The researchers studied the sedimentary microfacies of the Fuyu reservoir in the Songliao Basin. They identified different types of rock layers and analyzed the colors, structures, and data from drilling. They found that the reservoir was formed by a shallow delta with two subfacies: delta plain and delta front. They also discovered branch channels, curved channels, and flood fans as important features. Over time, the water in the sedimentary layers became shallower and then deeper, leading to changes in the types of rocks deposited. The channels and flood fans contain sandstone with good properties for potential oil exploration.