Corrosion Prediction And Anticorrosion Research In The Gathering Pipeline Of TZ Condensate Gas Field

TZ is a gas field whose CO2 containing is relatively high.Not only the formation water is acidic but the chloride ions and salinity content is high.The frequent corrosion and perforation in the ground gathering pipeline poses a serious threat to the safe operation of the pipeline.In order to accurately grasp the along the inside of the corrosion degree of gas pipeline and guide field production department take targeted pipeline detection and protection,within set No.1 serious corrosion of the transmission line as the research object,the paper establishes suitable prediction method for wet natural gas pipeline internal corrosion and the puts forward corresponding anti-corrosion measures research.This provides some theoretical and practical value for corrosion protection in the similar working conditions.This paper studies the corrosion research status,corrosion prediction method and progress of the domestic and foreign intensive pipeline to provide a theoretical basis for the establishment of corrosion prediction model in pipeline.Collecting the basic process parameters of TZ1 and the pipeline mapping data can provide the data base for the corrosion prediction model.The pipeline is more serious in 4km to 6km and the corrosion serious point is distributed in the gas liquid junction at the lower part of the pipeline through the analysis of perforation analysis records,magnetic flux leakage testing data of pipeline corrosion.The current monitoring value of the corrosion in the pipe entrance is 0.2019 mm/a,according to the ASTM G46 evaluation standard that the pipeline belongs to serious corrosion and needs to be prevented.Using the corrosion model Norsok and De Warrd to simulate the pipeline and comparing the results with the magnetic flux leakage monitoring data analysis,the two models can not meet the corrosion rate of the 1 line prediction requirements in Engineering,while the De Waard model to route TZ1 simulation more effectively than Norsok.The De Waard model and multiphase flow module are used to predict the sensitive position of the pipeline corrosion,which provides the basis for the location selection in the off-line detection of the pipeline.The parameters of multiphase flow that affect the internal corrosion rate of CO2 are analyzed.In a certain range,the corrosion rate firstly increases with the increase of temperature,moisture content,flow rate,and then decreases,which is positively correlated with CO2 partial pressure and pipeline operating pressure.This provides guidance for gas field design laboratory device to study the corrosion rule of CO2.In order to establish the internal corrosion prediction method for No.1 gathering pipeline,selecting the six parameters of the pipeline with the high weight of the corrosion rate in 399 locations and each point corresponding to the magnetic leakage detection of corrosion data are as the BP neural network,GA-BP neural network input samples for training and learning.This can get the prediction method of two kinds of corrosion rate.Through the error analysis of the prediction results,the trained GA-BP neural network method is used as the internal corrosion prediction method of TZ1 pipeline.Thinking about the corrosion of TZ1 pipeline,two aspects of anti-corrosion measures are proposed.On the one hand,it should increase the corrosion offline detection methods,such as combining the ultrasonic with C scan thickness technology to measure the 32 test points which are selected after considering various factors in the pipeline;on the other hand,four of the corrosion inhibitors are conducted by the lab and the comprehensive performance evaluation.Finally,the TZ-02 with slow release effect and water-soluble carboxyethyl bimidazoline is selected as the slow release additive and recommended to add a concentration of 100mg/L.The intermittent filling cycle of the release agent in the TZ gas field is simulated in laboratory and it is recommended that the filling period be 10d.