Sam Zell, the real estate mogul, has acquired oil assets across the United States at ‘fire-sale’ prices, as U.S. drillers sell assets to raise cash which is scarce in the oil patch these days, the billionaire told Bloomberg TV in an interview on Thursday. Zell, founder and chairman of Equity Group Investments, has bought assets of oil companies in Texas, Colorado, and California at advantageous prices because firms are increasingly looking to have cash buffers, anticipating potential further slowdown in drilling and cash available to…