HOUSTON, Aug 10 (Reuters) – Exxon Mobil Corp (XOM.N) has begun marketing U.S. shale gas properties as it ramps up a long-stalled program that aims to raise billions of dollars to shed unwanted assets and reduce debt taken on last year. Three years ago, the top U.S. oil producer set a goal of raising $15 billion from sales by December 2021. More recently, it promised to accelerate lagging sales to whittle a record $70 billion debt pile. The company’s XTO Energy shale unit is seeking buyers for almost 5,000 natural gas wells in the Fayetteville Shale in Arkansas, spokeswoman Julie King confirmed. The assets are among gas projects with declining…
