Royal Dutch Shell PLC warned Friday that fourth-quarter profit would be significantly weaker than recent levels partly because of higher exploration costs and lower oil and gas volumes. The company also cited weaker industry conditions in downstream oil products for the weaker performance. The oil major expects to post fourth-quarter earnings of $2.2 billion on a current cost of supplies basis—a figure that factors out the impact of inventories, making it equivalent to the net profit reported by U.S. oil […]