Visualization of Liquid Slugging Using Detailed, High-Quality Pressure Monitoring

Abstract Liquid slugging in gas gathering systems is a costly problem. It is difficult to manage because it is hard for pipeline operators to know where and when slugs form and how they move. This paper demonstrates how detailed pressure measurement across pipelines in a gathering system can be used to visualize slug formation and movement, thereby enabling pipeline operators to better manage slugging issues at facilities. Pressure monitoring devices, based on an internet of things (IoT) architecture, were installed on the main branch lines feeding the inlet separator of a gas gathering system. Each device continuously captured, stored, and delivered high-quality, time-synchronized, per-second pressure measurements to a cloud-based data service. Detailed pressure data from several days of normal operations was integrated with operational data that showed slug arrival times and volume at the inlet separator, along with timing of pigging operations. The data was assessed for correlations between slugging activity and changes in pressure patterns along each line. Pigging operations were optimized based on the results. Clear correlations were observed between slugging events and changes in differential pressure over time along a given branch line. By recognizing the pressure pattern associated with slugging events, the location and timing of liquid slug formation in the lines of the gas gathering system were determined. Pressure patterns were distinct and could be alarmed on to provide early notification of a slugging event. The magnitude of differential pressure was found to be loosely correlated to slug size in most branch lines. The impact of pigging on pipeline operations could also be visualized as changes in pressure patterns. This visualization enabled pigging to be optimized to reduce liquid build-up in branch lines that contributed to large slugging events. The optimization resulted in a reduction in labor costs for managing slugging issues such as compressor shutdowns and flooding the inlet separator as slugging events became smaller and less frequent. It also resulted in a sustained production increase of 20% for wells feeding one of the most problematic branch lines as line pack pressure was reduced enough to impact productivity. This case study demonstrates a new way for pipeline operators to visualize slug formation and movement in their gas gathering systems as changes in pressure along a pipeline. Once visualized, slugging can be better managed, potentially leading to production increases, reduced costs, or both. The use of detailed pressure monitoring to visualize fluid dynamics within pipes or process equipment may have many applications in the oil and gas industry for enabling operational improvements.