About The Unique Arun Gas Field
The Arun field is a supergiant gas field. It had 16 trillion cubic feet of original gas in place and was discovered in 1971 by Mobil Oil in Aceh, Sumatra.
Interestingly, the gas concession was initially held by Asamera. Due to unsuccessful exploration by Asamera, it was sold to Mobil Oil in 1968.
The Arun gas reservoir had abnormally high temperatures and pressure of 178 degrees C and 7100 PSIG respectively. The reservoir is made up of carbonate rock located at 10,000 feet in depth.
Due to its high pressure, porosity, permeability, and reservoir thickness of about 500 feet, the Arun gas wells were extremely productive. Each well could produce more than 100 MMSCF of gas per day.
The highly prolific Arun field produced over 3000 MMSCF of gas per day from its 78 wells for more than 10 years. The produced natural gas was fed into the Arun LNG plant to recover the condensate and liquefy the gas.
The field is estimated to have produced over 14 trillion cubic feet of natural gas and 840 million barrels of condensate.
As a retrograde gas reservoir with no water drive, Mobil Oil took extreme care to manage the reservoir to achieve the highest gas recovery possible. Steps, such as gas reinjection, were taken to manage the reservoir pressure. Up to 900 MMSCF of dry gas were injected back into the reservoir daily through 11 injection wells.
As the reservoir and wellhead pressures eventually declined, gas compressors were used to boost gas production.
By 2014, the Arun field gas production had become so low that the LNG plant was shut down permanently.
The now depleted and low-pressure Arun gas reservoir is a great candidate for storing captured CO2 as it is a volumetric reservoir meaning the reservoir is completely sealed. It is enclosed by impermeable barriers that prevent any fluid from entering or leaving the reservoir.
The Arun LNG Plant
The Arun LNG plant was built to monetize the huge amount of the discovered gas. It is the first LNG plant built in Indonesia and Southeast Asia.
Initially, the Arun LNG plant consisted of three LNG trains that started to operate in August 1978, September 1978, and February 1979 respectively.
Two trains were later added to the plant in October 1983 and January 1984 respectively.
All five trains produced a total of 55,000 M3 per day of LNG and 115,000 barrels per day of condensate.
The LNG plant eventually had six trains. The sixth train was completed in November 1984.
Up till 1999, Indonesia produced one-third of the LNG in the world.
A major problem in processing Arun gas is that the gas has a large percentage of mercury and it reacts with aluminium in the cryogenic system to form an amalgam.
After 36 years in operation, the Arun LNG plant was finally shut down in 2014.
The Gas Well Blowouts
The massive blowout in the Arun field happened in 1978 when the CII-2 well in the Arun field was being drilled.
The blowout killing efforts were led by Red Adair. Initially, the well control team attempted to kill the well from the top. However, it failed.
Finally, the blowout was killed by drilling a directional well and then pumping a huge amount of acid followed by heavy mud into the bottom of the CII-2 well.
The blowout was so huge and due to the extremely high reservoir pressure, more than fifty high-pressure and high-volume mud pumps, and more than one hundred pump operators and engineers were brought in from several countries to kill the blowout.
Another Arun well, CIII-8, blew out two years later in 1980.
The Ambitious Arun CCS Project
Although the huge Arun field reservoir has been almost completely depleted for some time, it may have a second life.
As the world is committed to reducing carbon emissions by capturing emitted CO2, the Arun field has a huge potential to become the largest storage facility for captured carbon in Asia.
PEMA (Pembangunan Aceh) has formed a joint venture company, Carbon Aceh, to perform a feasibility study up to the development, implementation, and operation of the Arun CCS project which is planned to start operating in 2029.
The depleted Arun gas reservoir is a perfect candidate for storing CO2 for the following reasons:
- It is almost completely depleted and therefore it has low pressure.
- It is completely enclosed and therefore the storage space is completely sealed.
- It has an enormous volume of storage space. It can store more than 1 billion metric tonnes of CO2.
Moreover, the Arun field already has infrastructure that can be used to facilitate the CCS project such as offshore terminals that can receive CO2 shipments from CO2 tankers and pipelines that can transport the CO2 to the Arun field.
Marzuki Daham, former Chairman of BPMA – Aceh Oil & Gas Regulatory Body – gave his comment on this important CCS project.
“A great location with the existing infrastructure will surely be a plus to support the project. It would be even more interesting if Arun can be an open-access storage for captured CO2 from many countries around the area. It is a step to save the planet.”
When the Arun carbon storage facility becomes operational, the Arun field will be known not just as one of the largest gas fields and LNG plants in the world, but it will also be known as one of the largest carbon storage facilities in the world.
This article is adapted from various sources by Jamin Djuang – Chief Learning Officer of LDI Training and author of “The Story of Oil and Gas – How Oil and Gas are Explored, Drilled and Produced”.
