低压易漏深井大温差低密度水泥浆体系

针对塔中低压深井长封固段大温差固井面临的低密度水泥浆高温稳定性差、易漏失、返出井口后长时间无强度等固井技术难题，开展了密度 1.20~1.60 g/cm3大温差低密度水泥浆体系研究。从抗压、抗剪切性能、颗粒形态等方面对漂珠进行优选；基于颗粒级配原理，从提高水泥浆稳定性和抗压强度出发对减轻剂、填充剂、超细材料进行优选及合理组配，结合缓凝剂和降失水剂之间的协同作用，设计出一套长封固段大温差低密度水泥浆体系。实验结果表明:该低密度水泥浆体系流变性好，失水低，模拟工况条件下，水泥浆上下密度差小于 0.02 g/cm3,稠化时间和强度发展满足施工要求，能满足温差 70~120 ℃、一次性封固 6 000 m左右的固井需要。

Temperature stable low density slurry for low pressure loss deep wells

To solve the cementing difficulty that the low density slurry has poor temperature stability and loss issues,and has no strength during a long period after the flowback,faced by the situation of low pressure deep well inTazhong area cementing long vertical section with big temperature difference,it is studied that the temperature stable of low density slurry with density of 1.20~1.60 g/cm3.The floating potential is optimized from the aspects of pressure and shearing resistance and grain morphology.Based on grain composition principle,the light weight additive,filling agent,and superfine material are screened and matched,in view of improving slurry stability and pressure strength.Combining with the synergetic effect between retarder and filtrate reducer,a type of temperature stable low density slurry for long cementing sections is obtained.The results show that the slurry system has good rheology and low loss,and the density difference in the wellbore is lower than 0.02 g/cm3.The thickening time and strength increase satisfy with operation demand,especially the cementing need of temperature difference of 70~120 ℃ and cementing length of 6 000 m with one run.