Drilling operations are moving to deeper waters and harsher environments. It is imperative to have robust equipment that can withstand the challenges of these environments and allow operators to extend their field life. Subsea equipment has to cope with some of the most severe fatigue conditions in offshore drilling and is affected by a myriad of factors, including vessel motion, larger and heavier BOPs, and extended field operations. This is of particular concern in areas core to the advancement of offshore operations such as the Gulf of Mexico, the North Sea, Sub-Saharan Africa and the Caspian region.
Concerns about system fatigue, particularly in the fatigue-critical zone of wellhead and first-joint con- nections, has driven conservatism and rigorous quality requirements, with increasing technical specifications as a way to ensure fatigue resistance in wellhead per- formance. This significantly adds both time and cost to operations and leads to another challenge in the subsea arena: inefficiency.
Currently, the industry relies on bespoke products for individual operations. Historically, industry specifica- tions have been written to address quality and design. However, a lack of guidelines or accepted standards for fatigue or forging qualifications led to the development of bespoke solutions for every project. In the current environment, with most players having to cope with sig- nificant cost pressure, this is not sustainable.
With several projects running late and/or over budget, the industry continues to suffer from scheduling delays. GE Oil & Gas is looking to solve the problem of fatigue as well as other equipment issues with product standardization and process simplification. The company’s SFX Wellhead System is a result of this vision.
SFX is a standardized system that provides up to 16 times fatigue resistance improvement over GE Oil & Gas’ existing systems for ultrareliability in fatigue-critical zones.
The company developed this technology building on its field-proven MS-700 and MS-800 systems. Rather than moving fatigue issues elsewhere in the system, SFX directly addresses them and maintains stiffness in each component.
Nick Dunn, global leader of Subsea Services & Off- shore at GE Oil & Gas, said, “Currently, a key challenge facing operators is the need to improve efficiencies, eliminate nonproductive time and reduce costs. The SFX wellhead system addresses all these areas, starting a new chapter of reliability, affordability and flexibility for sub- sea wellhead systems.
“Subsea wellheads are a core technology supporting drilling activities, but their lifespan can be affected by a multitude of factors such as vortex-induced vibrations. These loads are transferred through the riser to the well- head and casing system, causing fatigue at critical con- nectors and welds.
“Traditional mitigation techniques led to project-spe- cific customization, which translates into high engi- neering costs and long lead times. While no previously configured system delivered extreme fatigue reliability, cost-efficiency or flexibility across many different installations, the SFX wellhead system takes a fundamental step in this direction.”
Geometries for the SFX are optimized to reduce stress concentrations in all components. Preload between the high- and low-pressure housings is achieved through casing weight instead of additional tooling, creating a rigid connection for effective load transfer.
For fabrication, lengthened forgings improve thermal effects during welding, tighter pipe tolerances reduce stress and the weld profile is fatigue-friendly. Advanced nondestructive examination techniques ensure material soundness and maximize the probability of detection.
Stronger by design
We have taken our field-proven MS-700 and MS-800 architectures to the next level with an optimized design that directly addresses fatigue issues and maintains system stiffness. We didn’t just increase wall thickness or move the fatigue issues elsewhere in the system — we developed a comprehensive solution that provides more days of confident drilling in the harshest environments.
Fatigue improvement factors
- Stress-reducing geometries
- Longer socket spacing
- Extended length forgings
- Tougher materials: A707 and F22
- Tighter pipe tolerances
- State-of-the-art welding
- Improved inspectability
- Reduced number of welds
- Eliminatedshortpipesections
High-quality materials and processes
Standardizing materials and processes requires guidelines and collaboration. We worked with operators around the globe to develop one common material specification and adopted DNVGL-RP-0034 and API 20B to source and stock raw materials while meeting or exceeding customer quality certification requirements.
All SFX components have newly developed Inspection Test Plans (ITPs) carried out by an independent 3 party which allows for improved lead times and reduced cost to the customer while maintaining stringent quality verification expectations.
We’ve adopted the most stringent practices and acceptance criteria from raw material sourcing through system completion to ensure each SFX system provides inherent quality and optimized fatigue performance no matter how extreme the conditions.
Core building blocks
These building blocks provide the foundation to ensure that every system delivered from our global supply chain adheres to our high standards for design, testing, and manufacturing.
SFX subsea wellhead
- Standardized design enables both MS-700 and MS-800 configurations
- Maintains all familiar system interfaces, tools, and operating procedures
- 5″ of extra sealing surface for compatibility with all completion systems
State-of-the-art welding practices ensure enhanced fatigue life
- Stringent fabrication requirements and receiving inspection
- Part selection and checks prior to fabrication
- Tight control for axial and radial misalignmentwithamaxSCFof1.3
- Highly controlled welding and grinding
- Advanced NDE
DSAW pipe
- Above and beyond API 5L
- Improved material properties and tolerances
22” Ulti-Max SFX casing connector
- ISO13679:2011CALI-Ewithgas
- Gas tight metal-to-metalseal
- Single thread start with advanced threads and stress-relieving groove for enhanced fatigue performance
- Full scale resonant testing
36″ RL-SFX conductor casing connector
- Based on field-proven RL-2HCX
- Single thread start with advanced threads and stress-relieving groove for enhanced fatigue performance
Optimized Fatigue Performance
Raw Materials
- A707 and F22 materials to provide greater toughness and fatigue life
- Highly controlled chemical composition, grain size,and imperfections for optimal performance
- DSAW pipe goes above and beyond API 5L
Component Design and Manufacturing
- Optimized geometries to reduce stress concentrations in all components:wellhead housings, conductor connectors, and subs
- Radial preload between low and high pressure housing achieved without additional tooling
- Reduced number of welds
System Fabrication
- Lengthened forgings to improve thermal effects during welding and inspectability
- Tighter pipe tolerances to reduce stress
- Fatigue-friendly weld profile
- Advanced NDE ensures base material soundness and maximizes probability of detection
Wellhead installation
- Up to 16X fatigue life improvement
- Maintains all familiar system interfaces, tools, and operating procedures
- Suitable for global use
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