Resource Assessment and Hydrocarbon Exploration Risk of Deep and Ultra-Deep Waters of the Sergipe-Alagoas Basin

The Sergipe-Alagoas basin is perhaps the highest potential area out of Brazil’s pre-salt province. The basin is mature in shallow waters and onshore but remains a frontier in the deep and ultra-deep waters (Fig. 1). Recent ultra-deep discoveries confirmed light oil in turbidite reservoirs with 30 to 100 meters of thickness and API of 26º to 43º (depths of targets > 4.500 m, at water depths of 2,000 to 3,000m, on average).

Figure 1. Map of Sergipe-Alagoas Basin showing the oil fields, exploration blocks, oil, gas and dry wells and 2D seismic PSDM data used in the BPS/ TGS 3D quantitative petroleum system basin modeling study.

BPS, in partnership with TGS, recently performed a detailed study integrating the most up to date 2D PSDM seismic data from TGS with well date from more than 50 nearshore and deep-water wells from the BPS Geodatabase and a comprehensive oil slick survey (Fig.2). This was used to create a quantitative petroleum system basin model and identify leads using both Petromod and Trinity software, substantially increasing the potential of the basin.

Figure 2. Map of Sergipe-Alagoas Basin showing the oils slick distribution, oil types and the location of the high resolution 2D PSDM TGS data used for the 3D petroleum system basin modeling performed by BPS in the Basin. Important to note that most the oils analyzed are mixtures of blacked marine and cracked lacustrine oil.

The petroleum system efficiency in the Sergipe-Alagoas Basin was already proven via several onshore and nearshore fields in production (e.g., Carmópolis, Pilar, Dourado, Piranema, among many others), as well as new ultradeep-water discoveries (e.g., Barra, Cumbe, Farfán, Moita Bonita, Poço Verde, Muriú, and others; Fig. 2) that proved the widespread presence of an active petroleum system in the basin. The high quality of the seismic imaging made it possible to map several leads in the rift and open-marine plays, mainly composed of fluvio-deltaic and turbiditic sandstones, as well as carbonates located over structural highs, which add significant volumes in combined or structural traps (Fig. 3). The results of the 3D petroleum system basin modeling (PSBM) study, based on 2D seismic data from TGS (processed using advanced and broadband techniques) and both Trinity and PetroMod basin modeling software, suggests the presence of world-class oil, condensate and gas volume containers, thus opening a huge new frontier for Sergipe-Alagoas Basin exploration (Fig. 4).

Figure 3. Example of a strike seismic line showing the nine (09) regional horizons and isolated igneous bodies mapped. The horizons correspond to limits of 2nd to 3rd order sequences, dividing the section in packages of tectono-sedimentary significance and predominant seismic facies.
Figure 4. Map of the transformation Ratio of lower rift lacustrine fresh to brackish source rock system. Green bodies are the modelled accumulations and the well symbols are the known discoveries up to now.

The leads in the Rift Plays are positioned in the areas of charge convergence from the generative depocenters, fed with black and cracked oils. Likewise, the bypass to Cretaceous and Paleogene plays will likely be effective for mixed marine non-cracked oils with lacustrine cracked and highly cracked oils recently identified in the basin reaching the overlaid turbiditic reservoirs. The results showed that the mapped leads are of world-class size, illustrating the importance of systematic seismic & well mapping in conjunction with advanced geochemistry and basin modeling. The mixing characteristic of non-cracked and cracked oils with multi-charge histories charging all marine reservoirs is consistent with the deep troughs mapped on the seismic, indicating a well-developed rift section with high probability of being the main generative source system basin (Fig. 5).

Figure 5. Isopach’s map of Synrift R3 and R2 indicating a well-developed rift section with high probability to be the main generative basin of the lacustrine depocenters.

The complete evaluation encompassed petrophysical characterization of the reservoirs, trap mapping, analysis of oil characteristics, petroleum system modeling and stochastic volume & risk quantification, which led to the identification of outstanding opportunities for future exploration and drilling.

Download the full brochure of this paradigm shifting study or get in touch to learn more.

Share this post