The relationship between the oil shale density and the structural features of corresponding kerogens

Abstract

Based on the difference in the density and content of kerogen and inorganic minerals, oil shale can be separated into different density fractions. The structural features of kerogens in Beipiao oil shale (a kind of typical low-grade oil shale resources) with densities of 1.8–1.9, 1.9–2.0 and 2.0–2.1 g/cm3 were studied. Combined with our previous study on the structural features of Longkou and Huadian oil shales (two kinds of high-grade oil shale resources) with different densities, the relationship between the oil shale density and the structural features of corresponding kerogens was revealed from aromatic, aliphatic structures and heteroatom species. The results show that with increasing the density, the content of minerals increases, whereas that of kerogen decreases. With increasing the density, the aliphaticity, average methylene chain length and average number of attachments on each aromatic ring increase. Whereas, the aromaticity and average size of aromatic cluster are inversely proportional to the oil shale density. For Longkou, Huadian and Beipiao oil shales with different densities, the change rules of aromatic and aliphatic structures with the density are similar, indicating that these change rules are independent of the grade and origin of oil shale. The change rules of heteroatom species in Beipiao oil shale are different from that of Longkou and Huadian oil shales.