Modular thread connection with high fatigue resistance

A method for coupling a first and second member disposed along a work string adapted for use in a wellbore, comprising:

• (a) providing the first member with a pre-determined outside diameter and a nose, the nose having external threads formed thereon;
• and
• (b) providing a second member with a box end having internal threads that mate with the external threads;
• wherein the internal threads and the external threads have one of:
• (i) pitch-to-root radius ratio that is less than approximately 6.5;
• (ii) a thread height-to-root radius ratio that is less than approximately 3.5.

A connector for use in oilfield applications, comprising:

• (a) a first member having a pre-determined outside diameter and a nose, the nose having external threads formed thereon;
• (b) a second member having a box end provided with internal threads that mate with the external threads, the internal threads and the external threads being defined by:
• (i) a pitch-to-root radius ratio that is less than specified by the American Petroleum Institute (API);
• (ii) a thread height- to-root radius ratio that is less than that specified by the API;
• (iii) a flank angle that is less than that specified by the API;
• and (iv) a taper that is less than that specified by the API for the pre-determined outside diameter.

A system for servicing a wellbore, comprising:

• (a) a rig positioned at a surface location;
• (b) a work string conveyed into the wellbore by the rig;
• (c) a bottom hole assembly connected to an end of the work string;
• and
• (d) a connector associated with the bottom hole assembly, the coupling including:
• (i) a first member having a pre-determined outside diameter and a nose, the nose having external threads formed thereon;
• (ii) a second member having a box end provided with internal threads that mate with the external threads, wherein the internal threads and the external threads have one of pitch, taper, and root radius different from that specified by the American Petroleum Institute (API) for the pre-determined outside diameter;
• and wherein the first and second members when coupled to each other provide the connector that has a greater resistance to bending stresses compared to API specified coupling for the pre-determined outside diameter.