固井泵关闭过程中的井筒流体流动特性研究

Research on the fluid flow characteristics in the process of closing pump in cementing

在石油天然气井固井过程中,固井泵关闭过程中由于排量的变化,井筒内的流体流量和压力都会产生一定的波动,势必影响井筒压力安全和环空井壁稳定,因此研究固井泵关闭过程中的井筒流体流动特性十分重要。本文针对该过程中排量瞬时变化导致流体排量和压力波动的问题,将井筒内的流体流动看作一元流体,将管柱看作线弹性体,考虑钻井液与套管的弹性,建立了井筒流体流动控制方程,研究确定了求解方法与边界条件,并开发了相应的计算分析软件。基于实例计算分析了固井泵关闭过程中的井筒流体流动特性。研究结果表明,固井泵瞬时关闭会对井筒压力和环空流量产生不容忽视的波动影响,而随着关泵时间的延长、井深的增大,波动幅度逐渐减小。因此为了保证固井施工安全和防止回流导致水泥浆掺混,优化关泵方式十分重要。本文研究成果也将对于保障固井施工安全和提高固井质量具有一定的指导意义。

In the cementing process of narrow density window formation,the fluid flow and pressure in the wellbore will produce certain fluctuations due to the change of displacement during the closure of cementing pump,which will inevitably affect the safety of well pressure and the stability of annular wall.Therefore,it is very important to study the flow characteristics of well fluid during the closure of cementing pump.In this paper,aiming at the problem of fluid displacement and pressure fluctuations caused by the instantaneous change of displacement in this process,the fluid flow in the wellbore is regarded as a univariate fluid,and the pipe string is regarded as a linear elastomer.Only considering the elasticity of drilling fluid and casing,the well fluid flow control equation is established,the solving method and boundary conditions are determined,and the corresponding calculation and analysis software is developed.The flow characteristics of well fluid during the closure of cementing pump are calculated and analyzed based on an example.The results show that the instantaneous closure of cementing pump will produce fluctuations that cannot be ignored on the well pressure and annular flow,and the fluctuation range gradually decreases with the extension of the closure time.Therefore,in order to ensure the safety of cementing construction and prevent the mixing of cement slurry caused by backflow,it is very important to optimize the closure mode of cementing pump.The research results of this paper will also have certain guiding significance for optimizing cementing construction technology and improving cementing quality.