川渝裂缝性地层自动压井环空多相压力波速特性研究北大核心CSCD

考虑虚拟质量力、环空沿程压力、气液相间阻力、气体滑脱、环空空隙率等因素,基于小扰动理论,提出了裂缝性地层自动压井环空多相压力波速数学模型,结合半显式差分方法,以彭州PZ-5-3D井(垂深5827 m)为实例,对模型编程求解.结果表明:裂缝性地层出气具有段塞流特点,随空隙率增大,压力波速呈现先减小后增大趋势;空隙率在0%至16%区间,压力波速以液弹为主,压力波速呈急剧下降趋势;空隙率在16%至40%区间,压力波速趋于平缓恒定值;空隙率在42%至100%区间,压力波速呈现增大趋势,压力波速以气弹为主;随环空井深减小,环空空隙率减小,压力波速整体呈现减小趋势;随压井循环排气井口回压增大,压力波速整体呈现增大趋势;环空空隙率在0%至13%区间内,气体滑脱速度对压力波速影响不大;环空空隙率在13%至85%区间内,随气体滑脱速度增大,压力波速呈现减小趋势;节流阀调阀时间间隔与井底压力响应时间具有跟随性,随井底压力响应时间增大,调阀时间间隔增大.

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

In view of the virtual mass force, the annulus pressure, the gas-liquid resistance, the gas slippage, the annulus void fraction and other factors, the mathematical model for annular multiphase pressure wave velocities of automatic kill in fractured formation, was proposed based on the small perturbation theory. With the Pengzhou PZ-5-3D well (vertical depth 5 827 m) as an example, the model was solved programmatically with the semi-explicit difference method. The results show that, the gas from the fractured formation is characterized by the slug flow. With the increase of the void fraction, the pressure wave velocity first decreases and then increases. For a void fraction between 0% and 16%, the pressure wave velocity is mainly of liquid slug, and decreases sharply. For a void fraction between 16% and 40%, the pressure wave velocity tends to be flat and constant. For a void fraction between 42% and 100%, the pressure wave velocity shows an increasing trend, and is mainly of bubble slug. With the decrease of the annulus well depth, the void fraction decreases and the pressure wave velocity falls. The pressure wave velocity increases with the back pressure of the kill circulating exhaust wellhead. For an annular void fraction between 0% and 13%, the gas slippage velocity has little influence on the pressure wave velocity. For an annular void fraction between 13% and 85%, the pressure wave velocity decreases with the gas slippage velocity. The time interval of the throttle valve follows the response time of the bottom hole pressure, and increases with the response time.