The West Seno Oil Field

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From top left clockwise: The tension leg platform of West Seno (TLP-A), a tender unit 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 began in 2003. 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 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.

The field is currently operated by Chevron.

History of the Giant Attaka Oilfield

Pres. Soeharto di Santan

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.

If you like to read more about the Attaka field here is The Ten Interesting Facts About Attaka.

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10 Interesting Facts About The Super-Giant Oil Field of Attaka

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Attaka central platforms from left to right: Wellhead platform, Central Processing Platform, Compression Platform, and Quarter Platform

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. Attaka field is considered a giant oil field having 1023 MMBOE of recoverable reserves.

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.  Pertamina Hulu Kalimantan Timur assumed the operatorship of the field beginning on 25 October 2018.

Here are the interesting facts about the Attaka unit:

  1. Two years after its discovery, the Attaka field started producing oil in November 1972, making it the first offshore field in Indonesia.
  2. It has 10 platforms, 6 of which are remote wellhead platforms producing oil and gas from 109 wells.
  3. 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.
  4. Following the first discovery well, the Attaka Well 1A, seven appraisal wells were drilled to assess to size and potential of the hydrocarbon accumulation.
  5. The huge Attaka reservoir, formed in the very prolific Kutei basin, is a faulted anticline. It has an areal closure of 8000 acres. Attaka field is one of five super-giant fields discovered in the Kutei basin.
  6. Its oil reserves are attributed to oil found in 22 separate sands at a depth between 2800 feet and 7600 feet.
  7. Attaka sands have very high permeability. It is as high as 5 Darcy in some wells.
  8. Attaka field daily oil production was 110,000 BOPD at its peak and gas production was 150 MMSCFPD.
  9. 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.
  10. Attaka field has more than 50 sands with variable oil reserves. Reservoir sand thickness ranges from 5 to 100 feet. To produce them economically, multiple zone completion method using dual tubing strings and multiple packers was selected. 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 from.

Jamin Djuang