务古4井复杂深井钻井液技术

务古4井为一口重点探井，完钻井深5 750 m。该井二开裸眼井段钻遇巨厚层泥岩，选用聚磺钻井液体系，解决了地层严重造浆及井眼稳定问题；三开裸眼井段存在多套压力系统和多处断层，钻遇石膏、含膏泥岩、大套玄武岩以及凝灰岩和碳质泥岩等地层，特别容易发生坍塌和井漏，井壁极为不稳定。现场采用有机盐钻井液体系，有效解决了石膏、膏泥岩污染和严重井壁垮塌导致的大段划眼、严重蹩钻及遇阻卡等复杂问题；添加低渗透处理剂和屏蔽暂堵剂及复合堵漏剂，提高井壁的承压能力，解决了三开施工出现的压差卡钻风险，确保了钻井安全顺利，完井电测一次成功，钻井周期大幅度降低。

Complex deep well drilling fluid technology for Well Wugu-4

Well Wugu-4 is a key exploration well with total depth of 5750m. During drilling the 2nd interval open hole, thick mudstone was penetrated. Polysulfonate drilling fluid was taken to solve the serious mud-making and wellbore stability issues. For the 3rd interval, multiple pressure system and faults were encountered, and plaster, plaster mudstone, huge basalt, tuff, and blacks were penetrated, which makes it prone to collapse, leaking and wellbore instability. Organic salt drilling fluid was taken to slove the issues of reaming down, bit bouncing, bit sticking, etc. The low permeability additive, temporary blocking agent, and sealing agents were added to improve wellbore pressure bearing ability. The risk of bit sticking from pressure difference during the 3rd interval drilling was solved and drilling safety was ensured. The completion logging was successful with only one run, and the drilling cycle was decreased significantly.