Offshore Rig Caisson Anchoring Mechanism
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Solution Overview
Problem
The installation of offshore production platforms, such as oil platforms, is hindered by the high cost and complexity of anchoring legs into the seabed using traditional methods, including large caissons that increase transportation resistance and require heavy infrastructure for handling.
Innovation Solution
The platform design incorporates a caisson that can move along the axis of each leg between retracted and extended positions, with locking mechanisms to anchor into the seabed, allowing for reduced seabed contact area during transport and simplified handling, and includes a pumping unit to penetrate the seabed, reducing the need for extensive seabed anchoring and heavy equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional piles are used to anchor legs in the seabed, then anchoring reliability is improved, but installation time and cost increase due to heavy equipment requirements
Solution Approach 1:
The anchoring system is divided into separate functional components: the caisson (for penetration and anchoring) and the foot/stand (for seabed contact). This segmentation allows the caisson to be pre-assembled with the leg and transported as a unit, eliminating the need for time-consuming on-site pile driving operations while maintaining reliable anchoring through the caisson's penetration into the seabed.
2Reliability
If large caissons are used for anchoring, then anchoring capability is improved, but transportation resistance increases and energy expenditure rises
Solution Approach 1:
The caisson is nested inside the leg structure, with the caisson positioned within the leg's internal space. This nesting arrangement allows the caisson to be transported within the leg assembly as a compact unit, significantly reducing the overall volume and resistance encountered during water transportation, while still providing adequate anchoring capability when deployed.
3Reliability
If caissons are extended below the foot for anchoring, then anchoring reliability is improved, but handling complexity increases due to large volumes
Solution Approach 1:
The caisson is designed to be movable along the leg axis between retracted and extended positions, rather than being fixed. This dynamic configuration allows the caisson to be easily handled and positioned during assembly, then extended to its anchoring position only when needed. The locking mechanism secures the caisson in the extended position to provide reliable anchoring, while the retractable design simplifies handling operations.
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 design reduces installation costs and energy expenditure by minimizing seabed resistance during transport and simplifying the anchoring process, enabling more efficient and cost-effective offshore platform deployment.
Implementation Method 1
each caisson is combined with a pumping unit to reduce the caisson internal pressure and to cause this caisson to penetrate into the seabed to the required depth
Implementation Method 2
these caissons, which are several meters high, are in the water and create high resistance to platform forward movement and thus additional energy expenditure
Data Source
AI summary
An offshore oil-drilling rig comprising a deck mounted mobile on legs, each leg including a support base on the sea floor and a caisson open at its base and designed to penetrate into the sea floor. Each caisson is arranged inside the leg and is mobile along the axis of the leg between a retracted upper position and a projecting lower position at which it is anchored on the sea floor. The invention also concerns methods for installing such a rig on an oil-drilling site.