PetroChina said 2014 net profit dropped 17% amid low oil prices, and pledged to slash spending on exploration and production and other areas this year. Above, a PetroChina oil factory in Dalian, China. Photo: Reuters BEIJING—Global oil companies are unwinding some big bets they made on China—and that is bad news for the Chinese companies, which need their know-how. Falling oil prices have forced oil bosses to slash planned investments that now look less likely to provide good returns. Projects in China, often expensive and geologically risky, are high on the list of those to be cut. Royal Dutch Shell PLC emerged as one of the industry’s biggest China proponents in recent years, pledging billions of dollars to hunt for shale gas while building up businesses producing and selling oil products. The company is now scaling back investment in China shale exploration after several years of costly challenges. […]