控压钻井井控过程中排量优化设计

控压钻井井控是处理气侵溢流问题的有效新方法,包括前期控制和循环排气两个阶段。基于快速施加井口回压控制方法,根据气液固多相流理论,建立控压钻井井控数学模型,并采用有限差分法迭代求解。在此基础上,分析排量对最大井口回压、最大套管鞋处压力和最大立管压力的影响,并提出基于井控安全目标函数的排量优化设计方法。模拟结果表明:在循环排气阶段,立管压力维持不变且为最大值,井口回压达到最大值与气体前沿运移到井口之间存在明显的时间滞后性,气体运移到套管鞋处时套管鞋处压力最大;验证了以出入口流量一致表征井底气侵停止的合理性。模型计算得到的压力值与实验测量值吻合较好。

Optimization of pumping rate for well control during managed pressure drilling

Well control via managed pressure drilling (MPD) is a new and effective method to deal with gas kicks and overflow problems, which includes two stages:initial control response and circulating out of gases. According to the gas-liquid-solid multiphase flow theory, a MPD well control model based on rapidly applying wellhead back pressure method was established, and a finite difference method was used to iteratively solve the model. The effects of pumping rate on the maximum wellhead back pressure, maximum casing shoe pressure and maximum standpipe pressure were analyzed using the model, and an optimized design method for the pumping rate as the objective function for well control safety was proposed. The simulation results show that, in the stage of gas circulating out, the standpipe pressure remains unchanged with its maximum value, and the peak value of the wellhead back pressure appears before the gas front migrates to the wellhead, while the maximum value of the casing shoe pressure appears when the gas front migrates to the casing shoe. The reasonability of using the consistence of outlet flow and inlet flow to indicate the stoppage of bottom hole influx can be verified using the model. The calculated pressure values using the model agree well with the experimental results.