Application of Thermal Infrared Reflectance Spectroscopy in the Evaluation of Quartz Content

ZHANG Hong; GAO Peng-xin; GAO Qing-nan

doi:10.15898/j.cnki.11-2131/td.202104190053

ZHANG Hong, GAO Peng-xin, GAO Qing-nan. Application of Thermal Infrared Reflectance Spectroscopy in the Evaluation of Quartz Content[J]. Rock and Mineral Analysis, 2021, 40(5): 710-719. DOI: 10.15898/j.cnki.11-2131/td.202104190053

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Application of Thermal Infrared Reflectance Spectroscopy in the Evaluation of Quartz Content

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BACKGROUNDQuartz is not only an important prospecting indicator of hydrothermal deposits, but also a key factor affecting the evaluation of shale gas reservoir fracturing. It is of great significance to carry out the rapid evaluation of quartz content in field drilling. However, the analysis process of conventional methods (X-ray diffraction method and scanning electron microscope) is relatively long.OBJECTIVESTo establish a rapid and large-scale quantitative evaluation model of quartz based on thermal infrared reflectance.METHODSHandheld FTIR spectrometer and mineral quantitative analyzer were used to analysis the content and characteristic absorption peak intensity of quartz, from mudstone, sandstone, conglomerate, limestone and dolomite samples in the Qiangtang Basin.RESULTSThe relative depth (D₈₆₂₅, D₁₂₆₄₀, D₁₄₄₅₀) of quartz at the three characteristic center wavelength positions of 8625nm, 12640nm and 14450nm can be used to distinguish terrigenous clastic rocks from carbonate rocks. When D₈₆₂₅>0.14 or D₁₂₆₄₀>0.02 or D₁₄₄₅₀>0.02, the samples are mainly terrigenous clastic rocks. In addition, three quartz spectral characteristic parameters D₈₆₂₅, D₁₂₆₄₀, and D₁₄₄₅₀ all have a high correlation with the quartz content, and the least square method can be used to construct a quartz content evaluation model. Two indicators of goodness of fit (R²) and root mean square error (RMSE) were used to evaluate the accuracy of the three models. Among them, the quartz content estimation model based on D₈₆₂₅ parameters had the highest goodness of fit (R²=0.9237), with the smallest root square error (RMSE=8.51). Based on this, it is believed that the D₈₆₂₅ quartz spectral parameters can be used as the optimal spectral index for evaluating the quartz content.CONCLUSIONSBased on thermal infrared reflectance spectroscopy technology, a field method for quickly estimating the content of quartz in drilling core has been established, which provides reference for prospecting and exploration of hydrothermal deposits and shale gas exploration and development.

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Application of Thermal Infrared Reflectance Spectroscopy in the Evaluation of Quartz Content

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