The unique agreement spares BP of paying out cash and gives the capital of the United Arab Emirates' stake in a company that first arrived there in 1939, back when the country was still a British protectorate of sheikhdoms.

The deal also makes the UAE one of the biggest single stockholders in BP as oil prices have climbed out of a 13-year low in February.

"This agreement will provide BP with long-term access to significant and competitive resources that we already understand very well," BP CEO Bob Dudley said in a statement.

News of the deal came without warning Saturday after years of negotiations between London-based BP and Abu Dhabi, the capital of the seven sheikhdoms that form the UAE.

BP had held a 9.5-percent interest in the onshore concession that expired in late 2014. That year, the company's overall crude production dropped 2.4 percent, something it blamed in part on losing the Abu Dhabi concession.

BP said Saturday's deal includes the UAE's Bab, Bu Hasa, Shah and Asab fields, which will produce between 20 billion to 30 billion barrels of oil equivalent over the 40-year term of the concession. BP will be entitled to 10 percent of its anticipated production of 1.66 million barrels of oil per day under the deal.