欠平衡钻井随钻监测系统的开发及应用

Development and application of a monitoring-while-drilling system for underbalanced drilling

欠平衡钻井技术具有突出优点,因而得到了广泛应用,但欠平衡钻井条件下,施工设备、流程和钻井液体系等诸多变化常导致常规监测技术不能满足现场工作的要求。针对欠平衡钻井的特殊性,开发了一套适用于欠平衡钻井的随钻监测系统。该系统将地层和井筒看作一个系统,通过监测注入参数、返出参数和钻井工程参数,结合井筒多相流模型及地层渗流模型来对地面、井筒和地层进行综合监测与评价;通过对地层产出流体的监测,井筒压力及流态的监测,地层压力和孔隙度的监测,钻井安全、井控和有害气体的监测,实现了对欠平衡钻井状态下的包括流量、压力和气体组成等多参数的监测;结合地层渗流及井筒多相流耦合模型,可以实现对所钻井段井筒压力、地层压力、储层特性和流体特征进行全面监控与评价。通过在欠平衡钻井现场的多次实际应用,验证了该监测系统的合理性与实用性。该成果有助于提高欠平衡钻井的工艺水平和储层保护效果,同时还有利于早期识别和控制井下复杂情况。

The underbalanced drilling(UBD) technology has been widely applied because of its obvious advantages.Under the working condition of UBD,some traditional monitoring methods can not meet the requirements,due to the unexpected changes in operating equipment,procedures,and drilling fluid systems.Aiming at the particular working conditions,a monitoring-while-drilling system for UBD is developed,assuming the formation and the wellbore as a system.With the injection and return parameters,and the drilling parameters combined with the multiphase wellbore model and the formation seepage model,wellhead,wellbore,and formation can all be monitored and evaluated.With the information of the produced fluids,the wellbore pressure,the flow pattern,the formation pressure and porosity,and drilling safety,well control,and toxic gases,the UBD parameters of flow rate,pressure and gas composition can be monitored.Together with formation seepage and multi-phase coupled models,the hole pressure,the formation pressure,the reservoir properties and fluid features can be monitored and evaluated in the drilling process.This monitoring system has been proved to be reliable and practical in field practices and will be helpful not only in the UBD technology and reservoir protection but in downhole problems forecast so that the well can be put under control.