Threaded joint for production tubing

A thread connection for tubing;

• said thread connection comprises:
• male and female elements, at the ends of which on the outer and inner surfaces, respectively, trapezoidal threads with a taper of 1:16 are provided;
• said trapezoidal threads each includes a turn profile root with a taper of 1:16 and a turn profile crest parallel to a thread axial line;
• sealing surfaces and shoulder end face surfaces collectively forming an internal sealing unit, wherein an angle in the range from 14 to 16° is provided between the shoulder end face surfaces and a thread axis normal line;
• wherein:
• the trapezoidal threads of the male and female elements are arranged with a slope angle of a load flank of the turn profile in the range from −1 to +1° to the thread axis normal line, and a slope angle of a stab flank of the turn profile is arranged in the range from 14 to 16° to the thread axis normal line;
• the internal sealing unit is formed by:
• the sealing surfaces arranged on the male and female elements with the slope angle in the range from 17 to 19° to the thread axial line, and the shoulder end face surfaces of the male and female elements;
• and
• the internal sealing unit is provided with:
• additional surfaces arranged between the sealing surfaces and the shoulder end face surfaces on the male and female elements, and a joint of the sealing surfaces with the additional surfaces is provided in the form of a concave spherical surface on the male element and a convex spherical surface on the female element.