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Integrated Structural and Charge Modeling in Compressional Areas – Application in the Monagas Fold and Thrust Belt (Venezuela) and Decompaction Uncertainty

Martin Neumaier¹,², Laurent Maerten², Thomas Hantschel², Adrian Kleine², Jean Pierre Joonnekindt², and Ralf Littke¹
¹RWTH Aachen University, Aachen, Germany
²Schlumberger, Aachen, Germany

Conventional basin and petroleum system modeling (BPSM) uses the vertical backstripping approach to describe the structural evolution of a basin. In structurally complex regions this is not sufficient. Wherever lateral rock movement and faulting must be incorporated in the models, BPSM should be performed on structurally restored models. Following this approach, pressure evolution and compaction can be modeled in a decoupled way: the overall geometry is taken from the structural restoration, pressure and compaction are modeled, and porosity is derived from the calculated effective stress. On this basis, other geologic processes, such as temperature evolution, source rock maturity, hydrocarbon migration and accumulation can be modeled.

We demonstrate the strength of this approach in a case study from the Monagas Fold and Thrust Belt (Eastern Venezuela Basin). The different petroleum systems have been fully evaluated through geologic time within a calibrated pressure and temperature framework. Particular emphasis has been given to investigating the structural dependencies such as the relationship between thrusting and hydrocarbon generation, dynamic structure-related migration pathways, and the general impact of deformation on the petroleum systems.

We describe the uncertainty which is introduced by replacing backstripped paleogeometry by structural restoration, and discuss decompaction “adequacy”. We have built two end member scenarios: structural restoration assuming hydrostatic decompaction and one that neglects decompaction. We have quantified the impact through geologic time of both scenarios by analyzing important parameters such as rock matrix mass balance, depth, temperature and transformation ratio (TR). For the case study presented, hydrostatic decompaction seems to be the most appropriate methodology.

AAPG Search and Discovery Article #120098©2013 AAPG Hedberg Conference Petroleum Systems: Modeling the Past, Planning the Future, Nice, France, October 1-5, 2012