Study on mechanical behavior and fatigue life of defective ropes in HTHP gas well with high-sulfur content

Abstract

As demand for energy increases, the number of “three-high” (high-pressure, high-yield, high-sulfur) gas Wells has doubled, the severe stress fluctuation of pipe string caused by downhole high-pressure environment leads to the failure of rope fracture is particularly prominent. It is easy to cause pipeline blockage and large amount of high-pressure toxic gas leakage caused by tool string accidental falling. Therefore, based on the theory of Love and elastoplastic contact theory, and considering the influence of Poisson’s ratio effect, this article establishes a calculation model for tensile fatigue of interaction between rope strands to study the influence of key structural parameters and breaking wire position on stress distribution and fatigue life of rope. The results show that: the core strand of the rope is the main force position, the overall stress shows the trend of decreasing with the increase of winding radius; when the rope is stretched, the axial deformation near the core of the rope is smaller than the deformation far from the core; under the same number of broken wires, the fatigue life of different ropes is related to the location of broken wires, the farther the location of broken wires from the core of the rope, the higher the fatigue life. The research work in this article provides theoretical guidance for the safe operation of ropes in “three-high” gas wells.

Keywords:

• “three-high” gas wells
• rope operations
• fatigue life
• broken wire
• stress of rope

Additional information

Funding

This research was supported by National Natural Science Foundation （52204050)，Sichuan science and technology program (2021ZHCG0013，22ZDYF3009).