Subsea Riser Anchoring and Force Absorption
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Solution Overview
Problem
Offshore exploration and production systems, particularly self-standing casing riser systems, are susceptible to catastrophic failures that can lead to damage or destruction of drilling platforms and surface vessels due to sudden releases of buoyancy and tension forces, lacking effective safety features and flexibility in operation.
Innovation Solution
A method and system for restraining and controlling unintended subsurface releases by anchoring the riser system to the sea floor or wellhead and deploying a network of restraining members along the riser stack, combined with force-absorbing devices on receiving stations to mitigate impact forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If self-standing casing riser systems are deployed without restraining members, then operational flexibility and simplicity are improved, but safety and stability deteriorate due to susceptibility to catastrophic failures from sudden buoyancy and tension force releases
Solution Approach 1:
The system pre-deploys restraining members (anchors, chains, cables) and force-absorbing devices before operations begin. These safety features are prepared in advance and can be activated when needed, allowing the system to maintain operational flexibility during normal operations while having safety mechanisms ready to prevent catastrophic failures.
Solution Approach 2:
Force-absorbing devices are installed on receiving stations and restraining members are positioned along the riser stack before operations commence. These elements are designed to absorb and dissipate the sudden release of buoyancy and tension forces, cushioning against catastrophic failures while maintaining system simplicity and operational flexibility.
2Reliability
If restraining members and anchoring systems are added to the riser system, then safety and stability are improved, but device complexity increases
Solution Approach 1:
The restraining system is divided into modular components: multiple anchoring points distributed along the riser stack, separate restraining members (chains, cables), and distinct force-absorbing devices. This segmentation allows each component to be independently installed, maintained, and activated, reducing overall system complexity while enhancing safety through distributed protection.
Solution Approach 2:
Restraining members serve as intermediaries between the riser stack and the sea floor anchors, while force-absorbing devices act as intermediaries between the receiving station and the riser system. These intermediary elements isolate the complex safety functions from the main operational system, allowing the riser system to maintain simplicity while incorporating robust safety features.
3Reliability
If anchoring means are disposed on the riser system, then control over unintended releases is improved, but weight and structural load increase
Solution Approach 1:
The anchoring system uses the weight of anchors and restraining members to counterbalance the buoyant forces of the riser system. By strategically positioning anchors and using restraining members with appropriate weight characteristics, the system achieves control over unintended releases while distributing the weight load across multiple anchoring points rather than concentrating it on the riser stack.
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
Prevents unintended projectile-like releases of buoyancy devices and associated casing risers, reducing the risk of damage to drilling platforms and surface vessels, and enhancing operational safety and flexibility during exploration and production.
Implementation Method 1
a buoyancy device to support the casing riser from a sea-floor wellhead
Data Source
AI summary
A system for and method of limiting and controlling the unintended subsurface release of an exploration or production riser system is provided including one or more means for anchoring the riser or casing stack at one or more pre-determined points upon the length of the riser, and/or on the housing of an associated buoyancy chamber or the like, and/or on a particular portion of the riser as dictated by the operational environment, and/or on an anchor portion secured in the sea floor; and a network of restraining members disposed on the anchoring means. A lower anchoring portion includes one or more anchors disposed in communication with a wellhead, or with the sea floor or below the sea floor mud line, or with a well casing portion. A network of restraining members forms an essentially continuous connection from the buoyancy member portion to said bottom anchor portion. In a particular, though, non-limiting embodiment of the invention, a means for anchoring the system using pairs of anchors disposed at one or more predetermined points along the riser portion of the system is provided. Also disclosed is a variety of means and devices by which a surface vessel or a rig, etc., servicing a subsea well equipped with the present system may absorb or deflect impact forces originating from portions of the system that unexpectedly break free and rush upwards toward the surface vessel or rig.