Transform Margins : Reservoirs and Seals – The Equatorial Basins of Brasil

Core Laboratories is pleased to announce an all-new integrated geological sciences project (stratigraphy, geochemistry, reservoir geology and petrophysics) from c.60 wells in the Brazil Equatorial offshore basins. The study will be based on a suite of ditch cuttings, cores and fluids from these wells. The study has the full approval (under Ordinance 289) of ANP.

The Equatorial Basins of Brazil (Potiguar, Ceara, Barreirinhas, Para-Maranhao and Foz do Amazonas) are attracting considerable industry interest because of well-documented large hydrocarbon discoveries within the conjugate transform basins of West Africa, including large oil fields in Ghana and the more recent new oil discovery in Sierra Leone.

Transform Margin Basins in general show particularly high petroleum prospectivity because they are associated with (1) restricted oceanic circulation conditions suitable for accumulating thick organic-rich source rocks; (2) complex structural architecture characterized by mini-grabens which host ponded sands and intrabasinal horsts which form hydrocarbon traps and also focus hydrocarbon charge between source rock kitchens and reservoirs and (3) adjacent uplifted continental margins that provide large volumes of fairly coarse clastic sediment through incised feeder channel systems.

The offshore Brazil Equatorial Basins constitute a transform margin with high potential for large volume hydrocarbon discoveries. The shallow water province of the basin has been documented by more than 64 wells, an extensive 2-D and 3-D seismic grid and several productive fields. Exploration drilling began in Brazil the 1930s to evaluate the oil seeps known along the coast, while subsequent offshore exploration of the shallow shelf, yielded numerous oil and gas accumulations.

The deepwater province of the Brazilian Equatorial Basins is largely undrilled but available public domain data from ongoing seismic evaluation and prospect delineation projects suggests that there is high possibility of encountering turbidite plays similar to the Late Cretaceous reservoirs discovered in the conjugate margin Tano Basin of Ghana.

The primary objective of the study will be to undertake a full evaluation of all major reservoir intervals penetrated in the study wells, combined with an evaluation of associated seal rock lithologies and evaluation of regional source units and thermal maturity. All fluid occurrences will be characterized and correlated.

High resolution geological analysis of the full drilled succession in representative wells across the margin will allow systematic reconstruction of basin evolution through time and help elucidate the relationship between the major structural elements and the lateral and vertical distribution of sands, shales and (rare) carbonates observed across the region. In addition to providing an improved understanding of the sedimentation patterns in the Cretaceous to Tertiary succession of the shallow water region, this rock-based fundamental geology approach provides ‘ground truth’ data for interpreting the location of the main sediment transport pathways and sand-filled depocentres within the largely undrilled deepwater blocks, where currently seismic evaluation is the only option.

The key components of the study are as follows:

  • Biostratigraphy/Sequence Stratigraphy of key wells
  • Reservoir Description and Rock Property Evaluation of all major reservoir units
  • Rock Typing of uncored sections
  • Seal Atlas of major seal lithologies
  • Regional Source Rock evaluation and thermal maturity
  • Fluid characterization and correlation
  • Paleogeography Maps (illustrating sediment transport pathways sand depocentres)
  • Digital Database of laboratory and well data, including LAS files of the electric logs
  • HTML browser of the study dataset and report.

The study is scheduled for late 2012 completion.