Pre-salt is a sequence of sedimentary rocks formed more than 100 million year ago in the geographical space created by the separation of the former continent of Gondwana into the present-day continents of the Americas and Africa, which began around 150 million years ago. Great depressions were formed initially between the two continents, which gave rise to large lakes. Over millions of years, rocks that later generated pre-salt oil were deposited there. As all the rivers on the separated continents flowed down to lower regions, large volumes of organic matter were laid down there.

As the continents moved farther apart, the organic matter that had accumulated in this new space became covered by the waters of the Atlantic Ocean, which was then forming. At this moment, a layer of salt started to form, which is now up to 2,000 meters thick. This salt layer was deposited on top of the accumulated organic matter, retaining it for millions of years, until thermochemical processes transformed it into hydrocarbons (oil and natural gas).

In the current Brazilian exploratory context, the possibility of there occurring a set of rocks with the potential to generate and accumulate oil in the pre-salt layer exists in the so-called pre-salt province, an area approximately 800 km long and 200 km wide, along the coast between the states of Santa Catarina and Espírito Santo. This province’s reservoirs are 300 km from Brazil’s Southeast region, which accounts for 55% of the country’s gross domestic product (the sum of all goods and services produced in the country). The pre-salt province’s total area (149,000 km2) is almost three and a half times as large as the state of Rio de Janeiro.