球形超细矿粉改善水泥浆性能的研究与应用

常规超细矿物材料在改善水泥粉体紧密堆积度的同时，存在水泥浆需水量增大，对提高水泥石的密实度和抗压强度作用不明显等问题。针对该问题，利用特殊球磨工艺开发了一种正球形超细矿粉材料，系统研究了其对水泥粉体颗粒堆积率，水泥浆流变性，水泥石抗压强度的改善作用。研究结果表明，该矿粉材料能够实现水泥粉体材料紧密堆积，不改变水泥浆需水量，流动性达到21 cm，提高水泥石抗压强度15%以上，有害孔体积小于4%，对水泥石起到良好地填充密实作用，改善了孔结构，增强效果明显。同时水泥浆密度在1.89～2.35 g/cm3范围可调，具有良好的防窜、低失水、稳定和流变性等综合性能，在川渝地区的超深井中成功应用，效果明显。 

Study on Improving the Performance of Cement Slurry with Spherical Ultra-fine Mineral and the Application Thereof

Conventional ultra-fine minerals are used to improve the degree of density of cement powders. The use of these ultra-fine minerals, however, leads to increase in the amount of water required, and the results in enhancing the degree of density and compressive strength of the set cement are not as good as expected. To resolve these problems, a new spherical ultra-fine mineral was prepared using special ball milling technique. Improvement made to the packing of cement powders, rheology of cement slurry and compressive strength of set cement with the use of the spherical ultra-fine mineral was studied. It was found that use this new spherical ultra-fine mineral, close packing of cement powders can be realized, and the amount of water used to mix cement slurry remained almost unchanged. The mobility of the cement slurry reached 21 cm. The compressive strength of the set cement was increased by at least 15%. The percentage of poor volume in the set cement was less than 4%. These data show that the spherical ultra-fine mineral filled the pores in the set cement very well, and improved the pore structure of the set cement, remarkably enhancing the degree of density of the set cement. The cement slurry has density that is adjustable between 1.89 g/cm3 and 2.35 g/cm3, and has anti-channeling ability, low filtration rate and stable rheology. Good and obvious effects have been gained in using the spherical ultra-fine mineral on ultra-deep wells drilled in Chuanyu area.