By Ellen Chang Buffett’s Berkshire Hathaway acquired more shares of Occidental and owns a 16% stake. Berkshire Hathaway ( (BRK.A) – Get Berkshire Hathaway Inc. Report) purchased another 9.6 million shares of Occidental Petroleum ( (OXY) – Get Occidental Petroleum Corporation Report), increasing the behemoth’s total stake to 16.3% as oil prices remain volatile. The Berkshire conglomerate, run by billionaire Warren Buffett, said it spent $530 million acquiring the shares of the oil company, whose stock rose by 1% following the announcement, but had fallen by 13% during the past month, according …