In the wake of the Macondo incident, the drilling industry has focused on making improvements to offshore safety and developing methods to recover from similar incidents.
However, emergency release connector (ERC) technologies, which might prevent or significantly reduce the impact of such disasters, are yet to benefit from this innovative process.
While incremental developments to existing connectors might provide some benefits, their design contains a fundamental flaw.
Based on the traditional male-tofemale engagement, existing ERCs have operational limits, because of their geometry, and the connector may to fail to separate if unlocked with a high bending moment applied.
Failure to disconnect from the well head in this situation can lead to a major accident. The consequences of such incidents, as seen in the aftermath of Macondo and other disasters, including the 1988 blow-out on the Ocean Odyssey, are far-reaching.
Furthermore, there is no official record of the number of times that connectors fail to release on demand due to excessive rig offset. though unofficial figures suggest that such events could be occurring 15 to 20 times globally each year.
Additionally, when existing ERCs are disconnected with an offset, but within their design limitations, they still tend to become damaged by the disconnect process, leading to rig downtime and repair costs. It is therefore imperative that these issues are addressed by the industry.
The resulting emergency disconnect package (EDP), the XR connector, broke with several design conventions associated with existing connectors and solves its essential problems.
Using a face-to-face engagement, instead of the traditional male to female configuration, the XR connector is capable of releasing safely with 100% maximum bending moment applied.
It has no maximum disconnect angle and thus will not get stuck or fail to release when it is required to act.
Most importantly, the XR connector continues to provide options beyond normal operating limits and remains operational even after a complete riser failure.
This is especially problematic for floating vessels, on which an error in the dynamic positioning system or loss of position due to particularly bad weather can quickly precipitate a crisis, causing vessel and environmental damage and, potentially, casualties.
Conventional connectors have a geometry-limited maximum disconnect angle to prevent them from “locking up.”
This means that, to operate within the limited angle, the vessel is limited in the distance it can move from its central position, giving the crew little reaction time to identify a loss in positioning and respond accordingly.
As the XR connector uses a face-toface engagement, it does not require axial movement to separate the male from the female.
Instead, the female face will simply roll away from the male face, if triggered to release with full bending load applied. As a result, it does not even require the topside riser tensioning system to be operational in order to disconnect successfully.
When an operator analyzes the bending capacity (strength) of the riser system, the weakest point (in bending) will never be the XR connector. Even after the riser has been bent beyond the limit of its weakest point and has become damaged, the XR will still disconnect from the well.
What this means for those onboard a vessel encountering positioning problems, is that the risk to life and of damage to the vessel is greatly reduced.
Even in the event of a complete riser failure, the XR can be released to provide a competent and undamaged structural and sealing interface compatible with a capping stack.
In the event that it is unsafe or not possible to disconnect from onboard the vessel, the XR can be released using a remote acoustic trigger or ROV (though this is dependent on which control system it has been configured with).
When designing the system, the team at STL was keenly aware that, in an emergency situation, having time to plan a response and put that response into action is crucial to limiting damage and preventing fatalities.
The events of the Macondo incident in April 2010 were sobering for the international oil and gas industry, which prides itself on its high standards of HSEQ.
Though the XR was originally designed for use on intervention risers, plans are now in place to develop it for drilling purposes.
Had this process already occurred and the Macondo well been fitted with an XR connector, there may have been more options for the crew onboard the Deepwater Horizon and the first responders to make decisions on how to proceed. According to Ian Fitzsimmons, the XR connector, had it been configured to fit a drilling riser, would have “passed the Macondo test.”
Unfortunately, in 2010 the XR connector had only been designed and manufactured for well intervention applications which only require an ERC with a relatively small bore of 73⁄8-in.
However, STL plans to develop the XR, making it compatible with 18¾-in. drilling risers. This scaled-up version of the XR would offer operators the same benefits as those offered by the smaller XR, ensuring drilling crew are given options when faced with a well control emergency.
The XR connector would be particularly useful for drilling operations because it also increases productivity. Its ability to release at up to 100% maximum bending capacity means there is less need to shut down in poor weather conditions, increasing the operating window and reducing precautionary disconnects.
The STL team has completed a preliminary feasibility study for the 18¾- in. XR connector and is now looking to raise sponsorship or grant funding in order to undertake front end engineering design work. This is an ideal time to invest in the development of well control safety, as the industry adjusts to new challenges, such as drilling in deep water. Once developed for drilling purposes, the XR connector will provide an important buffer during operations, giving crew members the time and options required to make the best decisions during an incident. OE
Drummond Lawson, managing director of Subsea Technologies, began his career with Expro Group, Aberdeen, as a subsea design engineer. He has gone on to work Schlumberger IPM, working in Shell and Ramco Energy, and founded Lewis Limited before co-founding STL in 2010. He has a BEng in Manufacturing Engineering & Management from the University of Dundee and is a chartered engineer.
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