A simplified hydraulic model has been developed by TEA Sistemi in cooperation with ENI-AGIP Division. The model concerns the complete characterization of an atmospheric or underwater blow-out event. The model is basically a zero-dimensional momentum balance in which the well is simulated with a two-volume system: ® Single phase zone: the section of the well above the bubble point for oil wells and the section of the well above the dew point for gas wells; ® Two-phase zone: the section of the well below the bubble point for oil wells and the section of the well below the dew point for gas wells. The model calculates the blow-out oil and gas flow rates; the throat pressure and temperature; the outlet gas velocity; the flow conditions at the outlet section (critical or subcritical); the type of flow along the well (separated or dispersed flow); the fluid properties at the outlet during an atmospheric or underwater blow-out; the droplet size distribution at wellhead; the jet height and radius; the jet mean temperature; the air entrainment during an atmospheric blow-out. These data allow a correct prediction of the dispersion phenomena and the extension of the area affected by the gas and oil contamination. The droplet size distribution and the jet characterization has been developed and validated with an experimental investigation carried out at TEA's Laboratory. Making use of the minimum set of input data available in a blow-out emergency, the model supplies the total mass flow rate with an average uncertainty of 17.7%, with respect to the predictions made by means of the OLGA code, the throat pressure with an average uncertainty of 23.3% (8.5% during an underwater blow-out), the throat temperature with an average uncertainty of 31.1% and the outlet gas velocity with an average uncertainty of 30.1%. In simulating oil dispersion, the model use a ballistic approach. The model is able to consider a standard deviation on wind direction distribution, depending on meteorological condition; it leads to the capability to obtain a soil contamination map. In simulation of gas dispersion, the model use a gaussian approach. A tuning with the reference model Calpuff has done, in some reference scenarios, so that the deviation between TEA model and Calpuff is about 11.7% in concentration peak, and 4.5% in the respective distance from source. The output of gas dispersion model is a concentration map, 3D and 2D.
A Simplified Approach To Predict The Consequences Of A Blow-Out Event
Ansiati, A., Andreussi, P., Bonuccelli, M., Morale, G., and P. Blotto. "A Simplified Approach To Predict The Consequences Of A Blow-Out Event." Paper presented at the Offshore Mediterranean Conference and Exhibition, Ravenna, Italy, March 2003.
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