U.S. retail chains have about $70 billion in lease obligations set to expire over the next four years. This opens up opportunities for landlords to move in more-profitable tenants and for retailers to adjust their portfolios, according to Moody’s Investors Service. Moody’s studied 62 public chains and found that the $203 billion in lease obligations on their balance sheets would drop to $133 billion by 2018 as leases expire. Based on historical data, the vast majority of these chains are likely to renew, but some may be tempted to reallocate some of that capital toward e-commerce or other initiatives, wrote Jason Cuomo, a Moody’s senior accounting analyst, who authored the report. Office-supply chains have the fastest rate of lease expirations coming up relative to other sectors, while drugstores have the fewest, according to the report. Sears Holdings’ minimum lease obligations will fall 58 percent to $2.3 billion in 2018, from $5.5 billion this year. Meanwhile, J.C. Penney Co.’s lease obligations are set to drop by 48 percent to $1.1 billion. Wal-Mart Stores’ obligations will fall by 35 percent to $9.5 billion, and TJX Cos.’ will drop by 42 percent to $5.9 billion.