深部泥页岩水化特性研究

石油工程深部泥页岩吸水量很小,但也易产生严重水化井塌。室内用X衍射仪分析深部泥页岩黏土矿物成分构成主体为伊蒙混层。常温压浸泡泥页岩块,蒸馏水浸泡后岩块强度迅速降低甚至破碎,饱和KCl溶液浸泡强度降低30%~40%,K+向岩块内部运移防止黏土矿物水化。扫描电镜观察深部泥页岩分布大量不规则微米级孔缝,自由水分子在毛管力作用下进入岩体内部,黏土胶结物溶解强度下降及高强度缝尖应力导致岩石微裂缝不断扩展发生破坏。现场钻井宜使用K+抑制黏土矿物水化,钻具提放及停开泵应平缓防止损伤井壁泥页岩体。

Hydration Properties Research of Deep Formation Shale

The water absorption amount of deep formation shale in petroleum industry is very low, however sever wellbore caving may occur as hydration. The mainly components of deep formation shale are illite-smectite mixed layer by X-ray crystallographic analysis. Shale blocks were immersed in different solution at ambient environment. The strength of blocks in distilled water decreased rapidly and that in saturated KCl solution decreased by about 30%-40%. K migrated into the blocks and prevented clay minerals hydration. A large number of irregular micron-size aperture are distributed in shale detected by SEM. Free water molecules are draw into rock by capillary force. The failures of rock due to rock strength decrease as hydration and crack tip stress. Drilling fluid should use K to inhibit clay hydration, drill tool lifting putting and pump restart should be gently to prevent damage the shale rock.