Dry-tree semi-submersible riser tensioning
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Solution Overview
Problem
Conventional semi-submersible production and drilling platforms have not effectively integrated top-tensioned risers with dry trees or direct vertical access, lacking a comprehensive solution for design, construction, integration, operation, and decommissioning that addresses component reliability and safety throughout the entire life cycle.
Innovation Solution
A semi-submersible production and drilling platform unit is designed with a semi-submersible hull, mooring, topside, wellbay, top-tensioned riser, and catenary riser portions, featuring a ring pontoon and columns, anchored mooring, and a riser tensioning subsystem that compensates for vertical motion, with parameters optimized for efficient riser performance and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If top-tensioned risers with dry trees are supported by conventional semi-submersible platforms, then motion suppression requirements for steel catenary risers are met, but the integration of TTRs and dry trees has not been achieved with adequate component reliability and safety throughout the life cycle
Solution Approach 1:
The platform is divided into distinct functional modules: hull portion, mooring portion, topside portion, wellbay portion, top-tensioned riser portion, and catenary riser portion. Each module is designed and optimized independently with specific parameters (hull draft, mooring configuration, deck box design, well slot arrangement, riser tensioning system) that can be tailored to meet reliability requirements for TTR integration while managing overall system complexity through modular assembly.
2Reliability
If riser tensioning subsystem parameters are optimized for ultra-deep water fields with large well counts, then effective riser tension and platform stability are maintained, but the system becomes more complex and costly
Solution Approach 1:
The riser tensioning subsystem is designed with adjustable parameters including tension level, stroke length, and stiffness that can be optimized based on field water depth, number of wells, and topside capacity. This allows the system to maintain effective riser tension and platform stability across different operating conditions (ultra-deep water, large well counts) while managing complexity through parameter optimization rather than fundamental system redesign.
3Productivity
If a comprehensive solution for design, construction, integration, operation, and decommissioning is implemented, then the total value and efficiency of the integrated system is maximized, but the project duration and coordination complexity increase
Solution Approach 1:
The platform design incorporates preliminary considerations for the entire life cycle from design through decommissioning. The modular architecture and standardized interfaces are established in the design phase to facilitate efficient construction, integration, operation, and eventual decommissioning. This upfront planning maximizes total value efficiency by avoiding rework and coordination issues in later stages, while managing project duration through proactive rather than reactive project management.
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
The platform unit provides a cost-effective and reliable solution for deep water operations, maintaining effective riser tension and platform stability, suitable for ultra-deep water fields with large well counts, while minimizing technical and economic risks.
Implementation Method 1
Riser stroke induced by vertical motion of the host platform is compensated through tensioners by means of hydro-pneumatic hydraulic systems designed to control riser tension within allowable values.
Data Source
AI summary
A deep draft semi-submersible production and drilling platform unit with dry trees is described. The platform unit preferably comprises four columns, a ring pontoon, a two-axis symmetrical hull with draft in the range of 100 to 155 feet, top-tensioned risers with push or pull tensioners of preferred combined vertical stiffness of 10% to 30% of the platform water plane stiffness, a wellbay with a well spacing in the range of 12 to 18 feet, a riser guiding system supported by the pontoons or at an elevated level, topside facilities supported by a box type of deck structure, mooring lines, and catenary risers.