British energy company BP said Wednesday it was marking the start of a campaign west of the Shetland Islands with deepwater drilling in the Loyal oil field.

BP is working as the operator at the Loyal field on behalf of its partners at Royal Dutch Shell and Austrian energy company OMV using the Deepsea Aberdeen rig. BP President for North Sea operations Trevor Garlick said the start of drilling marks an "important milestone" for regional operations.

The British company said five wells are planned in the area. First oil is expected by the end of 2016 and will be moved to a new floating, production, storage and offload vessel.

BP, which has been the focus of potential takeover rumors, said Wednesday it's in the middle of a five-year $4.5 billion investment program in the North Sea. Combined with other developments in the region, the company said it should be able tap into the estimated 450 million barrels of reserves still available in Shetland maritime acreage.

The low price of oil is starving companies of the capital needed to fund exploration and production. This week, the British company said first quarter profits of $2.6 billion were 20 percent lower year-on-year, but 15 percent higher than the previous quarter.

BP Chief Executive Officer Bob Dudley said the company was navigating a "weaker environment" that's led most of its peers to cut staff and trim spending. Nevertheless, the company said that, outside of sanction-strapped Russia, oil and gas production of 2.3 million barrels of oil equivalent was 8.3 percent higher year-on-year.

Garlick acknowledged the challenging times, but said the Shetland campaign is a emblematic of the "long-term competitiveness of BP's North Sea business."