A New Method for Semi-Quantitative Analysis of Amorphous SiO2 in Terrestrial Shale a Case Study About Yanchang Formation

Yanchang Formation shale of Ordos basin contains a certain amount of amorphous SiO2, which proved by SEM observation and X-ray diffraction analysis of bulk rock. The three methods proposed by now to calculate the quantity of amorphous SiO2 have their own flaws. The disadvantages of chemical denudation are experimental period and unconvinced accuracy because of dissolving other minerals. Quantitative analysis of amorphous silica by X-ray diffraction possesses high personal error on the integrated intensity of dome-shaped scattering curve in XRD spectrum of amorphous SiO2. The doping method has high deviation and needs to compound standard sample, while some kinds of pure minerals are hard to get. On the basis of summarizing researches have been done, a new method that combines QEMSCAN and XRD is proposed for the issue of amorphous SiO2 calculation in multiphase system. The new method avoids the flaws in approaches have been proposed, and calculates the amount of amorphous SiO2 indirectly according to the quantities of quartz and SiO2 measured respectively.According to QEMSCAN 650F integrated with XRD and gravity drainage method, we can calculate the mass percentage of amorphous silica, and the mass percentage of amorphous silica of YQ8 sample is 7.75%.