On the Casing Wear Mechanism in Deep and Ultra-Deep Well Drilling

Casing wear in the deep and ultra-deep well drilling is regarded as one of the most important technical problems in the petroleum exploration in the west of China. It is necessary to realize the casing wear mechanism for the solution of this problem. A tribo-system model for the deep section of the drilling-pipe and casing is presented based on log data and mechanics analysis in this paper. In the model the lateral vibration of the drilling-pipe is taken into account which can cause a great dynamic load on the casing. Then the tribological interaction relationships in this situation are built up. Moreover, the wear mechanism of impact-sliding contact surfaces between the casing and the tooljoints is revealed by combining theoretical analysis with the field monitoring tests. It is noticed that the surface contact fatique play a very importan role to speed up the casing wear. The results can provide guidance for actual wear prevention in the drilling engineering.