Offshore oil and gas driller Ensco International Inc on Thursday reported a 32 percent drop in quarterly earnings as more of its rigs were left unused, but it beat Wall Street forecasts and its shares firmed in premarket trading.

Second-quarter net profit fell to $200.3 million, or $1.41 per share, from $296.7 million, or $2.05 per share, in the same quarter a year ago.

Earnings from continuing operations were $1.59 per share, topping analysts average forecast of $1.46 per shares, according to Reuters Estimates.

Ensco last week wrote off the value of a rig seized in Venezuela and booked an $18.1 million charge on top of the cost of the lost contract, and said the total second-quarter impact would be 26 cents per share.

Revenue fell 16 percent to $511.6 million.

Ensco's shares climbed about 1.3 percent in light premarket trading to $38.92. Those shares are up 35 percent in 2009, broadly in line with the performance of the Philadelphia Stock Exchange oilfield service index .OSX.