东海大位移井钻井井漏特征分析及风险识别

Analysis of lost circulation characteristics and risk identification of large displacement well in East China Sea

东海西湖油气田岩性复杂、断裂发育,深部平湖组地层孔隙压力高,安全泥浆密度窗口窄,钻井过程中易发生漏失,导致伴生复杂情况频发并延长了钻井周期,甚至造成井眼报废,严重制约了西湖油气田滚动扩储增产进程,特别是大位移井的钻进过程中,井眼轨迹难以避免穿越断层、破碎带等复杂地层,漏失现象更加频繁。西湖油气田主要存在4种漏失类型:高地层压力导致的窄压力窗口漏失、断层裂缝性漏失、高渗透砂岩渗漏、衰竭压力地层漏失,其中大位移井漏失以断层裂缝性漏失和衰竭压力地层漏失为主。综合考虑区域地球物理响应特征和漏失特点,基于叠后三维地震与测井数据综合评估,采用井震融合技术,形成了一种多因素控制的东海大位移井井漏风险预测评价方法,该方法可以预测井漏风险等级,为钻井过程中的防漏和堵漏工作提供技术参数和支持。

The lithology of Xihu oil and gas field in the East China Sea is complex,with well-developed faults and high pore pressure in the deep Pinghu Formation.The safe mud density window is narrow and lost circulation is easily to occur,resulting in frequent associated complications and prolonged drilling cycle,and even resulting in hole abandonment,which seriously restricted the rolling expansion and production process of Xihu oil and gas field.Especially in the drilling process of large displacement wells,the wellbore trajectory is difficult to avoid crossing complex formations such as faults and fractured zones,resulting in more frequent leakage phenomena.There are four main types of leakage in Xihu oil and gas field:narrow pressure window leakage caused by high formation pressure,fault fracture leakage,high permeability sandstone leakage,and depleted pressure formation leakage.Among them,the leakage of large displacement wells is mainly caused by fault fracture leakage and depleted pressure formation leakage.Taking into account the regional geophysical response and leakage characteristics,based on the evaluation of post stack 3D seismic and logging data,combined with well-seismic fusion technology,a multi factor controlled East China Sea large displacement well leakage risk prediction and evaluation method has been developed.This method can predict the level of well leakage risk and provide technical parameters and support for leak prevention and plugging work during drilling process.