Based on the characteristics of titanium alloy such as 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 surface equipment load and the hydraulic loss of joints. Especially for short radius wells, titanium alloy drill pipe can significantly improve the life of 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 BHA: PDC bit + rotary steering BHA+ Φ 4 73.02 mm titanium alloy drill pipes+ Φ 02 mm ph-6 steel drill pipe. In 1999 and 2000, six wells were drilled successively. In the 8.5 m long well section, the well inclination angle was 66.5 ° Gradually increased to 89.5 °。
In the early 21st century, grant pfideco subsidiary of Weatherford and Texas subsidiary of RTI used titanium alloy to prepare titanium alloy drill pipe with yield strength of 840 MPa. Its fatigue life in air medium is 10 times that of steel drill pipe, and 100 times that in corrosive medium. In 2000, it was successfully applied in directional drilling of several highly deviated wells in taxes state, USA.
At present, there are hundreds of small curvature wells in a foreign oilfield with titanium alloy drill pipe, and good economic benefits have been obtained. The relevant reports show that TC4 and ti38644 have slight crevice corrosion in simulated drilling and completion fluid with CaCl2 + cabr2, which has a great influence on fatigue life, so the evaluation and assessment of material application should be strengthened in the process of material selection.
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