Abstract:

During summer production, the dry gas processed at Station A is conveyed at low pressure via the DN 400 interconnection line to Injection Station B, where it is pressurized by the gas injection machine and reinjected at high pressure for peak shaving purposes. Conversely, during winter production, high-pressure wet gas separated by the two-phase separator at Injection Station B is transported via the DN 400 interconnection line to Station A for processing. Prior to dry gas injection, pigging is performed for the interconnection line to enhance transportation efficiency and ensure the normal functioning of equipment at the injection station. In March 2024, the first pigging of the DN 400 interconnection line was performed, resulting in a total clearance of 320 cubic meters of accumulated liquids along with significant quantities of black powder through both forward and reverse pigging operations. To address the issues related to excessive accumulation of liquid and black powder, an analysis was performed focusing on factors such as equipment conditions at Injection Station B and elevation profiles along the interconnection line, and sampling and testing of black powder were conducted to determine its chemical composition. Based on the investigation of site-specific characteristics of wet natural gas alongside operational parameters, some appropriate countermeasures were proposed. These measures not only enhance pipeline transportation efficiency, mitigate corrosion risks, ensure safe, stable and efficient pipeline operations, but also reduce potential damage caused by accumulated liquids and black powder to equipment at the stations.

Key words: wet gas transportation, liquid accumulation, black powder, cause analysis, countermeasure