Breccia Hazards in the South Caspian Basin

Abstract

Ejection of breccia from mud volcanoes for the onshore and offshore South Caspian Basin provides hazards for rigs, pipeline, and subsea completion equipment. Here we investigate the lateral ranges of ejected rock fragments for aeolian and submarine conditions. In addition, the consequences are considered of emission from a raised or depressed crater, with or without a surrounding crater wall. Also investigated is aeolian transport to an ocean surface, and subsea motion thereafter. Rough rules of thumb for aeolian hazards from breccia would indicate that seconds to tens of seconds after breccia emission is the onset time of hazard, with hazard distances typically of order a few hundred meters, but occasionally reaching about a kilometer or so for fairly large (5 kg) rocks emitted at high (∼500 m/s) speeds, with impact speeds of order 10–100 m/s. Submarine hazards yield 0.1-4 m/s impact speeds on the ocean floor for water depths in excess of about 2 m. For shallower water depths the aeolian impact speed is a good approximation. The hazard potential to equipment from breccia is one of concern, with a worst case distance estimate of about 1 km from the ejection point.