Managing Liquid Holdup Problems at Complex Gas-Pipeline Network: A Case History from East Kalimantan

Abstract

Abstract The East Kalimantan Gas Pipeline Network extends from the south part of the Mahakam Delta transporting the natural gas from East Kalimantan PSCs (VICO Indonesia, TOTAL Indonesie, and Chevron Indonesia Company) to the largest LNG complex in the world - 8 trains at PT Badak NGL and also to the Fertilizer/Industrial Plants in Bontang. Normal daily production rates of East Kalimantan PSCs are 3,300 – 3,400 MMscfd with a maximum of 3,700 MMscfd. The majority of the East Kalimantan Gas Supply to the Customers are transported through 56 km 4 (four) main pipelines i.e. 2X36" and 2X42", known as Badak-Bontang Pipelines, operating in parallel, from the common Gas Export Manifold at Badak Field. Daily operations of the 4 pipelines have to deal with a number of constantly changing parameter i.e. production rates from the producers that will impact to the change of gas composition. Because of the gas composition, temperature and pressure change along the pipelines, a certain fraction of the gas is naturally converted into liquid in the pipelines. As most of liquids are carried through a system of parallel pipelines, some of them will stay in the bottom section of pipelines which is referred as Liquid Hold Up (LHU). This LHU, if become excessive, eventually will restrict gas flow and increase backpressure to the upstream production facilities which could further reduce the total gas delivery from the production plants/platforms. Identification of which pipeline having LHU problem is not easy since the pipelines share the common header at both ends. VICO Indonesia as Operator of East Kalimantan Pipeline Network and Coordinator of East Kalimantan Gas Operation therefore is challenged to manage the pipeline operations under conditions of fluctuating gas supply in order to optimize gas production from the producers. Several procedures and technologies have been implemented. When first introduced, Switching Guideline of Badak-Bontang Pipelines was derived from semi empirical analysis with steady state process simulation and limited field data. This guideline is designed to provide criteria for switching operation between Pipelines operating modes to minimize LHU. Over period of time, the guideline has gone through a couple of revisions, including the introduction of term ‘Operating Green Box’ (the name given to operating parameters of pipelines in low LHU condition) as supported operational data from experiences increases. Pigging guideline was also developed to determine at what kind of flow and pressure conditions in Badak-Bontang Pipelines that are considered adequate for pigging operation. The purpose is to avoid getting a pig stuck in a pipeline. Last improvements in Badak-Bontang Pipeline Operations include the development of more efficient and effective sweeping procedure to reduce high LHU in one of four main pipelines by Pipelines segregation at Badak Export Manifold and the utilization of Dynamic Process Simulation to better predict and anticipate fluid dynamic behavior inside the Pipeline. The installations of Ultrasonic Flow Meter at individual pipeline and Telemetry system in Pipeline network help Pipeline Operations to quickly identify which pipeline having LHU problem. With those continuous improvements, VICO Indonesia has been able to successfully manage LHU problems at the complex gas pipeline network in East Kalimantan. This paper provides a case history of the experience in managing the complex pipelines operations in East Kalimantan and shows the solution to solve the liquid hold problem due to changing of operating conditions.