Research on Mechanism of Casing Wear in Sliding-Impact Wear Condition

Casing wear already becomes one key technological problem in the west and offshore oilfield in China. The severe casing wear in the deep and ultra-deep well drilling in these area, usually takes place in the deep of well where the lateral pressure on the casing inner surface seems to be lower, sometimes even the dog-leg severity was very small. Many investigators considered that the lateral vibration of the drilling pipe is the main reason which brings serious casing wear in the section of drilling pipe under the neutral point. Indoor impact-sliding tests show that fatigue wear is one of the main wear types of casing on impact-sliding condition. Higher frequency and impact load are, more serious fatigue wear is. Field monitoring shows that chips, adhesive and fatigue wear are main wear mechanism of casing in deep and ultra-deep well drilling process. If wellbore quality is bad, adhesive wear and chips wear caused easily in drilling process. And if the wellbore quality is good, there are rather less stable contact points between casing and tooljoint, vibration energy of drilling pipe abates rather slowly, influence of lateral vibration has become more prominent and fatigue wear become main wear mechanism.