SCREW JOINT FOR OIL WELL PIPE

摘要

A screw joint for an oil well pipe is equipped with either one, or both, of an inner surface shoulder portion and an outer surface shoulder portion comprising a seal portion and a torque shoulder portion, and satisfies further the following conditions 1 and 2:1) effective diameter of seal formation surface before fastening is greater on the pin side than on the box side; and 2) inclination of torque shoulder formation surface is smaller on the pin side than on the box side, and difference DELTAθof the inclinations is at least 0.50 and not greater than 4.0 DEG . The screw joint for the oil well pipe of this invention is excellent in gas sealability and clearance corrosion resistance. The production cost is equal to that of conventional screw joints, and handling is easy, too. This screw joint is extremely suitable for probing and mining of burried matters at a depth and at a higher pressure and burried matters containing high corrosive impurities such as gases and crude oils.