The method of distinguishing sedimentary environment of sandstone reservoirs by XRF

Although XRF elemental analysis is one of the major methods of depositional environment research in shale, it has not formed a unified standard in sandstone. With XRF portable analysis technology developing recently, the advantages of its portability, economy, high efficiency and the protection of the original sample make it more widely used. This study area has only few wells in the northern part of Xihu Sag with the problem of unclear sedimentary facies and sedimentary environment definition. In this case, the work attempts to determine the ancient depositional environment and typical sedimentary microfacies by using XRF core dense sampling method. According to the test accuracy of the hand-held X fluorescence spectrometer, the environmental discrimination elements of Sr, Mn, Ti, Mg, Ca and Fe were selected. The data of the cementing development layer were excluded by the casting and scanning electron microscopy. This paper normalized the relevant elements by GR curve, and the content of related elements in the fine sediment of one unit is obtained, which eliminates possible misjudgement caused by the content of fine sediment in determination of sedimentary environment in the sandstone reservoir. Then this study uses the standardized elemental and elemental ratio of the study area to determine the ancient depositional environment. Finally, according to the relationship between sedimentary microfacies and elements in the study area, two types of reference plate are selected to determine the sedimentary microfacies, providing the basis for fine grading of sedimentary microfacies.