In the production phase gas flows out of the well, through a flowline to the production facility, then down the pipeline to be used by consumers. All gas Mitsui E&P Australia (MEPAU) produces is provided to industrial and retail clients based in the Perth region.

When preparing for production, the drilling rig is removed from the wellhead and a ‘Christmas Tree’ is positioned over the top.

The Christmas Tree, also known as the Production Tree, controls the well. It’s a collection of barriers, valves and seals, as well as a gas and water separator. The Production Tree controls flow rates, regulates pressure and connects the well to the pipeline heading towards the Production Facility.

The Production Tree also enables MEPAU to test the pressure of the well to make sure it’s safe, both for humans and the subsurface environment.

During the production phase there are typically two staff members working at each gas field, which operates around the clock.

Once the well is exhausted it is decommissioned and rehabilitated.

Production well examples include Senecio-03 and Waitsia-01.

Waitsia Gas Field

Waitsia Stage 1A, an extended production test, has been in production since August 2016. Find out more about the Waitsia Gas Field.

Care and Maintenance

Care and Maintenance

When a facility is not being used, it’s put into care and maintenance. Read more about Care and Maintenance.

What we do at Mitsui E&P Australia

What we do

We are actively exploring, appraising, developing and producing oil and gas in a number of locations in the north Perth Basin. Read more about what we do


Before anything can happen we need to plan carefully. Read more about the planning process.


We look for gas, and when we find it we figure out if it’s worth pursuing further. Find out more about our exploration and appraisal process.


Once we’ve confirmed a well is commercially viable we get ready to put it into production. Read more about the development process.

Decommissioning and Rehabilitation

When the exploration or production activity has finished it’s time to clean up. Read more about how we decommission and rehabilitate a well and its surrounding area.


The Northern Perth Basin

The Northern Perth Basin is a prolific oil and gas producing area covering a large portion of the Mid West region of Western Australia. The town of Dongara, located approximately 360km north of Perth, is the regional economic hub for a number of industries, including oil and gas.