Fahliyan Formation, the main target zone in the Block Y, is a permeable limestone formation with developed porosity, small amount of micro-fractures and high permeability. High pressure and low pressure layers are coexisting in the same formation with high pressure existing in the upper part of that formation. Pipe sticking is easy to happen under high differential pressures. To solve these problems, a drilling fluid with high lubricity and high plugging capacity was developed based on the analysis of the characteristics of the Fahliyan Formation and the mechanism of pipe sticking. The lubricity of the drilling fluid came from a high performance vegetable oil lubricant developed. Laboratory studies showed that at 25 ℃, 6% bentonite slurry treated with 1% vegetable oil lubricant, had its extreme pressure friction coefficient and adhesion coefficient reduced by 88.57% and 86.67%, respectively. The treatment of the bentonite slurry with a nonionic surfactant tween-80 and a Gemini surfactant C12-2-12 enhanced the high temperature stability of the bentonite slurry to 170 ℃. A lubricating drilling fluid was formulated with these additives and a plugging agent. This drilling fluid had mud cake friction coefficient that was less than 0.05, extreme pressure friction coefficient less than 0.2, and effectively functioned at 170 ℃. The application of this drilling fluid, together with a set of appropriate engineering measures in 9 wells (penetrating the Fahliyan Formation) proved successful. No pipe sticking accident occurred during drilling, ensuring the success of the drilling operation.%国外Y区块主力油层为Fahliyan地层,属于渗透性灰岩地层,以孔隙为主,含少量微裂缝,地层渗透率强,而且属于高、低压同层,上部地层压力高,在较大的压差作用下极易发生压差卡钻现象.在分析Fahliyan地层特点及卡钻机理的基础上,提出了"高效润滑、强化封堵"的解决思路,研制了高性能的植物油润滑剂,并建立了润滑防卡钻井液体系.研究表明:在25℃时,在6%膨润土浆中加入1%的植物油润滑剂,体系的极压润滑系数降低率和黏附系数降低率分别达到88.57%和86.67%,而且在体系中引入非离子表面活性剂Tween 80和双子表面活性剂C12-2-12的混合物作为高温保护剂,将其抗温能力提高至170℃;以植物油润滑剂和封堵材料为基础,建立了润滑防卡钻井液体系,该体系泥饼摩阻系数小于0.05,极压润滑系数小于0.1.该区块的9口井使用该润滑防卡钻井液体系钻Fahliyan地层后,均无卡钻事故发生,确保了现场施工的顺利进行,取得了良好的应用效果.
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