--> Abstract: Prediction of Sub-Seismic Sealing Faults Using Simple Numerical Simulation Models; #90063 (2007)

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Prediction of Sub-Seismic Sealing Faults Using Simple Numerical Simulation Models

 

Bain, Richard C.1, Kirk H. MacIvor1, Brooke E. Holt1, D. Scott Beaty1 (1) Chevron North America Exploration and Production, Houston, TX

 

In order to justify development drilling in partly-depleted, highly faulted gas reservoirs in which untapped higher-pressure compartments may exist, convincing evidence for fault separation from existing wells must be provided, either by obvious fault breaks on 3-D seismic or by missing section due to faults encountered in a well. Lacking such evidence, it is uncertain that prospect reserves will be incremental, as opposed to acceleration, even when volumetric analysis suggests that existing wells will not capture all of a reservoir's producible reserves.

 

Two examples from the Lobo Trend of Webb County, South Texas, demonstrate how simple, "fit-for-purpose" 3D-earth models and numerical simulation models provide a level of confidence sufficient to predict the location and expected reservoir conditions of prospective compartments. The key to their success is the proper integration of flowing pressure data with observed production decline curves.

 

In the first example, a simple simulation predicted the presence of sub-seismic faulting that provided a seal for the objective reservoir. The proposed location was in a syncline between two wells that had produced large volumes of gas and were producing at very low bottom-hole pressures. An iterative approach involving the seismic interpreter and reservoir engineer resulted in a geologic model that was supported by seismic data and agreed with history matching efforts. The well, which would not have been drilled without the model's support, encountered near-virgin reservoir conditions.

 

The second example provides a lesson learned, demonstrating a reservoir in which the simulation and history match correctly predicted the presence of a sealing fault, but incorrectly predicted which of several faults was sealing. The wellbore penetrated the sealing fault and the seal was ruptured during fracture stimulation.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California