EXCAVATION METHOD OF WELL, AND DRILL PIPE AND TOOL JOINT USED IN EXCAVATION METHOD

摘要

PROBLEM TO BE SOLVED: To provide an excavation method of a well capable of suppressing abrasion in the inner surface of a casing.SOLUTION: An excavation method comprises the steps of inserting a casing formed by connecting a plurality of steel pipes into a well and performing inclined excavation by inserting a drill string having a plurality of drill pipes and a tubular tool joint 7 connecting end parts of the drill pipes with each other into the casing. The respective surface of the drill pipes and/or the tool joint 7 has a steel coating film 10 in which the total content of Cr and Ni is, by mass%, 1% or less (including 0%).SELECTED DRAWING: Figure 4