U.S. energy giant Chevron sold its entire stake in refiner Caltex Australia Ltd for A$4.7 billion ($3.7 billion) in Asia’s biggest block deal this year, as falling oil prices and high costs hurt margins. Offshore institutional investor demand for the 50 percent stake in Australia’s biggest refiner was strong, with bidding driving the final price to A$35 a share, a spokeswoman for Goldman Sachs, the sole underwriter for the deal, confirmed on Saturday.