A Dynamic Simulation Assessment for Relocating Flare System into Separated Platform Utilizing Idle Subsea Main Oil line

Abstract

KLB is an offshore platform that consists of production wells and two train gas lift compressors. During well intervention, the KLB operation team must turn off the flaring system due to potential flare radiation of more than 500 BTU/hr-ft2at the working area and gas dispersion more than 50 %-LEL at the flare tip. The relocation of the KLB flaring system to the nearest platform keeps the KLB gas lift compressor operating during this activity. The relocation scenario can maintain the KLB platform production of 700 BOPD. KLA Flowstation is the nearest platform to the KLB. It is separated one kilometer, connected by an idle subsea oil pipeline, but there are no pigging facilities due to limited space at the KLB platform. Therefore, the comprehensive assessment to relocate the KLB flaring system is a) Flare system study using Flare Network software to simulate backpressure and Mach Number at tailpipe in the KLA and KLB flaring system; b). Dynamic transient simulation using Flow Assurance Software to calculate backpressure, liquid hold up, and slugging condition in the flare KO drum; and c). Flare radiation and dispersion study. The initial condition of the idle subsea oil pipeline was full of liquid as the preservation for a pipeline to prevent a further oil spill in case of a leak during the idle condition. The dewatering process for the idle subsea pipeline has been conducted by purging the pipeline utilizes 0.7 MMscfd gas lift with a pressure of 100 psig to displace liquid content to 20 bbl. The transient simulation for gas swapping was conducted at a gas rate of 4.1 MMscfd as the train compressor's flaring condition. The calculated backpressure at the KLB safety valve is 12.3 psig below the required maximum of 30 psig. The calculated liquid surge volume in the Flare KO drum during flaring is 17 bbl and can be handled by surge volume inside the KO drum. The predicted condensation inside the subsea pipeline shows that the maximum operation of the flaring system is limited to 30 days. The radiation and gas dispersion to the nearest facility is within a safe limit. The KLB teams successfully conducted the relocation of the flaring system from the KLB platform to the KLA platform. The result was no interruption of production, no risk of radiation, and no potential explosion during a well intervention. Experience in the last two activities has confirmed that this method can prevent revenue loss of 19 billion rupiahs. This study has initiated a new engineering standard and best practice for flaring systems as opposed to the current practice which states that the flare location shall be at the same location as the production facilities with no pocket piping in between. This study and field experience have proved that the flaring system can be located on a different platform by conducting engineering assessments to ensure process and process safety criteria are within Company and International Standard.