coupling

Tubing couplings, as downhole drilling tools in the petroleum industry, serve primarily for tubing interconnection. They are engineered to address the fatigue fracture issue of conventional couplings, which is predominantly caused by stress concentration.

In terms of structure, the tubing end interfaces with the inner wall of the coupling body via tapered threads, while the coupling body end connects to the tubing through horizontal threads of identical profile and pitch. This design mitigates stress concentration at the root of the single - conical - threaded tubing connection, thereby reducing the likelihood of fatigue fracture and ensuring a robust connection, effectively precluding tubing string disconnection incidents.

Phosphating treatment is applied to these couplings, endowing them with superior tribological properties, corrosion resistance, and resistance to thread galling.

Couplings are categorized into tubing couplings and casing couplings.