2D Modeling of overpressure in a salt withdraw basin, Gulf of Mexico, USA
Jeff Alwardt, Eric Michael, and Chuck Shearer
ConocoPhillips, Houston
This study represents an illustration of how 2D basin models can be utilized to address the overpressure developed due to compaction disequilibrium in a basin with very high sedimentation rates and highly mobile salt bodies. Full 3D basin models that include a robust salt restoration through time are often impractical either due to a lack of data to constrain salt movement or the evaluation time required to conduct this restoration. By using a partial calibration and the proper 2D line selection from a grid stack, it is possible to obtain reasonable timing of overpressure development and approximate present-day overpressures. In the best case, a model using a single shale-sand lithology (low resolution) with default porosity and permeability compaction curves reproduced pressure measurements to an average of about 0.4 ppg with a maximum error of 1.0 ppg. This suggests that knowing the age, depth, and the approximate lithology (sand net-to-gross) is adequate to approximate pressure in highly overpressured basins to address issues around trap
containment and first pass well planning purposes. Forward modeling pressure for purposes of well planning may require more localized information on rock properties and stratigraphy; albeit these data are not always available in exploration. In addition, this presentation shows the quality of overpressure prediction utilizing different model stratigraphic resolution, available calibration data and sensitivity of overpressure modeling to 2D line selection.
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AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands
AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands