Sedimentary microfacies in the Lower Shaximiao Formation in the Xichong-Zitong region, western Sichuan depression

With the help of the depositional symbols of the petroloy, sedimentary structure and well-logging curves and on the bases of the observation of the field profile, drilling core and microscopic observation, the reasearch on the sedimentary micro-facies type and characteristics were conducted for lower Shaximiao Formation in the Xichong-Zitong area of western Sichuan. The study showed that the main lithology of the lower Shaximiao Formation in the Xichong-Zitong area were feldspar lithic sandstone and lithic feldspar sandstone by the sub-angular shape, moderate sorting. The debris components were mainly sedimentary rock cuttings, calcite and chlorite were the main cements. It developed Parallel layering, staggered bedding and bottom-scouring sedimentary structures. The Lower Shaximiao Formation in the study area developed the meandering river delta-lake sediments. The meandering river delta mainly developed the delta-front and the prodelta microfacies in the study area. Subaqueous distributary channel microfacies in delta front was the main enrichment environment for sand bodies. Its spatial distribution was mainly from north to south, and the three sand body development areas of Shehong, Xichong and Nanchong were sequentially distributed on the plane.