For the cementing of extended‐reach well ,it’s easy to form free fluid channel in the upper annulus during the coagulation of solid slurry .At the same time due to the effect of gravi‐ty ,upper and lower sides of the annular are easy to form the density difference ,which leads low cement strength and high permeability of the upper annular with interporosity flow .This serious‐ly affects cementing quality and subsequent operations to increase production .A latex cement formula with zero drainage ,low water loss ,high compressive strength over 21 MPa for 24 h and permeability below 0 .001 × 10 -3 μm2 was designed by using novel latex BCT‐800L .Triaxial rock mechanics test system and SEM were used to analyze the mechanical deformation behavior ,and micro‐structure of the latex cement .The experimental results and preliminary mechanism analy‐sis showed that the latex could improve the stability of cementing fluid and mechanics perform‐ance of cement ,decrease the density difference in upper and lower sides of the annular ,reduce the permeability of cement by changing the particle retardant migration and polymer filming ,and prevent fluid channeling through cementing transformation .%大位移井固井水泥浆凝固时易在环空上侧形成游离液通道，同时，由于重力作用，环空上下侧容易形成密度差，使得环空上侧形成的水泥石强度低、渗透率高，极易破碎而引发窜流，严重影响固井质量以及后续增产作业。采用新型胶乳BCT‐800L ，设计了一种零析水，低失水，24 h抗压强度大于21 M Pa ，渗透率低于0．001×10－3μm2的胶乳水泥配方，并利用三轴岩石力学测试系统和环境扫描电子显微镜，分析了大位移井水泥石的力学形变行为以及微观形貌。实验结果和初步机理分析发现，胶乳通过胶结方式转变，运移阻滞和高分子网架成膜等机理有效提高大位移井固井液的稳定性，减小水泥环上下侧差异，降低水泥石渗透率，提高水泥石的韧性，有效防止油气、水窜的发生。
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