Eighty years ago, CALTEX discovered the huge Duri oil field in the Rokan block in Riau, Sumatera.
Oil was found at a shallow depth of 400 feet when CALTEX began drilling its exploration wells in 1941. However, the exploration drilling was interrupted due to the onset of the World War 2.
After the war ended, CALTEX managed to obtain the approval from the newly formed government of Indonesia to operate in the Rokan block under a work contract scheme. Eventually, oil production from the Duri field began in February 1954.
The giant Duri field – 10 km wide and 18 km long – is one of the many oil fields discovered in the Rokan block. Minas is another giant oil field discovered in this block.
Oil production peaked at 65,000 BOPD in the 1960s.
Due to the high viscosity of the low gravity oil, to enhance the production, the steam injection was introduced in 1985.
The Duri steam flood project was so successful that it became one of the largest and the best steam floods in the world.
Thanks to the successful steam injection, Duri oil production increased significantly to 185,000 BOPD.
After 30 years of the steam flood, the production had declined to about 50,000 BOPD by 2017.
With more than 2.6 billion barrels of cumulative oil produced, the giant Duri field is still producing today.
Chevron handed over the operatorship of the Duri field and the Rokan block to Pertamina in August 2021.
With Pertamina Hulu Rokan as the new operator, the Duri field and the Rokan block are undergoing a massive expansion.
More than 400 wells were drilled in the Rokan block with mostly done in the Duri field in 2022 and the company plans to drill another 500 wells in 2023.
Pertamina built a 17 MWp solar plant in the Duri field in 2022 to meet the electricity need of the field.
The giant Carcara is a pre-salt oil and gas field located in the Santos basin offshore Brazil. It lies in water depths of 2027 meters and is one of the biggest discoveries in the world. It was discovered by Petrobras in 2012.
The oil reservoir lies in the pre-salt layer and its total thickness is more than 400 meters. It is estimated to contain recoverable reserves of more than one billion barrels of oil.
Operated by Equinor, oil production from the Carcara field is scheduled to start in 2024. Two FPSOs will be used to produce the oil and gas.
The Interesting Pre-Salt Basins
Oil was discovered in the Pre-Salt Basin in offshore Brazil in 2005. Oil-rich formations sit deep in the water and under thick layers of rock and salt.
Pre-salt basins were formed more than 100 million years ago when the South American and African continents separated, and therefore pre-salt layers are especially common off the coast of Africa and Brazil.
The hydrocarbon sits under layers of salt formations that are 2000 meters thick. The pre-salt production rates are some of the highest in the world for deepwater fields.
In Africa, the first pre-salt oil discoveries took place in Angola in 1983. The presence of pre-salt basins in eastern offshore Brazil and western offshore of Africa is proof that the South American and African continents were connected at one time.
The average crude oil production in Indonesia in 2018 is 803,000 barrels per day according to SKK Migas of Indonesia.
Here are the top ten crude oil-producing companies in Indonesia in 2018.
Chevron Pacific Indonesia – 209,000 BOPD
Chevron is the biggest oil producer in Indonesia in 2018 and has been a leading oil producer in Indonesia for more than 90 years. It started operating in Indonesia in 1924 under Standard Oil Company of California (SOCAL).
Chevron operated oilfields in Sumatera and East Kalimantan. It’s East Kalimantan assets came from the acquisition of Unocal in 2005. Chevron handed back all the assets in East Kalimantan to the Indonesia government on October 24, 2018, after 50 years of operation under Unocal and Chevron.
Currently, Chevron’s oil production comes mainly from the oil fields located in Riau, Sumatera under the Rokan Production Sharing Contract. The biggest oil field in the Rokan PSC is the Duri field which has been under steam-flood since 1985 and is one of the largest steam flood projects in the world. Minas is another giant oil field that Chevron discovered and operated in the Rokan Block.
ExxonMobil Cepu Ltd – 208,000 BOPD
ExxonMobil Cepu Ltd is the operator of the Cepu block located in Central Java and East Java. The Cepu Cooperation Contract (KKS) was signed on 17 September 2005 and will continue until 2035. ExxonMobil holds a 45% interest in the Cepu block.
ExxonMobil started exploration in 1999, and the oil from the Banyu Urip field started to flow in December 2008.
Pertamina EP – 79,000 BOPD
Pertamina EP operated 21 oil and gas fields located in various parts of Indonesia. These oilfields are managed under five asset groups based on their geographical locations.
Located in North Sumatera and some parts of South Sumatera, the Asset One oilfields include Rantau Field, Pangkalan Susu Field, Lirik Field, Jambi Field, dan Ramba Field.
Located in South Sumatera, the Asset Two oilfields include Prabumulih Field, Pendopo Field, Limau Field dan Adera Field.
Located in West Jawa, the oilfields included in Asset Three are Subang Field, Jatibarang Field dan Tambun Field.
Located in Central and East Jawa, the Asset Four oilfields include Cepu Field, Poleng Field dan Matindok Field.
Located in the eastern part of Indonesia, the oilfields in Asset Five are Sangatta Field, Bunyu Field, Tanjung Field, Sangasanga Field, Tarakan Field dan Papua Field.
Pertamina Hulu Mahakam – 42,000 BOPD
Pertamina Hulu Mahakam became the operator of the oil and gas fields located in the Mahakam Block on 1 January 2018. The fields were previously discovered and operated by Total along with Inpex as its partner. They acquired the block in 1966.
Several giant oil and gas fields are located in this block such as the Handil field, the Tunu field, and the Peciko field.
Pertamina Hulu Energi OSES (Offshore South East Sumatera) – 30,000 BOPD
Pertamina Hulu Energi OSES became the operator of the oil fields in Block South East Sumatera on September 6, 2018. The fields were previously operated by CNOOC, China National Offshore Oil Company.
Pertamina Hulu Energi ONWJ – 29,000 BOPD
Pertamina Hulu Energi ONWJ (PHE ONWJ) is currently the operator of the Offshore North West Java (ONWJ) production sharing contract following the change of company ownership from BP to Pertamina in July 2009.
The contract area, located in the Java Sea, covers an area of approximately 8,300 square kilometers – stretching from the North of Cirebon to Kepulauan Seribu.
The giant Ardjuna field is located in this Production Sharing Contract area. It was discovered by ARCO – Atlantic Richfield Company – in 1969 and operated by ARCO until BP – British Petroleum – acquired ARCO in 2000.
The production facilities consist of 670 wells, 170 shallow water platforms, 40 processing and service facilities and some 1,600 kilometers of sub-sea pipeline.
Medco EP Natuna – 16,000 BOPD
Medco EP Natuna, a subsidiary of Medco Energi, is the operator of the South Natuna Sea Block B. The field was initially operated by ConocoPhillips until Medco Energi acquired it in 2016.
Besides producing oil, Medco EP Natuna also supplies gas to Singapore using a 656 KM long 28” subsea pipeline.
Petronas Carigali (Ketapang) – 15,000 BOPD
Petronas Carigali Ketapang operates the Bukit Tua Field located in the Ketapang Block in East Java. Bukit Tua is an oil field but with a significant amount of associated gas. The offshore field is situated at a water depth of about 57 m.
The production facilities consist of wellhead platforms, an FPSO – Floating Production, Storage and Offloading – and onshore receiving facilities (ORF) in Gresik.
PetroChina International Jabung – 14,000 BOPD
PetroChina International Jabung operates the prolific Jabung Block located in Jambi in Central Sumatera.
The company produces crude oil, condensate, LPG and gas. PetroChina supplies gas to Singapore using a 450 KM long subsea pipeline.
An interesting aspect of the block is that PetroChina discovered the fractured basement rock contains a significant quantity of gas that can flow at significant rates.
Pertamina Hulu Kalimantan Timur – 13,000 BOPD
Pertamina Hulu Kalimantan Timur operates the East Kalimantan-Attaka Work Area. Chevron was the previous operator of the work area until it handed over the operatorship to Pertamina on October 25, 2018.
Attaka, the famous giant oil field is located in this block. The Attaka field was discovered and operated by Unocal until Chevron acquired it in 2005.
The oil fields in this work area are in the late declining phase. Around one billion barrels of oil and 3 TCF of gas have been produced from this work area.
Since 1966 when Indonesia began offering production sharing contracts (PSC) for international companies to explore and produce oil and gas in Indonesia, many giant and super-giant oil and gas fields were discovered.
Giant fields are those with estimated ultimate recoverable reserves (EUR) of 500 million barrels of oil or gas equivalent (MMBOE) and super giant oil fields are those holding an equivalent of 5.5 billion barrels of oil reserves.
Here are the ten giant offshore oil and gas fields in Indonesia discovered between 1966 and 2000.
1. Abadi Field
Abadi is a giant gas field discovered by Inpex in 2000 in the Masela contract area in the Arafura Sea. The Abadi field has an estimated ultimate recovery (EUR) of 768 MMBOE and it is located 93 miles offshore from the province of Maluku in the eastern part of Indonesia.
Originally the field would be developed using a subsea production system and a floating LNG (FLNG) facility. The plan now is to develop the field based on an onshore LNG development concept.
Inpex in partnership with Royal Dutch Shell is currently conducting preliminary front-end engineering design (Pre-FEED) studies for the Abadi field development based on an onshore concept. The LNG project will produce 9.5 MM tons of LNG annually.
When developed, the Abadi field may become the biggest deepwater gas project in Indonesia. It is expected to produce more than 1 billion SCF of gas per day and 20,000 barrels of condensate per day for 24 years.
2. Gula Field
The Gula field is an offshore gas field discovered by Unocal in its Ganal production sharing contract area located in the Kalimantan strait in 2000. With an estimated ultimate recovery (EUR) of 545 MMBOE, it is a giant gas field.
The Gula field, along with the Gendalo discovery and the Gada discovery, is one of the many discoveries made by Unocal in the deep-water area between Kalimantan and Sulawesi. These discoveries confirm that the Central Delta play contains world-class gas resources.
The Gula field is currently an undeveloped discovered resource.
3. Ubadari Field
Ubadari is a giant offshore gas field discovered in 1997. The Ubadari field has an EUR of 500 MMBOE and it is located at Bintuni Bay in West Irian province.
The Ubadari field will supply its gas to the Tangguh LNG plant when the Tangguh LNG Train-3 project is completed in 2020. The Tangguh expansion aims at meeting the ever-increasing demand for energy in Indonesia and accelerating the development of West Irian.
PLN, Indonesia’s electricity company, has signed a sales and purchase agreement to buy up to 1.5 million tons of LNG produced by Tangguh LNG plant annually.
Tangguh LNG plant is scheduled to process the gas produced from the six gas fields located at Bintuni Bay: Vorwata, Wiriagar Deep, Ofaweri, Roabiba, Ubadari, and Wos.
4. Vorwata Field
Vorwata is an offshore giant gas field located in Bintuni Bay in West Irian Province. The Vorwata field, with an EUR of 1833 MMBOE, was discovered by ARCO in the Berau block in 1997. BP became the operator of the Vorwata field after it acquired ARCO.
Gas production from the Vorwata field started in 2009. The field is capable of producing more than 1 BCF of gas per day and the gas is processed into LNG by the Tangguh LNG plant.
5. West Seno Field
The West Seno field is a deepwater oil field discovered by Unocal in 1996. Having an EUR of 553 MMBOE, it is a giant oil field and is currently operated by Chevron.
Lying in water depths of 2,400 to 3,400 feet, the West Seno field is Indonesia’s first deepwater development. It lies in the Makassar Strait PSC off Kalimantan on the continental slope of the northern Mahakam Delta.
The oil is produced using a tension leg platform and a floating production unit, tied back by two export pipelines to onshore infrastructure.
6. Peciko Field
Peciko is a gas field located offshore in the Mahakam Delta in East Kalimantan. The field was discovered by Total with INPEX as its partner in 1991. The Peciko is a giant gas field having an EUR of 1180 MMBOE.
Of all the producing fields in the Mahakam River delta, the Peciko field is unique in that its reservoir trap is both structural and stratigraphic.
The Peciko wells are highly productive having an average well productivity of 80 MMSCF of gas per day. Total daily gas production reached 1700 MMSCFD during its peak in 2005-2006. A substantial quantity of condensate is being produced along with the gas.
7. Tunu Field
The Tunu field is a supergiant gas field discovered by Total along with Inpex as its partner in 1977. It is located in the shallow waters along the outer limits of the delta offshore Mahakam Block in East Kalimantan. It has an EUR of 4378 MMBOE.
Started in 1978, the Tunu field produces gas and condensate having negligible CO2 or H2S, with the main productive reservoirs lying at depths from 2,200 to 4,900 meters.
Developing the large Tunu field is challenging and producing the gas requires drilling a large number of wells. The field has a large surface area of 20 Km wide and 75 Km long and it is located at the wetland of Mahakam swamp.
8. East Natuna Field
The offshore East Natuna gas field was discovered by AGIP in 1970. It is located 140 miles northeast of the Natuna Islands, Indonesia’s northernmost territory. It is a super-giant gas field with estimated recoverable reserves of 46 trillion cubic feet (TCF) of gas.
There were serious studies done and attempts made by Exxon-Mobil and Pertamina to develop this field.
The field is currently undeveloped due to its very high CO2 content of 71%. To produce the gas will require removing the CO2 from the gas and injecting it back into the reservoir. Production can be commercially viable when the price of oil is above $100 per barrel.
9. Attaka Field
The Attaka field is a giant oil and gas field discovered by Unocal in partnership with Inpex in 1970. Chevron became the field operator after it acquired Unocal in 2005. Having an EUR of 1000 MMBOE, the Attaka field is located 12 miles from the shore of East Kalimantan.
The huge Attaka reservoir, formed in the very prolific Kutei basin, has an areal closure of 8000 acres. Due to its large areal extent, originally the oil and gas were produced from more than 100 wells located in 6 remote wellhead platforms.
Ten years later, five subsea wells were completed in 1981-1984 to produce the untapped oil accumulation in areas out of reach of the existing remote platforms. These are the first subsea completions in Indonesia.
Attaka field daily oil production was 110,000 BOPD at its peak and gas production was 150 MMSCFPD. Now the Attaka field is quite depleted.
10. Ardjuna Field
The Ardjuna Field is a giant oil field having an EUR of 698 MMBOE. This is the first offshore giant field discovered since the birth of the Indonesian PSC system in 1966.
The Ardjuna field was discovered by ARCO in the Offshore North West Java (ONWJ) production sharing contract area in 1969. Subsequently, it was operated by BP when it acquired ARCO in 2000. Now the field is operated by Pertamina Hulu Energy ONWJ Ltd.
Interesting facts about the Ardjuna field include the drilling of the first horizontal well in Indonesia in 1985 and supplying gas to PLN’s power plant in Muara Karang in Jakarta in 1993.
Pertamina’s refinery in Cilacap began using crude oil from the Ardjuna field in 1986.
Attaka field, a giant offshore oil field located 12 miles from the shore of East Kalimantan in Indonesia was discovered by Union Oil of California (UNOCAL) in August 1970. This giant oil field having 1023 MMBOE of recoverable reserves is the first commercial oil field discovered in offshore Kalimantan.
General Soeharto, the president of Indonesia at that time, inaugurated the Attaka field and the Santan terminal on 22 January 1973.
Santan terminal is the onshore complex where the crude oil from the Attaka field is processed and stored before it is exported by oil tankers. Santan terminal is also where the produced gas is processed before it is sent to Badak LNG for liquefaction.
Unocal along with its 50-50 partner, Inpex, operated the Attaka field until it was acquired by Chevron in August 2005. Later on, Pertamina Hulu Kalimantan Timur assumed the operatorship of the field on 25 October 2018 when the production sharing contract expired.
Interesting Facts About the Attaka Field
Two years after its discovery, the Attaka field started producing oil in November 1972, making it the first offshore field in Kalimantan.
Following the first discovery well, the Attaka Well 1A, seven appraisal wells were drilled to assess to size and potential of the hydrocarbon accumulation.
The huge Attaka reservoir, formed in the very prolific Kutei basin, is a faulted anticline. Its areal extent of oil accumulation is nearly 10 square miles. Attaka field is one of five giant oil fields discovered in the Kutei basin.
Initially, the Attaka field consisted of six wellhead platforms producing oil from 52 wells, and the central platforms comprised the Quarter Platform, Processing Platform, and Gas Compression Platform. After 1980, additional platforms and wells were added to maintain production and maximize the hydrocarbon recovery. It eventually had a total of 22 platforms and 109 wells, five of which are subsea wells.
Five subsea wells were completed in 1981-1984 to produce the oil accumulation in areas out of reach of the existing remote platforms. These are the first subsea completions in Indonesia and in Asia.
Initially, its produced associated gas was flared. Finally, the flaring stopped with the completion of the Badak LNG plant in 1977. Unocal, Total Indonesie, and Huffco were the gas suppliers to the Badak LNG plant.
Attaka wells have very high permeability. It is as high as 5 Darcy in some wells.
Attaka field’s daily oil production peaked at 116,950 BOPD in December 1977 and gas production peaked at 174 MMSCFD in October 1980.
A significant milestone was reached when cumulative oil production of 600 million barrels was recorded at 6:42 PM on March 7, 2001. Cumulative gas production in that same year was 1.3 trillion SCF.
Attaka field has more than 50 sands with variable oil reserves at depths between 2800 and 7600 feet. Reservoir sand thickness ranges from 5 to 100 feet. A multiple zone completion method using dual tubing strings and multiple packers was selected to produce them economically. This method allows the engineers the flexibility to select from which of the 2 to 4 perforated zones in each well they would like to produce
Decommissioning of Platform EB
The Attaka field has been producing oil and gas for 50 years and its production has been declining for the past 30 years. The field is currently producing less than 5000 BOPD.
Finally, the Attaka field’s EB Platform was decommissioned in November 2022. It is the first decommissioned offshore oil platform in Indonesia.
Interestingly, the EB Platform was not the oldest platform in the Attaka field. In fact, it was one of the latest platforms built in Attaka. Platform EB was built in 2000 to replace Platform E that was burnt down due to the blowout of Well E-20 in August 1997.
The EB platform was built to accommodate the drilling of seven 7 fully insurance-reimbursable wells to tap reserves estimated at 3.25 million barrels of oil and 18.5 BSCF of gas.
Jamin Djuang – A former Production Supervisor of the Attaka Field in 1980.