There are certain technical difficulties in tripping the down-hole instruments easily through the tubing-casing annulus.Several kinds of eccentric tubing hangers can resolve these problems.

• 在环空测试技术中,可转动偏心井口是一关键设备,它解决了在抽油井油、套管环形空间顺利起下下井仪器的多项技术难题。