The influence of clay, mudstone and shale layer: It is easy to absorb the free water in the mud and expand, which will reduce the diameter of the well, causing the drill to encounter the resistance, even the stuck drill. As the soaking time is prolonged, the block will be peeled off and the well will be The diameter is enlarged, causing the well to collapse. Water should be used as much as possible in low water or low viscosity mud. Carbon shale has weak coupling and is easy to collapse. The argillaceous rock is soft and has a fast drilling speed and is also easy to pack.

Sandstone: Its properties vary greatly depending on the size of the particles, the composition, and the cement. The finer the particles, the more quartz particles, the harder the siliceous and iron cements, the harder the bit wear, such as quartz sandstone; the more muddy cement, the more components of mica and feldspar are softer. Easy to drill; the coarser the particles, the less the cement, the better the permeability, the leakage of the mud is easy to occur, and the thick mud cake is formed on the well wall, causing complicated conditions such as stuck stuck, resulting in the bit of the bit. Normal use.

Conglomerate: drilling in the conglomerate layer is prone to jump drilling, boring and wall collapse; when the pump displacement is small or the mud viscosity is low, the gravel particles are not easy to return, and the bit body and teeth of the drill bit are damaged.

Limestone: generally hard, slow drilling speed and less footage. Some have seams and caves. When drilling a seam, it will cause boring, venting, mud loss, etc. Sometimes a blowout will occur after a leak.

Limestone formations have a significant impact on drill footage, ROP and bit failure. In addition, the local layer is soft and hard, such as mudstone and hard sandstone, which is easy to produce well inclination; when the ground angle is large, it is easy to produce well deviation. Drilling in a deviated well can cause damage. When the rock layer contains soluble salts, such as gypsum layer and rock salt layer, it will destroy the performance of the mud and affect the normal use of the drill bit.