Petrology and Maturation of Dispersed Organic Matter in New Albany Shale Group of Illinois Basin: ABSTRACT

Abstract

The New Albany Shale group of the Illinois basin is being studied to evaluate its potential for yielding hydrocarbons. As part of this study, coal petrographic techniques have been employed to evaluate the composition and thermal maturity of dispersed organic matter in the shales. Vitrinite reflectance was measured on acid-macerated kerogen separates from 11 cores and 126 cuttings from drill holes through the New Albany Shale in Illinois, Indiana, and western Kentucky. No significant variations in reflectance values were observed within the New Albany at any single location with respect to either depositional facies or depth. An isoreflectance map prepared from the data shows large areas of the Illinois basin where reflectance is uniformly low (> 0.5% Roil) and the organic matter has not yet reached the stage of petroleum generation. Several areas of higher reflectance also are present: (1) near the northern erosional truncation of the New Albany in central Illinois; (2) in east-central Illinois, an area associated with a broad southward-plunging yncline just west of the La Salle anticlinal belt; (3) in Wayne and Hamilton Counties, Illinois, the present area of maximum burial depth; and (4) in extreme southeastern Illinois, where the highest reflectances yet observed (> 1.0% Ro) correspond to a complexly faulted and mineralized area with nearby igneous intrusions. Changes in color and intensity of UV fluorescence of liptinites are generally in good agreement with reflectance data. Occurrence and abundance of amorphous organic matter, alginites (mainly Tasmanites), vitrinites, and exinites are facies-dependent. Solid hydrocarbons that occur as pore fillings in fusinite are present mainly in samples from southeastern Illinois. Their presence suggests that hydrocarbon generation and expulsion have occurred in the New Albany in southeastern Illinois. End_of_Article - Last_Page 1575------------