Romanian environmentalists hope to emulate the Bulgarian example. “We don’t want exploration for shale gas to go ahead, because of the method used, which is the only one available at the moment,” Miruna Ralea, executive director of the environmental group Alma-Ro in Bucharest, said in an interview.

“Fracking is strongly polluting, and, in our view, the risks are by far higher than the benefits,” Ms. Ralea added, citing the dangers of polluting arable land, chemical leaks and the huge use and pollution of water resources.

Romanian activists are not fighting Chevron, they are fighting the government, Ms. Ralea said, lamenting a “lack of transparency and information” on planned exploration programs. Contracts between Chevron and the authorities have been classified as secret, she said.

Alexandru Patruti, head of the mineral resources agency, was not available to answer questions on shale gas operations, despite repeated calls: But in an interview with the local Web site HotNews earlier this month, he said unconventional gas was “a resource that not a single state or company can afford neglecting.”

“We are at the start of a period in which we will study rocks that contain unconventional reserves,” Mr. Patruti said, adding that a study conducted by Romanian researchers was looking at archival geological information to be able to determine where reserves might lie.

Concerning the effect that shale gas operations could have on the environment, Mr. Patruti said, “Exploiting any mineral resource is a process that has an impact on the environment. But this impact can be controlled and minimized by respecting good practices and further regulation of operations being carried out.”

According to Pierre Thomas, professor at the École Normale Supérieure in Lyon, hydraulic fracturing is “relatively secure,” but only if drilling is preceded by expensive studies, and the operation is monitored thoroughly.