--> Abstract: New Methods for Integrated Modeling of Deformation and Petroleum Generation in Fold and Thrust Belts, by W. Sassi, J-L. Rudkiewicz, and R. Divies; #90937 (1998).

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Abstract: New Methods for Integrated Modeling of Deformation and Petroleum Generation in Fold and Thrust Belts

SASSI, WILLIAM, JEAN-LUC RUDKIEWICZ and RENAUD DIVIES, lnstitut Francais du Petrole

Abstract

In many orogenic belts around the world, a complex history of basin formation and deformation often require in-depth integrated basin studies. We propose a methodology based on the use of 2D modeling tools, combining cross section balancing (LOCACE software) and forward reconstruction of structural and thermal histories (THRUSTPACK software).

The purpose of this paper is to describe a second generation of 2D forward basin modeling tools with major improvements including: (1) a new method to simulate the kinematics of tectonic deformation (FOLDIS model, Divies, 1997) and (2) the implementation of a compositional kinetic model for hydrocarbon generation (Behar et al., 1992).

The deformation mode in thrust belts is generally complex. In early stages of compressional loading, layer parallel shortening prevails with almost no macroscopic features in the rocks. As shortening increases thrust faults and folds develop and their geometries are mainly controlled by flexural slip. The FOLDIS algorithm (Divies, 1997), has been developed to reconstruct the successive stages in deformation of a cross section, simulating folding by flexural slip (due to faulting) and mechanical compaction due to burial increase. In this method, a sedimentary unit is defined by a number of layers (bedding planes) discretized into quadrilateral elements. The simulation of the folding process results from sliding at layer's interfaces and strain concentration in fold hinges. The interplay of discontinuous and continuous deformation allows a reliable simulation of a fault-bend folding mechanism without the need to compute the attitude of kink axes. This new method allows modelization of a wide range of structural configurations including anthithetic faults, backthrusts, and non-isopachous stratigraphic sequences; and it accounts for sediment compaction.

The geochemical part of the modeling allows characterization of the hydrocarbons generated from a given source rock stratum, taking into account its richness in organic matter and its possible complex burial history. The thermal degradation of the organic matter is simulated using a compositional kinetic scheme which includes primary cracking of kerogen and secondary cracking of kerogen and oil. Hydrocarbon products generated and expelled out of the source rock are simulated using temperature histories derived from thermal modeling. The final analysis requires the integration of geological, geophysical and geochemical constraints to calibrate the structural evolution and extrapolate the temperature loading history.

An example from the Western Alps, with modeling of the Vercors, Chartreuse and Savoie thrust systems, is presented to illustrate these new methodologies.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah