Production from the commissioning of the domestic gas export facilities started flowing into the Dampier to Bunbury Natural Gas Pipeline earlier this month.

The gas flowed between August 2 and August 11, with a maximum rate of 120 terajoules a day achieved on August 8. A total of 675 terajoules of gas was delivered.

No production has been recorded since on the WA Gas Bulletin Board, which is run by the Australian Energy Market Operator.

A spokesperson for Chevron confirmed to Energy News that the company was undertaking final commissioning and testing activities on the Gorgon domestic gas facility, export pipeline and meter station.

According to a number of industry sources, some of the gas delivered into the Dampier-to-Bunbury Natural Gas Pipeline has not met the required specification.

The problem is said to be the dewpoint of the gas, leading to heavier fractions of gas entering the pipeline than is allowed by the DBNGP specification.

The Gorgon domestic gas plant uses MEG/Joule-Thomson (JT) processing to meet pipeline moisture and hydrocarbon dewpoint specifications, according to a Chevron document on its website.

The Chevron spokesperson would not be drawn on any issues with the gas specification but stated that system testing was a normal part of final commissioning and has been coordinated with customers.

Commissioning hiccups not unusual

Energy News spoke to an industry insider about what issues can occur when commissioning a domestic gas plant in WA.

Normally the primary concern is to ensure the treated gas meets the required specification, the insider said.

Typically, early gas production from the new field is flared while production settles down, and the expected gas composition into the treatment plant is better known. In the case of Gorgon, LNG production had also occurred before the commissioning of the domestic gas plant.

If early gas production does not meet specification it can be blended with other gas in the pipeline so the overall gas composition meets the specification.

The vast majority of WA domestic gas production - North West Shelf, Devil Creek and Varanus Island - is upstream of Gorgon and would help dilute any out-of-specification issue.

For more severe out-of-specification events DUET, the operator of the DBNGP, can store batches of the out-of-specification gas and gradually bleed it into the main flow.

This is possible as the DBNGP has been ‘looped' and is two parallel pipelines. One pipeline can be used for continuous flow while the other pipeline acts as a storage tank for the batch of out-of-specification gas.

If any gas did not meet the hydrocarbon dew point requirement, it is possible that heavier fractions of hydrocarbons would remain in liquid form at the pipeline operating pressure. Hydrocarbons in their liquid state can damage compressors designed for gas.

Third time lucky?

Chevron, the operator of the Gorgon project, has had well-publicised issues with commissioning both Angola LNG and more recently the first Gorgon LNG train.

Woodside Petroleum CEO Peter Coleman commented on Chevron's commissioning track record earlier this month when discussing the start-up of the Chevron-operated Wheatstone project.

Coleman said "we got our fingers crossed" and they were looking forward to being "third time lucky" for their 13% interest in Wheatstone.

The waiting customer

The principal customer for Gorgon domgas is Synergy, WA's state-owned electricity generator and retailer, which will also be looking on in interest.

Synergy signed a gas supply contract with Gorgon in November 2011. The purchase of 125 terajoules a day for 20 years was originally due to commence in 2015.

At the time media reported industry sources saying the price was $6-8/gigajoule. This was compared to the current contracts with the NWS that were thought to be about $2.50GJ based on legacy pricing.

Gorgon participants sold the gas to Synergy jointly under an authorisation from the Australian Competition and Consumer Commission that expired at the end of 2015.

Further domestic gas sales from Gorgon are expected to be on an equity basis, where each participant sells their share of the production separately.

Domestic gas was not optional

The WA government required Gorgon to reserve sufficient gas to deliver 2000 petajoules to the domestic market and be capable of delivering 300TJpd to the market.

The Barrow Island Act of 2003 that underpins the project's right to operate on the Class-A reserve does not specify when the 300TJpd capacity must be achieved. It is not known whether the current commissioning is for the full plant capacity.

Gorgon capacity outlook was first listed on the Australian Energy Market Operator Gas Bulletin Board on August 2 as 170TJpd. Since August 10 the capacity outlook has been a reduced to 156TJpd.

There has been industry speculation that only part of the eventual 300TJpd capacity will be brought on initially.

The remainder is expected to follow some years later once the project is assured it can sustain a sufficient flow of gas to fill the three LNG trains.