Three Dimensional Basin Modeling of Overpressuring, Megacompartments, Fracturing, and Episodic Fluid Release

J. M. Maxwell and Peter J. Ortoleva

We have developed a three dimensional basin simulator which models the generation of abnormal pressures and fluid migrations during burial diagenesis. Our model accounts for the development of overpressure, pressure seals, fractures, episodic fluid release, and fracture healing in a sedimentary basin in response to its depositional stress and thermal histories. The model is based on a set of coupled nonlinear partial differential equations and ordinary differential equations derived from Darcy's law, the conservation of energy, grain growth and dissolution. Input for the model consists of a detailed petrologic description of the sediment history and the time course of basement subsidence.

The model predicts the formation of overpressured compartments, three dimensional domains isolated from the surrounding rock by very low permeability diagenetic and sedimentologic seals. The pressure seals for these compartments form through the combination of mechanical and pressure mediated compaction. The latter, in particular, yields the tightly fitted fabrics that allow for the sub-nanodarcy permeabilities that can maintain significant pressure abnormalities on the 100 million year time frame. Simulation results are compared with observed petrologic and pressure data obtained for the Anadarko Basin.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California