Study On Internal Corrosion Of Oil-gas-water Mixed Pipeline And Its Direct Evaluation Method

Multiphase flow transportation technology more and more used in oil and gas exploration in oil field.The transmission medium of mixed oil-gas-water transportation,in the gas phase medium ofen contain CO2 and H2S.They will inevitably produce corrosion within the pipeline.Once the oil-gas-water mixed transportation pipeline is damage for corrosion.It will cause serious economic losses and the repair of pipeline is also very difficult.So it should be timely and effective to predict and prevent the oil-gas-water mixed transportation pipeline corrosion.Domestic and foreign experts and scholars already do a lot of theory and experimental research on the mechanism of internal corrosion and influence factor.In this paper based on a large number of relevant literatures about internal corrosion,analysis the internal corrosion type,corrosion mechanism and influence factors of oil-gas-water mixed transportation pipeline,and briefly introduce the protection method.The thesis mainly focused on two problems about the internal corrosion and direct evaluation of oil-gas-water mixed transportation pipeline with CO2.The thesis researches on internal corrosion by theoretical analysis method and numerical simulation method.The main contents of the thesis are as follows:Using the multi-phase flow simulation software OLGA to make calculations.It must be collect and analyze the pipeline-related run parameters,route parameters and transport media components.Combined with the corrosion module in OLGA and select suitable CO2 corrosion forecasting model of oil-gas-water mixed transportation pipeline.It will be deeply analyze the pipeline operating conditions about the pipeline outlet pressure,inlet temperature and the flow rate on the internal corrosion rate.Then deeply analyze the different components about water content,CO2 partial pressure,gas-liquid ratio and chloride ion content on internal corrosion rate.Then deeply analyze the different terrain conditions about upslope degrees and downslope degrees on internal corrosion rate.Then deeply analyze the differen the different pipeline diameter on internal corrosion rate.Based on the gray relation method,analyze the impact of high or low weight to the corrosion rate about fifteen factors:temperature,pressure,CO2 partial pressure,PH value,liquid holdup rate,gas superfical velocity,liquid superfical velocity,flow pattern,chloride ion content,heat transfer coefficient of inner wall,gas density,liquid density,pipe angle,the maximum shear force of the wall,the maximum shear force of the liquid on the wall.For the pipelines that are not suitable internal inspection,it must adopt direct evaluation method.This paper based on the internal evaluation method(ICDA)proposed by NACE,and combine with the example to research the direct evaluation method of the internal corrosion of oil-gas-water mixed transportation pipeline.Then determines the sub-evaluation interval that need to be inspected and the specific location of the subinterval.