Subsea Riser Load Estimation via Multi-Point Sensor Feedback
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Solution Overview
Problem
Current riser monitoring systems struggle to accurately estimate loads on subsea components like wellhead systems, subsea trees, emergency disconnect packages, and lower riser packages due to limited measurement positions and the complexity of numerical finite element models, leading to conservative operating assumptions and premature component replacement.
Innovation Solution
A method and system that utilize multiple measuring devices at strategic positions along the riser to measure section forces, inclination, and acceleration, allowing for accurate calculations of loads on subsea components by considering equilibrium and inertia forces, with strain gauges and inclinometers providing data for tension, bending, and shear force estimates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conservative assumptions are used in structural analysis based on ISO 13628-7, then safety is ensured, but operating windows become narrow and components may be replaced prematurely
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring actual loads on the riser system using measurement devices at multiple positions. This real-time data feeds back to update the structural analysis, replacing conservative assumptions with actual measured values. This allows operators to safely extend operating windows beyond what conservative standards permit, while maintaining reliability through continuous verification of actual load conditions.
2Measurement precision
If complex numerical finite element models are used to estimate loads, then measurement precision may be improved, but calculation time increases and uncertainty is introduced
Solution Approach 1:
The patent segments the riser system into multiple sections with measurement devices placed at specific positions (lower tapered stress joint, above and below the rucker tension wire ring). Instead of using a single complex model for the entire system, the patent divides the structure into manageable segments, measuring loads at key locations and using simplified relationships to estimate loads at other positions. This reduces calculation time while maintaining precision by focusing measurements on critical sections.
Solution Approach 2:
The patent introduces measurement devices as intermediaries between the physical load conditions and the analysis system. Rather than relying solely on complex numerical models to infer loads, physical sensors directly measure section forces and provide intermediate data that simplifies the estimation process. These measurement intermediaries bridge the gap between actual physical conditions and analytical models, reducing both calculation time and model uncertainty.
3Device complexity
If measurement positions are placed far from subsea components (EDP, LRP, XT, WH), then device complexity is reduced, but load estimation accuracy for these components deteriorates
Solution Approach 1:
The patent applies local quality by placing measurement devices at specific strategic locations where they can most effectively capture load characteristics relevant to the subsea components. Rather than uniformly distributing sensors or placing them as far as possible, the patent positions devices at the lower tapered stress joint and other critical positions where local measurements provide maximum insight into component loads. This targeted local measurement approach maintains system simplicity while improving accuracy for specific components.
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 reduces errors in load estimation to less than 2-3%, enabling more precise fatigue life assessment and optimal positioning of surface vessels to minimize loads on subsea components, thereby extending their operational life.
Implementation Method 1
The strain gauges or similar sensors are constructed to produce estimates of tension, bending moments and or inclination at the respective positions.
Implementation Method 2
The inclinometers or similar sensors are constructed to produce estimates of tension, bending moments and or inclination at the respective positions.
Implementation Method 3
measuring the inclination and acceleration of the subsea component using a set of sensors placed in a location of the subsea component
Implementation Method 4
the calculations involving: an assessment of dynamic equilibrium for the subsea component and the part of the riser below the lower section (A) including load terms, gravitational and inertia forces for the subsea component based on said measurements
Implementation Method 5
the calculations involving: an assessment of dynamic equilibrium for the subsea component and the part of the riser below the lower section (A) including load terms, gravitational and inertia forces for the subsea component based on said measurements
Data Source
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AI summary
Method for estimating section forces including bending moments on a subsea component, the subsea component being connected to a riser and a well, wherein the method comprises the steps of; -measuring the section forces and/or deformations in a lower section (A) and a first upper section (B) at the lower part of the riser by the use of at least two independent measuring devices, -measuring the inclination and acceleration of the subsea component using a set of sensors placed in a location of the subsea component (section E), -calculating the section forces for any section (Z) of the subsea component by the use of a processing device adapted for receiving data from said measuring devices and performing calculations, the calculations involving: -an assessment of dynamic equilibrium for the subsea component and the part of the riser below the lower section (A)including load terms - considering the magnitude and directionality of section forces in the section (A), and - gravitational and inertia forces for the subsea component based on said measurements.