Plexus Responding to the Subsea Call - Press and Journal

Published in the Press & Journal – 2nd September 2013


In an interview, CEO Ben van Bilderbeek explains what Plexus can contribute to wellhead safety that is so out of the ordinary.

In the aftermath of recent Gulf of Mexico incidents, a group of major oil and gas operators united in supporting Plexus, an Aberdeen-based oil and gas engineering company and owner of the POS-GRIP® known for its safety, time and cost saving capabilities, by becoming consulting partners in a joint industry project (JIP). The JIP is aimed at addressing a number of systemic subsea wellhead deficiencies that became evident following such incidents.

As a result, Plexus is now over halfway through the JIP to design and develop a new “HGSS” subsea wellhead. This will utilise the POS-GRIP wellhead technology which the company and its backers believe will address a number of key safety and operational challenges that conventional subsea wellhead equipment has not resolved to date.

These include long term true metal-to-metal sealing, instant casing hanger lock-down, and solving the challenge of subsea annulus management in terms of monitoring and remedial capability. Interestingly, the subsea JIP is also gaining increasing interest among various industry bodies.

We spoke to Ben van Bilderbeek regarding the new sub-sea JIP:

Bearing in mind that the subsea market is dominated by five major companies who have supplied subsea wellhead technology to a market for over 40 years that is now growing at record pace, what can Plexus contribute that is so out of the ordinary?

Inherent in conventional wellhead design are a number of systemic deficiencies, and as a result it is not immediately obvious that in many cases the subsea wellhead is at the heart of well integrity incidents. The difficulties of using conventional casing hanger lockdown solutions lay behind the delays that occurred in controlling the 2010 GOM blowout. Since the accident, it is now against the US drilling rules to leave subsea casing hangers loose in the wellbore and, to meet these new regulations a more dependable way of achieving “instant” lockdown is being sought. We believe that our new POSGRIP HGSS subsea wellhead JIP initiative is uniquely placed to address such issues.

Recently the industry has put out a call for solutions to deal with annulus pressure management in subsea wells. Can you comment?

Annulus pressure management is necessary to deal with sustained casing pressure (SCP) situations that can be caused when fluid trapped between the cement seal lower down the annulus and the casing hanger seal in the wellhead heats up during production. Pressures can build to the point that the well casing is damaged, which can result in well control incidents. A further cause of SCP can be hydrocarbons entering the casing annulus because of failures in the well.

On surface applications access to the casing annuli is readily available, but to date such annulus management facilities are not available subsea, and it is key innovative features such as these that we are engineering into our new subsea wellhead design.

What are Plexus’ plans with respect to providing monitoring capability in subsea applications?

The issue with current subsea wellheads is that unlike operating on the surface, one cannot readily and safely provide penetrations through the wellhead body to gain access to the various casing annuli. It is just not practical to fit a subsea system with valves through which pressure can be monitored, bled off, and through which remedial procedures can be conducted to manage SCP.

Our unique and patented POS-GRIP friction grip method of wellhead engineering can be used to provide removable seal sleeves in the wellhead bore to open and close porting systems which remain within the wellhead shell.

These monitoring ports can eventually be directed through the tubing hanger into the subsea tree, to give operators continuous access to selected casing annuli.

To be considered a safe solution over the production life cycle of a well, surely the Plexus system would have to provide integrity over a long period of time?

Yes indeed, and that is precisely what POS-GRIP technology uniquely delivers. By using the natural flexibility of steel we are able to shrink the wellhead bore within elastic range limits to physically grip the seal sleeve device, engaging multiple metal-to-metal seals on either side of the proposed monitoring ports.

Our “HG" seal system, which has been proven on numerous applications around the world for a decade, has been qualified to 20,000psi at 375 degrees Fahrenheit.

The design stage of Plexus’ JIP initiative, which was launched in March 2011, is due to be completed by mid-2014 and will be followed by testing of a prototype.

Ben van Bilderbeek, CEO, Plexus Holdings plc Ben van Bilderbeek, CEO, Plexus Holdings plc