Peter W Homewood¹, Gregor P Eberli²

(1) TotalFinaElf, Pau, France
(2) RSMAS University of Miami, Miami, FL

ABSTRACT: Carbonate Sequences, Time And Time Again

Sequence stratigraphy in carbonates has matured from being a special case within a general concept, to be a fully integrated, specific aspect of lithological prediction and geological interpretation. The test of subsurface applications confirms the robustness of this "time-unit" approach to understanding stratigraphic architecture.

Harmonisation of "top-down" analysis of regional data sets (exploration scale), and "bottom-up" analysis of the stacking of high resolution stratigraphic units (reservoir scale), as well as the confrontation of outcrop case studies with 2D and 3D seismic, core, wireline logs and production data from subsurface equivalents, has established the workflow for industrial application.

Although carbonate sequences obey the same fundamental rules as clastics, significant differences result from the nature of the carbonate factory. Beyond changes in successive dominant ecosystems through geological time, ecological succession affects sediment production at the scale of transgressive and regressive stacks of genetic units, and in some cases may even govern individual cycles. This constraint adds to those from climatic, geomorphic and oceanographic settings. Present understanding of carbonate systems heralds robust and geologically reasonable numerical simulation.

The partitioning of primary lithologies, facies tracts and organic matter depends upon the geometry of the depositional profile. Precise correlation of sequences may be difficult across margins which are steep, or which bound eutrophic basins. Diagenetic modification, commonly shown to be early in origin, is still less tightly constrained. So the ultimate goal of confident prediction of poro-perm (and other petrophysical characteristics) from some knowledge of stratigraphic architecture and age, remains a "blue sky" research topic.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado