LCF Life Prediction Model of Coiled Tubing Based on Fatigue Damage Accumulation

Abstract

This paper establishes a model to predict the fatigue behavior of coiled tubing subjected to variable total strain conditions. The approach based on nonlinear fatigue cumulative damage rule of effective hysteresis energy dissipation, but requires additional experimental results from fatigue tests that were performed under constant strain amplitude. Cyclic plastic strain energy is measured curve area of cyclic stress-strain curves. it is proved to be quite consistent between theoretical predictions and experimentl datas.

Corrosion Behavior and Mechanical Performance of Drill Pipe Steel in a CO2/H2S-Drilling-Fluid Environment

“…In the process of drilling operations, acid gases such as CO 2 and H 2 S from gas intrusion are easily dissolved or dispersed in the drilling fluid. At the same time, the handling time of drilling-gas-intrusion accidents is long, and the drill pipe will be subjected to complex underground loads, corrosive media, temperatures, and pressure couplings, which can easily cause deformation, corrosion failure, and even perforation and fracture of the drill pipe body and connections [1,2]. Therefore, it is of great practical significance to study the mechanical-performance damage of drill pipes in CO 2 /H 2 S-containing drilling fluids to ensure the safety of drill pipes during deep oil and gas drilling.…”