Shell is to restart offshore drilling operations in Canadian waters, with the Stena IceMAX drillship, after authorities gave the green light following a recent incident.
Drilling had been taking place on the Cheshire L-97 exploration well, offshore Nova Scotia, but was stopped following the loss of the drillship’s riser, which dropped to the sea floor during heavy storms on the 5 March.
The Canada-Nova Scotia Offshore Petroleum Board (CNSOPB) have now completed a full investigation into the incident and are happy to allow offshore drilling to resume.
“This has been a rigorous and exhaustive review of the incident,” said CNSOPB CEO Stuart Pinks.
“We are satisfied that the cause of the incident has been properly determined and that appropriate corrective actions have been taken so that drilling may resume safely
Offshore Drilling Incident
According to the CNSOPB report, the drilling crew onboard the Stena IceMAX anticipated and prepared for the incoming storm correctly.
Preparations involved suspending drilling operations, installing two barriers to secure the well (a downhole plug and the closing of the Blowout Preventer, BOP), and displacing drilling fluids in the riser to sea water.
Stena IceMAX Harsh Environment Drillship
When vessel motion exceeded the operational limits, the decision was made to disconnect and ride out the weather with the riser attached to the vessel through the tensioner riser system, a standard procedure.
To maximize the distance between the bottom of the riser and the BOP so as to protect the integrity of the well, the tensioner system holding the riser was fully retracted.
During the height of the storm, the riser became detached from the tensioner riser system, and fell to the sea floor.
The CNSOPB added that no one was injured and no well fluids or synthetic oil-based drilling fluids were spilled to the environment.
The key factors in the cause of the incident were the heave of the vessel andthe inability of the riser tensioner system to compensate for the difference in the movement between the riser and the vessel with the tensioner system in a fully retracted position and with the Riser Anti-Recoil System (RARS) inactive.
Shell Restarts Offshore Drilling With IceMAX
A CNSOPB spokesman concluded: “As an additional safeguard, the CNSOPB has introduced a condition further tightening operating limits under which drilling may occur.
“Until such time as the CNSOPB completes further reviews, Shell Canada is required to lower its well disconnect criteria on the Stena IceMax based on vessel heave of five metres. The previous criteria was eight metres.
Stena IceMax Drillship
The Stena IceMax Drillship, is an ultra deepwater, harsh environment drillship, delivered in 2012, by Samsung Heavy Industries.
IceMAX has a design capability to operate in a maximum water depth of 10,000 feet (3,048m) and drill to a maximum depth of 35,000 feet (10,668m).