Shale gas well blowout fire and explosion modelling

Highlights: • Mathematical modelling is applied for hazard evaluation of shale gas well blowouts. • Hypothetical scenarios of well blowout at a shale gas exploration site were studied. • The effects of the formation pressure, wind speed and degree of confinement were investigated. • Safe distances have been determined corresponding to the fire and explosion harm thresholds. -- Abstract: The development and application of a computational model for predicting the thermal radiation and explosion over-pressure in the event of an accidental well blowout during shale gas production is described. The transient discharge rate, the fluid phase composition, temperature and pressure at the ruptured wellhead, serving as the source term for fire and explosion modelling are determined based on the numerical solution of the conservation equations using the Method of Characteristics. Two scenarios covering immediate and delayed ignition of the escaping gas respectively leading to a jet fire or an explosion are considered. The efficacy of the well blowout model is demonstrated by simulating the accidental well-head rupture of a real 4000 m deep shale gas production well at a maximum reservoir pressure of 600 bar. The simulated time variant explosion overpressures and thermal radiation heat fluxes are in turn employed to specify the minimum safe distances to people and equipment during the rapid well depressurisation.