Shell (NYSE: SHEL) is launching yet another $3.5 billion share buyback program after booking better-than-expected earnings for the second quarter of the year. The UK-based supermajor reported on Thursday adjusted earnings of $6.3 billion, down from $7.7 billion for the first quarter of the year, on the back of lower prices and volumes and lower trading results due to seasonality and reduced volatility. The second-quarter result, however, easily beat the market expectation of earnings of $6 billion. Lower refining margins, driven by a stabilizing…