大位移钻井全井段岩屑动态运移规律

Transient cuttings transport laws through all sections of extended reach well

根据固液两相流理论,综合考虑岩屑的悬浮、滚动和滑动运移方式以及悬浮层固液相速度差和钻杆旋转的影响,建立大位移井全井段三层岩屑动态运移模型,用于模拟计算实际钻井中正常钻进和停钻循环的全部过程;基于有限体积法原理,引入SETS方法对模型进行数值求解,并进行模拟分析。结果表明:对于具有长斜井段的大位移井,环空岩屑床分布达到稳定状态需要很长时间,使用稳态模型计算环空岩屑床高度和压力会产生较大误差;排量对岩屑床形成速度影响较大,排量越小,环空达到稳定状态时形成的岩屑床越高,环空达到稳定所需时间越长;排量对岩屑床冲蚀速度影响较大,而初始岩屑床高度对完全清洗井眼所用时间影响不大。所建模型计算结果与试验回归模型计算结果吻合较好,从而验证了所建模型的正确性和广泛的适应性。

Based on the theory of solid-liquid flow,a three-layer transient cuttings transport model for all sections of extended well was developed,and the mechanisms of suspension,rolling and sliding of cuttings,the relative velocity between solid and liquid in suspension layer and the effect of drill pipe rotation were all taken into account.The model was used for calculating and stimulating all sections and processes on actual drilling and circulating conditions.The model was solved numerically by SETS method on the basis of the finite volume method theory,and some simulation cases using actual field data were made.The results show that it takes a long time to reach steady state for cutting bed transport because of long inclined wellbore of extended reach well,which leads to a big error by using steady models to calculate cuttings height and annular pressure.Pump rate has a great effect on the speed of cuttings bed formation,that is,the smaller pump rate,the higher steady cuttings bed height and the longer time to reach steady state is.Pump rate also has a deep effect on the speed of cuttings bed erosion,while the original cuttings bed height has little effect on the time of cleaning hole entirely.Finally the calculated results by this model agree well with the results of models obtained by experimental data,which indicates the validity and applicability of this model.