Experimental Study of Erosion in Diverter Systems Due to Sand Production

ABSTRACT When drilling from a bottom supported structure, the best procedure for handling a threatened blowout from a shallow gas formation is to divert the gas flow away from the structure and drilling personnel. Case histories were reviewed in which failures occurred during diverter operations due to erosion caused by sand production. A model diverter system was constructed to evaluate this problem and provide information that can be used in the design of diverter systems. A number of pipe fittings used at bends in diverter systems were experimentally evaluated. The effect of flow velocity, liquid content, and sand concentration were included in the study. It was found that very rapid wear can occur at velocities near sonic velocity. Wear rates of 8-in./hr were measured for short radius "Ells." The rate of erosion was found to be about two orders of magnitude higher for gas/sand mixtures than for liquid/sand mixtures. An equation was developed for predicting the wear rate for various field conditions. Recommendations are given for improving the erosion resistance of diverter systems.