Regulator issues order following ‘West Mira’ disconnection incident

Norwegian offshore safety regulator, the Petroleum Safety Authority (PSA), has completed its investigation of the incident on West Mira rig where the lower marine riser package (LMRP) was unintentionally disconnected.

The PSA said
on Tuesday that several breaches of the regulations were identified, and
Seadrill has now been given an order. The incident occurred on 14 March 2020.

The
unintentional disconnection of the LMRP occurred during a drilling operation on
the Maria field in the Norwegian Sea, where Wintershall Dea is the operator.

After the
facility lost position under the impact of dynamic weather forces, the
automatic disconnection system (ADS) was activated. That, in turn, initiated the
separation of the LMRP.

Drilling was
not underway in hydrocarbon-bearing layers of the well, which meant no danger
existed of discharges from the reservoir to the natural environment.

The well was
isolated by the shear ram in the blowout preventer. Since the weight of the
drilling mud included a riser margin for the section, the barriers remained
intact. Most of the oil-based drilling fluid in the riser was drained to the
sea.

West Mira is
a sixth-generation semi-submersible drilling facility built to the Moss
Maritime CS60 design. Operated by Seadrill Europe Management, it received an
acknowledgement of compliance (AoC) from the PSA in 2019.

The incident
caused the discharge of 49.9 cbm of drilling fluid from the riser to the
sea/natural environment. The drill string was cut and had to be fished out of
the well. The drilling operation was delayed for about three days. Fortunately,
no personal injuries were caused by the incident.

The PSA concluded
that the probability of losing well control while drilling in the reservoir
section was low. Plans called for the well to be drilled with a fluid able to
balance pressure in the formation if the mud column in the riser was lost.

In the event
of an unintentional disconnection, the BOP would cut the string and shut in the
well. The PSA concluded that the incident could have caused material damage to
the facility and its equipment.

The incident
occurred when the facility lost position because of dynamic weather forces. The
drilling contractor concluded that the drift-off activated the ADS.

A
combination of sub-optimal mooring lines and extensive use of thruster capacity
to maintain position meant thruster power was insufficient to withstand the
dynamic forces at the time of the incident.

The
disconnection signal was given after the ADS exceeded the five-degree
activation point, which in turn automatically cut the string and shut in the
well.

The
investigation has identified several underlying causes for the West Mira
incident. These relate primarily to reduced situational awareness and
assessment of risk, procedures and compliance with these, use of analyses, management
of change, design of the facility, cost cuts and concentration on efficiency.

As for regulatory
breaches, the investigation identified four non-conformities with the
regulations. These are in regards to procedures and compliance with procedures,
risk understanding and prioritisation of risk-reduction solutions, learning
lessons from incidents and preventing recurrences, and deficiencies in meeting
the operator’s see-to-it responsibility.

The last of
these concerns relates to operator company Wintershall Dea. It was given a
deadline of 17 September to explain how this non-conformity with be dealt with.

The three
others relate to Seadrill. They coincide to a great extent with identified non-conformities
following an earlier incident on West Mira in January 2020.

Seadrill has
thereby failed to ensure that management of HSE is corrected, followed up and
improved to take account of lessons learnt from the earlier incident on West
Mira

On that
basis, Seadrill has now been given the following order to identify and initiate
measures which ensure that similar incidents do not recur on West Mira, and
present a plan for ensuring that the necessary measures will be implemented and
are effective on all relevant facilities covered by an acknowledgement of
compliance (AoC) within Seadrill’s area of responsibility in Norway.

According to
the PSA, the deadline for compliance with the order is set to 15 October 2020.