Oil prices to rise to $70 a barrel by 2020, says Opec

The price of oil, which has fallen sharply over the past year to less than $40 a barrel, has created a challenging environment for the oil industry, according to the producers' group, Opec.

However, Opec says prices should slowly pick up over the next few years as demand recovers, and could reach $70 a barrel by 2020.

John Moylan reports.