Research on Paired T-test Method for Evaluating Dynamic Measurement Shortage in Crude Oil Custody Transfer Process
Measurement shortage occurs in the custody transfer of crude oil,which leads to measuring disputes due to the errors of flowmeters,the dynamic variations of pressure and temperature,and other uncertainty factors.A new method,which combines the paired t-test and the error analysis of flowme-ters,is proposed to evaluate the measurement shortage for the custody transfer of crude oil.The nor-mality and correlation tests are conducted on the measurement shortage data between the incoming oil flow rate and the return oil flow rate in the dynamic measurement process.The results show that the correlation between the crude oil custody transfer data of the oil production plant and the light hydrocar-bon plant is very obvious,and the measurement shortage data follows a normal distribution.The pro-duction data of the crude oil custody transfer measurement from the oil production plant and the light hydrocarbon plant meet the requirements of paired t-tests.A quantitative evaluation of the measurement shortage data is conducted through the paired sample t-test,and a reasonable deviation range for dy-namic measurement shortage is provided.The rationality of the measurement shortage between the in-coming oil flow rate and the return oil flow rate in the dynamic metering process is analyzed.The analy-sis of the confidence interval for flowmeters indicates that the relative position between the confidence interval of the incoming oil flow rate and the return oil flowrate can only qualitatively indicate whether the measurement shortage is significant,but cannot quantitatively provide the measurement tolerance like paired t-tests.A new quantitative index of measurement tolerance,can be calculated by paired t-test,which can be combined with the error analysis of flowmeters to evaluate the dynamic measure-ment shortage in the custody transfer of crude oil.
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