Ingenieur Vol 73 ingenieur Jan-March 2018 | Page 44

INGENIEUR Methodologies for Petronas Sabah-Sarawak Gas Pipeline Commissioning By Ir. Akbal Abu, Principal Commissioning Engineer, Group Project Delivery, PETRONAS P ETRONAS has successfully commissioned a 36”x 513 km Sabah-Sarawak Gas Pipeline (SSGP) to transport dry gas from the Sabah Onshore Gas Terminal (SOGT) in Kimanis, Sabah to Malaysia LNG Sdn Bhd (MLNG II & MLNG III) in Bintulu, Sarawak as well as to domestic customers; the Sabah Ammonia & Urea Plant (SAMUR) and PETRONAS Methanol Labuan (PML). The feed gas comes from the offshore Kinabalu and Kebabangan fields in Sabah and is processed in SOGT prior to distribution. The SSGP pipeline is designed at 96 Barg to transport up to 750 MMscf/d of dry gas with compression to meet the gas delivery requirement of each customer. The initial commissioning of the SSGP pipeline took place in early 2014 and continued until 2016 for partial and entire re-commissioning of the pipeline after a fire explosion incident in June 2014. The most challenging aspect of the commissioning was the massive co-ordination amongst the stakeholders involved as gas network commissioning needs to be done in an integrated manner. In complying with the stakeholders’ expectations, various pipeline commissioning options were considered and adopted to suit available resources, schedules, and most importantly to meet safety and customer specifications stipulated in the Gas Sales Agreement (GSA). This article is mainly focused on the purging aspects of pipeline commissioning to ensure safe introduction and export of dry gas to the customers and avoid creating a flammable mixture of natural gas with the air left post pre- commissioning activities such as hydrotesting, dewatering, cleaning and drying. The presence 6 42 VOL VOL 73 55 JANUARY-MARCH JUNE 2013 2018 of residual water in lines can have very serious consequences, both in terms of the potential for corrosion, and the possibility that hydrates may form if water is present as the line is brought up to pressure. HYDROCARBON GAS PIPELINE COMMISSIONING Three methodologies were considered for the Gas- In pipeline: Method 1 - Natural gas injection under pipelines vacuum conditions without the use of pigs; Method 2 - Natural gas injection as propellant of a pig train confining a nitrogen batch; Method 3 - Natural gas injection under pipelines pressure conditions without the use of pigs Method 3.1 - Inert purge by complete filling with inert gas, Method 3.2 - Inert purge using an inert slug to separate natural gas and air. Before choosing the pipeline commissioning method, it was essential to identify the following factors and parameters: ● ● Environmental and safety conditions; ● ● Pipeline characteristics (length, diameter, coating, geographical zone, trenching, subsea); ● ● Operating requirements, such as power and space availability and existence of an available venting system; ● ● Cost and time limits;