The Research Of Quartz Source Of Wufeng-longmaxi Group In The Northeast Of Sichuan Basin

Wufeng-longamxi group is the key strata in shale gas exploration and development, the research of it has entered into a deeper level, but further research is still needed. Quartz is an important mineral composition of shale, makes a significant contribution to the shale brittleness, and it has a positive correlation with the shale content of TOC, gas content. At present, many scholars have carried the thorough research on the source of quartz of Wufeng-longmaxi group shale, but all of these researches are qualitative. This paper quantified the content of different types of quartz combining with the scanning electron microscopy(SEM), after summarizing the field work or core observation and the microscopic indoor study, and recording the morphological characteristics of quartz at the same time.Then this paper reconstructed the depositional model of Wufeng-longmaxi Group coupling with geochemical method, under the constraint of large structure and sedimentary background at that time. Through the above analysis, this paper got the following results:(1) Quantified the quartz in the study area. In the north of the study area-Mingzhong, Chengkou, main types of quartz of Wufeng Group are terrigenous clastic quartz and biological quartz, main type of quartz in longmaxi group was given priority to with terrigenous detrital quartz, biological quartz next. Wuxi 1 Well in the north of the study area is given priority to with terrigenous clastic quartz. Jiaoshiba in southern of the study area, main type of quartz of Wufeng Group is given priority to terrigenous detrital quartz, biological quartz next, the Longmaxi Group is given priority to detrital quartz.(2) In combination with geochemical data analysis, this paper holds that in the north of the study area-Mingzhong, Wufeng Group are greatly influenced by ascending currents, developmental radiolarian siliceous shale, the affect of ascending currents to Longmaxi Group is abate, developmental siliceous shale. The affect of ascending current to Wuxi 1 Well in the north of the study area is small, the overall quartz source is far source terrigenous detrital quartz. Wufeng Group of Jiaoshiba in southern is affected by the ascending current, quartz source is given priority to far source terrigenous detrital quartz or wind transportation, biological quartz next. Longmaxi Group should be arounded by gradually rising underwater uplift, ascending currents affect little, the mian source of quartz is far source terrigenous clastic quartz or wind transportation and broken objects of underwater uplift.(3) The study of the correlation between quartz and shale evaluation parameters showed that quartz component, TOC content, shale gas free volume, total air content and shale brittleness has a positive correlation, and the affect of quartz to shale has two sides, excessive development of the siliceous goes against shale pore preservation.