Royal Dutch Shell PLC on Thursday swung to a third-quarter loss after taking chunky write-downs on projects amid a 16-month slump in oil prices. The giant Anglo-Dutch oil company took charges of $7.9 billion in the quarter after scrapping a number of big ticket projects. The hefty figure included $2.6 billion related to the company's decision to abandon its exploration project in the Alaskan Arctic after drilling its costliest dry hole ever and $2 billion for scrapping a major oil sands project in Canada. It also reflected impairment charges of $3.7 billion, reflecting a weaker long-term oil and gas price outlook and mostly relating to North American shale gas properties. The price of international benchmark Brent crude averaged around $50 a barrel in the third quarter, the lowest level since the financial crisis and roughly half its level in the same period last year. Shell's quarterly loss on a current cost-of-supplies basis--a number similar to the net income that U.S. oil companies report--was $6.1 billion down from a profit of $5.3 billion a year earlier. Stripping out its impairments and write offs, Shell reported a profit of $1.8 billion, down 70% compared with a year earlier "While our cash flow and our operating performance in the quarter were strong, the headline numbers we're reporting today include substantial impairments and well write-offs," Chief Executive Ben van Beurden said. "These reflect both a lower oil and gas price outlook and the firm steps we are taking to review and reduce Shell's longer-term option set." The company's sizable loss in the third quarter comes as Shell moves ahead with its $70 billion acquisition of BG Group, which is expected to complete early next year. The deal remains a "springboard to focus Shell into fewer and more profitable themes, especially deep water and integrated gas," Mr. van Beurden said. More from MarketWatch