Sensitivity analysis and uncertainty of density correction factor of natural gas based on the AGA8-standard modeling to operational and environmental parameters

The exact calculation of the flow rate of natural gas is a very effective factor in economic, operating conditions control, equipment maintenance, and etc., of the gas industry of the importing and exporting countries. Today, in the country's gas industry, the flow rate is estimated by natural gas density correction factor (NG-DCF) calculated by the equations of state as a cost-effective method. Permanent access to input data required for equations of state, in particular, the composition of all gas components, requires high costs, hence the information estimated as model input data is mostly applied. Since the calculation accuracy of the NG-DCF can be affected by the model inputs, it is necessary to recognize and analyze the effect of each of them on the model output, to investigate the model output sensitivity from the model inputs, and to determine the uncertainty of the model output. In this study firstly, the NG-DCF was modeled by a precise-standard equation of state, AGA8-DCM (Detail Characterization Method), then various analytical and numerical methods have been applied to calculate the sensitivity analysis and uncertainty of the NG-DCF to avoid from estimation error. The results of the sensitivity analyses showed that after the gauge operating pressure and operating temperature, the composition percentage of methane, ethane and nitrogen in natural gas are the most effective linear parameters on the NG-DCF. Also, the atmospheric pressure changes, which are often neglected, are known as one of the parameters affecting the NG-DCF.