Water Evacuation and Separation Improvement for Onshore Facilities

Abstract This abstract aims to showcase the activities conducted for a basic engineering study on water separation and improvement for onshore facility. The facility is equipped with crossover line between two trains and a common storage known as the Hair Pin Loop (HPL) designed to handle pigging slug volume. Over the years, an increase in water forecast has led to significant flow assurance issues. Thus, this study was initiated to comprehensively evaluate the liquid handling network. Due to limited water processing capabilities at onshore facilities, flow assurance analysis was performed to manage liquid handling. Initially, model tuning screening was performed based on the historical data for respective feeders. The tuning activity resulted in a close match in pressure drop using a pipeline roughness of 10mm. The pressure drops also closely aligned with the historical trend scatter plot. Additional tuning check was performed by comparing the pig travel time against the historical pigging data. Based on the flow assurance result, study proceeded with adequacy check calculations to capture any debottlenecking issues at current facilities. The analysis revealed that Train A with a maximum water content of (WC=35%) would result in HPL total liquid volume of 4246 m3 for pigging based on Max Liquid Case. Meanwhile, Train B, with a water content of (WC=5%), only reaches ~2100 m3 after 90 days. Hence regular pigging can be reimposed, as the water content in the HPL would be lower than in the case of Train A. For design purposes, assuming 20% margin on Train A total liquid volume, the condensate/water processing volume should be 5095 m3. On top of that, considering available days for liquid evacuation, minimum drain rate from HPL should be at least 27 m3/hr. Hence, it is recommended to follow the suggested pigging schedules. Furthermore, several facilities modification need to be implemented to support minimum drain rate from HPL to ensure the water evacuation inside HPL can be evacuated timely and pigging schedule can be followed. The identified modification involves modifying the piping from HPL coupled with the implementation of fluid density measurement to allow for larger water draining rate to Closed Drain System. Additionally, the condensate outlet nozzle in Condensate Separator will be elevated to enable higher water holding volume. The paper explains a more analytical approach for liquid handling issues where liquid handling is the most common operational problem in Oil & Gas Industry for aging facilities. By having this basic engineering study and implement it in near future, the service life of assets can be extended, maintaining good integrity and reduce the risk without compromising HSE requirement.