Chevron Corp. /quotes/zigman/289939/quotes/nls/cvx CVX -0.67% plans to drill three more wells in shale formations in China, but the company doesn't expect any 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 plans for now to drill four shale wells in China, Mr. Geagea, who is on a visit to Tokyo, said, but didn't specify a timeframe for the remaining 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 such as Chevron and Royal Dutch Shell PLC (RDSA).

Chinese state firms, including China National Petroleum Corp., China Petrochemical Corp. or Sinopec Group and Cnooc Ltd. (CEO), have been investing billions of dollars in North American shale-gas projects both for investment reasons and to help them learn the hydraulic fracturing and horizontal drilling technologies 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.