PARK, ANTHONY J., and PETER ORTOLEVA
Laboratory For Computational Geodynamics, Indiana University, Bloomington, IN

Abstract: Affects of Compaction and Diagenesis on the Development of Compartment Seals

Compartmentation can occur due to enhancement of inherent sedimentology through mechanical means, as well as through water-rock interaction processes involving chemical compaction and diagenesis. In this study, the importance of the coupling of the grain-size scale chemical compaction and pressure solution model and the reservoir-scale diagenesis and mass-transport is evaluated using the simulator CIRF.B.

During chemical compaction mass transfer occurs between grain contact surfaces and adjacent pore. The driving force for the mechanism is the difference between the pore fluid pressure and the stresses on various grain contacts, as well as the pore fluid composition. For reservoir-scale diagenesis fluid flow is dictated by the matrix permeability and the fluid pressure, and mass can move considerably greater distance.

Chemical compaction has been shown to produce stylolites in both carbonate and siliciclastic rocks, as well as millimeter-scale layering that are similar to the chert layering observed in some deep basin siltstones associated with compartments. In larger scale, silica overgrowths, feldspar dissolution and clay authigenesis are evaluated. These two processes are coupled to determine when the interaction enhances or interferes with the formation of diagenetic seals through porosity reduction or enhancement. The utility of the model is to aid in interpreting the paragenetic relations one observes.

Comparisons of simulation results with previous models, case studies, and observations from select U. S. basins will be presented.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas