硅酸盐钻井液对泥页岩地层井眼稳定性影响研究

油基钻井液的使用对保护环境和降低成本造成了越来越大的压力，研制出一种具有油基钻井液特性而又没有环境污染的水基钻井液成为必然。室内实验验证了硅酸盐钻井液稳定泥页岩地层井壁的机理，当硅酸盐钻井液渗入泥页岩地层时，就会和泥页岩孔隙流体迅速作用，发生聚合和沉淀反应；由凝胶物和硅酸盐沉淀物形成的屏障和高选择性渗透膜系统将进一步阻止滤液侵入和压力渗透，对页岩中的裂缝和裂纹起封堵作用。对硅酸盐钻井液性能研究表明，其流变性可通过控制钻井液的pH值（不小于11）调节；现场硅酸盐加量最好不要超过5％；无论是加重前还是加重后，硅酸盐钻井液的常规性能均能满足钻井工程的一般要求；抗粘土污染能力强。在WZ12-1-7井的应用表明，硅酸盐钻井液在钻进过程中性能良好，钻井、下套管施工顺利。

Influence of Silicate Base Drilling Fluid on Wellbore Stability of Shale

It is inevitable to develop a water base drilling fluid with the characteristic of oil base drilling fluid while without environment contamination due to unfavorable environmental effects and high costs of oil base fluid.By experimental verification,the mechanism of silicate stabilizing wellbore of shale formation is as follows.The silicate can have the instant reaction of polymerization and precipitation with the pore fluid as soon as the silicate base fluid infiltrated into shale.The barrier formed by the gel and precipitation of silicate can further prevent the filtrate invasion and pressure permeation to seal fractures and cracks in shale.It can be seen from the performance evaluation that silicate base drilling fluid is characterized by high inhibitive and low cost and also is environmentally friendly.The favorable rheology of this drilling fluid can be controlled by pH and it can not be lower than 11 in the practical application.The practice in the well of WZ12-1-7 shows that the silicate drilling fluid is a qualified WBM for stabilizing shale and has preferable rheological properties,satisfactory performances and had not any trouble in drilling and casing.