The Research On The Wax Deposition Rule And The Pigging Period Of The Oil Transportation Pipelines Of Oil-water Of Sanan Oilfield

This paper is supported by the National Natural Science Foundation of Youth Science Fund Project(project number: 51404068) support.The crude oil of Sanan Oilfield is typical "three high" crude oil, high-content wax, high condensation point and high wax precipitation point. In order to make the crude oil keep good flowbility and high temperature, water heating process is generally used in the gathering and transportation system. However, because of the temperature decreasing during the conveying process, the wax molecules will gradually crystallize, and then adhered on the inner wall of the pipeline. The deposition of wax molecules will decrease the effective circulation section of the pipeline, cause conveying pressure rise, transmission capacity reduce, energy consumption and production costs increase, sometimes it may cause solidification accidents. Therefore, in order to ensure the safe and efficient operation of oil pipeline, it is necessary to study wax deposition in pipeline and develop a reasonable economic pigging period.Through laboratory experiments, studies the characteristics of wax precipitation in Sanan oilfield oil samples, obtained its pour point crude oil composition, the WAT eigenvalues and microstructural features. And typical of the rheological properties oil samples analyzed in order to identify its viscosity-temperature characteristics, viscoelastic properties and low temperature rheology. Then based on analysising the based data statistics, according to the Daqing Sanan oilfield Pipeline of pipeline flow boundaries, calculated the current condition of the pipeline safety throughput in order to meet the premise of safe production. Secondly, compared to conventional wax deposition model, from which to select the most appropriate model, takes account the moisture content into the wax deposition rate calculation by changing the part of relevant parameters.Established a dynamic model of wax deposition, to study and predict the oil-water two-phase system wax deposition in the pipeline, and clear variation of wax deposition rate under different moisture content, the different oil temperature and the different amount of infusion on the changes of wax deposition rate.Finally, established a economic pipeline pigging period model which takes the pipeline operation cost as objective function. It can calculate pigging periods of Sanan oilfield Pipeline in different transportation conditions. According to the actual production situation of Sanan oilfield and some research on the domestic and foreign common pigging technology, select the single pipe pigging technology.