Chevron Corp (CVX.N) is cutting staff on its global energy trading desks this week, sources said on Thursday, making it the latest division to face reductions as part of a $3 billion cost-saving plan brought on by low crude oil prices. The Supply and Trading group, based in Houston, but with offices in Singapore, London and San Ramon, California, may be reduced by as much as 10 percent as part of a company-wide job reduction plan, according to two people familiar with the measures.