Research On Safe And Economical Operation Of High Waxy Crude Oil Pipeline Under Low-flowrate

Low-flowrate operation refers to the operation of the pipeline below the design flowrate,and most of the crude oil produced in China is high waxy crude oil.When the pipeline is running at low flow conditions,the temperature drop along pipeline is larger,wax deposition is serious and easy to cause wax plug the pipeline accident.In addition,in order to prevent the occurrence of condensate pipe accident,need to greatly improve the station temperature,but this will lead to increased energy consumption.High waxy crude oil in low flow conditions operating is not safe and uneconomical.Therefore,it is necessary to study the safe and economical operation technology of high waxy crude oil pipeline under low flow condition.Based on the previous research results,this paper takes into account the thermal characteristics,hydraulic characteristics and wax deposition regularity of the high waxy crude oil pipeline in the low flow operation,and combines the indoor wax deposition loop experiment,established the RVM algorithm Mathematical model of wax deposition rate prediction.Taking the oil pipeline in Daqing Oilfield as an example,the prediction results of wax deposition rate are compared with the dynamic model of wax deposition and the model of neural network.The results show that the average error of the model in this paper is 1.27%,the mean square error is 0.3,the correlation coefficient is 0.921,the prediction accuracy is high,the stability is good.The model proposed in this paper can describe the wax deposition phenomenon of crude oil pipeline in the actual operation condition more accurately.Secondly,based on the study of wax deposition regularity and the study of thermal characteristics and hydraulic characteristics.the importance of each influencing factor is analyzed by introducing the interval number method,and then the order of the importance of each parameter is determined,and the probability distribution of each influencing factor is obtained.Then,the influence factors are sampled,and the conclusion is drawn that the probability distribution of the minimum safe flow corresponding to the certain station temperature is normal distribution.At the same time,the method of calculating the probability of different flow which is greater than the minimum flow rate,and the safety of a pipeline running in Daqing Oilfield is evaluated according to the safety evaluation standard of pipeline operation.The results show that the oil pipeline runs every season SOSI?2,the pipeline operating safety is high.Then,considering the mutual coupling between the optimal temperature,the optimal pressure and the optimal pigging period.Taking the minimum cost of oil in a certain period of time as the goal,taking the safety of pipeline low-volume operation as the constraint condition and the three economic indicators as decision variables,the mathematical model of safe economic operation optimization is put forward,and gives the iterative solution method.Taking the oil pipeline in Daqing Oilfield as an example,the interval of each economic index is calculated,and the probability distribution of each economic index is obtained through statistical analysis.Finally,based on the above importance analysis,the concept and calculation of the Stable operation economic index(SOEI)of three kinds of economic indicators considering optimal outbound temperature,optimal outbound pressure and optimal waxing cycle are put forward for the first time,so that the pipeline stability operation economic index(SOEI)can be a comprehensive evaluation of the economy of high-wax crude oil pipeline at low flowrate.Taking the oil pipeline in Daqing Oilfield as an example,the results of safety and economic evaluation show that the economic evaluation index SOEI grade is 3 in February and August due to the low economic index of outbound temperature.It has deviated from the economic operating range.This shows that there should be a specific adjustment of the outbound temperature,so that it can be restored to the operating range of the economic range,and gives the economic indicators of the optimal economic operation range.