Holdfast Training Services Trial Blog

Since the last update I’ve continued working on Glen Lyon. It appears that it is something akin to Hotel California, in that you can check out – but can never leave. The list of operational vulnerabilities is growing, with many of the top ones preventing production ramp-up to full potential. As it currently stands they are limited to 87mbd (1000 barrels a day) (87*1000*$62.65~$5.5m a day) when they should be producing at 130mbd. The delta created between these 2 values is quite considerable for a daily profit. Since these figures are so great, intervention was required. This is in the form of a ‘Vulnerability Strike Team’ made up of a multi-discipline team of engineers, in which I am the mechanical/project representative. A quick outline of 2 scopes (8 in total) below:

Rundown cooler change-out

The production of crude oil requires cooling from 90degC to 50degC for storage within the offload tanks. This cooling is achieved through 2-off rundown coolers, consisting of plate heat exchangers. Over the past couple of months the pressure differential across the coolers has increased from the allowable of 0.7bar to it’s current level of 2.7bar. This level displays high signs of fouling/blockage. The current understanding is that through the operating conditions which has been used recently this may have resulted in the build up of wax, where the wax appearance level is 38degC. Both coolers must be online to ramp-up above 87mbd. Current options to solve this were as follows:

1. Perform a chemical de-wax procedure using a solvent based chemical. This was completed but showed no signs of improvement.
2. Accept higher export temperature, as long as it does not exceed the safe working limit of the offload storage tanks. There was even talk of offloading at a higher temperature and chartering a tanker to drive around the North Sea to allow the crude to cool to 40degC so that it can be offloaded in port.
3. Change-out the cooler for the spare unit held in storage.

After a failed attempt at option 1 we pulled the trigger on option 3, which was my bag. This change-out required a 16Te vessel-vessel lift (heaviest lift conducted on Glen Lyon since production started earlier this year) which required a sea state of <2.5m significant wave height. It then involved an unknown weight (based upon unknown quantity of wax) of an inboard lift, over live plant to remove the old cooler. Long story short, they managed to lift the cooler but it was 102kg below the allowable 10904kg safe working limit (~99%). This was an imposed limit by the mechanical handling contractor based upon stress analysis performed on the cooler lifting points. Some photos below to show you what I’m talking about.

Spare unit – lifting point circled

Trial lift conducted after a design of rigging

Offshore cooler – required removal of closing spools and complex lift

Offshore unit – confined lifting space

Heating Medium – leak mitigation

A further scope of work I’ve been SPA for has been the remedial works required to recover from the discovery of unreliable/failed flow transmitters (as described in previous blog). This scope involves the works required to mitigate against the potential of instrument failure of a 16″ and 8″ heating medium line. Both options below are being worked up concurrently:

1. Drain down of approximately 25m3 of heating medium, removal of old flow transmitters and replacement with blank pipe spools. This will require a 7 day outage, which would cost them around $30-40m in deferred revenue. This is not currently acceptable but is the base case.
2. Engineer an external pipe clamp for mounting over the top of the flow transmitters. This involves a case filled with resin. We are currently working up the control of works required to enable this work to be done while the line is hot, reaching temperature of 110-140degC. The 16″ clamp weights around 800kg so stress analysis of the pipe is required, which is still unknown. The decision was to buy these regardless since if this option is feasible it will prevent a 7 day outage.

To provide a little context I’ve included a couple of photos below showing what the flow transmitters look like.

16″ flow transmitters

8″ flow transmitter – bunding in place for potential leaking

8″ – constrained construction

I guess in summary, something that I’ve not been exposed to before is the realities of the importance of production revenue. The vulnerabilities we are currently working on will hopefully help Glen Lyon reach its potential of 130mbd, bringing in ~$8m a day. The pace of life is very different to planned project delivery, but it makes things far more interesting anyway. Although there is currently no time for thesis….