Presalt

Presalt, or pre-salt, is a term used in petroleum geology to describe hydrocarbon-bearing formations that lie beneath thick layers of evaporite salt. The salt acts as a strong, impermeable cap that can trap and preserve hydrocarbons in the underlying pre-salt sequence. The concept is widely applied in offshore exploration, particularly in Brazil, where extensive presalt plays have been identified in several offshore basins.

Geologically, the presalt interval comprises rocks deposited before the emplacement or thickening of the salt layer. The salt itself is often several hundred meters to kilometers thick and can deform over time, creating structural traps such as folds and faults that help accumulate hydrocarbons beneath or adjacent to the salt. Because the seal is salt, imaging and drilling beneath or around it presents specific challenges for exploration and production.

Exploration and production under presalt conditions require specialized seismic imaging and drilling approaches. The high velocity contrast between salt and surrounding rocks complicates seismic data interpretation, and wells must be designed to navigate through or around salt bodies while maintaining well integrity. Advances in 3D seismic processing, salt model building, and offshore drilling have been central to accessing presalt reservoirs.

Presalt discoveries, particularly in offshore basins near Brazil, have been notable for their potential to deliver substantial volumes of oil and gas with favorable quality. The term also appears in other basins worldwide where thick salt exists, though it is most closely associated with Brazilian offshore geology and industry.