Based on the characteristics of titanium alloy's high specific strength and low elastic modulus, titanium alloy drill pipe is more suitable for small radius wells and horizontal wells, which can greatly reduce the load of surface equipment and reduce the hydraulic loss of joints. Especially for short radius wells, titanium alloy drill pipes can significantly increase the life of the drill string. A series of researches have been carried out at home and abroad, hoping to use titanium alloy drill pipe to provide more reliable equipment support for deep and ultra-deep well drilling.
Torch Drilling Technology Service Company uses drill tool assembly: PDC drill bit + rotary steering drill tool assembly + 4 Φ73. 02 mm titanium alloy drill pipes + Φ73. 02 mm PH-6 steel drill pipes, which were completed in 1999 and 2000. In the drilling work of two wells, in the 8.5m long section, the inclination angle gradually increased from 66.5° to 89.5°.
The Grant Pfideco subsidiary of Weatherford and the Texas subsidiary of RTI used titanium alloys to prepare titanium alloy drill pipes with a yield strength of 840 MPa in the early 21st century. The fatigue life of the drill pipes is 10 times that of steel drill pipes in air. Under medium conditions, it is 100 times that of steel drill pipe. In 2000, it was successfully applied in directional well drilling of many highly deviated wells in Taxes State, USA. At present, there are hundreds of small-curvature wells using titanium alloy drill pipes in a foreign oilfield, and good economic benefits have been achieved. Related reports show that in the simulation of drilling and completion fluids with CaCl2 + CaBr2, the two titanium alloys TC4 and Ti38644 have slight crevice corrosion, which has a greater impact on their fatigue life. Therefore, the material selection process still needs to be strengthened. Evaluation and assessment of material application.