Whilst significant efforts have been made worldwide on developing solutions for capping offshore blowouts, less has been done to ensure safe and reliable kill operations through a relief well. This paper presents new solutions to challenging kill operations.

Well-kill operations through a relief well are still considered the most reliable and ultimate method for killing a blowing well. Strict legislation has been enforced for such operations, which challenges technical operational limits and margins. The requirement to be able to dynamically kill a blowing well through one single relief may restrict well design and thereby reduce contingencies.

By pumping of ultra-high density kill fluid (UHDKF) or by injecting a slug of UHDKF as part of a staged well-kill operation, more reliable operations can be planned for with reduced pumping pressures, reduced horsepower requirements, significant fluid volume reductions and cost reductions. Furthermore, these ultra-high density fluids can enable kill operations that would otherwise require changes to the original well design.

Some ultra-high density kill fluids have been formulated based on high density cesium brines. A clear brine with a density of 3.20 g/cm3 and very low viscosity has been formulated by blending cesium phosphate and cesium tungstate brines. Higher densities can be achieved by adding a small amount of solid weighting material to cesium brines.

The new ultra-high density kill fluids represent a great technological step. It is recommended that the findings presented in this paper are implemented in future Blowout Contingency Plans in order to ensure sufficient operational margins in the relief well planning and the kill programs.

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