Comparative optical properties of macerals and statistical evaluation of mis-identification of vitrinite and solid bitumen from early mature Middle Devonian - Lower Mississippian New Albany Shale: Implications for thermal maturity assessment

摘要

Vitrinite reflectance (VRo in ) is used routinely to quantify thermal maturity in sedimentary basins. Reflectance and fluorescence of other macerals such as solid bitumen and amorphous organic matter (AOM) can provide an independent means to assess thermal maturity and hydrocarbon generation potential. However, similarity in petrographic characteristics of these macerals, solid bitumen and vitrinite in particular, often causes difficulties with their identification and, consequently, reflectance can be measured on misidentified particles, making reported VRo values unreliable. The purpose of this study is to compare reflectance values of various macerals in early mature shales and to evaluate the implications of misidentifying solid bitumen and vitrinite for assessing thermal maturity. To address this issue, 15 organic-matter-rich samples from the Middle Devonian/Lower Mississippian New Albany Shale from a corehole in Daviess County, Indiana, were selected. These samples were chosen because they had distinct and easily identified AOM, solid bitumen, vitrinite, and inertinite particles, allowing for statistically relevant comparisons.