Offshore Unit Motion Control for Safe Jackup Transition
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Solution Overview
Problem
The transition phase for self-elevating units, such as jackups, from afloat to elevated mode, is not well understood, leading to uncertainties in determining the feasibility of installing these units on the seabed due to wave-induced motions and impact loads on the legs, which can cause damage.
Innovation Solution
A control system utilizing onboard sensors to measure and analyze motion data, comparing it against predetermined acceptable criteria to determine the feasibility of going on location and potentially controlling the process to avoid excessive impact loads, thereby making informed decisions in real-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If self-elevating units transition from afloat to elevated mode, then the unit can operate as a stable platform on the seabed, but wave-induced motions cause impact loads on the legs that can damage the structure
Solution Approach 1:
The system performs preliminary assessment of ocean conditions using onboard sensors before initiating the transition to elevated mode. By evaluating wave height, period, and direction in advance, the system determines whether conditions are suitable for going on location, preventing damage from excessive impact loads before they occur.
Solution Approach 2:
The system continuously monitors ocean conditions and unit motion during the transition process using onboard sensors. This real-time feedback allows the system to assess whether conditions remain within acceptable limits and to make informed decisions about proceeding with or aborting the transition to elevated mode.
2Speed
If the unit transitions to elevated mode in rough ocean conditions, then the unit can reach the desired location, but the impact loads exceed acceptable limits and risk damage
Solution Approach 1:
The system assesses ocean conditions before initiating transition and can wait for suitable conditions rather than forcing transition in rough seas. This preliminary assessment prevents structural damage by ensuring conditions are appropriate before beginning the transition process.
Solution Approach 2:
The system provides real-time feedback on whether ocean conditions remain within acceptable limits during transition. This allows operators to monitor structural integrity risks and make decisions to pause or abort the transition if conditions deteriorate, maintaining reliability while pursuing the goal of reaching the desired location.
3Object-affected harmful factors
If the unit delays transition until ocean conditions are calm, then impact loads are reduced, but the time required to reach the desired location increases
Solution Approach 1:
The system performs preliminary assessment of ocean conditions to identify suitable transition windows. By planning ahead and understanding acceptable condition thresholds, the system can efficiently transition when conditions are appropriate without unnecessary delays, balancing time requirements with safety.
Solution Approach 2:
The system provides real-time feedback on ocean conditions and their acceptability for transition. This enables operators to make informed decisions about when to proceed with transition, minimizing delays while ensuring impact loads remain within acceptable limits through continuous monitoring.
4Device complexity
If traditional methods are used to assess going on location feasibility, then the process is simple, but the determination is imprecise due to lack of real-time data
Solution Approach 1:
The unit uses its own onboard sensors to self-assess whether ocean conditions are suitable for transitioning to elevated mode. This self-service capability provides precise, real-time feasibility determination without requiring external assessment systems, maintaining simplicity while improving accuracy.
Solution Approach 2:
The system replaces traditional mechanical or manual assessment methods with electronic sensor-based measurement and automated analysis. This substitution provides more precise measurement of ocean conditions and unit response, improving feasibility determination accuracy while adding minimal complexity through integrated electronic systems.
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 allows for more precise determination of the feasibility of installing self-elevating units on the seabed, reducing the risk of damage from impact loads and ensuring safe operation by using real-time data analysis and comparison with established criteria.
Implementation Method 1
The self-elevating unit is designed such that the hull is buoyant and can float, supporting itself and the legs and its cargo (e.g., in an 'afloat' mode)
Implementation Method 2
A lifting system or 'jacking system' is installed on the unit for the purpose of raising or lowering the legs relative to the hull
Implementation Method 3
The jacking system lowers the hull until the buoyancy of the hull is sufficient to extract and raise the legs
Implementation Method 4
The legs of a self-elevating unit may have an individual footing for each leg (spudcan) or the legs may share a common footing (mat)
Data Source
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AI summary
Techniques and devices to assist an offshore unit (2) in going on location and coming off location. A device (20) may include an interface (34) configured to receive a signal indicative of motions of an offshore unit (2). The device (20) may also include a memory (28) configured to store a set of values corresponding to acceptable motions of the offshore unit (2), as well as a processor (26) configured to determine if a measured motion of the offshore unit (2) exceeds at least one value of the set of values and generate an indication that going on location by the offshore unit (2) can be undertaken when the processor (26) determines that the measured motion of the offshore unit (2) is less than or equal to the at least one value.