China's shale-gas industry is still in its early days, with production nowhere near the commercial stage, but that hasn't deterred foreign companies from trying to get in on the ground floor.

U.S. companies that provide oil-field services are looking to gain a foothold in China by investing in local partners before the country launches a second round of bidding later this year for its huge reserves of natural gas trapped within shale. Chinese state-owned companies were allocated shale-gas blocks in the first round in June 2011.

"There's money to be made here," said Simon Powell, head Asian-Pacific oil and gas analyst at broker CLSA. "It's like the gold rush—it's the guys who sold the picks and shovels who made the money, not the miners themselves."

Last week, U.S.-based oil-field-services giant Schlumberger Ltd. bought a 20.1% stake in Hong Kong-listed Anton Oilfield Services Group for about $80 million, making it the second-largest shareholder of the Chinese company, which provides a range of operational services for shale-gas developers. With the deal, Schlumberger gains access to China's largest energy producers—China National Petroleum Corp. and China Petrochemical Corp., also known as Sinopec Group—both of which are Anton's primary customers.

Schlumberger's decision to take a minority stake better protects its intellectual property, unlike joint ventures where overseas companies may have less control over the transfer of technology that China craves.

Meanwhile, China's big three energy producers—CNPC, Sinopec Group and China National Offshore Oil Corp., or Cnooc Group—have been investing in shale-gas assets in North America. Some analysts have said they appear to be doing so as a way to obtain advanced technology for use at home.

However, China's state-owned producers say these deals are mainly driven by a search for higher returns and that most expertise remains firmly owned by oil-services companies such as Schlumberger, Baker Hughes Inc. and Halliburton Co., which are reluctant to pass on unconventional drilling know-how to their Chinese counterparts.

Now that Schlumberger has moved deeper into China, more U.S. competitors may follow, analysts say. Halliburton and China's SPT Energy Group Inc. already have a strategic alliance to provide drilling operations, while Honghua Group Ltd., another local oil-services company, is already 14% owned by Nabors Drilling, a U.S. oil-field-equipment manufacturer.

Honghua is even in talks to form a joint venture with a leading foreign oil-services company to provide shale-gas drilling, according to its chairman, who declined to name the company.