砂岩地层井壁稳定性分析

 南海某油田深部地层砂岩存在因蠕变导致的缩径现象，有必要分析该油田砂岩地层蠕变性质，为砂岩地层安全钻井提供借鉴。使用某油田深部地层砂岩岩心进行室内蠕变实验，测定不同差应力下岩心蠕变率。使用西原模型拟合了实验结果，拟合精度较高，并计算了某油田砂岩缩径井段安全钻井周期。计算结果表明，提高钻井液密度可大幅提高安全钻井周期，也可采用定期起下钻、下套管封固缩径井段等工程措施阻止或减缓砂岩蠕变。

Wellbore Stability of Sandstone Formation

The creep happens in the deep sandstone formation of an oilfield in South China Sea. It is necessary to analyze the sandstone creep behavior to ensure the safety drilling in the field. Creep experiments were carried out with sandstone cores from the field, and creep rates under different differential stress were determined. The experimental data were treated by regression based on the Xiyuan model with a high regression accuracy. The creep rate of the oilfield sandstone based on the Xiyuan model shows that an improving drilling fluid density can greatly improve the safety drilling cycle. The regular tripping and casing and cementing shrinkage hole can also be used to prevent the sandstone creep.