Genesis of Basin Chambers and Sealing Structures. Final Report, March 1989-June1992. Volume 1 and Volume 2

摘要

Basin compartmentation is a significant phenomenon that influences natural gasaccumulations. In the Anadarko basin, a basin-wide overpressured compartment has been documented that encompasses most of the Pennsylvanian and the Mississippian Systems. The 'megacompartment,' which crosses stratigraphy, is completely encased by top, lateral, and basal seals. Its interior is subdivided into a network of smaller compartments with distinct overpressured regimes. Seals form as the result of diagenetic processes that modify existing depositional features. Breached overpressured compartments may partially leak their hydrocarbon contents via fault or hydro-fracture conduits into overlying satellite reservoirs. Computer simulation of diagenetic reaction, transport, and mechanical processes explain in detail how many observed compartments can form and evolve over geological time. Such codes are a major breakthrough in predictive modeling for the exploration, production, and reserve assessment of compartment-related gas reservoirs by predicting compartment location, size, and permeability. A classification of compartments on the basis of stratigraphy, pressure regimes, size, and mechanism of genesis indicates that they may exist on several spatial scales and exist as one of a number of distinct types. Mechanical reduction of grain size within single faults has been found to significantly inhibit fluid flow across them. In contrast, flow parallel to the fault may be enhanced by fractures developed during fault displacements. Fault arrays are found to be asymmetrical with some faults acting as conduits and the main fault as a seal.