Danish energy company Maersk Oil said it started drilling the first production well from a field that's expected to meet 5 percent of British demand for gas.

Maersk said it started drilling the first of six wells in the Culzean field off the British coast. Drilling will take place continuously for the next five years with the first volumes of gas set for production in about two years.

"This is an important milestone in ensuring that we can deliver Culzean on schedule, and with it 5 percent of U.K. gas demand in 2020-21," Maersk Oil CEO Gretchen Watkins said in a statement.

The company started cutting steel at a Singapore shipyard early this year for a platform associated with its $4.5 billion Culzean project in the British waters of the North Sea.

Culzean is located about 145 miles offshore and, once in full swing, should remain in production for at least 13 years. With a peak production rate of up to 90,000 barrels of oil equivalent per day, the company said Culzean field is the largest discovered in the area in more than a decade.

Facing pressure from the downturn in the energy sector, Maersk in April closed offices in Houston and said it would manage any of its assets in the U.S. waters of the Gulf of Mexico from its offices in Copenhagen.

The company in June advanced on a restructuring plan by sidelining top executive. Last week, the parent group A.P Moeller-Maersk said it was splitting the company in two, with its oil-related business spinning off to focus on the North Sea.

The company said the split created a separate entity to focus on transport and logistics, and another to focus on building a strong position in the British, Danish and Norwegian waters of the North Sea.