Until sufficient casing can be set to allow a well to be shut-in during a threatened blowout, diverter systems are used as a means of well control. Diverters permit flow to be directed away from the rig and rig personnel while minimizing pressures in the well. If the well were to be shut in prior to setting sufficient casing, contained pressures could fracture the formations at the conductor shoe and possibly broach to the surface.

Diverter systems must be designed to provide backpressures which will not result in fracture at the conductor shoe. Current diverter sizing calculations often assume atmospheric pressure at the diverter exit and assume that the component of the pressure gradient due to fluid acceleration effects is negligible. This study has shown experimentally that these assumptions introduce large errors into the calculation of backpressures. Experiments were carried out in model diverter systems for a wide range of critical flow rates for both gases and gas-liquid mixtures. Improved pressure loss calculation procedures were developed which gave acceptable agreement to the experimental results.

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