Transient Analysis of Flowlines and Slug Catcher Level Control

摘要

The feasibility of handling increased flow from an expanded gathering system with the existing slug catcher was analyzed. Transient analysis simulations for the flowlines were conducted to determine the surge flow at the receiving facilities when changes in flow rates, restart operations and pigging operations occur. Knowing the surge flow (inlet liquid flow) vs. time, the operating volume of the slug catcher and the drain rate (processing flow) to the plant, it can be determined if the existing slug catcher volume is big enough for handling the flow variations and the incoming slugs for different scenarios. A PI level controller was proposed to control the level in the slug catcher. It was possible to find the tuning parameters (Gain and Integral Time) in order to keep the liquid volume within the desired levels, avoiding undesirable sudden drain rate changes that are difficult to handle in the process units downstream of the slug catcher. Several operating cases were analyzed and it was concluded that pigging cases, especially those for the lowest gas flow rates, produce the biggest slugs. A properly tuned PI level controller helps to optimize the slug catcher volume. The conclusions of this study are applicable to Gas Oil Separation Plants.