ARUN GAS FIELD

Proven reserves of the Arun gas field supply 6 LNG trains, each with a capacity of 8 million cubicmeters of feed gas per day. The gas field has 4 clusters of producing equipment. Each cluster has 16 producing wells with cooling and separating facilities.A portion of the gas produced from the Arun gas field is re-injected back into the reservoir. Natural gas liquids (NGL) are extracted from the re-injection stream.
Separation of the NGL mixture into propane, butane and condensate is done at the Arun plant LPG facilities.

THE ARUN LNG PLANT

1. Receiving facilities: The gas and liquids are re-combined prior to being processed into LNG and condensate.
2. Condensate recovery facilities: The first step is to separate the gas from the liquid condensate by passing a condensate stream through 2 stages of separation at successively lower pressures. The condensate is stabilized in a tower with a fired re-boiler, cooled and sent to storage. The stabilized condensate is ready for market as refinery or petrochemical feed stock. Off-gas from the stabilizer and from the low pressure separator is re-compressed to join the main feed of gas stream to be treated and liquified into LNG.
3. Feed gas preparation facilities: Impurities in the gas must be removed prior to liquefaction. Trace amounts of mercury are removed from the feed gas. Carbon dioxide and hydrogen sulfide are removed in a treating unit containing carbonate and amine solution(‘Benfield’ Treating Process). Water vapor is also removed. Heavy hydrocarbons are extracted by fractionation in a scrub tower.
4. Liquefaction facilities: Liquefaction takes place in specially constructed heat exchanger which uses a multi component refrigerant (MCR) consisting of nitrogen, methane, ethane, and propane. The MCR is used to liquify the natural gas. The MCR is cooled by a propane refrigeration system. The propane refrigeration system us cooled by a seawater cooling system.
5. Storage, loading, and shipping facilities: The liquefied gas, now at minus 160 degrees centigrade and reduced to 1/600th of its gaseous volume, is stored in specially constructed insulated storage tanks. These storage tanks have an inner shell of 9% nickel steel to withstand these low temperatures, and an outer carbon steel shell. The Arun LNG plant has 5 storage tanks with a capacity of 127.200 cubic meters each. LNG is loaded onto specially designed vessels in about 12 hours.

ABOUT PLANTSITE

Plantsite Location

The Arun LNG plant, owned and built by Pertamina is located at Blang Lancang, Lhokseumawe region, in the special province of Aceh along the northern coast of Sumatra.

The plant location was chosen because it satisfactorily met the criteria of access to deep water, proximity to the gas field, and minimum site preparation costs.

Plantsite Discovery

The decision to build the Arun LNG plant followed the discovery in 1971 of one of the world’s largest gas reservoirs by Mobil oil Indonesia Inc. working under a production sharing contract with Pertamina.

PT. Arun NGL Company’s well publicized success has exceeded expectations and the plant is presently one of the largest LNG processing facilities in the world.

As the nation’s reliance on LNG revenues continues to grow, the challenges confronting PT. Arun also increases. Some of the major challenges are human resource development; mastery of advanced technologies; new growth in a competitive market;daily operational demands which require optimum levels of safety and security; maintaining, stabilizing and improving upon production levels; and increasing the realibility of plant performance.

About Plantsite Construction

Construction of the Arun LNG processing facilities, which initially consisted of 3 LNG trains, was set in motion in late 1974 by Bechtel Inc., as the main contractor. Mobil Oil Indonesia Inc., as Pertamina’s production sharing contractor, discovered, developed and presently operates the Arun gas field which provides the entire feed stock for the Arun LNG plant.

Feed gas was first introduced into the plant in March 1978. Train 1 yielded its first drop of LNG in August 1978, train 2 in September 1978 and train 3 in February 1979. Condensate production commenced in May 1977. The Arun LNG processing plant is operated by PT Arun NGL Co., a non-profit operating company. PT Arun NGL Co. is owned by Pertamina (55%), Mobil Oil Indonesia Inc. (30%) and JILCO (Japan Indonesia LNG Co. – 15%), which represents the buyers.

In early 1981, the gas treating units of Trains 1, 2 and 3 were modified to increase the capacity to 115% of their original design of 1.7 million tons of LNG per train per year. In 1982, the Arun plant expansion program started with 2 additional trains (4 & 5). This expansion increased annual production capacity by an additional 3.4 million tons, all of which was exported to Japan. The expansion project was awarded to Chiyoda Chemical Engineering and Construction Co Ltd., in association with Mitsubishi Corporation and PT Purna Bina Indonesia.

Train 4 came on-stream in October 1983 and train 5 in January 1984. The expansion continued with train 6, engineered and constructed by JGC Corporation, and was on-stream in October 1986, one month ahead of schedule.

The contruction of the LPG facilities was started in February 1987. The project included extraction facilities in the Arun gas field and at the Arun LNG plant. Separate LPG storage and loading facilities located at the Arun LNG plant were also built. This project was awarded to JGC Corporation and was completed in October 1988. In order to fulfil targeted production assigned by the buyers, a capacity improvement project was initiated in 1990 and completed in 1993. Several pieces of LNG Trains equipment were modified and the plant capacity now reaching 138% of their original design capacity. These modifications increase the yield to more than 2 million tons of LNG per train per year.

To meet future demand, new gas fields will be integrated into the existing gas supply system. the South Lhoksukon gas field located 10 miles South inland of the Arun gas field will be online. Also, the Pase gas field which is located further south and the NSO gas field located 100 miles north east offshore of the Arun plant will be online before the year 2000.

The new gas fields will ensure adequate gas supply to meet contractual LNG demand until the year 2015.

LNG PROCESS OVERVIEW

Welcome to the PT. Arun NGL system, Arun LNG plant is located at Lhokseumawe the northern coast of Sumatra 275 km from Banda Aceh capital of Nanggroe Aceh Darussalam Province – Indonesia.

PT. Arun LNG plant processes natural gas from ExxonMobil Gas Fields The ExxonMobil fields consists of 2 major fields On-shore and Off-shore fields. The Onshore fields is called Arun field located at Lhoksukon about 30 Km away from LNG Plant. This field was discovered in late 1971 by Mobil Oil Ind. Inc. The Offshore fields named NSO (North Sumatra Offshore) Plat-form discovered in late 1990’s located approximately 100 KM from LNG Plant.

PT. Arun NGL operates Arun LNG plant, which includes the Condensate and LNG facilities. The LNG facilities include separation, treating, fractionation and storage and loading. Instead of uses some processes to produce stabilized condensate and Liquefied Natural Gas (LNG), there are also two facilities that used to produce LPG’s but no longer in operation.

Natural gas and un-stabilized condensate feed to Arun LNG plant deliver via separate pipelines. The 42 inches natural gas pipeline that carries feed gas from the Arun field and 24 inches treated gas from NSO onshore facilities goes to Inlet separation drum referred as «First Stage Flash Drums» to separate any hydrocarbon liquid from feed gas.
Hydrocarbon liquid in the bottom of separators is sent to condensate recovery unit for further treatment, while the overhead vapor flows to gas Treating Units. The 10 inches pipeline that carries un-stabilized feed condensate from Arun field and the 3 inches pipeline carriers small amount of condensate feed from NSO onshore facilities combined with hydrocarbon liquid from bottom of First Stage Flash drum goes to Condensate Recovery/Stabilization Unit referred as «Second Stage Flash Drums» for RVP (Raid Vapor Pressure) stabilization by heating and cooling. The overhead gas from the second stage separator then sent to low-pressure fuel gas system while the stabilized condensate product is cooled and sent to product storage.

The overhead vapor from First Stage Flash Drums will flow to LNG processing Units that referred as «Train» consists of Gas treating Unit ( Unit-30 ) where the impurities such as mercury (Hg), carbon dioxide (CO2) and hydrogen sulfide (H2S) are removed from the feed gas and then the sweet gas outlet Unit-30 goes to Liquefaction Unit ( Unit-40 ) where it is dehydrated to remove water content, cooled by using propane refrigerant and fractionated in scrub tower to remove heavy hydrocarbon from the feed gas. The lighter ends such as methane, ethane, propane and some butane are sent through the Ethane Extraction Unit ex LPG plant to recover ethane and propane plus to be prepared for MCR refrigerant components.

Residue gas outlet this unit (mostly ethane and lighter component) is boosted by the Residue Gas booster compressor and flow to the Main Cryogenic Exchanger in Unit-40 for liquefaction. The Scrub Tower bottom containing some mostly ethane, propane, butane and heavier hydrocarbon components become the feed to Fractionation/Refrigerant Preparation Unit.
Once the gas is liquefied in Main Cryogenic Exchanger ( spiral wound exchanger type ) using mixed refrigerant system that referred as «Mixed Component Refrigerant (MCR)», then pumped to storage tank and subsequent marine loading. MCR system receives a make up stream from Refrigerant Preparation Unit and Ethane Extraction Unit; the mixed-component refrigerant is pre-cooled by propane refrigerant system before circulated in the Main Heat Exchanger to liquefy the feed gas.

SOURCE: arunlng.co.id