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Compositional Mass Balance of Major Oil Fields in Recôncavo Basin, NE Brazil - from Integrated Previous Hit1-DTop, 2-D and 3-D Petroleum System Modeling Approach

Luiz Felipe C. Coutinho1, François Lorant2, Jean Luc Rudkiewicz2, and Henrique Luiz B. Penteado1
1Geochemistry, Petrobras, Rio de Janeiro, Brazil
2Institut Français du Pètrole, Rueil Malmaison, France

Recôncavo Basin, located in Northeastern Brazil, is an aborted continental half-graben formed during Lower Cretaceous. The basin evolved with three main sequences: The pre-rift sequence, mainly composed of siliciclastic sediments of continental origin, contains the main reservoirs of Sergi and Agua Grande formations; the rift sequence, of continental origin, shows a change from a lacustrine dominated sedimentation at its base (including the main source rocks from Candeias Formation) to a fluvial-dominated deposition at the top; and the post-rift sequence, characterized by patches of preserved sediments of Aptian, Tertiary and Recent ages.

Recôncavo Basin is presently in a mature stage of exploration. However, up to now, the petroleum systems evolution is not completely understood. A sequential basin modeling study combining 1D, 2D and 3D techniques was conceived in order to reproduce the petroleum generation history and the expulsion efficiency from Candeias Formation, as follows: a) 1D thermal reconstruction based on a two-layer thermo-mechanical approach, that calibrates the depositional and the superimposed erosive post-rift events of Aptian and Oligocene ages; b) 2D sensibility tests with a section at the Southern Compartment of Recôncavo Basin. Permeability and capillary pressure for shales and faults were tested; c) 3D maturation models to obtain the original restored TOC maps; d) 3D compositional expulsion models coupled with a simplified migration description (ray tracing). The partial cracking of NSO and aromatic C15+ fractions inside the source rocks was tested by reducing their main activation energies.

The proposed workflow above provided the compositional mass balance along the ten main oil fields from Sergi formation that encompass 36 % of total accumulated volume (VOIP). The expulsion efficiency was calculated from the best fit model results.


AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas