硅酸盐钻井液的抑制性及其影响因素的研究

Studies on the Inhibitive Character and Its Influence Factors of Silicate Drilling Fluid

硅酸盐钻井液具有良好的井壁稳定作用,且无毒、无荧光、成本低,被认为是具有发展前景的水基钻井 液之一。着重研究和探讨了硅酸盐的抑制能力、影响因素及稳定井壁的机理。研究表明,硅酸盐具有较强的抑制能 力,抑制效果明显地优于KCl、CaCl2等无机盐类;硅酸盐的模数、加量和钻井液的pH值是影响硅酸盐抑制能力的 主要因素;钻井液中硅酸钠的模数为2．8～3．0,加量为3％～4％,且钻井液的pH值维持在11以上时,硅酸钠的抑 制效果更好;硅酸盐能与无机盐和聚醇类产生协同作用,从而提高硅酸盐的抑制能力。硅酸盐稳定井壁的机理:硅酸 盐与地层矿物反应生成沉淀封堵地层微小裂缝和孔隙,改善和提高了泥页岩的半透膜效率;抑制粘土水化膨胀和分 散;降低地层孔隙中压力传递速度;与地层中粘土矿物发生反应。

As an effective wellbore stabilizer, silicate drilling fluid is one of the promising water-based fluids thanks to its characters of non-toxicity, non fluorescence and lower cost. This paper mainly dese/ibes the inhibitive ability and factors affecting this ability as well as the wellbore stability mechanisms of the sodium silicate drilling fluids. The results indicate that the inhibitive ability of silicate is much better than that of other inorganic salts, such as KCl, CaCl2 etc. ; the silicate ratio, pH and dosage are the main factors affecting inhibitive ability of sodium silicate; the best inhibitive ability of sodium silicate could be obtained when the sodium silicate ratio is 2.8-3.0, the dosage is 3%-4% and the value of pH of drilling fluids is kept above 11; the coordinated action of sodium silicate with inorganic salts and polyglyeol can improve inhibitive ability of sodium silicate. Wellbore stability mechanisms of the sodium silicate drilling fluids is that silicate can improve the clay semi-membrane efficiency by means of blocking the micro-fracture and pore of formation by precipitation due to the interaction of silicate and clay minerals, prevent clay from swelling and dispersing, reduce the pressure transmission rate, and react with clay minerals.