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ABSTRACT: Hydrocarbon Generation in Thrust Belts: A 2-D Numerical Model

Sylvie Wolf, Jean Burrus

Thrust belts which involve thin-skinned sedimentary sheets often contain potential hydrocarbon traps. Numerical models are used to understand hydrocarbon generation in these areas. Hydrocarbon generation is sensitive to both thermal regime and thrust-faulting history. But the first models oversimplified the thrusting (instantaneous thrust emplacement, one-dimensional thermal modeling). We have here developed a two-dimensional complete kinematic and thermal model. The kinematic code reconstructs through time the evolutive shapes of the thrust belts, based on balanced cross sections. The transient heat equation calculates temperature with a two-dimensional finite-element method.

Therefore, the model can take into account heterogeneous thermal conductivity and radioactive heat generation, several thrusting velocities, and erosion after thrust emplacement. Given the temperature, the maturation of source rocks in the basin is computed. Thermal cracking describes hydrocarbon generation, modelized by first-order kinetic reactions.

Based on actual data, the model shows the main effect on hydrocarbon generation timing of faulting velocity, upper thrust geometry, and thermal characteristics of the layers.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990