Saudi oil giant Aramco has issued a $4-billion bond as it tapped the debt market for the first time this year amid persistently weak oil prices in the low $60s per barrel. Aramco, the world’s top crude exporter and biggest international oil company, on Monday announced the start of issuing U.S.-dollar denominated international bonds under its Global Medium Term Note Programme, saying the issuance amount is subject to market conditions. Saudi Aramco ultimately placed $4 billion in a four-tranche bond, which received more than $21 billion in…