NRG Energy (NRG: sentiment, chart, options) was the center of some extremely heavy option trading on Thursday, as more than 95,500 contracts crossed the tape, according to data from WhatsTrading.com. This volume is more than 21 times the stock's average daily trading volume of 4,405 contracts. Furthermore, roughly 80% of the volume traded on the put side.

It appears that the shares were the focus of a ratio spread. The July 22.50 put added more than 50,000 contracts, putting its open interest at 50,768 contracts. At 2:13 p.m. Eastern time, a block of 24,500 contracts traded at an ask price of $0.70, while another block of 24,500 contracts traded at an ask price of $0.75. Several small blocks totaling 1,000 contracts crossed the tape at an ask price of $0.70.

At the same time, the July 17.50 put added more than 25,000 contracts, bringing its open interest to 25,600 contracts. At 2:13 p.m., the option had several large blocks totaling 25,000 contracts trade at a bid price of $0.05. In this strategy, the trader is looking for the shares to fall to the sold strike, but still close above it by July expiration. The sold July 17.50 put premium is to help offset the cost of the July 22.50 puts.

The surge in put trading caused the stock's Schaeffer's put/call open interest ratio to jump overnight from 1.05 to 2.79. This reading is higher than all those taken during the past year, pointing to extreme levels of skepticism among short-term options players.