China's energy heavyweights Sinopec Corp and PetroChina have upgraded their outlook on the country's shale gas industry, citing steadily declining costs, but stopped short of predicting a near-term boom.

China, estimated to hold the world's largest technically recoverable shale resources, is hoping to replicate the shale boom that has transformed the energy landscape of the United States. Industry experts caution that it would be much more difficult for China to monetize its shale gas reserves than the U.S. as it faces serious challenges from water shortages to complicated geological structure and a lack of infrastructure.