This study examined natural gas pipeline by the non-contact magnetic corresponding. To confirm the reliability for the examination of natural gas pipelines by non-contact magnetic corresponding, three abnormal nodes were detected by the appearance inspection and ultrasonic testing. The results suggested that the grade of abnormal nodes by non-contact magnetic corresponding were not absolutely agree with that of the corrosion by ultrasonic testing. However, there was an obvious relevance between the comprehensive index of F by non-contact magnetic corresponding and the maximum degree of corrosion by ultrasonic testing. To sum up, the magnetic corresponding was an effective non-contact detection technology for the natural gas pipeline, while it was necessary to rationally grade the abnormal node according to the comprehensive index of F.

An experimental study on the multiphase flow of heavy oil gas lift was conducted on 18.25 m high vertical tube. Based on the experimental results and the wellbore heat transfer mechanism, a coupling model of wellbore pressure-temperature gradients was presented for the gas lift with light oil injected from the annulus. Moreover, the solution of coupling annulus flow with tubing flow was also established through cyclic iteration. Experimental results showed that gas injection enables heavy oil and light oil to mix rapidly and completely. Evaluation of pressure drop models shows that the error of the Ansari model is approximately 12.12%, by comparison it is the least. A novel method of gas lift assisted with light oil from the annulus was proposed to solve the actual situation wherein heavy oil cannot be easily lifted from the wellbore at Tuyuke Block in Tuha Oilfield. An instance design based on the sensitivity analysis of the gas injection rate and diluting rate was also completed. The instance design shows that the productivity of heavy oil well can be significantly improved using gas lift and blending diluting oil technology. In order to verify the feasibility and effect of gas lift assisted with light oil in heavy oil well, a pilot test was implemented in Tahe Oilfield, Xinjiang, China. The results of pilot test show clearly that the daily production rate increased from 11.6 to 38 t/day, and the ratio of light oil with heavy oil decreased from 11:1 to 4:1. From the above, gas injection can significantly reduce the usage of light oil needed, and gas lift assisted with light oil injected from the bottom hole can significantly enhance the productivity of heavy oil wells.

Internal CO2/H2S corrosion of gathering pipelines is a serious problem in natural gas plant. It is important for field engineers to assess the corrosion degree and control corrosion risk. A multi-kernel support-vector-machine (SVM) method is presented to rank internal corrosion of gathering pipelines according to the NACE RP-0775-91 standard. By considering the nonlinear indivisibility between data, we combined three kinds of kernels (linear kernel, polynomial kernel, and Gaussian kernel) into a multi-kernel SVM to rank the internal CO2/H2S corrosion of gathering pipelines. The method was applied to a natural gas field in northwest China. Corrosion data were collected and analyzed. The prediction accuracy of the multi-kernel SVM method for ranking CO2/H2S corrosion was 66%, which is higher than the results of the single-kernel SVM methods (linear kernel, polynomial kernel and Gaussian kernel), whose prediction accuracies are 50%, 48% and 54% respectively. These findings could help field engineers rank corrosion and reduce the corrosion risk.

Cathodic protection was one of important method for the corrosion prevention. With the expand of pipeline at Jingbian gas field, the cathodic protection system had been not qualified for the corrosion prevention of pipeline at Jingbian gas field. The results of survey for pipeline in 2018 years suggested that there were less-protection or over-protection for the corrosion prevention of pipeline. In this study, it was simulated by the COMSOL software to clear the regulation of current for pipeline in different cathodic protection area, and learn the overall situation of cathodic protection station in Jingbian gas field. Finally, optimizing the cathodic protection system for improving the effect by cathodic protection and ensuring the safety production.

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