* Total, HSE to meet Monday to discuss risks in stopping leak
* HSE expected to give Total positive advice
* Danger of return to platform reduced since flare extinguished
By Karolin Schaps and Muriel Boselli
LONDON/PARIS, April 1 (Reuters) - French oil company Total , which wants to fly experts to a North Sea oil platform to plan how to cap a well that has been spewing gas for the past week, will discuss the safety of the scheme with British experts on Monday.
Total's Elgin platform is enveloped in a huge gas cloud, and company officials will discuss with the Health and Safety Executive the risks involved in sending experts there on a helicopter.
Total wants to stop the gas leak in two ways - by injecting drilling mud to 'kill' the well, which would involve sending experts to the wellhead platform; and by drilling two relief wells, a safer, slower, more expensive solution.
On Saturday Total confirmed that a gas flare, lit during the evacuation to burn off excess gas, had gone out of its own accord, reducing the threat of an explosion.
The flare had been burning only 100 metres from the site of the gas leak, and its extinction made a return to the abandoned platform considerably less dangerous.
"The company has prepared risk assessments for landing a helicopter on the platform and sending a team to carry out observations at the site of the gas release," an HSE spokesman said on Sunday.
Industry sources said the HSE, which can advise on compliance with regulations but cannot instruct Total how to proceed, was expected to say that both Total's planned projects were acceptable on safety grounds. One of the sources said this advice was expected as early as Monday.
The dual procedures Total wants to carry out will put the well - which is emitting potentially explosive gas - out of commission, at least temporarily.
In the first, Total will inject drilling mud into the well, using the weight of the mud to stop the gas flow, a scheme that would require workers to return to the wellhead platform, which might be dangerous because of the cloud of gas.
This operation could start within 7-10 days of Total deciding to go ahead.
The second involves digging two relief wells, which could take six months and cost up to $3 billion, but with virtually no risk attached.
Relief drilling would require boring down 4 kilometres to intercept the gas pocket at exactly the right point, engineers say.
Total had originally hoped the leak would run itself dry as reservoir pressure dropped. But the discovery that its source was just 1.5 kilometres from the main gas reservoir, one of the world's deepest, suggested that the amount of gas feeding the leak might be larger than first thought.
FLAME IS OUT
There had been fears that the gas flare might ignite the leaking gas. But the UK Energy Department said Total had assured it that the prevailing winds were blowing the gas away from the flare.
The leak, which began a week ago after pressure rose in a previously capped well, has been spewing an estimated 200,000 cubic metres a day of natural gas into the air, forming a potentially explosive gas cloud around the platform.
Total evacuated its 238 platform workers on March 25 and set up a two-mile exclusion zone for safety reasons, with fire-fighting ships on standby.
A senior union official said on Friday that Total had repeatedly assured workers a leak was impossible until just hours before evacuating them.