Study on friction reduction effect and mechanical properties of light drill pipe under different wall thickness in extended reach wells

Light drill pipe can effectively reduce the friction of drill string in extended reach wells, but the existing research on the friction reduction effect and axial force transfer characteristics of light drill pipe with different wall thickness in extended reach wells is not clear. Based on Hamilton’s principle and field data, this paper establishes and verifies the correctness of the dynamic finite element model of the whole well drill string in extended reach wells. Based on Hamilton’s principle and field data, the dynamic finite element model of the whole well drill string in extended reach wells is established and verified. The frictional torque, buckling and axial force transfer characteristics of aluminum alloy, titanium and steel drill pipe under different wall thicknesses were compared and studied. Based on these three indicators, a method for selecting the wall thickness of light drill pipes was proposed. The results show that compared with the steel drill pipe, the use of titanium alloy drill pipe (wall thickness = 9.17 and 10.54 mm) and aluminum alloy drill pipe (wall thickness = 13 and 15 mm) can reduce the frictional torque of the whole well drill string is reduced by 23.2%–31.7% and 19.8%–48.1% respectively. The aluminum alloy drill pipe with a wall thickness of 11 mm has serious helical buckling, but with the increase of the wall thickness, the spiral buckling becomes sinusoidal buckling, and the degree of deformation gradually decreases. The axial force transfer efficiency of titanium alloy drill pipe (wall thickness = 9.17 and 10.54 mm) increased by 27.6% and 17.3% respectively, the aluminum alloy drill pipe (wall thickness = 11, 13, and 15 mm) increased by 32.7%, 36%, and 12.9% respectively. The research results provide a theoretical basis for the application of light drill pipe and the design of wall thickness.