Raman Spectrum Characteristics of Organic Matter in Silurian Longmaxi Formation Shale of Well Anye-1 and Its Geological Significance

Cong ZHANG; Xiang-hua XIA; Yu-ru YANG; Ming-gang BAI; Feng DAI; Jie XIONG

doi:10.15898/j.cnki.11-2131/td.201803220025

Cong ZHANG, Xiang-hua XIA, Yu-ru YANG, Ming-gang BAI, Feng DAI, Jie XIONG. Raman Spectrum Characteristics of Organic Matter in Silurian Longmaxi Formation Shale of Well Anye-1 and Its Geological Significance[J]. Rock and Mineral Analysis, 2019, 38(1): 26-34. DOI: 10.15898/j.cnki.11-2131/td.201803220025

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Raman Spectrum Characteristics of Organic Matter in Silurian Longmaxi Formation Shale of Well Anye-1 and Its Geological Significance

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BACKGROUNDThe higher thermal maturity of organic matter and the shortage of terrestrial plants are the main characteristics of Lower Paleozoic marine shale in China, which results in the difficulty of distinguishing macerals. Nowadays the existing methods of vitrinite reflectance, rock eval, Tm/Ts and other biomarker indices cannot be effectively used to evaluate the maturity of organic matter in shale.OBJECTIVESTo evaluate the maturity of organic matter in highly evolved shale.METHODSThe shale of the Silurian Longmaxi Formation of Well Anye-1 in Zheng'an area of Guizhou Province is used in the experiments. Field Emission Scanning Electron Microscopy and Laser Raman Spectroscopy are used to obtain the Raman Spectra of organic matter in different occurrences of highly evolved shale, independent of the type of organic macerals.RESULTSIt can be found that there are four types of organic matter in the Silurian Longmaxi Formation of Well Anye-1, i.e. bio-structural type, vein-like or clump-like type, euhedral and anhedral boundary filling gap shape. The euhdedral boundary filling gap shape has an organic aperture larger than 80nm, whereas the anhedral boundary filling gap shape has an organic aperture less than 60nm. These two types of organic matter are the main reservoir space of rock reservoirs, which account for more than 90%. Four types of organic matter have different thermal evolution degrees. Moreover, the Raman maturity ranges from 2.8% to 3.0%, which is calculated from the laser Raman surface scanning data. The proportion of Raman maturity of various organic matters to the total amount is consistent with the semi-quantitative statistical results observed by Field Emission Scanning Electron Microscopy.CONCLUSIONSThe methods used in the experiments are effective in measuring the maturity of organic matter in highly evolved marine shale in China.

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Raman Spectrum Characteristics of Organic Matter in Silurian Longmaxi Formation Shale of Well Anye-1 and Its Geological Significance

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