By Sonali Paul

MELBOURNE (Reuters) -Woodside Energy Group Ltd, Australia's top independent gas producer, flagged on Thursday a drop in free cash flow over the next few years, which raised alarm among analysts about future dividend payouts.

Woodside's shares fell 1.8% after its annual investor briefing in a broader market that was up 0.9%, even after Chief Executive Officer Meg O'Neill said the company was committed to paying out at least 50% of net profit after tax.

Analysts are forecasting a payout of around $4 billion a year over the next few years, which Barrenjoey analyst Dale Koenders said would use up free cash flow and potentially leave no room for growth projects like the Trion oil project off Mexico, estimated to cost between $6 billion and $8 billion.

The company, which completed a merger with the petroleum arm of BHP Group in June, indicated in a graph that free cash flow would slump from more than $6 billion in 2022 to well below $2 billion in 2023 and exceed the 2022 level only after 2026.

Woodside, 60% owner and operator of Trion, aims to make a final investment decision on the project in 2023. Trion is 40% owned by Mexican state owned oil company Pemex.

"Our current assessment is that we can afford to take FID on Trion and we can afford to take FID on Oklahoma," O'Neill told analysts at the briefing, referring also to a Oklahoma-based hydrogen project.

Woodside's biggest growth project, the $12 billion Scarborough gas development and Pluto LNG expansion in Western Australia is on track to start producing liquefied natural gas (LNG) in 2026.

However, O'Neill said the company has faced a slowdown in securing approvals for environmental plans for drilling, seismic programs, subsea installations, and its pipeline, after a court overturned a drilling permit for rival Santos Ltd's $3.6 billion Barossa project.

"We are certainly concerned and processes are slowing down to be really frank," O'Neill said.

Australia's Federal Court is set to rule on Friday on Santos' appeal seeking to reinstate the environmental approval for drilling on Barossa.

(Reporting by Sonali Paul; Editing by Himani Sarkar and Rashmi Aich)