--> Abstract: Basin Modeling: Facts and Hopes, by P. Y. Chenet; #91004 (1991)

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Basin Modeling: Facts and Hopes

CHENET, P. Y., BEICIP Petroleum Software Division, Rueil-Malmaison, France

Basin modeling has been recognized as a useful tool for helping evaluate the petroleum potential of a basin or a prospect, as it is a unique way to integrate various geological and geochemical phenomena involved in petroleum formation and occurrence. However, our knowledge of the various phenomena remains partial, and simplifications must still be made when undertaking a basin study. A typical basin modeling study will encompass the reconstruction of the structural evolution of the basin, the simulation of the petroleum generation, and its subsequent expulsion and migration from the source rocks toward traps. These various phenomena will have to be quantified, involving various equations and their corresponding computer solutions.

A number of 1-D computer models are currently operated and allow for a satisfactory description of the structural evolution and petroleum generation of the basin when tectonics remain limited to vertical movements (sedimentation and erosion), and oil and gas are differentiated only by means of kinetic chemical reaction schemes (Tissot and Espitall, 1975). In tectonically complex environments, 2-D balanced section models now give proper images of the cross section but are not yet connected to petroleum generation modules. This is due to temperature calculations, which require description of the heat, transferring between the moving tectonic units and the influence of underground fluid flow. The description of petroleum migration is far more complex, as it requires the integration of th generation of petroleum, its movement across a compacting porous medium, and its compositional changes due to temperature and pressure evolution and cracking. 2-D models integrating this chain of process are now operating and are successfully applied in quiet tectonic settings, though they are dealing only with oil and gas phases without accounting for thermodynamic changes.

3-D integrations of 1-D and 2-D models are being done but remain reliable only under certain limiting conditions, such as simple tectonic setting and limited changes of the temperature and pressure conditions during migration. Recent progress has been made in the understanding of compositional cracking of petroleum, thus opening the way to an accurate description of the thermodynamic evolution of petroleum during expulsion, migration, and entrapment. The advances in computer capabilities for rapid calculation and display make it possible to build true 3-D models using the principles of the existing 2-D migration models.

A major challenge that remains is the description of petroleum fate in tectonically complex zones including salt diapirs. This will require the understanding of fluid movements within faults or fluid movements induced by intense sediment deformation, and permeability changes due to stress related rock fractures. Another challenge includes a satisfactory prediction of diagenetic phenomena and petroleum evolution due to thermodynamic changes or biochemical degradation.

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)