Application of high precision mineral component interpretation method in lithofacies evaluation of tight sandstone:Take the outcrop of the second member of Xujiahe Formation in Gongnong Town,Guangyuan,western Sichuan as an example
Aiming at the problems of high-quality tight sandstone reservoir controlled by rock composition,which changes rapidly in vertical direction,accurate classification of reservoir lithofacies is an important factor to evaluate the quality of tight sandstone reservoir.Taking the outcrop of the second member of Xujiahe Formation in Gongnong Town,Guangyuan,western Sichuan as an example,XRF(X-ray fluorescence spectroscopy)element and scanning electron spectroscopy experiments were carried out based on the 239 outcrop samples drilled,a high-precision mineral component interpretation model has been established.The model results show that both Herron model and multiple linear regression analysis model can reflect the changing trend of minerals well,but the Herron model has poor interpretation accuracy for illite,kalifeldspar,plagioclase,chlorite and dolomite.The error between multiple linear regression analysis model and scanning energy spectrum test is very small,which can better explain the content of different types of minerals.The multiple linear regression analysis model is used to interpret the high precision lithofacies of the outcrop of the second member of Xujiahe Formation,and the accuracy is much higher than that of the rock sample description interpretation,the lithofacies are divided into 6 categories and 14 sub-categories,the quartz content gradually decreases from the bottom to the top,resulting in the porosity of the quartz-rich section at the bottom is better than that of the upper section.The favorable lithofacies in the outcrop area include medium-grained quartz sandstone with feldspar debris,coarse-grained quartz sandstone with feldspar debris,medium-grained quartz sandstone with feldspar debris,medium-grained quartz sandstone with feldspar,medium-grained quartz sandstone and calc medium-grained quartz sandstone.
tight sandstonefavorable lithofaciesmineral compositionXRF elementthe second section of Xujiahe Formationoutcrop
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