HAZOP of Well Control Procedures Provides Assurance of the Safety of the Subsea MudLift Drillina System
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abstract
To meet the challenges of drilling in intermediate to ultra-deep waters (depth greater than 5000'), a drilling technique referred to as dual gradient drilling, DGD, is being developed and tested by four industry projects. These projects are being conducted by the SubSea MudLift Drilling (SMD) JIP, the Deep Vision JEP, Shell Oil Company, and Maurer Technology. The first three achieve dual gradient by placing pumps at or near the seafloor to lift the drilling fluid and cuttings from the well annulus to the surface via a return line. The fourth project proposes the injection of hollow glass spheres into the riser near the mudline. All four DGD projects must address well control issues affected by the dual pressure gradient imposed by the drilling fluid, the possible u-tube that is associated with the dual gradient systems, and the equipment that is being designed for each individual project. Very early in the SMD JIP well control techniques for dual gradient drilling were identified as a key success factor in the project. The members of the SMD JIP Well Control Team were given the task to study the current state of the art in floating drilling well control, determine which procedures need to be modified for SMD, and make such modifications. The goal of the team was to develop a well control program that was at least as safe, if not safer, than the current practices. One tool that was utilized to assure that the Well Control Team met it goal was the Hazard and Operability Analysis, HAZOP. Here we describe the HAZOP process in application and how it was utilized to provide assurance that the well control procedures written by the team members are as safe or safer than the current state of the art in floating drilling well control.
