Royal Dutch Shell PLC is , as the Anglo-Dutch oil giant sheds assets across the globe amid falling oil prices.

The company has started a sale process for its 75% stake in the Tongyi oil lubricants joint-venture with bids expected to come in between $350 million and $500 million, according to people familiar with the situation, offering prospective buyers a rare majority stake in a Chinese company.

Blackstone Group LP appears to be in a strong position for first round bids among the private-equity firms looking at the Chinese operation, according to these people. The U.S. private-equity firm is working with the founder of the Tongyi joint-venture, Huo Zhenxiang, to craft a joint bid, they said. Mr. Huo owns the other 25% stake in Tongyi not owned by Shell.

Shell's management is looking to raise cash and slim down to boost returns as falling oil prices pressure results. When Shell chief executive Ben Van Beurden took the helm in January he laid out plans to sell $15 billion worth of assets by the end of 2015. He's turned his focus away from growing investments and toward improving free cash flow and hiking stock dividends to appease investors. The company's shares have declined by more than 5% this year.