Breaking Barriers and Paradigms in Presalt Exploration: The Pão de Açúcar Discovery (Offshore Brazil)

Abstract

Pão de Açúcar is certainly one of the most impressive and challenging hydrocarbon accumulations found in the prolific Campos Basin, offshore Brazil. This discovery opened a new frontier for exploration in Brazil’s ultradeep waters, in depths ranging from 2500 to 2900 m (8202 to 9514 ft). Pão de Açúcar is the third discovery made by a consortium integrated by Repsol Sinopec Brasil (operator), Statoil do Brasil, and Petrobras in the Concession BM-C-33, with estimated resources of 700 million bbl of light oil and 3 tcf of gas. This discovery is the result of the integrated work of a multidisciplinary international team using some of the most advanced technologies available today in the oil exploration industry in seismic imaging, drilling, formation evaluation, and fluid-rock sampling analysis. This discovery consists of a significant hydrocarbon column hosted within a unique reservoir made up of a variety of basic volcanic rocks overlain by pervasively silicified microbial carbonate platform/ramps, grading toward profundal lake facies. This chapter summarizes the main results of the exploration and ongoing appraisal work regarding this unique hydrocarbon accumulation, highlighting both the complexity of the discovered reservoirs and the operational and technical challenges faced, and still to overcome, before beginning production.

Silicification, flow pathways, and deep-seated hypogene dissolution controlled by structural and stratigraphic variability in a carbonate-siliciclastic sequence (Brazil)

“…Many productive oil and gas deposits hosted in carbonate reservoirs are characterized by silicification and/or processes that can be assigned to hypogene karstification, like the Parkland field in Western Canada (Packard et al, 2001), the Tarim basin in China (Wu et al, 2007;Zhou et al, 2014;Dong et al, 2018;You et al, 2018), pre-salt reservoirs in Santos and Kwanza basins (Girard and San Miguel, 2017;Poros et al, 2017), and Campos Basin offshore Brazil (De Luca et al, 2017;Lima et al, 2020). Networks of deep-seated conduits formed by dissolution are often intercepted during drilling in hydrocarbon exploration within soluble rocks (Maximov et al, 1984;Mazzullo et al, 1996;Mazzullo, 2004).…”

Hydrothermal silicification and hypogene dissolution of an exhumed Neoproterozoic carbonate sequence in Brazil: Insights from fluid inclusion microthermometry and silicon‐oxygen isotopes

“…Bulk permeability in the silicified and karstified layers at Calixto Cave reached 10 3 mD, as reported by Pisani et al (2022), with rock plugs permeability that can reach up to 200–250 mD (2 to 3 orders of magnitude higher than surrounding carbonates) and porosity up to 16%. The formation of pervasive cavernous porosity‐permeability in silica is common in many hydrocarbon reservoirs affected by hydrothermal silicification (De Luca et al, 2017; Lima et al, 2020; Packard et al, 2001; Poros et al, 2017; Teboul et al, 2019; Wei et al, 2021). These reservoirs show incredibly complex porosity‐permeability heterogeneities, fault‐ and fracture‐controlled conduit systems, secondary mineralization and reactive fronts associated with vuggy pore space.…”

“…Solutional voids and karstic vugs are commonly found in quartzites and silicified (cherty) carbonates in many hydrocarbon reservoirs in sedimentary basins, such as North Slope in Alaska (e.g. Shanmugan & Higgins, 1988), offshore Brazil (De Luca et al, 2017; Fernández‐Ibáñez, Jones, et al, 2022; Lima et al, 2020) and Tarim Basin in China (Dong et al, 2018; Wei et al, 2021; You et al, 2018).…”

“…Silicified reservoirs are typical of the lower Cretaceous pre‐salt sequences of the Campos and Santos basins in Brazil (Lima et al, 2020; Lima & De Ros, 2019), the Kwanza‐Congo Basins of Africa (Poros et al, 2017; Teboul et al, 2019) and the Parkland gas field in Canada (Packard et al, 2001). On the basis of petrographic, isotopic and fluid inclusion studies, pervasive silicification and porosity enhancement processes in these basins were ascribed to the circulation of high‐temperature fluids (De Luca et al, 2017; Girard & San Miguel, 2017; Lima et al, 2020; Poros et al, 2017; Teboul et al, 2019). However, the link between silicification and hypogene karst dissolution, and their evolution in space and time, are still poorly understood.…”

Stratigraphy of Architectural Elements of a Buried Monogenetic Volcanic System and Implications for Geoenergy Exploration

“…Hydrothermal fluids can induce secondary porosity by mineral dissolution (e.g. Vieira de Luca et al, 2017;Mordensky et al, 2018;3 in Figure 21), or can clog potential reservoirs by precipitation of cements (e.g. Schutter, 2003;5 in Figure 21).…”