On Friday, Santos managing director Kevin Gallagher told analysts the operator of the remote gas field was aiming to reach a final investment decision in late 2018 or early 2019.
Engineering work for the option, which is expected to piggy-back off the Bayu-Undan facility, is expected to begin later this year.
ConocoPhillips operates the two adjacent gas discoveries for Santos, which is a partner in Darwin LNG, and South Korea's SK Holdings, which is not.
ConocoPhillips and its partners invested in the Bayu-Undan field and Darwin LNG without sufficient reserves cover to support the project's initial 20-year life, although Australia's smallest LNG plant, which was developed at a cost of a mere $US3 billion ($A3.9 billion), an early 2000s pricetag far below what could be achieved today.
The JV had expected to see further exploration success, and develop Darwin LNG up to 10MMtpa, but that did not happen quite as planned as the LNG and shale gas booms took off.
With Bayu-Undan expected to be depleted as early as 2023, the pressure has been on for some time to find new gas for the 3.7MMtpa plant.
Caldita-Barossa and the Greater Poseidon fields in the Browse Basin were studied for development, but last week Origin Energy revealed the Browse option was too expensive and had fallen by the wayside.
Caldita-Barossa would require a 250km pipeline to connect to the existing Bayu-Undan pipeline, and is the cheaper of the two options, although it lacks liquids reserves that would help offset some of the costs
There are already seven wells in the Barossa field, with up to three new appraisal wells planned to be added to the mix this year to help better define the field.
Exploration of the fields dates back to the mid-1960s.
ConocoPhillips joined Santos in the exploration permits in 2004 and the presence of a significant accumulation of natural gas was confirmed in 2006.
The most recent appraisal campaign involved the drilling of three wells in 2014-15.
The results from two wells were in line with expectations, with one well in the higher end of the expected range.
Thorough interpretation of those results during 2015 informed the need for further appraisal.
