井下双级串联式油水分离器工作特性研究

Research on Operating Characteristic of Downhole Dual-stage Tandem Oil-water Separator

井下双级串联式油水分离器的工作特性对于井下油水分离系统的工况诊断及调节必不可少。基于代数滑移混合物模型（Algebraic slip mixture model，ASMM）和大涡模拟（Large eddy simulation，LES）模型，针对T228井井况设置相关参数及边界条件，研究井下双级串联式油水分离器的分流特性和分离特性，并与地面试验结果对比。结果表明，入口流量为80～200 m3·d-1时，总分流比的范围随着入口流量的增大而增大，一、二级水力旋流器的溢流口流量之比与总分流比的变化关系是确定的函数关系，底流含油质量分数随着总分流比的增大先减小后增大；额定工况下，第一级水力旋流器起主要分离作用，第二级对于进一步降低底流含油质量分数起关键作用；入口流量和总分流比的组合为（120～140 m3·d-1/0.36～0.74）、（140～160 m3·d-1/0.31～0.77）或（160～180 m3·d-1/0.33～0.76）时，底流含油质量分数不大于0.02%；数值模拟预测的分流特性与试验结果一致，预测的总分流比和底流含油质量分数的关系与试验结果定性一致。通过综合分析分流特性和分离特性，得出进行井下工况调节时入口流量和总分流比的合理范围，为现场试验提供指导。

The operating characteristic of down dual-stage tandem oil-water separator is essential for the condition diagnosis and adjustment of downhole oil-water separation system. Based on algebraic slip mixture model（ASMM） and large eddy simulation（LES）, related parameters and boundary conditions are set according to T228 well status to research the split and separation characteristics of down dual-stage tandem oil-water separator. And the numerical simulation results compared with the ground text results. The results show that：When the inlet flow rate is between 80 m3·d-1 and 200 m3·d-1, the range of total split ratio become larger and larger, and the variation relationship between the ratio of the first and second hydrocyclones’ overflow and the total split ratio is deterministic function, and the oil mass fraction of underflow decreases firstly and then increases with the increasing total split ratio; under the rated condition, the first hydrocyclone separates most of the oil and the second one plays a key role in further reducing the oil mass fraction of underflow; when the combinations of inlet flow rate and total split ratio are （120-140 m3·d-1/0.36-0.74）, （140-160 m3·d-1/0.31-0.77） or （160-180 m3·d-1/0.33-0.76）, the oil mass fraction of underflow is not more than 0.02%;the split characteristic predicted by numerical simulation is consistent with ground text result, while the relationship between the total split ratio and the oil mass fraction of underflow predicted by it is qualitatively consistent with ground text result. The reasonable ranges of inlet flow rate and total split ratio for the adjustment of downhole operating conditions are given through the comprehensive analysis of split and separation characteristics. It will provide guidance for field text.