Experimental and theoretical study on the mechanical properties of titanium alloy drill pipe in short radius and long horizontal wells

Titanium alloy drill pipe as a new type of drill pipe has attracted much attention in the field of unconventional oil and gas development. In order to study the performance of titanium alloy drill pipe in the complicated wells, the hardness, flattening and tensile test were carried out firstly. The results indicated that the hardness of titanium alloy drill pipe is similar to steel pipe and it has good toughness and plastic deformation ability. The tensile strength (1017 MPa) and yield strength (927.5 MPa) of the tube body are the highest, and the weld zone has the highest elongation (15.29%). Then, the fatigue tests of titanium alloy drill pipe in air and mud were conducted to evaluate the fatigue behavior. The results indicated that titanium alloy pipe in air or mud could up to 10 7 cycles when suffering 50% yield strength (395 MPa) and the mud had little effect on fatigue life. The titanium alloy drill pipe can be used for a smaller radius of curvature and a larger build slope than the G105 and S135 drill pipes. Finally, the friction between titanium alloy and steel drill pipe under different operation types were analyzed by using an actual long horizontal shale gas well. The results indicated that the friction of titanium alloy drill pipe in the horizontal well was only 60% of that steel under the same conditions. This work provides the experimental and theoretical basis for the applicability of titanium alloy drill pipe in short radius and long horizontal wells.