--> Rock Thermo-Acoustic Emission, Laser Raman Spectroscopy and Infrared Spectroscopical Technique Applied to the Study of Organic Matter Maturity of the Lower Paleozoic Marine Shales in Southern China

AAPG ACE 2018

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Rock Thermo-Acoustic Emission, Laser Raman Spectroscopy and Infrared Spectroscopical Technique Applied to the Study of Organic Matter Maturity of the Lower Paleozoic Marine Shales in Southern China

Abstract

Thermal maturity is critical to assessing the overall petroleum generation potential, which is usually applied to account the organic matter decomposition so as to demonstrate if it is in the oil or gas window stage. Vitrinite is an organoclast descended from catagenetically altered woody plant tissues. However, shales of Lower Paleozoic marine strata in south China are considered to be of high degree of thermal evolution, lack of vitrinite. Vitrinite reflectance (Ro) is an evidence of the maximum paleo-temperature exposure to which source rocks have been exposed. Thermo-acoustic emission experiment is applied to describe the organic matter decomposition in the Lower Cambrian Niutitang Formation (TA1 and TB1 well) in Guizhou area of south China, with Laser Raman Spectroscopy and kerogen fourier transform infrared spectroscopy (FTIR) used to validate its correctness due to sum up characteristics of marine shales. The thermos-acoustic emission experiments indicate that maximum paleo-temperature experienced by TA1 well samples and the simulated Ro are 314.5-344.9 and 2.85-3.43%, with an average of 331.03°C and 3.16%, respectively, while that of TB1 well samples are 232-311.7°C and 1.76~2.80%, with the average of 280.68°C and 2.37%,respectively. Equivalent vitrinite reflectance (EqVR%) of TA1 well and TB1 well samples obtained from laser Raman Spectroscopy vary from 2.87 to 3.16% and from 2.27 to 2.81%, with an average of 3.02% and 2.63%, respectively. The minimum wave number (Wmin) of TA1 well and TB1 well samples show in FTIR analysis range from 1574.81 to 1584.38 cm-1 and from 1582.82 to 1585.20 cm-1, with the transformational Ro in the range from 2.4 to 3.4% and from 2.2to 2.5%, respectively.

Obviously, the simulated Ro of thermo-acoustic emission experiments is basic anastomotic with the transformational Ro of Laser Raman Spectroscopy analysis and kerogen FTIR, which is representative of the real degree of thermal evolution. After comparing the advantages and shortcomings of each technique, it is pointed out that, Thermo-acoustic emission experiment is also an efficient method of evaluating the maturation degree of highly-evolved organic matters with practicability , cost and accuracy taken into account.