Venezuela plans to begin its first shale gas exploration campaign in western Lake Maracaibo in a joint venture with Brazil's state-run Petrobras, Venezuela's energy minister said on Wednesday.

"We've approved in the ministry the first explorations for shale gas here in Lake Maracaibo," Rafael Ramirez, who is also the head of Venezuelan state oil company PDVSA, told a conference in the city of Maracaibo.

The Petrowayu joint venture is to run the project.

According to PDVSA, it has a 60 percent stake in the company, while Petrobras has 36 percent and U.S.-based Williams has the remaining 4 percent.

The minister did not say when exploration would start, nor how much PDVSA and its partners would likely spend.

PDVSA also has run initial tests for shale gas at La Guajira, also in western Zulia state, in the hope of discovering significant reserves of unconventional resources.

The OPEC nation has vast reserves of conventional gas, but several offshore gas projects with foreign partners are still waiting to start output. (Reporting by Alexandra Ulmer; Writing by Andrew Cawthorne; Editing by Marianna Parraga and Paul Simao)