This paper addresses the performance of in-depth flow assurance analyses to resolve an ongoing fluids gathering and handling concern at the Glady and Artemas compressor stations located in Glady, West Virginia, and Artemas, Pennsylvania. Efforts included complete analysis of two separate flow line systems, from the gas storage reservoirs to the compressor stations. Steady-state and transient behavior of the production systems were modeled, and hydraulic behavior of the systems over expected operating conditions was analyzed. The study also included a thorough analysis of the compressor station equipment to determine process equipment capacities during heavy draw-down times. Fluid flow from the gas storage fields to the compressor stations was analyzed to identify liquid holdup volumes and locations as well as liquid slugging flowing conditions. Liquid accumulation rates and liquid carryover volumes into the compressor stations were also determined. Pigging operations were also modified based on the results of the analysis.
Columbia Gas Transmission encountered liquid accumulation and liquid carryover from storage wells into the company's Glady and Artemas compressor stations, located in Glady, West Virginia, and Artemas, Pennsylvania, respectively. During unpredictable times during the storage withdrawal season, large volumes of fluids were carried through a series of gas conditioning devices leading into the dehydration contactor. These fluids contaminated the glycol and were carried into the dehydration reboiler and flared out. This condition created a safety hazard for the personnel at the station and violated the site-specific Title V air permit for the station. The liquids problem occurring at the plant stemmed from changes in operating conditions at the wells and at the pipeline outlet. Each well was assumed to produce water at a rate of 24 gals/mmscf for the Glady field and between 0.67 - 2.7 gals/mmscf for the Artemas field. The amount of liquid in the system and the sizes of the liquid slugs exiting the system were affected by many factors, including individual well gas production rates, operating pressures and temperatures, and pipeline sizes and profiles. As a result, a series of sensitivity cases was evaluated to determine the following in the Glady/Artemas pipelines:
Total accumulated liquid volumes in the pipeline segments (in BBLS)
Rate of liquid accumulation (in gals/hr) Ascertaining the total liquid volumes in the pipelines helped to determine the maximum amount of liquid that could accumulate in the system if pigging of the pipelines ceased. The volumes were identified in accordance with the assumption that the system would be allowed to flow for long periods of time (five to six months) without pigging and at constant flow rates. Although the volumes generated from these cases will likely never be seen at the Glady/Artemas facilities, they provided an insight into the potential liquid volumes that could exist in the pipelines. Rates of liquid accumulation were determined at various flow rates for an average arrival pressure at the Glady/Artemas facility. These cases helped identify the amount of liquid that could build up in the pipeline over time.