Organic geochemistry of the kerogen and bitumen from the Ohio Shale by pyrolysis-gas chromatography |
| |
| Institution: | 1. Langfang Branch of PetroChina Research Institute of Petroleum Exploration & Development, Langfang 065007, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. Institute of Flow and Fluid Mechanics, Chinese Academy of Sciences, Langfang 065007, China;1. Universidade Federal do Rio de Janeiro, Instituto de Química, LAGOA/LADETEC, Ilha do Fundão, Rio de Janeiro, RJ 21941-598, Brazil;2. Division of Geochemistry, Petrobras Research and Development Center (CENPES), Petrobras, Ilha do Fundão, Rio de Janeiro, RJ 21941-915, Brazil;1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing 102249, People''s Republic of China;2. Key Laboratory of Earth Prospecting and Information Technology, China University of Petroleum (Beijing), Beijing 102249, People''s Republic of China;1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102200, China;2. College of Geosciences, China University of Petroleum, Beijing 102200, China |
| |
| Abstract: | An exposure of the Ohio Shale at Bristol Ridge, Ohio in the Bellefontaine Outlier was sampled into 53 channel units. Proximate and elemental (CHN) analyses were performed on these samples to determine the concentration of organic matter. The organic content averaged 6.82% with the highest both in the lower half (11.08%) and extreme upper part (10.43%) of the section.Fragmentation of the kerogen of each of the whole rock samples was accomplished by pyrolyzing for 10 s at 750°C in the injection port of a gas chromatograph with a FID detector. The concentration and distribution of the diagnostic hydrocarbons fragmented at this temperature were used to infer the molecular construction of the high molecular weight kerogens. The suite of identified hydrocarbons for each of the samples throughout the section was similar, but a very large fluctuation in the amount of pyrolysis products was observed. This fluctuation is strongly related to organic richness as defined by the proximate and elemental analyses. The identification of diagnostic normal alkanes and aromatics and SCI indicates that the kerogen assemblage is composed of both marine and terrestial components — most likely a mixed Type II kerogen. The contribution of individual aromatic and normal alkanes is variable, which suggests that there were minor fluctuations in the proportions of terrestrial and marine organic matter during decomposition.Bitumen pyrolized from the whole rock and bitumen removed by Soxhlet extraction using a 4:1 benzene/methanol solvent mixture were analyzed. Comparison of these two techniques yield similar pristane/phytane ratios and Carbon Preference Index (CPI) values. On decomposition the whole rock bitumen exhibited a mean pristane/phytane ratio of 1.5 and a mean CPI value of 1.4, whereas the Soxhlet-extracted bitumen exhibited a mean pristane/phytane ratio of 1.6 and a mean value of 1.3. The low pristane/phytane ratios from this outlier indicates a possible marine environment, with reducing conditions existing immediately below the sediment-water interface. The CPI values also indicate the sedimentary sequence is thermally immature. Reflectance of the vitrinite (%Ro 0.05) and fluorescence (Q 0.93) of the algal bodies indicate a maturation at the beginning of the oil window or at boundary between thermal immaturity and maturity. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
