Weak returns at U.S. shale producers could cost more executives their jobs and lead to increasing battles with activist investors, analysts said following changes at two producers. After years of outspending cash flow to expand oil and natural gas production, executives are under pressure to pull back on spending and deliver higher returns. Investors have sold shares in companies that increased their drilling budgets, and some have avoided the sector altogether. Pioneer Natural Resources Co Chief Executive f retired on Thursday after a two-year stint in the job, with founder and former CEO Scott Sheffield returning to the top role. Halcon Resources Corp CEO Floyd Wilson and two other executives – finance chief Mark Mize and Steve Herod, executive vice president of corporate development – resigned the same day. The company said it began the search for a new CEO. “It’s a what-have-you-done-for-me-lately scenario,” said […]