R D and Application of Φ149.2 mm Hi-torsion Drill Pipe for Ultra-deep Well

Described in the paper are the activities for the R & D of the Φ149.2 mm V150 hi-torsion drill pipe,and the details concerning relevant critical manufacturing techniques,the mechanical properties and application effectiveness of the product.To make the said drill pipe,the hi-strength and hi-toughness V150 steel pipe is used and subjected to upsetting process,and the BHDX57 thread is selected for the connection.Based on the analysis,it is regard that compared with the API S135 drill pipe,the said drill pipe has higher yield strength and impact toughness,and stable performance and rather long service span,having met the demand for safe and hi-efficiency drilling operation in the ultra-deep well with a depth over 8 000 m,and thus solved the problems of too low a tensile strength of the Φ139.7 mm S135 drill pipe,and too small an annulus of the Φ168.3 mm S135 drill pipe.