This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 30172, “A Streamlined Multidisciplinary Work Flow for Pipeline-Slugging Assessment,” by Jeff Zhang, Saurav Jha, and Tim Matuszyk, Wood, prepared for the 2020 Offshore Technology Conference Asia, originally scheduled to be held in Kuala Lumpur, 2–6 November. The paper has not been peer reviewed. Copyright 2020 Offshore Technology Conference. Reproduced by permission.
Free spans exist in subsea multiphase pipelines laid over undulating seabed profiles or across continental scarps for offshore field developments. Slug-flow-induced fatigue damage on the free spans can have a significant effect on project economics. Slug-flow assessments can prove time-consuming. The complete paper describes an integrated iterative approach between the flow-assurance and pipeline-engineering disciplines to streamline the work flow based on the value or cost associated with changes in input parameters that affect pipeline fatigue-assessment outcomes.
The complete paper further details key goals for each step.
Step 1: Plan Project Slug-Flow Design Requirements. Key to this step is to create a close interface between flow-assurance and pipeline engineers to discuss and align overall timing, critical decisions, and hold points that are required as part of the slug-flow assessment and any specific project-design considerations.
Step 2: Execute Slug-Flow-Prediction Assessment. Slug-flow prediction typically is conducted by engineers using industry-standard multiphase dynamic-flow simulators. The step requires significant time and effort because of long simulation times and large data post-processing requirements.
Step 3: Generate Slug-Flow Interface Data. The two methods typically used for converting flow-assurance slug-flow results into formats that can be used readily by pipeline engineers are the time-history approach and the time-dependent-matrix approach.
Step 4: Execute Slug-Flow Response Assessment. This assessment typically is conducted by pipeline engineers to assess the effects of predicted slug-flow interface data on proposed pipeline con-figuration designs. Industry-standard finite-element-analysis (FEA) tools are used for this step.
Step 5: Finalize Design Through Iteration and Optimization. Where the slug-flow response assessment results show excessive fatigue damage that affects feasibility of the proposed design, iteration and optimization are performed.
Step 6: Consider Operational Monitoring Requirements. Operational fatigue monitoring can be considered if operational restrictions are required or if some level of risk or concern remains with the final design.
