By David Russell, reporter at OptionMonsterNEW YORK -- Pipelines have been the dominant group in the last few sessions, and Monday the bulls came back to Oneok ( OKE). OptionMonster's tracking programs detected the purchase of about 15,000 October 52.50 calls for $1. The transaction dominated activity in a name that sees volume of fewer than 1,200 contracts in an average session. Calls lock in the price where investors can buy shares, so they can generate significant leverage in a rally. The trades have already been working for some investors because there was also call buying in the October 50s a month ago. Those calls more than doubled by Monday's session, despite the stock climbing barely 5% in the same period. Call buyers have increasingly targeted pipelines in the last week as awareness grows of the United States regaining its status as a major player in the energy industry. Kinder Morgan and Energy Transfer have also seen bullish option paper. Oneok closed Monday's session up 1.66% to $48.46. Total option volume was 22 times greater than average in the name, with calls outnumbering puts by 83 to 1. Russell has no positions in OKE.