瞬时关井对屈曲管柱内压力波动的影响研究

Influence of instantaneous shut-in on the pressure fluctuation in a buckling string

当气井发生屈曲且程度较为严重时,油管轨迹复杂,继续使用直井内的流体瞬变模型求解关井后的压力波动问题误差太大,计算结果失去参考价值。该文章基于摄动法,建立了适用于屈曲管柱内流体的瞬变流动模型,并考虑了关阀时间、井口终止开度及油管屈曲程度等因素,分析计算了气井突然关井后压力及流速的变化情况。通过计算分析可知,当油管存在螺旋屈曲时,在屈曲部位会产生局部摩阻,压力波会被耗散掉,相比不发生螺旋屈曲的情况,井口压力较小。随着关阀时间的增加,井口压力峰值随之减小,且随着关阀时间的增加,压力变化曲线的规律性越来越不明显;关阀用时越大,井口速度减小得越缓慢,波动幅度和持续时间也相应降低。螺距越大,油管屈曲程度越小,管内流体受到的摩阻减小,井口压力越大。该模型的计算结果更贴近真实数据,对现场作业具有积极的指导意义。

When the gas well buckles seriously,the tubing trajectory is complex,so the error of using the transient model for the fluid in a vertical well to solve the pressure fluctuation after shut-in will be too large,and the calculation results lose the reference value.Based on the perturbation method,a transient flow model suitable for the fluid in the buckling string was established.Taking into account the valve closing time,wellhead end opening and tubing buckling degree,the changes of pressure and flow rate in the gas well after sudden shut-in were analyzed and calculated.According to the calculation and analysis,results,when the tubing has spiral buckling,the local friction will be generated at the buckling part,and the pressure wave will be dissipated.Compared with the case of no spiral buckling,the wellhead pressure is smaller.With the increase of valve closing time,the peak value of wellhead pressure decreases,and the regularity of pressure change curve becomes less and less obvious.With the increase of valve closing time,the wellhead speed decreases more slowly,and the fluctuation amplitude and duration also decrease correspondingly.When the end opening of the valve is 0,the fluctuation of wellhead pressure lasts for a long time.The larger the pitch is,the smaller the tubing buckling is,the smaller the friction of the fluid in the tubing is,and the higher the wellhead pressure is.The calculation results of the model are closer to the real data,which has a positive guiding significance for the field operation.