LONDON/NEW YORK (Reuters) - U.S. oil services firm Weatherford International (>> Weatherford International plc) has appointed advisers including Morgan Stanley (>> Morgan Stanley) to sell units starting in the first quarter of 2018, banking sources told Reuters.

Alongside oil producers, companies that drill wells, haul water and provide other services to energy exploration firms have been hit by a slump in oil prices, with benchmark Brent tumbling to about $27 (£20.3) a barrel in 2016 from more than $100 in 2014. It is now trading at more than $60.

Weatherford, which carried out a three-month strategic review, said in a third quarter analyst call it would restructure some parts of the business and identify units "which are not critical to our strategy going forward."

It did not specify which businesses, but said it expected to raise about $500 million from these divestitures.

Three banking sources said the company was looking to offload the artificial lift business, the wellheads and the drilling tools units and the international pressure pumping assets.

Potential bidders for the pressure pumping assets included U.S. firm Superior Energy Services, Canada-based pressure pumper Calfrac and private equity backed energy funds, the sources said.

Weatherford did not respond to a request for comment, Superior Energy and Calfrac were not immediately available to comment. Morgan Stanley declined to comment.

Weatherford, whose debt amounted at $7.9 billion at the end of the third quarter, had put its land drilling business valued under $1 billion on sale in 2016, but failed to sell it.

One source said it would now sell it in parts based on its regional operations.

"This process is already underway and the company hopes to monetize some of the rigs before the end of the year," the source said.

A second source said that potential acquirers included firms with operations in the Middle East and North Africa, where Weatherford mostly operates.

Weatherford entered a joint venture with the world's largest oil services firm Schlumberger in March to combine their North American hydraulic fracturing and completion units to rival that of market leader Halliburton (>> Halliburton Company).

Analysts see more consolidation in the sector, after the acquisition of Baker Hughes by GE's (>> Genesis Healthcare Inc) oil and gas equipment and services operations in July.

"The way to grow differentially over the next couple of years is to be proactive with regards to acquisitions," Tudor Pickering managing director Byron Pope said.

(Reporting by Clara Denina and David French; Editing by Edmund Blair)

By Clara Denina and David French