The development stages:Exploration drilling/2010-12.The 370,000 square kilometers offshore São Francisco basin has one of the oldest geological formations in Brazil. It has 24 blocks where 59 exploratory wells have been drilled and 25,000 square kilometers of 2D seismic have been conducted. In 2013, Petra confirmed the existence of hydrocarbons at the 1-PTRA-17-MG well in block SF-T-121 and the presence of unconventional "tight" natural gas in 21 São Francisco wells. The company expects to begin production from the area in 2015.