Offline Calculation of Liquid Properties in Light Hydrocarbon Pipeline Using EOS Equations Available to Purchase

The advanced Equations of State (EOS) do an excellent job of accurately calculating fluid properties but at a tremendous computer time impact. For online modeling where the model is connected to the SCADA system and simultaneously calculating the current state of the pipe this presents a problem. In online modeling it must complete 1 sec of model time in under one sec, no exceptions. There are numerous offline techniques to improve overall computer time performance like varying the time step. But those techniques are not useful in an online model because even in the worst of cases it must finish its calculation for each time step under the real time elapsed. This paper will explore using the high-fidelity EOS offline to produce tables for the flowing liquid PVT properties based on temperature and pressure. Then the online model will use those tables to accurately calculate the properties but in a fraction of the time. This is especially important for large pipeline companies that have multiple pipelines. One large company has over seventy-five pipelines with a total of 10,000 nodes. This technique has its limits and is not suitable for all cases for example a light hydrocarbon fluid with concentrations that are varying. But for most oil pipelines/products, it can have a significant impact on required computer resources with minimal impact on fidelity.