Santos CEO David Knox recently said some costs were coming down by 10-30% for Santos while margins were stable.

"We seem to make the same amount of money in a $50 world as in a $100 world," he told the Australian Financial Review earlier this week.

"What happens on the down side is that the costs fall as well."

When extending development timeframe dates for the long-delayed Browse floating LNG project last month, Woodside also revealed there were opportunities to "significantly lower cost outcomes".

Using its own research along with data from IHS CERA upstream cost-related indices and EnergyQuest, Citi estimated that Australian LNG project savings of 15% could be achieved in the downturn times of 2015 compared to 2014.

Citi estimated the biggest savings were expected in the realms of "materials" (at 25% with steel, cement, diesel and nickel prices down 15-30% since mid-2014), "rentals", such as rig rates and shipping rates (10% saving), "energy" (40% saving) and "transportation/shipping" (30% saving).

"For opex (operating expenditure), we assume costs are 50% labour, 25% materials, 25% service costs," Citi said.

"Based on the previously discussed cost savings, we estimate opex saving of 15%."

However, Citi also warned that Australian dollar depreciation could undermine potential capex and opex savings, with LNG projects typically denominated in a mix of currencies such as US dollars for steel and service costs.

"This weakening AUD increases USD denominated costs in AUD-denominated budgets, and vice-versa a weakening AUD reduces AUD-denominated costs in USD-denominated budgets," Citi said.

"Hence while we estimate reduced industry activity may allow project cost savings of 15% all else equal, we think the true range may be more like 5-20% depending on exposure to USD/AUD expenditure and denomination of budgets."

Citi noted that Woodside's Pluto LNG operation and the Santos-led Gladstone LNG project would miss out as their capex was mainly clocked up during a high-cost environment.

Macquarie Wealth Management recently flagged potential impairments of $A4 billion for GLNG and $1 billion for Pluto due to the tumble in Brent crude prices.