Comparison of Hydrocarbon Potentials of New Albany Shale And Maquoketa Group in Indiana, USA

Abstract

Organic petrographic (maceral composition and vitrinite reflectance, Ro) and geochemical methods (Rock-Eval pyrolysis and total organic carbon, TOC) were used to compare hydrocarbon potentials of New Albany Shale (Middle Devonian to Lower Mississippian) and Maquoketa Group (Upper Ordovician) based on 51 samples from 5 drill cores from the Illinois Basin. New Albany Shale is an effective source rock due to its organic matter content and character (Type I and Type II kerogen) and its dominant placement in the oil window. The considerably higher thermal maturity of underlying strata has drawn attention to Maquoketa Shale as a possible source rock. Our results show that although Maquoketa Shale (Rock-Eval Tmax = 435 to 445 °C) is more mature than New Albany Shale (Tmax = 427 to 442 °C), the relatively higher organic matter content in New Albany Shale with up to 13.80 wt. % TOC supports a higher hydrocarbon potential than Maquoketa Shale’s TOC values between 0.09 to 1.32 wt. %. New Albany Shale’s notable differences between directly measured vitrinite reflectance values and calculated Ro values from Tmax are probably caused by suppression of vitrinite reflectance. Correction for suppression of Ro values would place New Albany Shale more favorably into the oil window.