Identification and Geochemical Implication of Sulfur Compounds in an Immature Lacustrine Shale Oil

The organic sulfur compounds were isolated from an immatureshaleoil in Hetao Basin, northern China, and characterized by Fourier transformion cyclotron resonance mass spectrometry and gas chromatography-massspectrometry. Various sulfur-containing biomarkers were identified,including C-15, C-20, and C-25 isoprenoidthiophenes and benzothiophenes, C-13 bicyclic terpenoidsulfide, and C-37/C-38 n-alkylatedsulfur compounds. The molecular composition indicates that the sulfurizationoccurred in the early stages of diagenesis through bacterial sulfatereduction, which contains a wealth of geochemical information. Inaddition, a series of novel spirosterene-derived sulfur compoundswere identified in combination with desulfurization results. The spirostereneskeletons are considered originating from the rearrangement of cholesteneswith the presence of clay minerals. The unstable spirosterene skeletonswere preserved through sulfurization, and the derived sulfides arepotential molecular markers.