Transform Margins – Reservoirs and Seals: The Equatorial Basins of Brasil – 2015 Extension

Core Laboratories is pleased to present in this proposal the generation of an all-new integrated geological sciences data set (stratigraphy, geochemistry, reservoir geology and petrophysics) from c.15 wells in the Brazil Equatorial offshore basins, drilled since 2010. 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 132/2013) of ANP. These 15 wells will form an extension to the 2014 completed Regional dataset consisting of 58 wells.

The Equatorial Basins of Brazil (Potiguar, Ceará, Barreirinhas, Pará-Maranhão and Foz do Amazonas) are the focus of 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 oil discoveries on both sides of the Equatorial Atlantic (e.g. French Guiana & Western Nigeria).

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 Transform Basins on the West African margin, and in particular the Ivorian-Tano Basins, form an exploration ‘sweet spot’ since they contain known source rocks, a proven petroleum system and multiple reservoir units within the syn-transform and post-transform succession. Multiple Cretaceous reservoir targets are found in a variety of structural and stratigraphic trap types, ranging from back-rotated fault blocks to submarine fans associated with the canyons that cut the hinge zone as the basin filled.

The offshore Brazil Equatorial Basins on the conjugate transform margin were subjected to a similar complex tectonic history and thus also hold high potential for the discovery of large volume hydrocarbon discoveries. The shallow water province of the Brazilian basins 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 in 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 Tano Basin of Ghana.

The primary objective of the Equatorial Basin 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. The study will focus primarily on full interpretation and integration of all rock data, but all fluid occurrences will also 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/Cyclo 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
  • 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 due for completion mid 2015.