Analysis Of Causes Of Blowout Accident, Simulation Of Gas Diffusion, And Lash-up Countermeasure Research

Both at home and abroad are actively developing gas fields. Due to the existing of high concentrations of H₂S, there must be gas cut which would decrease the drilling fluid density and thus lead a reduction of hydrostatic pressure straightforwardly. It's easy to occur blow out accidents,if the proper and effective measures are not adopted in time. Blow out accidents not only cause casualties but also the damage to the environment as well as losses property. Because people can not accurately grab the actual situation of diffusion law of toxic gas when the blow out occurs, consequently, they are unable to figure out the safe area and unable to develop any feasible evacuating suggestions. And it will lead us missing the good evacuating opportunities and eventually resulting in a large amount of loss. Therefore, to study the causes of blow out accidents, especially to study the diffusion law of toxic gas in actually occurred ones, is of great significance. In this paper, we analyzed the causes and hazard of blow out accidents and conducted some numerical simulations, developed an emergency plan for accidents prevention. The major work is summarized as follows:(1)Through the study of gas blowout we can get the internal cause of spewed and the danger of the spread of harmful toxic and harmful gases. Take"12.23"well explosion as an example, the internal cause of spewed is H₂S invasion, which leading the formation pressure is greater than the pressure of bottom hole, it is to say the drilling fluid pressure is negative; The spread of toxic gas of H₂S and flammable hydrogen of CH₄ caused a certain amount of harmful.(2)According to the fluid mechanics theory, "12.23" well explosion numerical simulation experiment shows that the jets flow is turbulent, the turbulence models is standard k-ε, which solving model is coupled solution.(3)The numerical simulation of "12.23" well explosion unconstrained conditions shows that the calculation and the export volume flow blowout velocity is correct, based on this, considering the external conditions, in the situation of the effects of wind speed and atmospheric stability, the diffusion of H2S and CH4 spread range and concentration distribution.(4)Based on the simulation results, considering the CH4 and H2S separately, set the safety ignition timing and the time required for clouds becoming stable from explosion in 15 minutes; set the safety ignition position at the downwind area, the lower limit of the explosion limits, change the wind direction when the accident happened to northwest wind, so the downwind area is located in southeast area, then simulate the process of ignition combustion.(5)According to the results of the analysis and numerical simulation about "12.23" well explosion, put forward a prevention of well explosion and emergency response, which provides strong foundation for the after accidents prevention and treatment.