The problem was that this device was installed some distance down the well. To retrieve it, a subsurface safety valve which sat higher up the borehole had to be pulled out first. This valve, which is found in all wells to provide a downhole barrier against a possible blowout, got struck as it was being manoeuvred through the wellhead on the platform.
This left only one barrier in the well – the upper swab valve, which could be operated manually. The remaining barriers in the Xmas tree were blocked. Shell, the PSA, and Seawall – responsible for the wireline job – joined forces to come up with a solution to this challenge, which was now serious.[REMOVE]Fotnote: Petroleum Safety Authority Norway, 25 May 2011. Investigation report. Loss of well barriers in connection with wireline operation on the Draugen facility (Activity number 005093016, 25 March 2011). Downloaded from http://www.ptil.no/getfile.php/1314059/Tilsyn%20p%C3%A5%20nettet/Granskinger/2010_1367_Granskningsrapport%20etter%20hendelse%20p%C3%A5%20Draugen%20og%20varsel%20om%20p%C3%A5legg.pdf.
The approach adopted was to return the safety valve to its position in the well. Two mechanical bridge plugs were then inserted in the borehole above the valve.[REMOVE]Fotnote: Petroleum Safety Authority Norway, 23 May 2011, “Order to Shell following well incident on Draugen”. Downloaded from http://www.ptil.no/barriers/order-to-shell-following-well-incident-on-draugen-article7873-960.html. After four days of intensive work, the well was secured.
Shell had notified the PSA of the incident immediately after it occurred. The regulator considered the event to be so serious that it launched an investigation.
This concluded that, since the well at one point only had a single remaining barrier to a hydrocarbon outflow, the incident involved a major accident potential.
The PSA also identified a big threat of dropped objects during rigging up, and that a possible wireline failure could have caused an uncontrolled fall of the toolstring down the well.
According to the report, Shell had committed a number of regulatory breaches – including inadequate management, risk assessment and well control. The failure to halt production from the rest of the wells was identified by the PSA as a gross breach of the regulations by Shell and Seawell.
A possible wireline failure could have eliminated the final well barrier, leaving nothing to contain the wellstream and leading to a blowout. Shell received a notice of an order from the PSA. This is part of the PSA’s administrative process where the recipient is asked to assess the factual basis, and represents only a first step before an administrative decision is made.
An order, on the other hand, is an administrative decision made pursuant to the regulations and legally binding on the recipient. The one issued to Shell in May 2011 was in three parts, which had to be complied with by 1 July of the same year.
First, the company had to assess and test its own criteria for continuing well intervention while maintaining production from other wells in an emergency when barriers are lost.
Second, its own criteria for conducting internal investigations or investigating serious incidents with loss of barriers in the well area on Draugen had to be assessed.
Finally, Shell had to assess its own criteria for prudent well control and the need for risk-reducing measures when implementing well intervention on the Draugen facility.