Introduction To Tubulars Page 09 Of 10

TUBULARS The Heavy Weight Using Heavy-Weight Drill Pipe for Bit Weight on Small Rigs Hevi-Wate drill pipe, run in compression for bit weight, can reduce the hook load of the drill stem, making it ideal for smaller rigs drilling deeper holes. Hevi-Wate drill pipe should not be used for bit weight in vertical holes larger than those listed below: · 5 in. Hevi-Wate pipe — maximum vertical hole 101/16 in. ·41/2 in. Hevi-Wate pipe — maximum vertical hole 91/16 in. · 4 in. Hevi-Wate pipe — maximum vertical hole 81/8 in. ·31/2 in. Hevi-Wate pipe — maximum vertical hole 7 in.

Using Heavy Weight Drill Pipe in the transition zone between drill collars and drillipe. Many drill pipe failures occur in the drill stem because of fatigue damage previously accumulated when the failed joint of pipe was run directly above the drill collars. This accelerated fatigue damage is attributed to the bending stress concentration in the limber drill pipe rotating next to the stiff drill collars.

Hevi-Wate drill pipe is an intermediate-weight drill stem member, with a tube wall approximately 1 in. (25.4 mm) thick. This compares to approximately 3/8 in. (9.5 mm) wall thickness for regular drill pipe and approximately 2 in. (50.8 mm) wall thickness for drill collars. Hevi-Wate drill pipe provides a graduated change in stiffness between the limber drill pipe above and the rigid drill collars below. This graduated change in stiffness reduces the likelihood of drill pipe fatigue failures when Hevi-Wate drill pipe is run in the critical transition “zone of destruction.”

Using Heavy Weight in Directional Drilling Excessive drill collar connection failures result from collars bending as they rotate through doglegs and hole angle changes. Rotating big, stiff collars through doglegs, developed in directional drilling, can cause very high-rotating torque and excessive bending loads at the threaded connections. Hevi-Wate drill pipe bends primarily in the tube. This reduces the likelihood of tool joint fatigue failures occurring in the Hevi-Wate drill pipe as it rotates through doglegs and hole angle changes. Hevi-Wate drill pipe design offers less wall contact area between the pipe and hole wall which results in: •· Less rotary torque. •· Less chance of differential sticking. •· Less vertical drag. •· Better directional control.