--> The Impact of Geologic Uncertainties in 3D Petroleum Systems Modeling: A Study in the Campos Basin (Brazil), Mavridou, Evangelia1 Bender, André A.; Mello, Marcio, #90100 (2009)
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The Impact of Geologic Uncertainties in 3D Petroleum Systems Modeling: A Study in the Campos Basin (Brazil)

Mavridou, Evangelia1
 Previous HitBenderTop, André A.2
 Mello, Marcio2

1Schlumberger, Aachen, Germany.
2
HRT and Petroleum, Copacabana Rio de Janeiro, Brazil.


The objective of the study is to estimate the impact of uncertainties related to the main petroleum system elements on the migration patterns and accumulations in the Campos Basin, offshore Brazil.

In general, in petroleum systems modeling a number of geologic uncertainties need to be taken into consideration and incorporated into the model in order to evaluate how the results depend on variations in key parameters. A scenario approach is often adopted in deterministic modeling to evaluate the impact of uncertainties by creating different model scenarios (e.g., worst, most likely and best cases). However, a more sophisticated, combined deterministic and stochastic approach has been employed here and probabilities of occurrence of hydrocarbon accumulations (discovered and yet to be discovered) have been calculated.

A 3D model of the
Campos basin covering an area of around 15,000 km2 was used in order to estimate the impact of uncertainties in input data on predicted hydrocarbon accumulations. The parameters risked include Total Organic Carbon (TOC) and Hydrogen Index (HI) of source rocks. Capillary pressure is also an important parameter since variations in a basin can result in areas with large hydrocarbon concentrations or none at all. Therefore, the capillary pressure of the seals over the main reservoir levels and of the most important carrier beds, was also risked in the present study. Reservoir permeabilities, together with the effect of Heat Flow (HF) and Sediment Water Interface Temperature (SWIT) were also taken into account. Additionally, restoration of paleogeometries of salt bodies is an important factor to consider, given that it controls the opening of salt windows and the amount of overpressure in the pre-salt sections. The dynamic behavior of halite is more difficult to incorporate in a risk analysis, but by varying the capillary pressure of the rocks immediately above the salt windows it has been possible to mimic its effect on migration.

Based on the data available, a specific distribution was assigned to each uncertainty and ~100 risk runs were performed after sampling the uncertainties using the Latin Hypercube method.

The results of this study include the interpretation of the correlations and dependencies between all risked factors (thermal and hydraulic) with respect to the predicted accumulations as well as the impact of uncertainties in migration patterns.

AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil