Abstract

The discovery of the Tupi Field in the pre-salt reservoirs of the rift and sag sections of the Santos Basin in 2006 completely changed the petroleum history of the entire South Atlantic realm. Until the Tupi discovery, the most important exploration targets in the South Atlantic basins were Tertiary and Upper Cretaceous marine turbidity plays, a model that had dominated exploration in the Campos and Santos basins for more than 40 years. The objective of this model was to find prospects with seismic bright spots in the drift section that could represent targets with low exploration risk and good analogy with the major hydrocarbon discoveries that had been made in turbidity current sandstones, such as those of the supergiant Marlim, Marlim South, and Roncador fields in the Campos Basin.

The Tupi Field has total proven oil and gas reserves of about 10 billion BOE, representing almost 40% of Brazil’s total reserves in 2019. The oil and gas are trapped in a faulted three-way dip-controlled structure of around 1300 km², where abiotic lacustrine carbonates—shrub, spherulitic, and reworked and laminated facies—and coquinas carbonate reservoirs more than 500 m thick are sealed by a massive halite and evaporite sedimentary unit that is more than 2000 m thick.

The field has already delivered more than 1.3 billion BOE since production started in 2009, having the highest daily oil production rate in the entire South Atlantic, with an average of around 1.1 MMbbl/d of oil and 45 MMm³/d of natural gas in December 2019. Tupi has several wells with average production rates of around 30,000 bbl/d, with some even surpassing 50,000 bbl/d. The field currently represents the second-largest proven hydrocarbon accumulation in the South Atlantic, only after Búzios, being responsible for more than 34% of daily hydrocarbon production in Brazil (ANP Bulletin, 2019).

The Tupi Field is the result of an unequaled conjunction of the petroleum system elements that are composed of uniquely overcharged upper Barremian lacustrine source rock spanning the entire oil window and directly connected with one of the best examples in the world of a very thick lacustrine mid-to-late Aptian shrublike texture, reworked and spherulitic carbonates, and upper Barremian coquinas reservoir rocks. These reservoirs were deposited in a stressed lacustrine environment in which the presence of primary and secondary porosities interconnected by a network of microfracture systems allowed the development of excellent permeability that sustains superb hydrocarbon flow rates.

This chapter includes a discussion about the Tupi Field, from source to trap, based on a solid foundation of geological, geochemical, and geophysical analysis and advanced 3-D petroleum system modeling (PSM). The most significant uncertainties regarding the ongoing and future exploitation of this supergiant light oil field are also discussed.