LONDON (Reuters) - Oil services companies will increasingly branch into activities currently the domain of their traditional customers, the international oil majors, a senior industry executive said on Tuesday.

Ayman Asfari, Chief Executive of and the largest shareholder in the UK's third-largest listed oil services company by market value, Petrofac PFC.L, said rather than just building and operating oil production facilities for a fee, oil services companies will in future seek a chunk of project profits.

“Most service companies are trying to migrate their businesses,” Asfari told Reuters in an interview.

The development could be a threat to opportunity-starved oil majors such as Royal Dutch Shell RDSa.L and Exxon Mobil XOM.N.

Historically, the oil companies negotiated concessions with resource holders and then hired the oil services companies to do much of the heavy lifting such as drilling, facilities construction and operating equipment.

But Asfari said companies like his and larger U.S. rival Schlumberger SLB.N can now often perform the project management function the oil majors previously did.

In return, they may seek a stake in the project, either from the oil major or from the National oil company (NOC) which owns the reserves or a return tied to successful project delivery.

“What they are doing is replacing, in most of these cases, the role that the international oil company would have played,” he said.

The world’s richest reserves are held by NOCs from countries like Saudi Arabia, Kuwait, Venezuela and Mexico which are reluctant to cede reserves to foreign oil companies.

Oil services companies may offer an attractive alternative because they don’t seek to book reserves or capture upside from higher oil prices.

Asfari cited his contract to manage Dubai oil and gas fields previously operated by ConocoPhillips COP.N, which was gained after Dubai refused U.S. oil majors demands for better terms, as an example of a service firm offering a more competitive solution.

However, Asfari said there was a limit to the extent to which companies like Petrofac could replace the big oil firms.

Oil services are likely to leave exploration, more complex projects such as liquefied natural gas and developments in tough locations such as the Arctic, to the oil majors. “They have areas of expertise that no one else has,” Asfari said.