high-accuracy clocks are used in OBS units, then timing accuracy is improved, but cost increases
Solution Approach 1:
The system replaces expensive high-accuracy clocks with conventional, less accurate clocks in the OBS units. The conventional clocks are sufficient for basic timing functions, and the expensive timing accuracy is achieved through the external acoustic communication system with the vessel, which can provide timing corrections as needed during the survey.
Solution Approach 2:
The acoustic communication system serves as an intermediary that provides high-accuracy timing information to the OBS unit without requiring the OBS unit itself to contain expensive high-accuracy clocks. The vessel's timing system acts as the high-accuracy reference, and acoustic signals transmit this reference information to the OBS unit.
3Device complexity
If limited communication is maintained during OBS deployment, then device complexity is reduced, but positioning accuracy deteriorates
Solution Approach 1:
The system maintains periodic communication between the OBS unit and the vessel rather than continuous communication. The OBS unit periodically transmits acoustic signals to the vessel and receives timing information in return. This periodic interaction is sufficient to maintain positioning accuracy while significantly reducing the complexity of the communication system compared to continuous communication requirements.
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 provides precise OBS unit positioning and timing, improving the accuracy of seismic data processing and reducing costs associated with high-accuracy clocks, while maintaining the reliability of OBS surveys.
Implementation Method 1
the position of each OBS unit is determined from the time of flight of acoustic signals
Implementation Method 2
acoustic signals
Data Source
AI summary
There is provided herein a system and method of seismic exploration that produces improved locations and timings for ocean bottom seismometers. The instant method utilizes linearized inversion in conjunction with a conventionally accurate clock to provide both time and positioning for each OBS unit with high accuracy as compared with the prior art approach. Inversion is one mathematical tool that effectively performs the requisite triangulation. Furthermore, the clock drift can be accounted for in the inversion scheme. The inversion not only determines the OBS position and shot timing errors, but also estimates the accuracy of the position and timing determination.