Research Of Friction And Wear Between Drill Pipe And Casing

Wear reduces the load bearing capacity of casing, which is of significant influence to the following well drilling, the well completion, the production, the repair of well. On the base of analyzing casing wear mechanism, the wear testing machine has been developed, which could simulate practical drilling operating condition. The general rule and primary factors of casing wear have been discovered though testing analysis. In the case of loading,temperature and time being invariable, the wear volume and rotary speed are linear relativity. The influence of loading is important to wear between the drilling pipe and the casing. If the loading were increased, which could cause vibration intensified and wearing accelerated. If loading being reasonable, which would reduce friction coefficient and wearing. It is found that water-base mud with high viscosity can effectively reduce the casing wear. Temperature is of little influence on wear while temperature is lower 60℃. At last, the forecast equation for drill pipe and the casing wear was established.The influence of wear to residual collapsing strength and fracture strength of casing was analyzed by finite element software, and compared with others methods. It is linear relation between residual collapsing strength of casing worn and wear radius. And if wear radius was smaller, residual collapsing strength were higher. It is exponential relation between residual collapsing strength of casing worn and wear loss, and more wear loss less residual collapsing strength. The influence of biggish axial loading to residual collapsing strength of casing worn is obvious. The axial compressed stress increases collapsing strength of casing and the axial tensile stress reduces collapsing strength of casing. Using analytic method and finite element measure to compute circumferential stress distribution of crescent casing worn. The wear model is uniform wear model approximate, the local bend of casing worn can increase circumferential stressand reduce fracture strength of casing.Under different operating condition, summarized the influence of wear to the drill pipe tensile and bend performance. The reformative advice is put forward to reduce wear. It provides proof for drill tools optimization and drilling parameter selection.