F19井沥青侵及相关井下复杂情况的处理

F19井212.7 mm井眼裸眼段长达2 445 m。与邻井相比,地层压力系统发生了明显的变化,高压沥青、盐水层与多个低压薄弱层共存,钻井液安全密度窗口窄。钻井过程中先后发生了沥青侵、井漏和盐水侵等一系列井下复杂情况。稠油沥青严重威胁着钻井安全,破坏钻井液流变性能,污染严重时钻井液呈现胶凝状,无法循环利用。在室内实验的基础上,应用混柴油钻井液预防和处理稠油沥青侵及问题;同时针对严重的井漏,优选出了桥塞堵漏和固结型堵漏2种堵漏浆配方。为保证尾管下到底,从钻井液、悬挂工具、操作等多方面制订了具体措施和应急预案。下尾管作业中,尽管多次出现阻卡和失返等异常情况,但由于措施和预案有针对性,可操作性强,最终成功实现尾管"坐底",挤水泥固井。

Treatments for bitumen contamination and associated downhole problems in Well F19

Well F19 has 212.7 mm openhole section of 2 445 m. Its formation pressure system is obviously different from adjacent wells,coexisting with high pressure bitumen formation,salt water layer,and thief zones. The safe density window of drilling fluid is narrow for the well. During drilling operations,some downhole problems such as bitumen contamination,lost circulation and salt water contamination have been experienced. Bitumen poses a great threat to drilling safety,and damages the rheological property of drilling fluids. Drilling fluids may become jelly and can not be recycled when seriously contaminated. On the basis of lab experiments,diesel-mixed drilling fluids have been used to prevent and treat bitumen contamination. For lost circulation,two slurry formulations have been optimized,which are bridge plug and solidification plug. Concrete measures and contingency plan have been worked out in regards to drilling fluids,hanging tools and operations to ensure liner running to bottom hole. Some abnormal situations such as sticking and mud loss had happened during liner running,but finally the liner was successfully set to the bottom hole and the well was cemented thanks to the proper measures and contingency plan.