By Sabrina Valle HOUSTON (Reuters) – Chevron Corp posted its biggest quarterly earnings ever on Friday, built on strong fuel margins and high prices for natural gas and oil, and boosted its share buyback target. The oil major posted second-quarter net profit of $11.6 billion, or $5.95 per diluted share, more than triple the $3.1 billion, or $1.60 per share, in the same period last year. Chevron’s ramped-up share buyback plan follows those of other oil majors, including European giants TotalEnergies and Shell, which this week increased buybacks to satisfy investors looking for bigger returns. “…