The purpose of perforation is penetrating the casing tube, cement sheath and a certain depth of the formation and forming unhindered channels for oil and gas flowing into the well casing.
射孔目的就是射穿套管、水泥环和地层内一定的深度，为地层的油气流入至井筒，形成一个顺畅的通道。
2
RF coaxial cable with gas expanded, PE insulation and aluminium tube sheath is mainly used in cable TV system as trunk and distrubution transmission lines.
铝管外导体物理发泡射频同轴电缆主要用于有线电视系统中作干线、配线传输线。
3
The yield of a natural gas well in an oilfield dropped suddenly, which was due to the piston sheath of the choke valve breaking into three parts with two pairs of fractures after inspection.