Depositional Model of Marine Organic Matter Coupled with a Stratigraphic Forward Numerical Model (Dionisos): Application to the Devonian Marcellus Formation

Chauveau, Benoit¹; Granjeon, Didier; and Huc, Alain-Yves
¹[email protected]

Predicting the occurrence and the organic attributes of source rocks is mandatory for modern 3D basin models, for exploration and for optimal production of shale gas. We propose a numerical model that integrates recent advances in marine biology and organic sedimentology. This approach consists in using simple laws to model the main processes controlling both the quantity and the quality of organic matter within marine sediments. A 3D stratigraphic forward numerical model, Dionisos, is coupled to a production, degradation and preservation model of marine organic matter. Our model simulates the production rate of the marine organic matter, its degradation through vertical transport from the water surface to the sea floor, the lateral transport of the residual organo-mineral aggregates, and the preservation factor during the early diagenesis. The parameters of the model are the paleobathymetry and climate conditions, which control sediment transport, oxygen supply and organic production rate. Our model describes the source rock by giving the quantity of organic carbon (TOC) and the quality of the kerogen (HI). Moreover, the mineralogy of the source rocks is estimated.

To validate our approach, we model the deposition of the Devonian Marcellus black shales, part of the Hamilton group. As a huge data set is available, the Marcellus formation is one of the best case studies. It allows a detailed comparison between observed and modeled data. These black shales deposited during the early stage of the Acadian orogeny. The marine depositional environment is characterized by shallow stratified water, involving an anoxic bottom layer. In the Appalachian basin, plankton is the main source of organic matter, which produces a type II kerogen. A sensitivity analysis is associated to the simulation to better estimate the controlling parameters and the uncertainties of the results.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013