Calls were the options of choice on Chesapeake Energy Corporation (NYSE:CHK - 17.15) during Monday's session, with volume rising to 1.23 times the usual level. About 26,000 calls were exchanged on the natural-gas stock, easily outpacing the roughly 10,000 puts that changed hands.

The most active strike was CHK's January 2013 20 call, where 7,057 contracts were traded. About 72% of those calls crossed the tape closer to the ask price, and implied volatility on the option ticked up 2.9 percentage points by the close to 40.3%. Open interest on the January 20 call climbed overnight by 3,055 contracts, confirming the addition of new bullish bets at this strike on Monday.

The volume-weighted average price (VWAP) on the January 20 call checked in at $0.24, which means most of the day's option bulls need CHK to rally above breakeven at $20.24 by the time the January series expires.

Generally speaking, CHK calls have been gaining popularity in recent weeks. During the past 10 days, traders have bought to open 1.53 calls for every put, according to data from the International Securities Exchange (ISE), Chicago Board Options Exchange (CBOE), and NASDAQ OMX PHLX (PHLX). This ratio registers in the 65th annual percentile, suggesting that speculative players have been purchasing calls over puts at a faster-than-usual pace lately.

While activist investor Carl Icahn is still on the CHK bandwagon, the stock has been a disappointment on the charts this year. The shares are off more than 22% year-to-date, and CHK is pinned below resistance at its 20-week and 40-week moving averages. Unfortunately, if traders continue to load up on 20-strike calls, this activity could create an additional layer of options-related resistance during the near term.