Asynchronous Seafloor Pressure Monitoring via Tidal Correction
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Solution Overview
Problem
Existing methods for monitoring seafloor subsidence are constrained by the need for synchronicity in depth and pressure measurements and require additional stationary short-term local reference measurements, making it challenging to accurately measure subsidence without tidal interference.
Innovation Solution
A method using asynchronous pressure signals from multiple seafloor locations, corrected by a mathematical model that accounts for spatial and temporal pressure variations, allowing for the estimation of harmonic tide-related effects and enabling the monitoring of non-vertical seafloor movements without the need for additional reference stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If asynchronous pressure measurements are used, then measurement flexibility and device simplicity are improved, but measurement precision deteriorates due to tidal interference
Solution Approach 1:
The pressure signal is segmented into distinct components: tidal pressure variations (short-term oscillations) and subsidence-related pressure changes (long-term trends). By applying spectral analysis, the method separates these components in the frequency domain, allowing independent analysis of each phenomenon without requiring synchronized measurements or additional reference stations.
Solution Approach 2:
The patent introduces an intermediary mathematical model that represents tidal pressure variations as a sum of harmonic oscillators with known frequencies. This model acts as a mediator between the raw asynchronous pressure data and the subsidence measurement, enabling the extraction of tidal components and their subsequent removal to reveal the underlying subsidence signal.
2Measurement precision
If additional stationary reference stations are deployed, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The system performs self-correction by using its own pressure sensor data to identify and remove tidal interference. The mathematical model of tidal variations is fitted to the pressure data from existing sensors, and the fitted model is then used to correct the measurements. This eliminates the need for external reference stations, as the system serves its own calibration needs through the self-service mechanism.
Solution Approach 2:
The pressure sensors serve multiple functions: they simultaneously monitor both tidal pressure variations and subsidence-related pressure changes. By designing the measurement system to extract multiple types of information from the same sensors, the patent eliminates the need for separate reference stations dedicated solely to tidal monitoring, thereby reducing overall system complexity.
3Measurement precision
If synchronous measurements are required, then measurement precision is improved, but ease of operation and productivity deteriorate
Solution Approach 1:
The patent transitions from a static measurement approach (synchronous sampling at fixed intervals) to a dynamic approach where asynchronous measurements are continuously collected and processed. The measurement system adapts to varying environmental conditions and sensor availability, processing data at different rates and times while maintaining measurement accuracy through the tidal correction model.
Solution Approach 2:
The method performs preliminary fitting of the tidal variation model to the pressure data before extracting subsidence measurements. By pre-characterizing the tidal signal components and establishing the correction model in advance, the system prepares the data processing pipeline to efficiently handle asynchronous measurements without requiring real-time synchronization, thereby improving measurement 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 provides accurate and repeatable subsidence measurements by disentangling tidal effects from pressure changes, improving the precision of subsidence monitoring beyond the limitations of existing technologies, particularly in offshore hydrocarbon reservoirs.
Implementation Method 1
measuring the ambient seawater pressure at a plurality of locations adjacent to the seafloor using asynchronous pressure signals generated by a plurality of pressure sensors
Implementation Method 2
harmonic tide-related pressure variations on the asynchronous pressure signals are corrected by an algorithm comprising a mathematical equation that models spatial and temporal pressure variations
Data Source
AI summary
Seafloor movements are monitored by measuring the ambient seawater pressure at a plurality of locations adjacent to the seafloor using asynchronous pressure signals generated by a plurality of pressure sensors mounted at different locations on the seafloor over a prolonged period of time(t), wherein harmonic tide-related pressure variations on the asynchronous pressure signals are corrected by an algorithm comprising a mathematical equation that models spatial and temporal pressure variations in an objective function. The method is unconstrained with regard to the synchronicity of depth and/or pressure measurements and does not require additional stationary short tem local reference measurements.