深水多梯度钻井过滤分离器结构设计与关键参数计算

Structural design and calculation analysis of key parameters of filter separator during multi-gradient drilling in deep water

为了提升注空心球多梯度钻井中井下分离器的分离效率,设计可以实现高效分离的过滤分离器。首先针对过滤分离器的过滤结构,建立相应的几何模型,进一步推导分离口直径与最小通道尺寸之间的数学关系;其次,针对过滤结构的内部流场,利用数值模拟研究分离口处的喷射速度与负压随注入速度的变化;然后,将多孔介质模型与多相流模型相耦合的数值模拟与室内试验相结合,研究空心球在不同条件下的分离规律;最后,推导分离口处的混合流体进入环空时所产生的压力波动数学模型,并通过钻井数据进行计算分析。结果表明:过滤分离器的分离效率随排量和空心球体积分数的增加而增加,最高可以达到98%;分离口处所占的分流比为5.7%,对钻井液排量的影响有限。

In order to improve the separation efficiency of downhole separator for multi-gradient drilling using hollow glass spheres(HGS)injection method,a filter separator that can achieve high-efficiency separation was designed and investigated.A geometric model was established based on the filter structure of the filter separator,and the correlation between the diameter of the separation port and the minimum size of the channel was further derived.For the internal flow inside the filter structure,numerical simulation was conducted to study the jet velocity and negative pressure variation with the injection velocity at the separation port.The numerical simulation coupled with the porous media model and the multiphase flow model was combined with the laboratory experiments to study the separation efficiency of the HGS under different conditions.A model to calculate the pressure fluctuation when the mixed fluid entering annulus from the separator port was also derived based on the drilling data.The results show that the separation efficiency of the filter separator increases with the improvement of the pump flow rate and the HGS volume fraction,in which a high value of 98%can be achieved.The split ratio at the separation port is 5.7%,which has a limited impact on the pump flow rate.