Study on Multiphase Pressure Wave Velocity Characteristics of Automatic Kill Annulus in Chuanyu Fractured Formation

Abstract

The virtual mass force, annulus pressure, gas-liquid resistance, gas slippage, void fraction and other factors were considered, the equation was combined with small perturbation theory, the mathematical model of annular multiphase pressure wave velocity for automatic killing the well in fractured formation is proposed. Taking pengzhou pz-5-3d well (vertical depth 5827m) as an example, the model is solved programmatically with the semi-display difference method, and the results show that: The gas of fractured formation is characterized by slug flow. With the increase of void fraction, the pressure wave velocity firstly decreases and then increases. When the void fraction is between 0% and 16%, The pressure wave velocity is mainly liquid projectile, and the pressure wave velocity decreases sharply. When the void fraction is between 16% and 40%, and the pressure wave velocity tends to be flat and constant. When the void fraction is between 42% and 100%, and the pressure wave velocity shows an increasing trend, and the pressure wave velocity is mainly aeroelastic. As the annulus well depth decreases, the void fraction decreases and the pressure wave velocity decreases. The pressure wave velocity increases with the increase of the back pressure of the kill circulating exhaust wellhead. When the void fraction is between 0% and 13%, the gas slippage velocity has little influence on the pressure wave velocity. In the range of 13% to 85%, the pressure wave velocity decreases with the increase of gas slippage velocity. The time interval of throttle regulating valve follows the response time of bottom hole pressure. The time interval of throttle regulating valve increases with the increase of response time.