what does the $50 barrell hedging mean, page-3

From the announcement it would appear that Beach has purchased a series of put options to cover a portion of expected production:

"Beach entered into the following new oil hedge, A$50/bbl Brent Put (floor) for April 2012 to March 2013 at 45,000 bbls/month."

i.e. they are not committed to sell at $50/bbl, but can exercise this put option if the prevailing price at the time is less than $50/bbl. They might do this to ensure that even if the world goes to hell in a handbasket over the next few months and the price of oil goes to $10/bbl, they can still cover operating costs.