Ukraine doubled underground gas stocks to 17.169 billion cubic meters (bcm) between April 4, when the last heating season ended, and August 17, according to preliminary data from pipeline and gas infrastructure operator Ukrtransgaz. Ukraine injected 74.36 million cubic meters (mcm) of gas into underground storage on August 17, importing 66.91 mcm and producing 54.8 mcm of its own gas.