Chevron Corp. plans to drill three more wells in shale formations in China in addition to one it has already drilled, but the company doesn't expect rapid progress in shale-oil and gas production there, a company executive said Wednesday.

"It's going to take time before the full shale potential is not only understood but also developed in China," Joseph Geagea, president of Chevron Gas and Midstream, told Dow Jones Newswires, citing a shortage of geological data and insufficient infrastructure to support shale exploitation on the scale now seen in North America.

Chevron doesn't have any drilling plans for shale gas in China for the moment, said Mr. Geagea, who is on a visit to Tokyo.

He didn't specify a time frame for the remaining three wells. The first was drilled last year.

China's shale reserves may exceed those in the U.S. and Canada combined, but so far only limited-scale drilling has been undertaken by Chinese companies working with Western oil majors, including Chevron and Royal Dutch Shell PLC.

Chinese state-owned firms, including China National Petroleum Corp., China Petrochemical Corp., or Sinopec Group, and Cnooc Ltd., are investing billions of dollars in North American shale-gas projects both for investment reasons and to gain technological know-how in the areas of hydraulic fracturing and horizontal drilling needed to extract gas and oil trapped in shale rock formations.

The Chinese government has set ambitious long-term shale-gas output targets of up to 6.5 billion cubic meters by 2015 and as much as 100 billion cubic meters by 2020 from zero now.