Modelling the effect of temperature on wax deposition for offshore and onshore pipeline corrosion
The study aims to model the effect of temperature on wax deposition for offshore and onshore pipeline corrosion. When the temperature of the producing stream dips during normal flow, gas lifting, or pumping, paraffins precipitate and cling to the liner, tubing, sucker rods, and surface equipment. Wax deposition is a complex process that is one of the primary unsolved difficulties in flow assurance in pipelines and manufacturing equipment. Another issue that the oil and gas industry is grappling with is corrosion in steel pipes. The paraffin wax on the surface of the crude oil pipeline provides good corrosion protection, whilst others only give poor or no protection. However, due to the long chain paraffin layer being physically removed from the surface during periods of elevated temperature, the majority of the corrosion protection has been lost. Despite the lack of surface chemical activity, paraffin can form on the pipe surface at low temperatures, below the so-called wax appearance temperature. When the wax layer covers the steel surface, it can slow down corrosion by preventing corrosive species from diffusing to the surface. An experimental flow loop was designed for the pipeline to investigate the effect of temperature of wax deposition on pipeline. The linear polarization resistance method was used to measure the corrosion rate in mils per year (mpy) against time (minutes) using MS1000 Corrosion Meter. MATLAB software was used for simulation with the experimental results and the input parameter from the wax physical properties and operating conditions. Based on the analysis, it was observed that at temperature of 15oC and flow rate at 10.21 L/min during the corrosion inhibition. At time 18 minutes, the experimental and model results predicted a significant reduction of corrosion rates and excellent corrosion protection while others gave only moderate or negligible protection to the pipeline. From the profile plot, the values of the corrosion rate (mpy) against time (min) of the experimental and model results are 3 (0.65 mpy, 0.57 mpy), 6 (0.41 mpy, 0.47 mpy), 9(0.35 mpy, 0.37 mpy), 12 (0.21 mpy, 0.26 mpy), 15 (0.16 mpy, 0.16 mpy), 18 (0.11 mpy, 0.06 mpy). But the variation of the experimental and model results in terms of deviation is (0%) indicating that both results are insignificant in variation, showing positive agreement between the experimental and model results.
Keywords –Modelling, offshore, onshore, wax, temperature, deposition
