Nexen has been climbing, and one investor wants to be on board.

optionMONSTER's Heat Seeker tracking system detected the purchase of 1,000 June 23 calls for $0.75 and the sale of an equal number of June 18 puts for $0.65. Volume was more than 7 times open interest in both strikes.

The position cost a net $0.10 and lets the trader manage an entry into Canadian oil and natural-gas stock. The transaction locks in an entry price at $23 if the stock rallies that high in the next four months but, if it pulls back to $18, the trader will be forced to buy shares at that level.

Given its extremely low entry price, the strategy has the benefit of generating significant leverage to movements in the share price. But the position will also expire worthless if NXY remains trapped between $18 and $23.

The stock is up 0.44 percent to $20.66 in early afternoon trading and 18 percent in the last month. It's been rallying as an improving economy and geopolitical risks drive crude-oil prices higher.

Overall option volume in the name is triple the daily average so far today.