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Designing and drilling deep-water wells
Every oil and gas well must be designed, drilled and prepared for production – a process known as “completion” – to suit local conditions. These include variations in temperature, pressure and geology. All Shell wells must meet rigorous industry design and construction standards.
While there is no uniform well design, Shell has strict standards for designing, drilling and completing deep-water wells. These require wells to have at least two barriers to safeguard against “blowouts” – a sudden uncontrolled burst of oil or gas out of the production equipment.Barriers include heavy fluids that exert downward pressure to contain the oil or gas, and mechanical barriers – such as cement plugs.
If for any reason well control is lost, a mechanical device, known as a “blowout preventer”, is designed to rapidly seal off the well. The blowout preventer is typically a three-story, 200-tonne stack of valves, pipes and controls. It includes two sets of cutting jaws – called shear rams – to slice through the pipe and seal off the well in an emergency.
Shell’s deep-water wells are designed to have a recovery system in case of a blowout. If the blowout preventer does not successfully shut off the flow from the well, the drilling rig will disconnect and move away from the well site while crews mobilise a capping system. The capping system would be lowered into place from its support barge and connected to the top of the blowout preventer to stop the flow of oil or gas.
Capping systems, or "stacks", are on ready for rapid deployment to any of our deep-water wells.
Before drilling can begin, the well design, drilling, preparation and completion plan goes through several stages of review. For example, experts from Shell and its drilling contractor model drilling and completing the well.
They make sure that the well design, drilling and completion plan and the safety measures are adapted to the conditions. This planning process is also used to check that everyone working on the rig is clear on roles and responsibilities.
“If something happens during drilling that we weren’t expecting, such as hitting an unexpected pocket of gas, we stop the job,” says Lewis Steven, Shell Drilling Supervisor on the West Navigator drill ship off the coast of Norway. “Work continues only when we are sure it is safe."
Once drilling is complete we run a series of tests to check that the well meets regulations and our own high standards before we bring it on-stream.
Shell drilling safely in deep water - Lewis Steven
Lewis Steven, Shell Drilling Supervisor on the West Navigator drilling ship off the coast of Norway, explains how the rig crew works to ensure that some of the world's largest gas wells are drilled safely.