Petrohawk Energy (HK, news, chart) is seeing double its normal trading volume, as players take positions in anticipation of volatility in the share price. The stock is trading up 80 cents to $41.85 and 15,000 puts along with 18,000 calls have traded on the day.

Although traders who are comfortable flipping stock and spreading options typically don’t look to Berkshire Hathaway for advice or for trading cues, an interesting idea showed up in Berkshire’s recently released 2007 annual report. On page 16, the chairman explains the two categories of derivative contracts that the company does hold.