为满足环境敏感性海域高温深井钻井作业和环境保护要求,研究了抗温200℃,生物毒性值LC50大于10×104mg/L的高性能抗高温聚合物钻井液,其以合成聚合物为主要处理剂,辅以优选出的纳米封堵剂、页岩抑制剂和极压润滑剂,该体系具有了油基钻井液抑制泥页岩水化的分散性能和润滑性能,对环境友好,可直接排海.实验表明,分别以重晶石和甲酸盐为加重剂,该抗高温聚合物海水基钻井液体系在200℃高温热稳定时间长达48 h以上,高温高压滤失量为12～25mL,抗20％氯化钠和0.5％氯化钙污染,生物毒性卤虫96 h半致死浓度LC50大于10×104 mg/L,发光细菌半数有效浓度EC50大于30×104 mg/L,符合一级海区生物毒性排放要求.在环渤海油田进行了现场应用,取得了良好的试验效果,试验最深井深6 066 m,最高井底温度204℃.%Laboratory study has been conducted on a high performance high temperature (up to 200 ℃) polymer drilling fluid which was to be used in high temperature deep well drilling in environmentally sensitive offshore area.The drilling fluid under investigation has LC50 of greater than 10× 104 mg/L,and was formulated with a synthetic polymer as the main additive,and auxiliary additives such as nanophase plugging agent,shale inhibitive agent and extreme pressure lubricant etc.,which rendered the drilling fluid shale inhibitive capacity and lubricity matching those of oil base drilling fluids.The drilling fluid formulation is environmentally friendly and can be discharged directly into the sea.The experimental results showed that the high temperature seawater drilling fluid,formulated with barite and formates was stable for more than 48 h at 200 ℃,and had HTHP filter loss of 12-25 mL.It was resistant to the contamination caused by 20％ NaC1 and 0.5％ CaC12.96 h LC50 of brine shrimp by the drilling fluid was greater than 10× 104 mg/L.EC50 of lnminescent bacteria was greater than 30×104 mg/L.The LC50 and the EC50 values indicate that the toxicity of the drilling fluid conforms to the bio-toxicity requirements of discharging the drilling fluid to Class Ⅰ sea area.The application of the drilling fluid in oilfields around the Bohai Sea has gained good results;the deepest wells drilled with the drilling fluid was 6,066 m,and the highest bottom hole temperature was 204 ℃.
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