Steam Blowout from an Over Pressured Geothermal Reservoir in Hungary

Abstract

The existence of a high temperature and highly over-pressured geothermal reservoir was proven during a steam blowout in Fabiansebestyen, South-eastern Hungary. The pressure balance of the drilling mud broke down during an incorrect drilling operation. An intensive inflow took place from a fractured dolomite reservoir at 3880m depth. The pressure of the reservoir was 73.1 MPa, its temperature was 199.6 oC. The damaged wellhead equipment released a powerful jet steam to the atmosphere. There was a unique feature of the blowout. The pressure permanently exceeded the value of 36 MPa in the immediate vicinity of the damaged wellhead. This was only possible if the liquid phase was sprayed through a narrow opening as with the case of the fuel injection nozzles of Diesel engine. The distortion of the continuous fluid flow into individual droplets reduced the 36 MPa pressure. The phase transition from liquid to steam phase took place in the droplets. The correlation of the calculated and measured data makes this assumption most probable.