The diverter is installed on top of the wellhead to enable flow from shallow formations to be diverted away from the work area in case of a shallow gas kick. However, current diverter equipment is not yet designed to withstand an erosive shallow gas kick for a prolonged period. The diverter system is still seen as a means of "buying time" to evacuate the drilling site.
Dirverters are not used for land operations, unless there is risk of shallow gas.
For offshore drilling operations diverters are used when drilling . . .