From top left clockwise: The tension leg platform of West Seno (TLP-A), a drilling support vessel, and the floating production unit (FPU).
Discovered by Unocal in 1998, the West Seno field, lying in water depths of about 3200 feet, is the first deepwater oil field in Indonesia.
Located in the Strait of Makassar, the West Seno field is about 50 km away from the giant Attaka field and 60 km from the Santan terminal in East Kalimantan.
The oil and gas are produced through a tension leg platform (TLP) which is also the first of its kind in Indonesia.
The floating topside of the tension leg platform is attached to the seafloor by four 3200 feet long tendons having a diameter of 26 inches and a wall thickness of 1.036 inches.
Currently, all the subsea wells are produced from platform TLP-A which can accommodate 28 wells. Unocal originally had planned to build two tension leg platforms.
Oil production from the West Seno wells began in 2003 and currently, they are producing about 1200 BOPD. The fluids from the subsea wells are initially separated into oil and gas on the FPU (Floating Production Unit).
The separated oil and gas are then transmitted via two 12-inch diameter and 60 km long pipelines to the onshore facilities at Santan for final handling and storage.
One of the oil production challenges of West Seno is handling the difficult-to-break emulsions. The emulsions are hard to break due to the presence of certain chemicals in the fluid, the decreasing fluid temperature as it rises to the surface, and the motion of the floating platform.
The West Seno offshore production facilities also handle the production from the nearby Bangka field. Bangka field produces about 1000 barrels of condensate daily and 40 MMSCF of gas per day.
The development of the West Seno field was made possible by having a favorable PSC profit splits of 35 percent instead of the regular 15 percent for shelf developments.
Fifty years ago, Union Oil of California (UNOCAL) along with its partner, INPEX, discovered the giant offshore oil field Attaka in East Kalimantan.
General Soeharto, the president of Indonesia at that time, then inaugurated the Attaka field and the Santan terminal on 22 January 1973.
In the early days of Attaka and the Santan terminal, there were many workers from the US and UK. Over time, they were gradually replaced by Indonesian workers.
Unocal operated the oil field for 25 years from its East Kalimantan headquarters located in Balikpapan. The Attaka field was subsequently acquired and operated by Chevron, and then by Pertamina Hulu Kalimantan Timur beginning on 25 October 2018.
At 50 years old, the field is still producing today.
Thousands of oil people – expatriates from many nations and Indonesians from every region – have visited and worked in the offshore facilities and the onshore Santan terminal including me.
I worked in the Attaka field as “Production Foreman” in 1980. I hope you like this snippet of the history of Attaka and the Santan terminal.
Attaka central platforms from left to right: Wellhead platform, Central Processing Platform, Compression Platform, and Quarter Platform
The Attaka Field Discovery
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.
