水基硅酸盐钻井液的页岩井眼稳定性研究

结合室内实验数据,分析了硅酸盐钻井液粘土稳定作用的主要影响因素。结果表明,硅酸盐的模数在2.8—3.2、加量在3％—5％时钻井液抑制性能较好,无机盐与硅酸盐的协同效应提高了硅酸盐的抑制性能。提出硅酸盐稳定页岩井壁的机理为:硅酸盐形成凝肢与沉淀堵塞微裂缝与页岩孔隙,阻止滤液进入地层,减少压力穿透;抑制粘土矿物水化膨胀与分散;与无机盐协同作用阻止水进入地层;与粘土矿物反应导致渗透率降低等。

Study on wellbore stability in water based silicate drilling fluid

Silicate based drilling fluid is very popular for its wide application in deep wells and easy maintenance. This paper tries to explain its wellbore stability mechanism with analysis and tests. Results show that it achieves best shale inhibition when the modulus is between 2. 8-3. 2 and the dosage is in the range of 3% -5%. The wellbore stability mechanism can be concluded like this: sediments and gels produced plug the microfractures and pores of shale, thus prevent the invasion of filtrate into formation and inhibit clay hy-dration and dispersion; their combination with inorganic salts prevent the entrance of water into formation, and its interaction with clay minerals reduces the permeability, etc.