Shell kicked off a $3.5bn (£2.74bn) share buyback program today as it posted better-than-expected numbers for the second quarter despite a previously announced $2bn (£1.6bn) impairment and a slide in revenue. The London-listed oil major reported adjusted earnings of $6.3bn (£4.91bn) for the three months to June 30, beating analyst consensus of $5.9bn (£4.6bn). Revenue was down quarter-on-quarter, falling 19 percent from $7.7bn in the first quarter, as lower liquified natural gas trading and refining margins and a weaker…