中扬子地区下古生界页岩拉曼光谱特征及其对页岩气勘探的启示OA

The objective of this research is to provide a comprehensive assessment of the shale gas exploration potential in the Lower Paleozoic of the Middle Yangtze region,based on a systematic division of the thermal evolution stages of organic matter across various structural and depositional units.We selected 30 representative shale samples from outcrops and investigation wells in the study region and analyzed them using a Raman spectrometer.The results show that the Raman spectral characteristics of the lower Paleozoic shale exhibit regular changes with the increase of the thermal maturity of organic matter,and correlate well with the gas display characteristics of the investigation well;from carbonaceous shale in the early stage of over mature to carbonaceous schist in the low metamorphic stage,according to the Raman bands type of the test samples,the D and G band spacing inversion node,and the D and G band height ratio(Dh/Gh)inversion node(Dh/Gh),the Raman bands of shale with different thermal maturities can be divided into six categories in turn.Organic matter maturity is relatively low in Type I and Type II shale development region,and gas display of the investigation wells is active with good commercial exploration prospect.Organic matter maturity is higher in Types III and Type IV shale development region where a certain degree of gas display is,but shale gas content is lower.We suggest focusing on basic investigation and evaluation in this region.Type V and type VI shales are mainly developed in Basin-controlling fault zone or intrusive rock development area,and the shales are graphitized in varying degrees.We suggest cautious investment in shale gas exploration in this region.Based on Raman spectroscopy-derived thermal maturity indices,favorable zones for shale gas exploration in the Middle Yangtze Lower Paleozoic are identified,offering a practical framework for regional prospect assessment.