Innovative Near-Online Flow Assurance Tool for Pipeline Historical Performance Analysis

This paper introduces an innovative in-house developed near-online flow assurance simulation concept for continuous monitoring of pipeline performance, such as deposition of solids. The tool can be retrofitted to the analysis of brown fields without specific requirements for the installation of customized instrumentation hardware. In addition to detailing the tool, a field application case is discussed to provide insight on the pipeline historical performance. The tool is based on a dynamic multiphase flow simulator and relies on the presence of a Digital Oil Field (DOF) system. The field data are acquired by the tool directly from the remote DOF database and used as input to automatically generate, run, and post-process various simulations representing stable production conditions of the field. The tool can perform periodical runs and the results obtained populate a historical database of the pipeline performance for further analyses. The near-online flow assurance tool has been applied to investigate the potential wax deposition in two subsea multiphase pipelines. Starting from the second year after the field start-up, due to the reservoir depletion, the temperature at riser base had fallen below the wax appearance temperature (WAT). Laboratory analyses confirmed the potential for wax deposition under current and past operating conditions and the use of wax inhibitor at the wellhead was recommended. However, there was uncertainty regarding the inhibitor effectiveness since pigging activities have been conducted unfrequently and on a discontinuous basis. Therefore, it became essential to monitor the pressure drop trend of the pipelines over time as a non-invasive wax detection technique. The analysis has been conducted over a seven-year period since the first start-up of the field. Given that the discrepancy of simulation data from field data turned out to be within the simulation's uncertainty range and it does not change throughout the whole timespan of the analysis, the tool has proven the effectiveness of the injected wax inhibitor. A traditional flow assurance analysis workflow would have required large time-consuming manual input for the case-study presented, since a substantial number of field data has been processed. This renders the traditional approach impractical. The near-online tool has proven to be capable and robust for different flow assurance applications by reducing the time effort and the error probability linked to manual input. In future, other pipeline studies will benefit from the definition of the presented workflow.