Simulation On The Corrosion Of Tubing In Multiphase Flow Of JZ20-2 Gas Field

In recent years,the corrosion of oil pipeline has become an important factor in the development of the oil industry.Serious oil pipe corrosion occurred in Jinzhou 20-2 oil and gas well when it was put into operation less than 10 years.Send some invalid tubing corrosion samples to inspect,it was found that the corrosion products of the tubing were iron carbonate,which determined that the corrosion of tubing was caused by carbon dioxide.The carbon dioxide produced by the gas well was dissolved in water to form carbonic acid,the electrochemical reaction was made to make the thickness of the tubing thinner,perforate and even break,and there was a serious safety hazard.Because the tubing corrosion degree is difficult to grasp,it is very important to predict the tubing corrosion behavior more accurately for prolonging the service life of the tubing.The corrosion mechanism of gas well tubing is very complicated due to the diversity of medium composition and the complexity of multiphase flow.Understanding the flow characteristics of the fluid is the prerequisite for the in-depth study of the mechanism of corrosion.In this paper,the physical model of gas-liquid two-phase flow is established by FLUENT software,several common flow patterns were numerically calculated and the distribution of water in the tubing was analyzed.The results show that: The flow pattern inside the tubing varies with the liquid mass flow.When the content of liquid was 0.05%、0.09%、0.11% and 0.16%,the bubble flow,ring flow,bullet flow and stopper flow appeared in wellbore.By observing the nephogram of phase distribution,it is very intuitive to explain the flow pattern of two-phase flow.Analysis of the corrosion of tubing shows that the corrosion of wellhead is more serious than that of the bottom hole.In order to analyze the cause of corrosion deeply,the corrosion rate of tubing is simulated by OLGA software.The results show that: according to the corrosion status of JZ20-2 field,the most severe corrosion location is at the wellhead,which is mainly due to the flow pattern.During the development of oil and gas fields,the flow pattern will change with each other,which is the main cause of tubing corrosion.Slug flow has the biggest influence on tubing corrosion,the annual average corrosion rate of up to 0.21 mm,followed by annular flow,and the annual average corrosion rate is 0.18 mm.In addition,the corrosion degree of the tubing is also related to the liquid velocity and the wall shear stress.Aiming at the corrosion reason of JZ20-2 gas well,reasonable anticorrosive measures are put forward to control the corrosion mechanism of tubing in multiphase flow.By installing a gas-liquid cyclone separator at the bottom of the well,or controlling the mass flow of the inlet to control the flow pattern,these methods can effectively prevent borehole corrosion,and are of great significance for ensuring the normal operation of gas well.