-bedded;bedding
-bedded;bedding-
The lower formation is mainly smectite mixed layer , bedded with mature bedding shale , and the uneven expansion of smectite mixed layer and degradation of shale often cause accidents such as hole collapse , hole shrinkage and pipe sticking .
下部地层主要为伊蒙混层且夹杂层理发育的泥页岩，伊蒙混层的不均匀膨胀及泥页岩的剥蚀掉块，使该井极易发生井壁垮塌掉块、缩径、卡钻等复杂事故。